General Description
The MAX6954 is a compact display driver that inter-
faces microprocessors to a mix of 7-segment, 14-seg-
ment, and 16-segment LED displays through an SPI™-
or QSPI™-compatible 4-wire serial interface. The serial
interface may be cascaded through multiple devices.
The MAX6954 drives up to 16 digits 7-segment, 8 digits
14-segment, 8 digits 16-segment, or 128 discrete
LEDs, while functioning from a supply voltage as low as
2.7V. The driver includes five I/O expander (or GPIO)
lines, some or all of which may be configured as a key-
switch reader, which automatically scans and
debounces a matrix of up to 32 switches.
Included on chip are full 14- and 16-segment ASCII
104-character fonts, a hexadecimal font for 7-segment
displays, multiplex scan circuitry, anode and cathode
drivers, and static RAM that stores each digit. The max-
imum segment current for the display digits is set using
a single external resistor. Digit intensity can be inde-
pendently adjusted using the 16-step internal digital
brightness control. The MAX6954 includes a low-power
shutdown mode, a scan-limit register that allows the
user to display from 1 to 16 digits, segment blinking
(synchronized across multiple drivers, if desired), and a
test mode, which forces all LEDs on. The LED drivers
are slew-rate limited to reduce EMI.
For a 2-wire interfaced version, refer to the MAX6955
data sheet. An evaluation kit (EV kit) for the MAX6955 is
available.
Applications
Set-Top Boxes Automotive
Panel Meters Bar Graph Displays
White Goods Audio/Video Equipment
Features
♦High-Speed 26MHz SPI/QSPI/MICROWIRE™-
Compatible Serial Interface
♦2.7V to 5.5V Operation
♦Drives Up to 16 Digits 7-Segment, 8 Digits
14-Segment, 8 Digits 16-Segment, 128 Discrete
LEDs, or a Combination of Digit Types
♦Drives Common-Cathode Monocolor and Bicolor
LED Displays
♦Built-In ASCII 104-Character Font for 14-Segment
and 16-Segment Digits and Hexadecimal Font for
7-Segment Digits
♦Automatic Blinking Control for each Segment
♦10µA (typ) Low-Power Shutdown (Data Retained)
♦16-Step Digit-by-Digit Digital Brightness Control
♦Display Blanked on Power-Up
♦Slew-Rate Limited Segment Drivers for Lower EMI
♦Five GPIO Port Pins Can Be Configured as Key-
Switch Reader to Scan and Debounce Up to 32
Switches with n-Key Rollover
♦IRQ Output when a Key Input Is Debounced
♦36-Pin SSOP and 40-Pin DIP and TQFN Packages
♦Automotive Temperature Range Standard
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
________________________________________________________________
Maxim Integrated Products
1
Ordering Information
19-2460; Rev 4; 3/09
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
PART TEMP RANGE PIN-PACKAGE
MAX6954AAX -40°C to +125°C 36 SSOP
MAX6954APL -40°C to +125°C 40 PDIP
MAX6954ATL+
-40°C to +125°C 40 TQFN-EP*
SPI and QSPI are trademarks of Motorola, Inc.
MICROWIRE is a trademark of National Semiconductor Corp.
+
Denotes a lead-free/RoHS-compliant package.
*
EP = Exposed pad.
Pin Configurations and Typical Operating Circuits appear
at end of data sheet.
ISET
OSC
OSC_OUT
BLINK
CLK
CS
DIN
DOUT
4-WIRE SERIAL INTERFACE
RAM
BLINK
CONTROL
CONFIGURATION
REGISTER
CHARACTER
GENERATOR
ROM
CURRENT
SOURCE
DIVIDER/
COUNTER
NETWORK
DIGIT
MULTIPLEXER
PWM
BRIGHTNESS
CONTROL
GPIO
AND KEY-SCAN
CONTROL
LED
DRIVERS
O0 TO O23
P0 TO P4
MAX6954
Functional Diagram
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
(Voltage with respect to GND.)
V+ .........................................................................-0.3V to +6V
All Other Pins............................................-0.3V to (V+ + 0.3V)
Current
O0–O7 Sink Current ......................................................935mA
O0–O18 Source Current .................................................55mA
DIN, CLK, CS, OSC, DOUT, BLINK, OSC_OUT, ISET ....20mA
P0, P1, P2, P3, P4 ...........................................................40mA
GND .....................................................................................1A
Continuous Power Dissipation (TA= +70°C)
36-Pin SSOP (derate at 11.8mW/°C above +70°C) .....941mW
40-Pin PDIP (derate at 16.7mW/°C above +70°C).....1333mW
40-Pin TQFN (derate at 37mW/°C above +70°C) ......2963mW
Operating Temperature Range
(TMIN to TMAX) ...............................................-40°C to +125°C
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
DC ELECTRICAL CHARACTERISTICS
(
Typical Operating Circuits
, V+ = 2.7V to 5.5V, TA= TMIN to TMAX, unless otherwise noted.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN TYP MAX
UNITS
Operating Supply Voltage V+ 2.7 5.5 V
TA = +25°C 10 35
Shutdown Supply Current ISHDN
Shutdown mode, all
digital inputs at V+
or GND TA = TMIN to TMAX 40
µA
TA = +25°C 22 30
Operating Supply Current I+
All segments on, all
digits scanned,
intensity set to full,
internal oscillator,
DOUT open circuit,
no display or
OSC_OUT load
connected
TA = TMIN to TMAX 35
mA
OSC = RC oscillator, RSET = 56kΩ,
CSET = 22pF, V+ = 3.3V 4
Master Clock Frequency fOSC
OSC driven externally 1 8
MHz
Dead Clock Protection Frequency
fOSC 95 kHz
OSC Internal/External Detection
Threshold VOSC 1.7 V
OSC High Time tCH 50 ns
OSC Low Time tCL 50 ns
Slow Segment Blink Period
fSLOWBLINK
OSC = RC oscillator, RSET = 56kΩ,
CSET = 22pF, V+ = 3.3V 1s
Fast Segment Blink Period
fFASTBLINK
OSC = RC oscillator, RSET = 56kΩ,
CSET = 22pF, V+ = 3.3V 0.5 s
Fast or Slow Segment Blink Duty
Cycle
49.5 50.5
%
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
_______________________________________________________________________________________ 3
DC ELECTRICAL CHARACTERISTICS (continued)
(
Typical Operating Circuits
, V+ = 2.7V to 5.5V, TA= TMIN to TMAX, unless otherwise noted.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN TYP MAX UNITS
Segment Drive Source Current ISEG VLED = 2.2V,
V+ = 3.3V TA = +25°C
-34.5
-40
-46.5
mA
Segment Current Slew Rate
ΔISEG/Δt
TA = +25°C, V+ = 3.3V 11
mA/µs
Segment Drive Current Matching
ΔISEG TA = +25°C, V+ = 3.3V 5 10 %
LOGIC INPUTS AND OUTPUTS
Input Leakage Current
DIN, CLK, CS, OSC, P0, P1, P2,
P3, P4
IIH, IIL -1 +1 µA
4-Wire Logic-High Input Voltage
DIN, CLK, CS VIHSPI 1.8 V
4-Wire Logic-Low Input Voltage
DIN, CLK, CS VILSPI 0.6 V
Port Logic-High Input Voltage
P0, P1, P2, P3, P4 VIHP 0.7 x
V+ V
Port Logic-Low Input Voltage
P0, P1, P2, P3, P4 VILP 0.3 x
V+ V
Port Hysteresis Voltage P0, P1,
P2, P3, P4 ΔVIP 0.03 x
V+ V
Port Input Pullup Current from V+
IIPU P0 to P3 configured as keyscan input, V+ =
3.3V 75 µA
Port Output Low Voltage VOLP ISINK = 8mA 0.3 0.5 V
Blink Output Low Voltage VOLBK ISINK = 0.6mA 0.1 0.3 V
DOUT Output High Voltage
VOHDO
ISOURCE = 1.6mA V+ -
0.2 V
DOUT Output Low Voltage
VOLDO
ISINK = 1.6mA 0.2 V
OSC_OUT Output High Voltage
VOHOSC
ISOURCE = 1.6mA V+ -
0.4 V
OSC_OUT Output Low Voltage
VOLOSC
ISINK = 1.6mA 0.4 V
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
4 _______________________________________________________________________________________
Typical Operating Characteristics
(V+ = 3.3V, LED forward voltage = 2.4V, typical application circuit, TA= +25°C, unless otherwise noted.)
TIMING CHARACTERISTICS
(
Typical Operating Circuits
, V+ = 2.7V to 5.5V, TA= TMIN to TMAX, unless otherwise noted.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN TYP MAX
UNITS
TIMING CHARACTERISTICS
CLK Clock Period tCP
38.4
ns
CLK Pulse Width High tCH 16 ns
CLK Pulse Width Low tCL 16 ns
CS Fall to CLK Rise Setup Time tCSS 9.5 ns
CLK Rise to CS Rise Hold Time tCSH 0ns
DIN Setup Time tDS 9.5 ns
DIN Hold Time tDH 0ns
V+ = 3.0V to 5.5V 19
Output Data Propagation Delay tDO V+ = 2.7V 25 ns
DOUT Output Rise and Fall Times tFT CLOAD = 10pF, V+ = 3.0V to 5.5V 10
Minimum CS Pulse High tCSW
19.5
ns
Note 1: All parameters tested at TA= +25°C. Specifications over temperature are guaranteed by design.
INTERNAL OSCILLATOR FREQUENCY
vs. TEMPERATURE
MAX6954 toc01
TEMPERATURE (°C)
OSCILLATOR FREQUENCY (MHz)
110805020-10
3.8
4.0
4.2
4.4
3.6
-40
RSET = 56kΩ
CSET = 22pF
INTERNAL OSCILLATOR FREQUENCY
vs. SUPPLY VOLTAGE
MAX6954 toc02
SUPPLY VOLTAGE (V)
OSCILLATOR FREQUENCY (MHz)
5.04.54.03.53.0
3.8
4.2
4.4
3.6
2.5 5.5
RSET = 56kΩ
CSET = 22pF
4.0
100ns/div
OSC: 500mV/div
OSC_OUT: 2V/div
MAX6954 toc03
OSC
0V
0V
OSC_OUT
INTERNAL OSCILLATOR WAVEFORM
AT OSC AND OSC_OUT PINS
RSET = 56kΩ
CSET = 22pF
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
_______________________________________________________________________________________ 5
Typical Operating Characteristics (continued)
(V+ = 3.3V, LED forward voltage = 2.4V, typical application circuit, TA= +25°C, unless otherwise noted.)
DEAD CLOCK OSCILLATOR FREQUENCY
vs. SUPPLY VOLTAGE
MAX6954 toc04
SUPPLY VOLTAGE (V)
OSCILLATOR FREQUENCY (kHz)
5.04.54.03.53.0
85
95
105
110
80
2.5 5.5
RSET = 56kΩ
OSC = GND
100
90
SEGMENT SOURCE CURRENT
vs. SUPPLY VOLTAGE
MAX6954 toc05
SUPPLY VOLTAGE (V)
CURRENT NORMALIZED TO 40mA
5.04.54.03.53.0
0.94
0.98
1.00
1.02
0.92
2.5 5.5
VLED = 1.8V
0.96
1V/div
200μs/div
MAX6954 toc06
O0
O18
WAVEFORM AT PINS O0 AND O18,
MAXIMUM INTENSITY
0V
0V
GPIO SINK CURRENT
vs. TEMPERATURE
MAX6954 toc07
TEMPERATURE (°C)
GPIO SINK CURRENT (mA)
11050 8020-10
5
10
15
20
25
30
35
40
45
0
-40
VCC = 3.3V
VCC = 2.5V
VCC = 5.5V
OUTPUT = LOW
VPORT = 0.6V
PORT INPUT PULLUP CURRENT
vs. TEMPERATURE
MAX6954 toc08
TEMPERATURE (°C)
KEY-SCAN SOURCE CURRENT (mA)
11050 8020-10
0.05
0.10
0.15
0.20
0.25
0.30
0
-40
VCC = 3.3V
VCC = 2.5V
VCC = 5.5V
OUTPUT = HIGH
VPORT = 1.4V
400μs/div
KEY_A: 1V/div
IRQ: 2V/div
MAX6954 toc09
KEY_A
0V
0V
IRQ
KEYSCAN OPERATION
(KEY_A AND IRQ)
MAX6954
Detailed Description
The MAX6954 is a serially interfaced display driver that
can drive up to 16 digits 7-segment, 8 digits 14-seg-
ment, 8 digits 16-segment, 128 discrete LEDs, or a
combination of these display types. Table 1 shows the
drive capability of the MAX6954 for monocolor and
bicolor displays.
The MAX6954 includes 104-character ASCII font maps
for 14-segment and 16-segment displays, as well as
the hexadecimal font map for 7-segment displays. The
characters follow the standard ASCII font, with the addi-
tion of the following common symbols: £, €, ¥, °, µ, ±,
↑, and ↓. Seven bits represent the 104-character font
map; an 8th bit is used to select whether the decimal
point (DP) is lit. Seven-segment LED digits may be con-
trolled directly or use the hexadecimal font. Direct seg-
ment control allows the MAX6954 to be used to drive
bar graphs and discrete LED indicators.
Tables 2, 3, and 4 list the connection schemes for 16-,
14-, and 7-segment digits, respectively. The letters in
Tables 2, 3, and 4 correspond to the segment labels
shown in Figure 1. (For applications that require mixed
display types, see Tables 37–40.)
Serial Interface
The MAX6954 communicates through an SPI-compati-
ble 4-wire serial interface. The interface has three
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
6 _______________________________________________________________________________________
Pin Description
PIN
SSOP
PDIP
T Q F N - EP NAME
FUNCTION
1, 2,
34, 35, 36
1, 2,
38, 39, 40
36, 37,
33, 34, 35
P0–P4
General-Purpose I/O Ports (GPIOs). GPIO can be configured as logic inputs or
open-drain outputs. Enabling key scanning configures some or all ports P0–P3 as
key-switch matrix inputs with internal pullup and port P4 as IRQ output.
3338CS Chip-Select Input. Serial data is loaded into the shift register while CS is low. The
most recent 16 bits of data latch on CS’s rising edge.
4 4 39 DOUT Serial-Data Output. The data into DIN is valid at DOUT 15.5 clock cycles later. Use
this pin to daisy-chain several devices or allow data readback. Output is push-pull.
5540CLK
S er i al - C l ock Inp ut. On C LK’ s r i si ng ed g e, d ata shi fts i nto the i nter nal shi ft r eg i ster . On
C LK’ s fal l i ng ed g e, d ata i s cl ocked out of D OU T. C LK i s acti ve onl y w hi l e C S i s l ow .
661DIN
Serial-Data Input. Data from DIN loads into the internal 16-bit shift register on CLK’s
rising edge.
7–15,
22–31
7–15,
26–35
2–10,
21–30
O0–O18
Digit/Segment Drivers. When acting as digit drivers, outputs O0 to O7 sink current
from the display common cathodes. When acting as segment drivers, O0 to O18
source current to the display anodes. O0 to O18 are high impedance when not
being used as digit or segment drivers.
16, 18
17, 18, 20 12, 13, 15
GND Ground
17 19 14 ISET Segment Current Setting. Connect ISET to GND through series resistor RSET to set
the peak current.
19, 21
21, 23, 24 16, 18, 19
V+ Positive Supply Voltage. Bypass V+ to GND with a 47µF bulk capacitor and a 0.1µF
ceramic capacitor.
20 22 17 OSC Multiplex Clock Input. To use internal oscillator, connect capacitor CSET from OSC
to GND. To use external clock, drive OSC with a 1MHz to 8MHz CMOS clock.
32 36 31
BLINK
Blink Clock Output. Output is open drain.
33 37 32
O S C _O U T
Clock Output. OSC_OUT is a buffered clock output to allow easy blink
synchronization of multiple MAX6954s. Output is push-pull.
— 16, 25 11, 20 N.C. Not Connected Internally
———EP
Exposed Pad (TQFN package only). Internally connected to GND. Connect to a
large ground plane to maximize thermal performance.
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
_______________________________________________________________________________________ 7
inputs: clock (CLK), chip select (CS), and data in (DIN),
and one output, data out (DOUT). CS must be low to
clock data into or out of the device, and DIN must be
stable when sampled on the rising edge of CLK. DOUT
is stable on the rising edge of CLK. Note that while the
SPI protocol expects DOUT to be high impedance
when the MAX6954 is not being accessed, DOUT on
the MAX6954 is never high impedance.
CLK and DIN may be used to transmit data to other
peripherals. The MAX6954 ignores all activity on CLK
and DIN except when CS is low.
Control and Operation Using the 4-Wire Interface
Controlling the MAX6954 requires sending a 16-bit
word. The first byte, D15 through D8, is the command,
and the second byte, D7 through D0, is the data byte
(Table 5).
Connecting Multiple MAX6954s to the 4-Wire Bus
Multiple MAX6954s may be daisy-chained by connect-
ing the DOUT of one device to the DIN of the next, and
driving CLK and CS lines in parallel (Figure 2). Data at
DIN propagates through the internal shift registers and
appears at DOUT 15.5 clock cycles later, clocked out
on the falling edge of CLK. When sending commands
to daisy-chained MAX6954s, all devices are accessed
at the same time. An access requires (16 x n) clock
cycles, where n is the number of MAX6954s connected
together. To update just one device in a daisy-chain,
the user can send the no-op command (0x00) to the
others. Figure 3 is the MAX6954 timing diagram.
The MAX6954 is written to using the following
sequence:
1) Take CLK low.
2) Take CS low. This enables the internal 16-bit shift
register.
3) Clock 16 bits of data into DIN, D15 first to D0 last,
observing the setup and hold times. Bit D15 is low,
indicating a write command.
4) Take CS high (while CLK is still high after clocking in
the last data bit).
5) Take CLK low.
Figure 4 shows a write operation when 16 bits are
transmitted.
If fewer or greater than 16 bits are clocked into the
MAX6954 between taking CS low and taking CS high
again, the MAX6954 stores the last 16 bits received,
including the previous transmission(s). The general
case is when n bits (where n > 16) are transmitted to
the MAX6954. The last bits are comprising bits {n-15} to
{n}, are retained, and are parallel loaded into the 16-bit
latch as bits D15 to D0, respectively (Figure 5).
DISPLAY TYPE
7 SEGMENT
(16-CHARACTER
HEXADECIMAL FONT)
14 SEGMENT/
16 SEGMENT
(104-CHARACTER ASCII FONT MAP)
DISCRETE LEDs
(DIRECT CONTROL)
Monocolor 16 8 128
Bicolor 8 4 64
Table 1. MAX6954 Drive Capability
1dp 2dp
fb
ec
d1
a1
i
l
g1 g2
hj
mk
a2
d2
dp dp
1a
1g
1f 1b
1e 1c
1d
2a
2g
2f 2b
2e 2c
2d
fb
ec
d
a
i
l
g1 g2
hj
mk
Figure 1. Segment Labeling for 7-Segment Display, 14-Segment Display, and 16-Segment Display
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
8 _______________________________________________________________________________________
Reading Device Registers
Any register data within the MAX6954 may be read by
sending a logic high to bit D15. The sequence is:
1) Take CLK low.
2) Take CS low. This enables the internal 16-bit shift
register.
3) Clock 16 bits of data into DIN, D15 first to D0 last.
D15 is high, indicating a read command and bits
D14 through D8 contain the address of the register
DIGITO0O1O2O3O4O5O6O7O8O9O10O11O12O13O14O15O16O17
O18
0 CCO — a1 a2 b c d1 d2 e
f
g1 g2 h
ij
k
l
m
dp
1 — CC1 a1 a2 b c d1 d2 e
f
g1 g2 h
ij
k
l
m
dp
2 a1 a2 CC2 — b c d1 d2 e
f
g1 g2 h
ij
k
l
m
dp
3 a1 a2 — CC3 b c d1 d2 e
f
g1 g2 h
ij
k
l
m
dp
4 a1 a2 b c CC4 — d1 d2 e
f
g1 g2 h
ij
k
l
m
dp
5 a1 a2 b c — CC5 d1 d2 e
f
g1 g2 h
ij
k
l
m
dp
6 a1 a2 b c d1 d2 CC6 — e
f
g1 g2 h
ij
k
l
m
dp
7 a1 a2 b c d1 d2 — CC7 e
f
g1 g2 h
ij
k
l
m
dp
DIGITO0O1O2O3O4O5O6O7O8O9O10O11O12O13O14O15O16O17
O18
0 CCO — a — b c d — e
f
g1 g2 h
ij
k
l
m
dp
1—CC1a—b c d—e
f
g1 g2 h
ij
k
l
m
dp
2 a — CC2 — b c d — e
f
g1 g2 h
ij
k
l
m
dp
3 a — — CC3 b c d — e
f
g1 g2 h
ij
k
l
m
dp
4 a—b cCC4—d—e
f
g1 g2 h
ij
k
l
m
dp
5 a — b c — CC5 d — e
f
g1 g2 h
ij
k
l
m
dp
6 a—b c d—CC6—e
f
g1 g2 h
ij
k
l
m
dp
7 a — b c d — — CC7 e
f
g1 g2 h
ij
k
l
m
dp
Table 2. Connection Scheme for Eight 16-Segment Digits
Table 3. Connection Scheme for Eight 14-Segment Digits
D IG IT * O0 O1 O2 O3 O4 O5 O6 O7 O8 O9 O10 O11 O12 O13 O14 O15 O16 O17
O18
0, 0a C C 0 — 1a — 1b 1c 1d 1dp 1e 1f 1g 2a 2b 2c 2d 2e 2f 2g
2dp
1, 1a — CC1 1a — 1b 1c 1d 1dp 1e 1f 1g 2a 2b 2c 2d 2e 2f 2g
2dp
2, 2a 1a — CC2 — 1b 1c 1d 1dp 1e 1f 1g 2a 2b 2c 2d 2e 2f 2g
2dp
3, 3a 1a — — CC3 1b 1c 1d 1dp 1e 1f 1g 2a 2b 2c 2d 2e 2f 2g
2dp
4, 4a 1a — 1b 1c CC4 — 1d 1dp 1e 1f 1g 2a 2b 2c 2d 2e 2f 2g
2dp
5, 5a1a—1b1c—CC51d1dp1e 1f 1g2a2b2c2d2e 2f 2g
2dp
6, 6a1a—1b1c1d1dpCC6— 1e 1f 1g2a2b2c2d2e 2f2g
2dp
7, 7a 1a — 1b 1c 1d 1dp — CC7 1e 1f 1g 2a 2b 2c 2d 2e 2f 2g
2dp
Table 4. Connection Scheme for Sixteen 7-Segment Digits
D15
D14
D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1
D0
R/W
ADDRESS
MSB
DATA
LSB
Table 5. Serial-Data Format (16 Bits)
*
Each cathode driver output (CC0-CC7) connects to two digit common cathode pins.
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
_______________________________________________________________________________________ 9
to read. Bits D7 to D0 contain dummy data, which is
discarded.
4) Take CS high (while CLK is still high after clocking in
the last data bit), positions D7 through D0 in the shift
register are now loaded with the register data
addressed by bits D15 through D8.
5) Take CLK low.
6) Issue another read or write command (which can be
a no-op), and examine the bit stream at DOUT; the
second 8 bits are the contents of the register
addressed by bits D14 through D8 in step 3.
Digit Type Registers
The MAX6954 uses 32 digit registers to store the char-
acters that the user wishes to display. These digit regis-
ters are implemented with two planes, P0 and P1. Each
digit is represented by 2 bytes of memory, 1 byte in
plane P0 and the other in plane P1. The digit registers
are mapped so that a digit’s data can be updated in
plane P0, plane P1, or both planes at the same time
(Table 6).
If the blink function is disabled through the Blink Enable
Bit E (Table 19) in the configuration register, then the
digit register data in plane P0 is used to multiplex the
display. The digit register data in P1 is not used. If the
blink function is enabled, then the digit register data in
both plane P0 and plane P1 are alternately used to mul-
tiplex the display. Blinking is achieved by multiplexing
the LED display using data plane P0 and plane P1 on
alternate phases of the blink clock (Table 20).
The data in the digit registers does not control the digit
segments directly for 14- and 16-segment displays.
Instead, the register data is used to address a charac-
ter generator that stores the data for the 14- and 16-
segment fonts (Tables 7 and 8). The lower 7 bits of the
digit data (D6 to D0) select the character from the font.
tCSS tCL tCH tCP
tCSH
tCSW
tDS
tDH
D15
CLK
DIN
CS
D14 D1 D0
D15
tDO
DOUT
Figure 3. Timing Diagram
MAX6954
DOUT
MICROCONTROLLER
CLK
DIN
MAX6954 MAX6954
CLK
DIN
CS
DOUT
CLK
DIN
CS
DOUT
CLK
DIN
CS
DOUT
CS
Figure 2. MAX6954 Daisy-Chain Connection
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
10 ______________________________________________________________________________________
The most significant bit of the register data (D7) con-
trols the DP segment of the digits; it is set to 1 to light
DP, and to zero to leave DP unlit (Table 9).
For 7-segment displays, the digit plane data register
can be used to address a character generator, which
contains the data of a 16-character font containing the
hexadecimal font. The decode mode register can be
used to disable the character generator and allow the
segments to be controlled directly. Table 10 shows the
one-to-one pairing of each data bit to the appropriate
segment line in the digit plane data registers. The hexa-
decimal font is decoded according to Table 11.
The digit-type register configures the display driver for
various combinations of 14-segment digits, 16-segment
digits, and/or pairs, or 7-segment digits. The function of
this register is to select the appropriate font for each
digit and route the output of the font to the appropriate
MAX6954 driver output pins. The MAX6954 has four
digit drive slots. A slot can be filled with various combi-
nations of monocolor and bicolor 16-segment displays,
14-segment displays, or two 7-segment displays. Each
pair of bits in the register corresponds to one of the four
digit drive slots, as shown in Table 12. Each bit also cor-
responds to one of the eight common-cathode digit
drive outputs, CC0 to CC7. When using bicolor digits,
the anode connections for the two digits within a slot are
always the same. This means that a slot correctly drives
two monocolor or one bicolor 14- or 16-segment digit.
The digit type register can be written, but cannot be
read. Examples of configuration settings required for
some display digit combinations are shown in Table 13.
7-Segment Decode-Mode Register
In 7-segment mode, the hexadecimal font can be dis-
abled (Table 14). The decode-mode register selects
between hexadecimal code or direct control for each of
eight possible pairs of 7-segment digits. Each bit in the
register corresponds to one pair of digits. The digit
pairs are {digit 0, digit 0a} through {digit 7, digit 7a}.
Disabling decode mode allows direct control of the 16
LEDs of a dual 7-segment display. Direct control mode
can also be used to drive a matrix of 128 discrete
LEDs.
CS
CLK
DIN D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
DOUT D15 = 0
Figure 4. Transmission of 16 Bits to the MAX6954
CS
CLK
DIN BIT
1
BIT
2
N-9 N-8 N-7 N-6 N-5 N-4 N-3 N-2
DOUT N-15
N-15 N-14 N-13 N-12 N-11 N-10 N-1
N-31 N-30 N-29 N-28 N-27 N-26 N-25 N-24 N-23 N-22 N-21 N-20 N-19 N-18 N-17 N-16
N
Figure 5. Transmission of More than 16 Bits to the MAX6954
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
______________________________________________________________________________________ 11
A logic high selects hexadecimal decoding, while a
logic low bypasses the decoder. When direct control is
selected, the data bits D7 to D0 correspond to the seg-
ment lines of the MAX6954. Write x0010000 to blank all
segments in hexadecimal decode mode.
Display Blink Mode
The display blinking facility, when enabled, makes the
driver flip automatically between displaying the digit
register data in planes P0 and P1. If the digit register
data for any digit is different in the two planes, then that
digit appears to flip between two characters. To make a
character appear to blink on or off, write the character
to one plane, and use the blank character (0x20) for the
other plane. Once blinking has been configured, it con-
tinues automatically without further intervention.
Blink Speed
The blink speed is determined by the frequency of the
multiplex clock, OSC, and by the setting of the Blink
Rate Selection Bit B (Table 18) in the configuration reg-
ister. The Blink Rate Selection Bit B sets either fast or
slow blink speed for the whole display.
Initial Power-Up
On initial power-up, all control registers are reset, the
display is blanked, intensities are set to minimum, and
shutdown is enabled (Table 15).
Configuration Register
The configuration register is used to enter and exit shut-
down, select the blink rate, globally enable and disable
the blink function, globally clear the digit data, select
between global or digit-by-digit control of intensity, and
reset the blink timing (Tables 16–19 and 21–24).
The configuration register contains 7 bits:
• S bit selects shutdown or normal operation
(read/write).
• B bit selects the blink rate (read/write).
• E bit globally enables or disables the blink function
(read/write).
• T bit resets the blink timing (data is not stored—tran-
sient bit).
• R bit globally clears the digit data for both planes P0
and P1 for ALL digits (data is not stored—transient
bit).
• I bit selects between global or digit-by-digit control
of intensity (read/write).
• P bit returns the current phase of the blink timing
(read only—a write to this bit is ignored).
Character Generator Font Mapping
The font is composed of 104 characters in ROM. The
lower 7 bits of the 8-bit digit register represent the char-
acter selection. The most significant bit, shown as x in
the ROM map of Tables 7 and 8, is 1 to light the DP
segment and zero to leave the DP segment unlit.
The character map follows the standard ASCII font for
96 characters in the x0101000 through x1111111
range. The first 16 characters of the 16-segment ROM
map cover 7-segment displays. These 16 characters
are numeric 0 to 9 and characters A to F (i.e., the hexa-
decimal set).
Multiplex Clock and Blink Timing
The OSC pin can be fitted with capacitor CSET to GND
to use the internal RC multiplex oscillator, or driven by
an external clock to set the multiplex clock frequency
and blink rate. The multiplex clock frequency deter-
mines the frequency that the complete display is updat-
ed. With OSC at 4MHz, each display digit is enabled for
200µs.
The internal RC oscillator uses an external resistor,
RSET, and an external capacitor, CSET, to set the oscil-
lator frequency. The suggested values of RSET (56kΩ)
and CSET (22pF) set the oscillator at 4MHz, which
makes the blink frequency 0.5Hz or 1Hz.
The external clock is not required to have a 50:50 duty
cycle, but the minimum time between transitions must
be 50ns or greater and the maximum time between
transitions must be 750ns.
The on-chip oscillator may be accurate enough for
applications using a single device. If an exact blink rate
is required, use an external clock ranging between
1MHz and 8MHz to drive OSC. The OSC inputs of multi-
ple MAX6954s can be tied together to a common exter-
nal clock to make the devices blink at the same rate.
The relative blink phasing of multiple MAX6954s can be
synchronized by setting the T bit in the control register
for all the devices in quick succession. If the serial inter-
faces of multiple MAX6954s are daisy-chained by con-
necting the DOUT of one device to the DIN of the next,
then synchronization is achieved automatically by
updating the configuration register for all devices simul-
taneously. Figure 6 is the multiplex timing diagram.
OSC_OUT Output
The OSC_OUT output is a buffered copy of either the
internal oscillator clock or the clock driven into the OSC
pin if the external clock has been selected. The feature
is useful if the internal oscillator is used, and the user
wishes to synchronize other MAX6954s to the same
blink frequency. The oscillator is disabled while the
MAX6954 is in shutdown.
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
12 ______________________________________________________________________________________
Scan-Limit Register
The scan-limit register sets how many 14-segment dig-
its or 16-segment digits or pairs of 7-segment digits are
displayed, from 1 to 8. A bicolor digit is connected as
two monocolor digits. The scan register also limits the
number of keys that can be scanned.
Since the number of scanned digits affects the display
brightness, the scan-limit register should not be used to
blank portions of the display (such as leading-zero sup-
pression). Table 25 shows the scan-limit register format.
Intensity Registers
Digital control of display brightness is provided and
can be managed in one of two ways: globally or individ-
ually. Global control adjusts all digits together.
Individual control adjusts the digits separately.
The default method is global brightness control, which
is selected by clearing the global intensity bit (I data bit
D6) in the configuration register. This brightness setting
applies to all display digits. The pulse-width modulator
is then set by the lower nibble of the global intensity
register, address 0x02. The modulator scales the aver-
age segment current in 16 steps from a maximum of
15/16 down to 1/16 of the peak current. The minimum
interdigit blanking time is set to 1/16 of a cycle. When
using bicolor digits, 256 color/brightness combinations
are available.
Individual brightness control is selected by setting the
global intensity bit (I data bit D6) in the configuration
register. The pulse-width modulator is now no longer
set by the lower nibble of the global intensity register,
address 0x02, and the data is ignored. Individual digital
control of display brightness is now provided by a sep-
arate pulse-width modulator setting for each digit. Each
digit is controlled by a nibble of one of the four intensity
registers: intensity10, intensity32, intensity54, and inten-
sity76 for all display types, plus intensity10a, intensi-
ty32a, intensity54a, and intensity76a for the extra eight
digits possible when 7-segment displays are used. The
data from the relevant register is used for each digit as
it is multiplexed. The modulator scales the average
segment current in 16 steps in exactly the same way as
global intensity adjustment.
Table 26 shows the global intensity register format,
Table 27 shows individual segment intensity registers,
Table 28 is the even individual segment intensity for-
mat, and Table 29 is the odd individual segment inten-
sity format.
GPIO and Key Scanning
The MAX6954 feature five general-purpose input/output
(GPIO) ports: P0 to P4. These ports can be individually
enabled as logic inputs or open-drain logic outputs.
The GPIO ports are not debounced when configured as
inputs. The ports can be read and the outputs set using
the 4-wire interface.
Some or all of the five ports can be configured to per-
form key scanning of up to 32 keys. Ports P0 to P4 are
renamed Key_A, Key_B, Key_C, Key_D, and IRQ,
respectively, when used for key scanning. The full key-
scanning configuration is shown in Figure 7. Table 30 is
the GPIO data register.
One diode is required per key switch. These diodes
can be common-anode dual diodes in SOT23 pack-
ages, such as the BAW56. Sixteen diodes would be
required for the maximum 32-key configuration.
The MAX6954 can only scan the maximum 32 keys if
the scan-limit register is set to scan the maximum eight
digits. If the MAX6954 is driving fewer digits, then a
maximum of (4 x n) switches can be scanned, where n
is the number of digits set in the scan-limit register. For
example, if the MAX6954 is driving four 14-segment
digits cathode drivers O0 to O3 are used. Only 16 keys
can be scanned in this configuration; the switches
shown connected to O4 through O7 are not read.
If the user wishes to scan fewer than 32 keys, then
fewer scan lines can be configured for key scanning.
The unused Key_x ports are released back to their orig-
inal GPIO functionality. If key scanning is enabled,
regardless of the number of keys being scanned, P4 is
always configured as IRQ (Table 31).
The key-scanning circuit utilizes the LEDs’ common-
cathode driver outputs as the key-scan drivers. O0 to
07 go low for nominally 200µs (with OSC = 4MHz) in
turn as the displays are multiplexed. By varying the
oscillator frequency, the debounce time changes,
though key scanning still functions. Key_x inputs have
internal pullup resistors that allow the key condition to
be tested. The Key_x input is low during the appropri-
ate digit multiplex period when the key is pressed. The
timing diagram of Figure 8 shows the normal situation
where all eight LED cathode drivers are used.
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
______________________________________________________________________________________ 13
ADDRESS (COMMAND BYTE)
REGISTER
D15 D14 D13 D12 D11 D10 D9 D8
HEX CODE
No-Op
R/W
0000000 0x00
Decode Mode
R/W
0000001 0x01
Global Intensity
R/W
0000010 0x02
Scan Limit
R/W
0000011 0x03
Configuration
R/W
0000100 0x04
GPIO Data
R/W
0000101 0x05
Port Configuration
R/W
0000110 0x06
Display Test
R/W
0000111 0x07
Write KEY_A Mask
Read KEY_A Debounce
R/W
0001000 0x08
Write KEY_B Mask
Read KEY_B Debounce
R/W
0001001 0x09
Write KEY_C Mask
Read KEY_C Debounce
R/W
0 0 0 1 0 1 0 0x0A
Write KEY_D Mask
Read KEY_D Debounce
R/W
0 0 0 1 0 1 1 0x0B
Write Digit Type
Read KEY_A Pressed
R/W
0 0 0 1 1 0 0 0x0C
Read KEY_B Pressed* 1 0 0 0 1 1 0 1 0x0D
Read KEY_C Pressed* 1 0 0 0 1 1 1 0 0x0E
Read KEY_D Pressed* 1 0 0 0 1 1 1 1 0x0F
Intensity 10
R/W
0010000 0x10
Intensity 32
R/W
0010001 0x11
Intensity 54
R/W
0010010 0x12
Intensity 76
R/W
0010011 0x13
Intensity 10a (7 Segment Only)
R/W
0010100 0x14
Intensity 32a (7 Segment Only)
R/W
0010101 0x15
Intensity 54a (7 Segment Only)
R/W
0010110 0x16
Intensity 76a (7 Segment Only)
R/W
0010111 0x17
Digit 0 Plane P0
R/W
0100000 0x20
Digit 1 Plane P0
R/W
0100001 0x21
Digit 2 Plane P0
R/W
0100010 0x22
Digit 3 Plane P0
R/W
0100011 0x23
Digit 4 Plane P0
R/W
0100100 0x24
Digit 5 Plane P0
R/W
0100101 0x25
Digit 6 Plane P0
R/W
0100110 0x26
Digit 7 Plane P0
R/W
0100111 0x27
Digit 0a Plane P0 (7 Segment Only)
R/W
0101000 0x28
Digit 1a Plane P0 (7 Segment Only)
R/W
0101001 0x29
Digit 2a Plane P0 (7 Segment Only)
R/W
0 1 0 1 0 1 0 0x2A
Digit 3a Plane P0 (7 Segment Only)
R/W
0 1 0 1 0 1 1 0x2B
Table 6. Register Address Map
*
Do NOT write to register.
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
14 ______________________________________________________________________________________
ADDRESS (COMMAND BYTE)
REGISTER
D15 D14 D13 D12 D11 D10 D9 D8
HEX CODE
Digit 4a Plane P0 (7 Segment Only)
R/W
0 1 0 1 1 0 0 0x2C
Digit 5a Plane P0 (7 Segment Only)
R/W
0 1 0 1 1 0 1 0x2D
Digit 6a Plane P0 (7 Segment Only)
R/W
0101110 0x2E
Digit 7a Plane P0 (7 Segment Only)
R/W
0101111 0x2F
Digit 0 Plane P1
R/W
1000000 0x40
Digit 1 Plane P1
R/W
1000001 0x41
Digit 2 Plane P1
R/W
1000010 0x42
Digit 3 Plane P1
R/W
1000011 0x43
Digit 4 Plane P1
R/W
1000100 0x44
Digit 5 Plane P1
R/W
1000101 0x45
Digit 6 Plane P1
R/W
1000110 0x46
Digit 7 Plane P1
R/W
1000111 0x47
Digit 0a Plane P1 (7 Segment Only)
R/W
1001000 0x48
Digit 1a Plane P1 (7 Segment Only)
R/W
1001001 0x49
Digit 2a Plane P1 (7 Segment Only)
R/W
1 0 0 1 0 1 0 0x4A
Digit 3a Plane P1 (7 Segment Only)
R/W
1 0 0 1 0 1 1 0x4B
Digit 4a Plane P1 (7 Segment Only)
R/W
1 0 0 1 1 0 0 0x4C
Digit 5a Plane P1 (7 Segment Only)
R/W
1 0 0 1 1 0 1 0x4D
Digit 6a Plane P1 (7 Segment Only)
R/W
1001110 0x4E
Digit 7a Plane P1 (7 Segment Only)
R/W
1001111 0x4F
Write Digit 0 Planes P0 and P1 with Same
Data, Reads as 0x00
R/W
1100000 0x60
Write Digit 1 Planes P0 and P1 with Same
Data, Reads as 0x00
R/W
1100001 0x61
Write Digit 2 Planes P0 and P1 with Same
Data, Reads as 0x00
R/W
1100010 0x62
Write Digit 3 Planes P0 and P1 with Same
Data, Reads as 0x00
R/W
1100011 0x63
Write Digit 4 Planes P0 and P1 with Same
Data, Reads as 0x00
R/W
1100100 0x64
Write Digit 5 Planes P0 and P1 with Same
Data, Reads as 0x00
R/W
1100101 0x65
Write Digit 6 Planes P0 and P1 with Same
Data, Reads as 0x00
R/W
1100110 0x66
Write Digit 7 Planes P0 and P1 with Same
Data, Reads as 0x00
R/W
1100111 0x67
Write Digit 0a Planes P0 and P1 with Same
Data (7 Segment Only), Reads as 0x00
R/W
1101000 0x68
Write Digit 1a Planes P0 and P1 with Same
Data (7 Segment Only), Reads as 0x00
R/W
1101001 0x69
Table 6. Register Address Map (continued)
The timing in Figure 8 loops over time, with 32 keys
experiencing a full key-scanning debounce over typi-
cally 25.6ms. Four keys are sampled every 1.6ms, or
every multiplex cycle. If at least one key that was not
previously pressed is found to have been pressed dur-
ing both sampling periods, then that key press is
debounced, and an interrupt is issued. The key-scan
circuit detects any combination of keys being pressed
during each debounce cycle (n-key rollover).
Port Configuration Register
The port configuration register selects how the five port
pins are used. The port configuration register format is
described in Table 32.
Key Mask Registers
The Key_A Mask, Key_B Mask, Key_C Mask, and
Key_D Mask write-only registers (Table 33) configure
the key-scanning circuit to cause an interrupt only when
selected (masked) keys have been debounced. Each
bit in the register corresponds to one key switch. The bit
is clear to disable interrupt for the switch, and set to
enable interrupt. Keys are always scanned (if enabled
through the port configuration register), regardless of
the setting of these interrupt bits, and the key status is
stored in the appropriate Key_x pressed register.
Key Debounced Registers
The Key_A debounced, Key_B debounced, Key_C
debounced, and Key_D debounced read-only registers
(Table 34) show which keys have been detected as
debounced by the key-scanning circuit.
Each bit in the register corresponds to one key switch.
The bit is set if the switch has been correctly
debounced since the register was read last. Reading a
debounced register clears that register (after the data
has been read) so that future keys pressed can be
identified. If the debounced registers are not read, the
key-scan data accumulates. However, as there is no
FIFO in the MAX6954, the user is not able to determine
key order, or whether a key has been pressed more
than once, unless the debounced key status registers
are read after each interrupt, and before the next key-
scan cycle.
Reading any of the four debounced registers clears the
IRQ output. If a key is pressed and held down, the key is
reported as debounced (and IRQ issued) only once.
The key must be detected as released by the key-scan-
ning circuit, before it debounces again. If the
debounced registers are being read in response to the
IRQ being asserted, then the user should generally read
all four registers to ensure that all the keys that were
detected by the key-scanning circuit are discovered.
Key Pressed Registers
The Key_A pressed, Key_B pressed, Key_C pressed,
and Key_D pressed read-only registers (Table 35)
show which keys have been detected as pressed by
the key-scanning circuit during the last test.
Each bit in the register corresponds to one key switch.
The bit is set if the switch has been detected as
pressed by the key-scanning circuit during the last test.
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
______________________________________________________________________________________ 15
ADDRESS (COMMAND BYTE)
REGISTER
D15 D14 D13 D12 D11 D10 D9 D8
HEX CODE
Write Digit 2a Planes P0 and P1 with Same
Data (7 Segment Only), Reads as 0x00
R/W
1 1 0 1 0 1 0 0x6A
Write Digit 3a Planes P0 and P1 with Same
Data (7 Segment Only), Reads as 0x00
R/W
1 1 0 1 0 1 1 0x6B
Write Digit 4a Planes P0 and P1 with Same
Data (7 Segment Only), Reads as 0x00
R/W
1 1 0 1 1 0 0 0x6C
Write Digit 5a Planes P0 and P1 with Same
Data (7 Segment Only), Reads as 0x00
R/W
1 1 0 1 1 0 1 0x6D
Write Digit 6a Planes P0 and P1 with Same
Data (7 Segment Only), Reads as 0x00
R/W
1101110 0x6E
Write Digit 7a Planes P0 and P1 with Same
Data (7 Segment Only), Reads as 0x00
R/W
1101111 0x6F
Table 6. Register Address Map (continued)
Note: Unused register bits read as zero.
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
16 ______________________________________________________________________________________
DIGIT 1
ONE COMPLETE 1.6ms MULTIPLEX CYCLE AROUND 8 DIGITS
DIGIT 0's 200μs MULTIPLEX TIMESLOT
DIGIT 0
200μs
DIGIT 2 DIGIT 3 DIGIT 4 DIGIT 5 DIGIT 6 DIGIT 7
START OF
NEXT CYCLE
LOW
2/16TH
1/16TH
(MIN ON)
HIGH-Z
HIGH-Z
LOW
3/16TH HIGH-Z
LOW
4/16TH HIGH-Z
LOW
5/16TH HIGH-Z
LOW
6/16TH HIGH-Z
LOW
7/16TH HIGH-Z
LOW
8/16TH HIGH-Z
LOW
9/16TH HIGH-Z
LOW
10/16TH HIGH-Z
LOW
11/16TH HIGH-Z
LOW
12/16TH HIGH-Z
LOW
13/16TH HIGH-Z
LOW
14/16TH HIGH-Z
LOW
15/16TH HIGH-Z
LOW
15/16TH HIGH-Z
(MAX ON)
HIGH-Z
HIGH-Z
CURRENT SOURCE ENABLED MINIMUM 12.5μs INTERDIGIT BLANKING INTERVAL
HIGH-Z
ANODE (LIT)
DIGIT 0 CATHODE
DRIVER INTENSITY
SETTINGS
ANODE (UNLIT)
Figure 6. Multiplex Timing Diagram (OSC = 4MHz)
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
______________________________________________________________________________________ 17
LED OUTPUT O0
LED OUTPUT O1
LED OUTPUT O2
LED OUTPUT O3
LED OUTPUT O4
LED OUTPUT O5
LED OUTPUT O6
LED OUTPUT O7
12.5μs TO 187.5μs DIGIT PERIOD
1.6ms MULTIPLEX CYCLE 1 1.6ms MULTIPLEX CYCLE 2 1.6ms MULTIPLEX CYCLE 8
THE FIRST HALF OF A 25.6ms KEY-SCAN CYCLE
1.6ms MULTIPLEX CYCLE 8
THE SECOND HALF OF A 25.6ms KEY-SCAN CYCLE
1.6ms MULTIPLEX CYCLE 1
START OF NEXT KEY-SCAN CYCLE
FIRST TEST OF KEY SWITCHES SECOND TEST OF KEY SWITCHES INTERRUPT ASSERTED IF REQUIRED
DEBOUNCE REGISTER UPDATED
C
A
A
BDE
Figure 7. Key-Scanning Configuration
SW A0
SW A1
SW A2
SW A3
SW A4
SW A5
SW A6
SW A7
P0
V
CC
LED OUTPUT O0
LED OUTPUT O1
LED OUTPUT O2
LED OUTPUT O3
LED OUTPUT O4
LED OUTPUT O5
LED OUTPUT O6
LED OUTPUT O7
P1
P2
P3
P4 MICROCONTROLLER INTERRUPT
SW B0
SW B1
SW B2
SW B3
SW B4
SW B5
SW B6
SW B7
SW C0
SW C1
SW C2
SW C3
SW C4
SW C5
SW C6
SW C7
SW D0
SW D1
SW D2
SW D3
SW D4
SW D5
SW D6
SW D7
Figure 8. Key-Scan Timing Diagram
MAX6954
The bit is cleared if the switch has not been detected
as pressed by the key-scanning circuit during the last
test. Reading a pressed register does not clear that
register or clear the IRQ output.
Display Test Register
The display test register (Table 36) operates in two
modes: normal and display test. Display test mode
turns all LEDs on (including DPs) by overriding, but not
altering, all controls and digit registers (including the
shutdown register), except for the digit-type register
and the GPIO configuration register. The duty cycle,
while in display test mode, is 7/16 (see the
Choosing
Supply Voltage to Minimize Power Dissipation
section).
Selecting External Components RSET and
CSET to Set Oscillator Frequency and
Peak Segment Current
The RC oscillator uses an external resistor, RSET, and
an external capacitor, CSET, to set the frequency, fOSC.
The allowed range of fOSC is 1MHz to 8MHz. RSET also
sets the peak segment current. The recommended val-
ues of RSET and CSET set the oscillator to 4MHz, which
makes the blink frequencies selectable between 0.5Hz
and 1Hz. The recommended value of RSET also sets
the peak current to 40mA, which makes the segment
current adjustable from 2.5mA to 37.5mA in 2.5mA
steps.
ISEG = KL/ RSET mA
fOSC = KF/ (RSET x CSET) MHz
where:
KL= 2240
KF= 5376
RSET = external resistor in kΩ
CSET = external capacitor in pF
CSTRAY = stray capacitance from OSC pin to GND in
pF, typically 2pF
The recommended value of RSET is 56kΩand the rec-
ommended value of CSET is 22pF.
The recommended value or RSET is the minimum
allowed value, since it sets the display driver to the
maximum allowed peak segment current. RSET can be
set to a higher value to set the segment current to a
lower peak value where desired. The user must also
ensure that the peak current specifications of the LEDs
connected to the driver are not exceeded.
The effective value of RSET includes not only the actual
external capacitor used, but also the stray capacitance
from OSC to GND. This capacitance is usually in the
1pF to 5pF range, depending on the layout used.
Applications Information
Driving Bicolor LEDs
Bicolor digits group a red and a green die together for
each display element, so that the element can be lit red
or green (or orange), depending on which die (or both)
is lit. The MAX6954 allows each segment’s current to
be set individually from the 1/16th (minimum current
and LED intensity) to 15/16th (maximum current and
LED intensity), as well as off (zero current). Thus, a
bicolor (red-green) segment pair can be set to 256
color/intensity combinations.
Choosing Supply Voltage to Minimize
Power Dissipation
The MAX6954 drives a peak current of 40mA into LEDs
with a 2.2V forward-voltage drop when operated from a
supply voltage of at least 3.0V. The minimum voltage
drop across the internal LED drivers is therefore (3.0V -
2.2V) = 0.8V. If a higher supply voltage is used, the dri-
ver absorbs a higher voltage, and the driver’s power
dissipation increases accordingly. However, if the LEDs
used have a higher forward voltage drop than 2.2V, the
supply voltage must be raised accordingly to ensure
that the driver always has at least 0.8V of headroom.
The voltage drop across the drivers with a nominal 5V
supply (5.0V - 2.2V) = 2.8V is nearly 3 times the drop
across the drivers with a nominal 3.3V supply (3.3V -
2.2V) = 1.1V. In most systems, consumption is an
important design criterion, and the MAX6954 should be
operated from the system’s 3.3V nominal supply. In
other designs, the lowest supply voltage may be 5V.
The issue now is to ensure the dissipation limit for the
MAX6954 is not exceeded. This can be achieved by
inserting a series resistor in the supply to the MAX6954,
ensuring that the supply decoupling capacitors are still
on the MAX6954 side of the resistor. For example, con-
sider the requirement that the minimum supply voltage
to a MAX6954 must be 3.0V, and the input supply
range is 5V ±5%. Maximum supply current is 35mA +
(40mA x 17) = 715mA. Minimum input supply voltage is
4.75V. Maximum series resistor value is (4.75V -
3.0V)/0.715A = 2.44Ω. We choose 2.2Ω±5%. Worst-
case resistor dissipation is at maximum toleranced
resistance, i.e., (0.715A) 2 x (2.2Ωx 1.05) = 1.18W. The
maximum MAX6954 supply voltage is at maximum
input supply voltage and minimum toleranced resis-
tance, i.e., 5.25V - (0.715A x 2.2Ωx 0.95) = 3.76V.
Low-Voltage Operation
The MAX6954 works over the 2.7V to 5.5V supply
range. The minimum useful supply voltage is deter-
mined by the forward voltage drop of the LEDs at the
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
18 ______________________________________________________________________________________
peak current ISEG, plus the 0.8V headroom required by
the driver output stages. The MAX6954 correctly regu-
lates ISEG with a supply voltage above this minimum
voltage. If the supply drops below this minimum volt-
age, the driver output stages may brown out, and be
unable to regulate the current correctly. As the supply
voltage drops further, the LED segment drive current
becomes effectively limited by the output driver's on-
resistance, and the LED drive current drops. The char-
acteristics of each individual LED in a display digit are
well matched, so the result is that the display intensity
dims uniformly as supply voltage drops out of regula-
tion and beyond.
Computing Power Dissipation
The upper limit for power dissipation (PD) for the
MAX6954 is determined from the following equation:
PD= (V+ x 35mA) + (V+ - VLED) (DUTY x ISEG x N)
where:
V+ = supply voltage
DUTY = duty cycle set by intensity register
N = number of segments driven (worst case is 17)
VLED = LED forward voltage at ISEG
ISEG = segment current set by RSET
PD= Power dissipation, in mW if currents are in mA
Dissipation example:
ISEG = 30mA, N = 17, DUTY = 15/16,
VLED = 2.4V at 30mA, V+ = 3.6V
PD= 3.6V (35mA) + (3.6V - 2.4V)(15/16 x
30mA x 17) = 0.700W
Thus, for a 36-pin SSOP package (TJA = 1 / 0.0118 =
+85°C/W from Operating Ratings), the maximum
allowed ambient temperature TAis given by:
TJ(MAX) = TA+ (PDx TJA) = +150°C
= TA+ (0.700 x +85°C/W)
So TA= +90.5°C. Thus, the part can be operated safely
at a maximum package temperature of +85°C.
Power Supplies
The MAX6954 operates from a single 2.7V to 5.5V
power supply. Bypass the power supply to GND with a
0.1µF capacitor as close to the device as possible. Add
a 47µF capacitor if the MAX6954 is not close to the
board's input bulk decoupling capacitor.
Terminating the Serial Interface
The MAX6954 uses fixed voltage thresholds of 0.6V
and 1.8V for the 4-wire interface inputs. These fixed
thresholds allow the MAX6954 to be controlled by a
host operating from a lower supply voltage than the
MAX6954; for example, 2.5V. The fixed thresholds also
reduce the logic input noise margin when operating the
MAX6954 from a higher supply voltage, such as 5V. At
higher supply voltages, it may be necessary to fit termi-
nation components to the CLK, DIN, and CS inputs to
avoid signal reflections that the MAX6954 could
respond to as multiple transitions. Suitable termination
components can be either a 33pF capacitor or 4.7kΩ
resistor fitted from each of the CLK, DIN, and CS inputs
to GND.
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
______________________________________________________________________________________ 19
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
20 ______________________________________________________________________________________
x000 x010 x011 x100 x101 x110 x111x001
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
MSB
LSB
Table 7. 16-Segment Display Font Map
x000 x010 x011 x100 x101 x110 x111x001
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
.
MSB
LSB
Table 8. 14-Segment Display Font Map
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
______________________________________________________________________________________ 21
REGISTER DATA
MODE
ADDRESS
CODE
(HEX)
D7 D6 D5 D4 D3 D2 D1 D0
14-segment or 16-segment mode, writing digit data
to use font map data with decimal place unlit
0x20 to 0x2F
0x40 to 0x4F
0x60 to 0x6F
0 Bits D6 to D0 select font characters 0 to 127
14-segment or 16-segment mode, writing digit data
to use font map data with decimal place lit
0x20 to 0x2F
0x40 to 0x4F
0x60 to 0x6F
1 Bits D6 to D0 select font characters 0 to 127
7-segment decode mode, DP unlit
0x20 to 0x2F
0x40 to 0x4F
0x60 to 0x6F
0 0 0 0 D3 to D0
7-segment decode mode, DP lit
0x20 to 0x2F
0x40 to 0x4F
0x60 to 0x6F
1 0 0 0 D3 to D0
7-segment no-decode mode
0x20 to 0x2F
0x40 to 0x4F
0x60 to 0x6F
Direct control of 8 segments
Table 9. Digit Plane Data Register Format
REGISTER DATA
MODE ADDRESS CODE
(HEX) D7 D6 D5 D4 D3 D2 D1 D0
Segment Line
0x20 to 0x2F
0x40 to 0x4F
0x60 to 0x6F
dp a b c d e f g
Table 10. Segment Decoding for 7-Segment Displays
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
22 ______________________________________________________________________________________
REGISTER
DATA ON SEGMENTS = 1
7-SEGMENT
CHARACTER
D7* D6, D5,
D4
D3 D2 D1 D0
DP*
ABCDEF
G
0 — X 0000—
111111
0
1 — X 0001—
011000
0
2 — X 0010—
110110
1
3 — X 0011—
111100
1
4 — X 0100—
011001
1
5 — X 0101—
101101
1
6 — X 0110—
101111
1
7 — X 0111—
111000
0
8 — X 1000—
111111
1
9 — X 1001—
111101
1
A — X 1010—
111011
1
B — X 1011—
001111
1
C — X 1100—
100111
0
D — X 1101—
011110
1
E — X 1110—
100111
1
F — X 1111—
100011
1
Table 11. 7-Segment Segment Mapping Decoder for Hexadecimal Font
REGISTER DATA
DIGIT-TYPE
REGISTER
ADDRESS
CODE (HEX) D7 D6 D5 D4 D3 D2 D1 D0
Output Drive Line
CC7 CC6 CC5 CC4 CC3 CC2 CC1
CC0
Slot Identification 0x0C Slot 4 Slot 3 Slot 2 Slot 1
Table 12. Digit-Type Register
*
The decimal point is set by bit D7 = 1.
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
______________________________________________________________________________________ 23
REGISTER DATA
DECODE
MODE
ADDRESS
CODE
(HEX)
D7 D6 D5 D4 D3 D2 D1 D0
HEX
CODE
No decode for digit pairs 7 to 0. 0x01 00000000 0x00
Hexadecimal decode for digit pair 0,
no decode for digit pairs 7 to 1. 0x01 00000001 0x01
Hexadecimal decode for digit pairs 2 to 0,
no decode for digit pairs 7 to 3. 0x01 00000111 0x07
Hexadecimal decode for digit pairs 7 to 0.
0x01 11111111 0xFF
Table 14. Decode-Mode Register Examples
REGISTER DATA
DIGIT-TYPE
REGISTER SETTING
ADDRESS
CODE (HEX) D7 D6 D5 D4 D3 D2 D1 D0
Digits 7 to 0 are 16-segment or 7-
segment digits. 0x0C 00000000
Digit 0 is a 14-segment digit,
digits 7 to 1 are 16-segment or 7-
segment digits.
0x0C 00000001
Digits 2 to 0 are 14-segment
digits, digits 7 to 3 are 16-
segment or 7-segment digits.
0x0C 00000111
Digits 7 to 0 are 14-segment
digits. 0x0C 11111111
Table 13. Example Configurations for Display Digit Combinations
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
24 ______________________________________________________________________________________
REGISTER DATA
REGISTER POWER-UP
CONDITION
ADDRESS
CODE
(HEX)
D7 D6 D5 D4 D3 D2 D1 D0
Decode Mode Decode mode enabled 0x01
11111111
Global Intensity 1/16 (min on) 0x02
XXXX0000
Scan Limit Display 8 digits: 0, 1, 2, 3, 4, 5, 6, 7 0x03
XXXXX111
Control Register Shutdown enabled, blink speed is
slow, blink disabled 0x04
00XX0000
GPIO Data Outputs are low 0x05
XXX00000
Port Configuration No key scanning, P0 to P4 are all
inputs 0x06
00011111
Display Test Normal operation 0x07
XXXXXXX0
Key_A Mask None of the keys cause interrupt 0x08
00000000
Key_B Mask None of the keys cause interrupt 0x09
00000000
Key_C Mask None of the keys cause interrupt 0x0A
00000000
Key_D Mask None of the keys cause interrupt 0x0B
00000000
Digit Type All are 16 segment or 7 segment 0x0C
00000000
Intensity10 1/16 (min on) 0x10
00000000
Intensity32 1/16 (min on) 0x11
00000000
Intensity54 1/16 (min on) 0x12
00000000
Intensity76 1/16 (min on) 0x13
00000000
Intensity10a 1/16 (min on) 0x14
00000000
Intensity32a 1/16 (min on) 0x15
00000000
Intensity54a 1/16 (min on) 0x16
00000000
Intensity76a 1/16 (min on) 0x17
00000000
Digit 0 Blank digit, both planes 0x60
00100000
Digit 1 Blank digit, both planes 0x61
00100000
Digit 2 Blank digit, both planes 0x62
00100000
Digit 3 Blank digit, both planes 0x63
00100000
Digit 4 Blank digit, both planes 0x64
00100000
Digit 5 Blank digit, both planes 0x65
00100000
Digit 6 Blank digit, both planes 0x66
00100000
Digit 7 Blank digit, both planes 0x67
00100000
Digit 0a Blank digit, both planes 0x68
00000000
Digit 1a Blank digit, both planes 0x69
00000000
Digit 2a Blank digit, both planes 0x6A
00000000
Digit 3a Blank digit, both planes 0x6B
00000000
Digit 4a Blank digit, both planes 0x6C
00000000
Digit 5a Blank digit, both planes 0x6D
00000000
Digit 6a Blank digit, both planes 0x6E
00000000
Digit 7a Blank digit, both planes 0x6F
00000000
Key_A Debounced No key presses have been detected 0x88
00000000
Key_B Debounced No key presses have been detected 0x89
00000000
Key_C Debounced
No key presses have been detected 0x8A
00000000
Key_D Debounced
No key presses have been detected 0x8B
00000000
Key_A Pressed Keys are not pressed 0x8C
00000000
Key_B Pressed Keys are not pressed 0x8D
00000000
Key_C Pressed Keys are not pressed 0x8E
00000000
Key_D Pressed Keys are not pressed 0x8F
00000000
Table 15. Initial Power-Up Register Status
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
______________________________________________________________________________________ 25
REGISTER DATA
MODE
D7 D6 D5 D4 D3 D2 D1
D0
Configuration
Register
PIRTEBX
S
Table 16. Configuration Register Format
REGISTER DATA
MODE
D7 D6 D5 D4 D3 D2 D1 D0
Shutdown
PIRTEBX0
Normal
Operation
PIRTEBX1
Table 17. Shutdown Control (S Data Bit DO)
Format
REGISTER DATA
MODE
D7 D6 D5 D4 D3 D2 D1 D0
Slow blinking. Segments blink on for 1s, off for 1s with fOSC = 4MHz.
P
I
RTE0X
S
Fast blinking. Segments blink on for 0.5s, off for 0.5s with fOSC = 4MHz.
P
I
RTE1X
S
Table 18. Blink Rate Selection (B Data Bit D2) Format
REGISTER DATA
MODE D7 D6 D5 D4 D3 D2 D1 D0
Blink function is disabled. P I R T 0 B X S
Blink function is enabled. P I R T 1 B X S
Table 19. Global Blink Enable/Disable (E Data Bit D3) Format
SEGMENT’S BIT SETTING
IN PLANE P1
SEGMENT’S BIT SETTING
IN PLANE P0
SEGMENT
BEHAVIOR
0 0 Segment off.
01
Segment on only during the 1st half of each
blink period.
10
Segment on only during the 2nd half of each
blink period.
1 1 Segment on.
Table 20. Digit Register Mapping with Blink Globally Enabled
REGISTER DATA
MODE
D7 D6 D5 D4 D3 D2 D1 D0
Blink timing counters are unaffected. P I R 0 E B X S
Blink timing counters are reset on the rising edge of CS.PIR1EBXS
Table 21. Global Blink Timing Synchronization (T Data Bit D4) Format
REGISTER DATA
MODE
D7 D6 D5 D4 D3 D2 D1 D0
Digit data for both planes P0 and P1 are unaffected.
P
I
0TEBXS
Digit data for both planes P0 and P1 are cleared on the rising edge of CS.
P
I
1TEBXS
Table 22. Global Clear Digit Data (R Data Bit D5) Format
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
26 ______________________________________________________________________________________
REGISTER DATA
MODE
D7 D6 D5 D4 D3 D2 D1
D0
Intensity for all digits is controlled by one setting in the global intensity register.
P0RTEBX
S
Intensity for digits is controlled by the individual settings in the intensity10 and
intensity76 registers.
P1RTEBX
S
Table 23. Global Intensity (I Data Bit D6) Format
REGISTER DATA
MODE D7 D6 D5 D4 D3 D2 D1 D0
P1 Blink Phase 0 I R T E B X S
P0 Blink Phase 1 I R T E B X S
Table 24. Blink Phase Readback (P Data Bit D7) Format
REGISTER DATA
SCAN
LIMIT
ADDRESS CODE
(HEX)
D7 D6 D5 D4 D3 D2 D1 D0
HEX
CODE
Display Digit 0 only 0x03 X X X X X 0 0 0 0x00
Display Digits 0 and 1 0x03 X X X X X 0 0 1 0x01
Display Digits 0 1 2 0x03 X X X X X 0 1 0 0x02
Display Digits 0 1 2 3 0x03 X X X X X 0 1 1 0x03
Display Digits 0 1 2 3 4 0x03 X X X X X 1 0 0 0x04
Display Digits 0 1 2 3 4 5 0x03 X X X X X 1 0 1 0x05
Display Digits 0 1 2 3 4 5 6 0x03 X X X X X 1 1 0 0x06
Display Digits 0 1 2 3 4 5 6 7 0x03 X X X X X 1 1 1 0x07
Table 25. Scan-Limit Register Format
REGISTER DATA
DUTY
CYCLE
TYPICAL
SEGMENT
CURRENT (mA)
ADDRESS
CODE (HEX)
D7
D6 D5 D4 D3 D2 D1 D0
HEX
CODE
1/16 (min on) 2.5 0x02 X X X X 0 0 0 0 0xX0
2/16 5 0x02 X X X X 0 0 0 1 0xX1
3/16 7.5 0x02 X X X X 0 0 1 0 0xX2
4/16 10 0x02 X X X X 0 0 1 1 0xX3
5/16 12.5 0x02 X X X X 0 1 0 0 0xX4
6/16 15 0x02 X X X X 0 1 0 1 0xX5
7/16 17.5 0x02 X X X X 0 1 1 0 0xX6
8/16 20 0x02 X X X X 0 1 1 1 0xX7
9/16 22.5 0x02 X X X X 1 0 0 0 0xX8
10/16 25 0x02 X X X X 1 0 0 1 0xX9
11/16 27.5 0x02 X X X X 1 0 1 0 0xXA
12/16 30 0x02 X X X X 1 0 1 1 0xXB
13/16 32.5 0x02 X X X X 1 1 0 0 0xXC
14/16 35 0x02 X X X X 1 1 0 1 0xXD
15/16 37.5 0x02 X X X X 1 1 1 0 0xXE
15/16 (max on)
37.5 0x02 X X X X 1 1 1 1 0xXF
Table 26. Global Intensity Register Format
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
______________________________________________________________________________________ 27
REGISTER DATA
REGISTER
FUNCTION
ADDRESS
CODE (HEX) D7 D6 D5 D4 D3 D2 D1 D0
Intensity10 Register 0x10 Digit 1 Digit 0
Intensity32 Register 0x11 Digit 3 Digit 2
Intensity54 Register 0x12 Digit 5 Digit 4
Intensity76 Register 0x13 Digit 7 Digit 6
Intensity10a Register 0x14 Digit 1a (7 segment only) Digit 0a (7 segment only)
Intensity32a Register 0x15 Digit 3a (7 segment only) Digit 2a (7 segment only)
Intensity54a Register 0x16 Digit 5a (7 segment only) Digit 4a (7 segment only)
Intensity76a Register 0x17 Digit 7a (7 segment only) Digit 6a (7 segment only)
Table 27. Individual Segment Intensity Registers
REGISTER DATA
DUTY
CYCLE
TYPICAL
SEGMENT
CURRENT (mA)
ADDRESS
CODE
(HEX)
D7 D6 D5 D4 D3 D2 D1 D0
HEX
CODE
1/16 (min on) 2.5 0x10 to 0x17 0000
0xX0
2/16 5 0x10 to 0x17 0001
0xX1
3/16 7.5 0x10 to 0x17 0010
0xX2
4/16 10 0x10 to 0x17 0011
0xX3
5/16 12.5 0x10 to 0x17 0100
0xX4
6/16 15 0x10 to 0x17 0101
0xX5
7/16 17.5 0x10 to 0x17 0110
0xX6
8/16 20 0x10 to 0x17 0111
0xX7
9/16 22.5 0x10 to 0x17 1000
0xX8
10/16 25 0x10 to 0x17 1001
0xX9
11/16 27.5 0x10 to 0x17 1010
0xXA
12/16 30 0x10 to 0x17 1011
0xXB
13/16 32.5 0x10 to 0x17 1100
0xXC
14/16 35 0x10 to 0x17 1101
0xXD
15/16 37.5 0x10 to 0x17 1110
0xXE
15/16 (max on) 37.5 0x10 to 0x17
See Table 29.
1111
0xXF
Table 28. Even Individual Segment Intensity Format
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
28 ______________________________________________________________________________________
REGISTER DATA
DUTY
CYCLE
TYPICAL
SEGMENT
CURRENT (mA)
ADDRESS
CODE
(HEX)
D7 D6 D5 D4 D3 D2 D1 D0
HEX
CODE
1/16 (min on) 2.5 0x10 to 0x17 0 0 0 0
0x0X
2/16 5 0x10 to 0x17 0 0 0 1
0x1X
3/16 7.5 0x10 to 0x17 0 0 1 0
0x2X
4/16 10 0x10 to 0x17 0 0 1 1
0x3X
5/16 12.5 0x10 to 0x17 0 1 0 0
0x4X
6/16 15 0x10 to 0x17 0 1 0 1
0x5X
7/16 17.5 0x10 to 0x17 0 1 1 0
0x6X
8/16 20 0x10 to 0x17 0 1 1 1
0x7X
9/16 22.5 0x10 to 0x17 1 0 0 0
0x8X
10/16 25 0x10 to 0x17 1 0 0 1
0x9X
11/16 27.5 0x10 to 0x17 1 0 1 0
0xAX
12/16 30 0x10 to 0x17 1 0 1 1
0xBX
13/16 32.5 0x10 to 0x17 1 1 0 0
0xCX
14/16 35 0x10 to 0x17 1 1 0 1
0xDX
15/16 37.5 0x10 to 0x17 1 1 1 0
0xEX
15/16 (max on) 37.5 0x10 to 0x17 1 1 1 1
See Table 28.
0xFX
Table 29. Odd Individual Segment Intensity Format
REGISTER DATA
MODE ADDRESS
CODE (HEX)
D7 D6 D5 D4 D3 D2 D1 D0
Write GPIO Data 0x05 X X X P4 P3 P2 P1 P0
Read GPIO Data
0x85 0 0 0
P4 or IRQ status
P3 P2 P1 P0
Table 30. GPIO Data Register
KEYS
SCANNED
PORTS
AVAILABLE P0 P1 P2 P3 P4
None 5 pins GPIO GPIO GPIO GPIO GPIO
1 to 8 3 pins Key_A GPIO GPIO GPIO IRQ
9 to 16 2 pins Key_A Key_B GPIO GPIO IRQ
17 to 24 1 pin Key_A Key_B Key_C GPIO IRQ
25 to 36 None Key_A Key_B Key_C Key_D IRQ
Table 31. Port Scanning Function Allocation
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
______________________________________________________________________________________ 29
REGISTER DATA
MODE ADDRESS
CODE (HEX)
D7 D6 D5 D4 D3 D2 D1 D0
GPIO
Configuration
Register
0x06 Set number of keys scanned Set port direction for ports P0 to P4:
0 = output, 1 = input
PORT ALLOCATION OPTIONS
0 Keys Scanned 0x06 0 0 0 P4 P3 P2 P1 P0
8 Keys Scanned 0x06 0 0 1 IRQ P3 P2 P1
Key_A
16 Keys Scanned
0x06 0 1 0 IRQ P3 P2
Key_B
Key_A
24 Keys Scanned
0x06 0 1 1 IRQ P3
Key_C Key_B
Key_A
32 Keys Scanned
0x06 1 X X IRQ
Key_D Key_C Key_B
Key_A
EXAMPLE PORT CONFIGURATION SETTINGS
No Keys
Scanned, P4 and
P2 Are Outputs,
Others Are Inputs
0x06 00001011
8 Keys Scanned,
P3 and P1 Are
Outputs, P2 Is an
Input
0x06 001X010X
32 Keys
Scanned, No
GPIO Ports
0x06 1XXXXXXX
Table 32. Port Configuration Register Format
REGISTER DATA
WITH APPROPRIATE SWITCH NAMED BELOW
KEY
MASK
REGISTER
ADDRESS
CODE
(HEX D7 D6 D5 D4 D3 D2 D1 D0
Key_A Mask
Register 0x08
SW_A7 SW_A6 SW_A5 SW_A4 SW_A3 SW_A2 SW_A1 SW_A0
Key_B Mask
Register 0x09
SW_B7 SW_B6 SW_B5 SW_B4 SW_B3 SW_B2 SW_B1 SW_B0
Key_C Mask
Register 0x0A
SW_C7 SW_C6 SW_C5 SW_C4 SW_C3 SW_C2 SW_C1 SW_C0
Key_D Mask
Register 0x0B
SW_ D7 SW_D6 SW_D5 SW_D4 SW_D3 SW_D2 SW_D1 SW_D0
Table 33. Key Mask Register Format
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
30 ______________________________________________________________________________________
REGISTER DATA
KEY
DEBOUNCED
REGISTER
ADDRESS
CODE
(HEX) D7 D6 D5 D4 D3 D2 D1 D0
Key_A
Debounced
Register
0x88
SW_A7 SW_A6 SW_A5 SW_A4 SW_A3 SW_A2 SW_A1 SW_A0
Key_B
Debounced
Register
0x89
SW_B7 SW_B6 SW_B5 SW_B4 SW_B3 SW_B2 SW_B1 SW_B0
Key_C
Debounced
Register
0x8A
SW_C7 SW_C6 SW_C5 SW_C4 SW_C3 SW_C2 SW_C1 SW_C0
Key_D
Debounced
Register
0x8B
SW_D7 SW_D6 SW_D5 SW_D4 SW_D3 SW_D2 SW_D1 SW_D0
Table 34. Key Debounced Register Format
REGISTER DATA
KEY
PRESSED
REGISTER
ADDRESS
CODE
(HEX D7 D6 D5 D4 D3 D2 D1 D0
Key_A
Pressed
Register
0x8C
SW_A7 SW_A6 SW_A5 SW_A4 SW_A3 SW_A2 SW_A1
SW_A0
Key_B
Pressed
Register
0x8D
SW_B7 SW_B6 SW_B5 SW_B4 SW_B3 SW_B2 SW_B1
SW_B0
Key_C
Pressed
Register
0x8E
SW_C7 SW_C6 SW_C5 SW_C4 SW_C3 SW_C2 SW_C1
SW_C0
Key_D
Pressed
Register
0x8F
SW_D7 SW_D6 SW_D5 SW_D4 SW_D3 SW_D2 SW_D1
SW_D0
Table 35. Key Pressed Register Format
REGISTER DATA
MODE
ADDRESS
CODE
(HEX) D7 D6 D5 D4 D3 D2 D1 D0
Normal Operation0x07 XXXXXXX 0
Display Test 0x07 X XXXXXX1
Table 36. Display Test Register
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
______________________________________________________________________________________ 31
C O N F I G U R A T IO N
C H O IC E
C o m m o n - C a t h o d e
D r i v e : D ig it Ty p e
CC0: 16-seg monocolor
CC1: 16-seg monocolor
CC0 and CC1:
(2) 7-seg bicolor
or (4) 7-seg monocolor
or (1) 7-seg bicolor
and (2) 7-seg monocolor*
CC0 and CC1:
(1)16-seg bicolor
CC0: 16-seg monocolor
CC0: (2) 7-seg monocolor*
or 7-seg bicolor
CC1: 14-seg monocolor
CC0: 14-seg monocolor
CC1: 16-seg monocolor
CC1: (2) 7-seg monocolor*
or 7-seg bicolor
CC0 and CC1: (2) 14-seg
monocolor or 14-seg
bicolor
00
CC0
—CC0
CC0 CC0 CC0
—
CC0
— — CC0
01
— CC1
CC1
CC1
——
CC1
—
CC1 CC1
CC1
02
a1 a1
1a a1 a1 1a a a a1 1a a
03
a2 a2
—a2 a2 — — — a2 — —
04 bb 1b bb1bbbb1b b
05 cc 1c cc1cccc1c c
06
d1 d1
1d d1 d1 1d d d d1 1d d
07
d2 d2
1dp d2 d2 1dp — — d2
1dp
—
08 ee 1e ee1eeee1e e
09 ff 1f ff1ffff1f f
010
g1 g1
1g g1 g1 1g g1 g1 g1 1g g1
011
g2 g2
2a g2 g2 2a g2 g2 g2 2a g2
012 hh 2b hh2bhhh2b h
013 ii 2c ii2ciii2c i
014 jj 2d jj2djjj2d j
015 kk 2e kk2ekkk2e k
016 ll 2f ll2flll2f l
017 mm 2g mm2gmmm2g m
018
dp dp
2dp dp dp 2dp dp dp dp
2dp
dp
ADDRESS
CODE (HEX) 0x0C
D7
D6 See Table 40.
D5
D4 See Table 39.
D3
D2 See Table 38.
D1 0101
REGISTER DATA
D0 0 0 1 1
Table 37. Slot 1 Configuration
*
7-segment digits can be replaced by directly controlled discrete LEDs according to settings in decode mode register (Table 11).
**
The highlighted row is used in Typical Operating Circuit 1 for display digits 0 and 1.
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
32 ______________________________________________________________________________________
*
7-segment digits can be replaced by directly controlled discrete LEDs according to settings in decode mode register (Table 11).
**
The highlighted row is used in Typical Operating Circuit 1 for display digits 2 and 3.
C O N F I G U R A T IO N
C H O IC E
C o m m o n - C a t h o d e
D r i v e : D ig it Ty p e
CC2: 16-seg monocolor
CC3: 16-seg monocolor
CC2 and CC3:
(2) 7-seg bicolor
or (4) 7-seg monocolor
or (1) 7-seg bicolor
and (2) 7-seg monocolor*
CC2 and CC3:
(1)16-seg bicolor
CC2: 16-seg monocolor
CC2: (2) 7-seg monocolor*
or 7-seg bicolor
CC3: 14-seg monocolor
CC2: 14-seg monocolor
CC3: 16-seg monocolor
CC3: (2) 7-seg monocolor*
or 7-seg bicolor
CC2 and CC3: (2) 14-seg
monocolor or 14-seg
bicolor
00
a1 a1
1a a1 a1 1a a a a1 1a a
01
a2 a2
—a2a2———a2——
02
CC2
— CC2
CC2 CC2 CC2
—
CC2
—— CC2
03
— CC3
CC3
CC3
——
CC3
—
CC3 CC3
CC3
04 b b 1b b b 1b b b b 1b b
05 c c 1c c c 1c c c c 1c c
06
d1 d1
1d d1 d1 1d d d d1 1d d
07
d2 d2
1dp d2 d2 1dp — — d2
1dp
—
08 e e 1e e e 1e e e e 1e e
09 f f 1f f f 1f f f f 1f f
010
g1 g1
1g g1 g1 1g g1 g1 g1 1g g1
011
g2 g2
2a g2 g2 2a g2 g2 g2 2a g2
012 h h 2b h h 2b h h h 2b h
013 i i 2c i i 2c i i i 2c i
014 j j 2d j j 2d j j j 2d j
015 k k 2e k k 2e k k k 2e k
016 l l 2f l l 2f l l l 2f l
017 m m 2g m m 2g m m m 2g m
018
dp dp
2dp dp dp 2dp dp dp dp
2dp
dp
ADDRESS
CODE (HEX) 0x0C
D7
D6 See Table 40.
D5
D4 See Table 39.
D3 0101
D2 0 0 1 1
D1
REGISTER DATA
D0 See Table 37.
Table 38. Slot 2 Configuration
MAX6954
C O N F I G U R A T IO N
C H O IC E
C o m m o n - C a t h o d e
D r i v e : D ig it Ty p e
CC4: 16-seg monocolor
CC5: 16-seg monocolor
CC4 and CC5:
(2) 7-seg bicolor
or (4) 7-seg monocolor
or (1) 7-seg bicolor
and (2) 7-seg monocolor*
CC4 and CC5:
(1)16-seg bicolor
CC4: 16-seg monocolor
CC4: (2) 7-seg monocolor*
or 7-seg bicolor
CC5: 14-seg monocolor
CC4: 14-seg monocolor
CC5: 16-seg monocolor
CC5: (2) 7-seg monocolor*
or 7-seg bicolor
CC4 and CC5: (2) 14-seg
monocolor or 14-seg
bicolor
00
a1 a1
1a a1 a1 1a a a a1 1a a
01
a2 a2
—a2a2———a2——
02 b b 1b b b 1b b b b 1b b
03 c c 1c c c 1c c c c 1c c
04
CC4
—CC4
CC4 CC4 CC4
—
CC4
— — CC4
05
—CC5
CC5
CC5
——
CC5
—
CC5 CC5
CC5
06
d1 d1
1d d1 d1 1d d d d1 1d d
07
d2 d2
1dp d2 d2 1dp — — d2
1dp
—
08 e e 1e e e 1e e e e 1e e
09 f f 1f f f 1f f f f 1f f
010
g1 g1
1g g1 g1 1g g1 g1 g1 1g g1
011
g2 g2
2a g2 g2 2a g2 g2 g2 2a g2
012 h h 2b h h 2b h h h 2b h
013 i i 2c i i 2c i i i 2c i
014 j j 2d j j 2d j j j 2d j
015 k k 2e k k 2e k k k 2e k
016 l l 2f l l 2f l l l 2f l
017 m m 2g m m 2g m m m 2g m
018
dp dp
2dp dp dp 2dp dp dp dp
2dp
dp
ADDRESS
CODE (HEX) 0x0C
D7
D6 See Table 40.
D5 0101
D4 0 0 1 1
D3
D2 See Table 38.
D1
REGISTER DATA
D0 See Table 37.
Table 39. Slot 3 Configuration
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
______________________________________________________________________________________ 33
*
7-segment digits can be replaced by directly controlled discrete LEDs according to settings in decode mode register (Table 11).
**
The highlighted row is used in Typical Operating Circuit 1 for display digits 4 and 5.
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
34 ______________________________________________________________________________________
*
7-segment digits can be replaced by directly controlled discrete LEDs according to settings in the decode mode register (Table 11).
**
The highlighted row is used in Typical Operating Circuit 1 for display digits 6 and 7.
C O N F I G U R A T IO N
C H O IC E
C o m m o n - C a t h o d e
D r i v e : D ig it Ty p e
CC6: 16-seg monocolor
CC7: 16-seg monocolor
CC6 and CC7:
(2) 7-seg bicolor
or (4) 7-seg monocolor
or (1) 7-seg bicolor
and (2) 7-seg monocolor*
CC6 and CC7:
(1)16-seg bicolor
CC6: 16-seg monocolor
CC6: (2) 7-seg monocolor*
or 7-seg bicolor
CC7: 14-seg monocolor
CC6: 14-seg monocolor
CC7: 16-seg monocolor
CC7: (2) 7-seg monocolor*
or 7-seg bicolor
CC6 and CC7: (2) 14-seg
monocolor or 14-seg
bicolor
00
a1 a1
1a a1 a1 1a a a a1 1a a
01
a2 a2
—a2 a2 — — — a2 — —
02 bb 1b bb1bbbb1b b
03 cc 1c cc1cccc1c c
04
d1 d1
1d d1 d1 1d d d d1 1d d
05
d2 d2
1dp d2 d2 1dp — — d2
1dp
—
06
CC6
—CC6
CC6 CC6 CC6
—
CC6
— — CC6
07
— CC7
CC7
CC7
——
CC7
—
CC7 CC7
CC7
08 ee 1e ee1eeee1e e
09 ff 1f ff1ffff1f f
010
g1 g1
1g g1 g1 1g g1 g1 g1 1g g1
011
g2 g2
2a g2 g2 2a g2 g2 g2 2a g2
012 hh 2b hh2bhhh2b h
013 ii 2c ii2ciii2c i
014 jj 2d jj2djjj2d j
015 kk 2e kk2ekkk2e k
016 ll 2f ll2flll2f l
017 mm 2g mm2gmmm2g m
018
dp dp
2dp dp dp 2dp dp dp dp
2dp
dp
ADDRESS
CODE (HEX) 0x0C
D7 0101
D6 0 0 1 1
D5
D4 See Table 39.
D3
D2 See Table 38.
D1
REGISTER DATA
D0 See Table 37.
Table 40. Slot 4 Configuration
MAX6954
f
a
Rcc
dp
g
Gcc
b
c
e
d
DIGIT 0b (RED), DIGIT 1b (GREEN)
7-SEGMENT BICOLOR LED
O16
O17
O18
O0
O1
O11
O12
O13
O14
O0
O2
O3
O4
O15
f
a
h
g2
g1
i
b
c
e
d
DIGITS 2 AND 3
14-SEGMENT BICOLOR
DIGIT 6
4 x 4 MATRIX OF DISCRETE MONOCOLOR LEDs
O8
O9
O10
O11
O12
O0
O4
O5
O6
m
Rcc
dp
Ccc
j
l
k
O16
O17
O18
O2
O3
O13
O14
O15
f
a
CC1
dp
g
CC0
b
c
e
d
DIGITS 0a AND 1a
7-SEGMENT MONOCOLOR
O9
O10
O7
O1
O0
O2
O4
O5
O6
O8
d2
a1
g1
f
e
g2
a2
b
d1
c
DIGIT 5
16-SEGMENT MONOCOLOR
O6
O7
O8
O9
O10
O0
O1
O2
O3
k
m
l
dp
h
j
i
O14
O15
O16
O17
O18
cc
O5
O11
O12
O13
d2
a1
g1
f
e
g2
a2
b
d1
c
DIGIT 4
16-SEGMENT MONOCOLOR
O6
O7
O8
O9
O10
O0
O1
O2
O3
k
m
l
dp
h
j
i
O14
O15
O16
O17
O18
cc
O4
O11
O12
O13
3.3V
100nF
47μF
O0
O1
O2
O3
O4
O5
O6
O7
O8
O9
O10
O11
O12
O13
O14
O15
O16
O17
O18
P0
P1
P2
P3
P4
ISET
56kΩ
OSC_OUT
OSC
V+
V+
GND
GND
DOUT
V+
GND
DIN
CLK
CS
BLINK
O5
O8
O9
O10
O11
O12
O13
O14
O15
O16
O17
O18
O6
22pF
O0
O2
O3
O4
DIGIT 7
4 x 4 MATRIX OF DISCRETE MONOCOLOR LEDs
O5
O8
O9
O10
O11
O12
O13
O14
O15
O16
O17
O18
O7
MAX6954
Typical Operating Circuits
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
______________________________________________________________________________________ 35
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
36 ______________________________________________________________________________________
d2
a
g1
f
e
g2
a2
b
d1
c
DIGIT 0
O6
O7
O8
O9
O10
O2
O3
O4
O5
k
m
l
dp
h
j
i
O14
O15
O16
O17
O18
cc
O0
O11
O12
O13
d2
a
g1
f
e
g2
a2
b
d1
c
DIGIT 2
O6
O7
O8
O9
O10
O0
O1
O4
O5
k
m
l
dp
h
j
i
O14
O15
O16
O17
O18
cc
O2
O11
O12
O13
3.3V
100nF
47μF
O0
O1
O2
O3
O4
O5
O6
O7
O8
O9
O10
O11
O12
O13
O14
O15
O16
O17
O18
P0
P1
P2
P3
P4
ISET
OSC_OUT
OSC
V+
V+
GND
GND
DOUT
V+
GND
DIN
CLK
CS
BLINK
d2
a
g1
f
e
g2
a2
b
d1
c
DIGIT 1
O6
O7
O8
O9
O10
O2
O3
O4
O5
k
m
l
dp
h
j
i
O14
O15
O16
O17
O18
cc
O1
O11
O12
O13
d2
a
g1
f
e
g2
a2
b
d1
c
DIGIT 3
O6
O7
O8
O9
O10
O0
O1
O4
O5
k
m
l
dp
h
j
i
O14
O15
O16
O17
O18
cc
O3
O11
O12
O13
d2
a
g1
f
e
g2
a2
b
d1
c
DIGIT 6
O4
O5
O8
O9
O10
O0
O1
O2
O3
k
m
l
dp
h
j
i
O14
O15
O16
O17
O18
cc
O6
O11
O12
O13
d2
a
g1
f
e
g2
a2
b
d1
c
DIGIT 7
O4
O5
O8
O9
O10
O0
O1
O2
O3
k
m
l
dp
h
j
i
O14
O15
O16
O17
O18
cc
O7
O11
O12
O13
d2
a
g1
f
e
g2
a2
b
d1
c
DIGIT 4
O6
O6
O8
O9
O10
O0
O1
O2
O3
k
m
l
dp
h
j
i
O14
O15
O16
O17
O18
cc
O4
O11
O12
O13
d2
a
g1
f
e
g2
a2
b
d1
c
DIGIT 5
O6
O7
O8
O9
O10
O0
O1
O2
O3
k
m
l
dp
h
j
i
O14
O15
O16
O17
O18
cc
O5
O11
O12
O13
MAX6954
56kΩ
22pF
Typical Operating Circuits (continued)
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
______________________________________________________________________________________ 37
40
N.C.
V+
OSC
V+
39
38
37
36
35
34
33
32
31
1
2
3
4
5
6
7
8
9
10
N.C.
GND
GND
ISET
GND
TOP VIEW
MAX6954APL
30
29
28
27
26
25
24
23
22
21
11
12
13
14
15
16
17
18
19
PDIP
20
SSOP
MAX6954AAX
1
2
3
4
5
6
7
8
9
10
11
12
13
14
O7
O6
O5
O4
O3
O2
O1
O0
DIN
CLK
DOUT
CS
P1
P0
15
16
17
18GND
ISET
GND
O8
36
35
34
33
32
31
30
29
28
27
26
25
24
23
P4
P3
P2
OSC_OUT
BLINK
O18
O10
O17
O16
O15
O14
O13
O12
O11
22
21
20
19 V+
O9
P4
P3
P2
OSC_OUT
BLINK
O18
O10
O17
O16
O15
O14
O13
O12
O11
O9
OSC
V+
O7
O6
O5
O4
O3
O2
O1
O0
DIN
CLK
DOUT
CS
P1
P0
O8
V+
O18
O17
O15
O14
O11
O10
O9
EP*
O13
O12
O16
O1
O2
O3
O4
O5
O6
O7
O8
O0
DIN 1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
GND
V+
OSC
V+
N.C.
ISET
GND
GND
N.C.
DOUT
CS
P1
P0
P4/IRQ
P3
P2
OSC_OUT
BLINK
CLK
TQFN-EP
+
MAX6954
V+
*EP = EXPOSED PAD. CONNECT EP TO GND.
Pin Configurations
Chip Information
PROCESS: CMOS
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
38 ______________________________________________________________________________________
Package Information
For the latest package outline information and land patterns, go
to www.maxim-ic.com/packages.
PACKAGE TYPE PACKAGE CODE DOCUMENT NO.
36 SSOP A36-2 21-0040
40 PDIP P40-2 21-0044
40 TQFN T4066-5 21-0140
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________
39
© 2009 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
3 6/08 Added TQFN package option 1, 2, 6, 37
4 3/09 Corrected errors in Tables 37–40 31–34
