Nexus Machines Ltd reserves the right to alter or withdraw the product specification and characteristics without prior notice at any time in line
with product development. Nexus Machines Ltd sole and exclusive warranty is that stated in the warranty article of the conditions of sale.
Although every effort is made to ensure this data is accurate no liability is accepted for errors or omissions that may affect the end product.
Week0802 - 1 -
4 digit 7 segment LED displays with Cascadable Serial driver
______________________________________________________
B14SC04 B20SC04 B25SC04 B38SC04
General Description
The B14SCM04, B20SC04, B25SC04 and B38SC04 displays are 4 digit seven segment LED
displays combined with an 8 digit, multiplexed drive, integrated circuit with a cascadable serial
interface. Four digits are mounted with the driver on to the PCB which also has connections for
the BM multiplexed display family allowing expansion to 8 digits. The devices are available in
high efficiency red, green and yellow colour variants. Each of the standard displays has a right
hand decimal point in each digit. LED sizes include 14mm (0.56inch), 20mm (0.8inch) 25mm
(1inch) and 38mm (1.5inch) display areas.
The on board driver chip has a serial input format that features serial data, clock and chip enable.
A single 5 volt supply is required. The serial bus signals interface is HCMOS levels and the
format is compatible with SPI, QSPI and MICROWIRE. It features slew rate limiting for
reduced EMI. Included on chip is a BCD code B decoder and digit ram. An undedecoded mode
is also available. The chip can be programmed to display from 1 to 8 digits using the scan limit
register. Only one external resistor is required to set the maximum brightness that can then be
digitally dimmed in 16 levels. A test mode forces all LED’s on. Low power shutdown reduces
current to 150uA.
Configuration Dimensions
Dim
(mm)
A
B
C
D
E
Depth
B14
58.5
2.54
14.0
37.0
51.5
16.0
B20
75.0
2.54
20.0
38.0
68.5
18.0
B25
97.0
2.54
25.0
44.0
90.0
18.0
B38
121.0
2.54
38.0
54.0
115.5
18.0
Pinout
1 3 5 7 9 11 13 15 17 19
+5V CS CLK 0V SEGA SEGC SEGE SEGG DIG1 DIG3
+5V DIN DOUT 0V SEGB SEGD SEGF SEGDP DIG2 DIG4
2 4 6 8 10 12 14 16 18 20
Nexus Machines Ltd reserves the right to alter or withdraw the product specification and characteristics without prior notice at any time in line
with product development. Nexus Machines Ltd sole and exclusive warranty is that stated in the warranty article of the conditions of sale.
Although every effort is made to ensure this data is accurate no liability is accepted for errors or omissions that may affect the end product.
Week0802 - 2 -
Electrical Characteristics
Parameter Min Typ Max Units Conditions
Supply voltage 4.0 5.0 5.5 V
Shutdown supply current 150 uA All leds off
Power supply current 330 mA All segs on
Display scan rate 500 800 1300 Hz 8 digits scanned
Input voltage logic 0 (VL) -0.3 0.8 VVcc=5.0 volts
Input voltage logic 1 (VH) 3.5 VVcc=5.0 volts
Segment drive current(seg
off) 1uA
Segment drive current(seg on) -30 -40 -45 mA
Segment matching 3%
Output sink current (digit off) 10 uA Vdig=10 volts
Output sink current (digit on) 320 mA Vout=0.65
Clock High time 50 ns tr = tf = 20ns
Clock Low time 50 ns
Clock period 100 ns
CS fall to SCLK rise setup 25 ns
Clk rise to CS rise hold time 0ns
Din setup time 25 ns
Din hold time 0ns
Output data prop delay 25 ns
Load rising edge to next clk
rising edge 50 ns
Minimum CS or load pulse
high time 50 ns
Data input to seg delay 2.5 ns
Data input hold time 300 ns
Brightness setting resistor 9.53 k ohms Vdd=5V +/- 10%
Operating temperature 0 70 deg C Vdd=5V 4 LED’s on
Nexus Machines Ltd reserves the right to alter or withdraw the product specification and characteristics without prior notice at any time in line
with product development. Nexus Machines Ltd sole and exclusive warranty is that stated in the warranty article of the conditions of sale.
Although every effort is made to ensure this data is accurate no liability is accepted for errors or omissions that may affect the end product.
Week0802 - 3 -
Pin Functions
+5v Pin 1,2
+5 volts power supply to LED
Chip enable Pin 3
Chip select - this pin must be low for a data transfer to occur. he last 16 bits of serial data are
latched on CS rising edge.
Data input Pin 4
Serial data input -data is loaded into the internal 16 bit register on the clocks rising edge.
Clock Pin 5
Clock line - On clocks rising edge data is shifted into the internal shift register. On clocks falling
edge data is shifted out of Dout.
Data output Pin 6
Serial data output -the data into DIN is valid at DOUT 16.5 clock cycles later. This pin is used to
daisy chain devices
0 Volts Pin 7,8
The chip and LED’s 0 volts line.
Segments A,B,C,D,E,F,G and DP Pins 9,10,11,12,13,14,15,16
Seven Segment drives and decimal point Drive that source current to the display
Digit 4,5,6,7 Pin 17,18,19,20
Digit lines 4 through 7 drive line that sinks current from the common cathode LED. These can
be used to drive an external 4 digit 7 segment LED display(BM series). Digit lines 0 to 3 are
connected to the “internal” display. Digit 0 is the LSB on the right hand side.
Serial Data Format (16 bits)
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
XXXXA3 A2 A1 A0 D7 D6 D5 D4 D3 D2 D1 D0
Nexus Machines Ltd reserves the right to alter or withdraw the product specification and characteristics without prior notice at any time in line
with product development. Nexus Machines Ltd sole and exclusive warranty is that stated in the warranty article of the conditions of sale.
Although every effort is made to ensure this data is accurate no liability is accepted for errors or omissions that may affect the end product.
Week0802 - 4 -
Register Address Map
Register D15-D12 A3 A2 A1 A0 Hex code
No operation X0000X0
Digit 0 X0001X1
Digit 1 X0010X2
Digit 2 X0011X3
Digit 3 X0100X4
Digit 4 X0101X5
Digit 5 X0110X6
Digit 6 X0111X7
Digit 7 X1000X8
Decode mode X1001X9
Intensity X1010XA
Scan limit X1011XB
Shutdown X1100XC
Display test X1111XF
Display command Register Functions
Shutdown register Format (address Xch)
Mode Address D7 D6 D5 D4 D3 D2 D1 D0
Shutdown
Mode XCh XXXXXXX0
Normal
Operation XCh XXXXXXX1
Decode Mode Register: Setting this register sets BCD code (0-9,E,H,L,P and -) or no decode
operation for each digit. Each bit in the register corresponds to one digit. A logic 1 selects Code
B decoding whereas a logic 0 enables non decode mode. In decode mode bits 0-3 correspond to
the BCD data for the digit and bit D7 is the decimal point. In non decode mode data bits 0 to 7
correspond to the segment lines as outlines in the table below.
Decode Mode register examples
Decode Mode D7 D6 D5 D4 D3 D2 D1 D0 Hex
code
No decode for digits 7-0 0000000000
Code B decode for digit 0
and no decode for digits 7-1 0000000101
Code B decode for digits 3-0
and no decode for digits 7-4 000011110Fh
Code B decode for digits 7-0 11111111FFh
Nexus Machines Ltd reserves the right to alter or withdraw the product specification and characteristics without prior notice at any time in line
with product development. Nexus Machines Ltd sole and exclusive warranty is that stated in the warranty article of the conditions of sale.
Although every effort is made to ensure this data is accurate no liability is accepted for errors or omissions that may affect the end product.
Week0802 - 5 -
Decode Mode
7 Seg
character D7 D6-D4 D3 D2 D1 D0
0DP 0n =1 Dont care 0 0 0 0
1DP 0n =1 Dont care 0 0 0 1
2DP 0n =1 Dont care 0 0 1 0
3DP 0n =1 Dont care 0 0 1 1
4DP 0n =1 Dont care 0 1 0 0
5DP 0n =1 Dont care 0 1 0 1
6DP 0n =1 Dont care 0 1 1 0
7DP 0n =1 Dont care 0 1 1 1
8DP 0n =1 Dont care 1 0 0 0
9DP 0n =1 Dont care 1 0 0 1
-DP 0n =1 Dont care 1 0 1 0
EDP 0n =1 Dont care 1 0 1 1
HDP 0n =1 Dont care 1 1 0 0
LDP 0n =1 Dont care 1 1 0 1
PDP 0n =1 Dont care 1 1 1 0
Blank DP 0n =1 Dont care 1 1 1 1
Non Decode Mode D7 D6 D5 D4 D3 D2 D1 D0
Segment line DP AB C DEFG
The LED current is set to a maximum value via an on board resistor. This provides the
maximum level of brightness. The LED display controller also features a facility to Digitally set
the display brigtness from the host microcontroller. This control allows the on board pulse width
modulator to control the segment current and thus the brightness.
Intensity Register Format
Duty Cycle D7-D4 D3 D2 D1 D0 Hex code
1/32 (min) Dont care 0 0 0 0 X0h
3/32 Dont care 0 0 0 1 X1h
5/32 Dont care 0 0 1 0 X2h
7/32 Dont care 0 0 1 1 X3h
9/32 Dont care 0 1 0 0 X4h
11/32 Dont care 0 1 0 1 X5h
13/32 Dont care 0 1 1 0 X6h
15/32 Dont care 0 1 1 1 X7h
17/32 Dont care 1 0 0 0 X8h
19/32 Dont care 1 0 0 1 X9h
21/32 Dont care 1 0 1 0 XAh
23/32 Dont care 1 0 1 1 XBh
25/32 Dont care 1 1 0 0 XCh
27/32 Dont care 1 1 0 1 XDh
29/32 Dont care 1 1 1 0 XEh
31/32 Dont care 1 1 1 1 XFh
Nexus Machines Ltd reserves the right to alter or withdraw the product specification and characteristics without prior notice at any time in line
with product development. Nexus Machines Ltd sole and exclusive warranty is that stated in the warranty article of the conditions of sale.
Although every effort is made to ensure this data is accurate no liability is accepted for errors or omissions that may affect the end product.
Week0802 - 6 -
The display also features a scan limit register that sets how many digits are displayed from 1 to
8.These are displayed in a multiplexed manner with a typical display scan rate of 800Hz. Since
the number of digits displayed affects the overall display intensity the scan limit registers should
not be used to provide leading zero suppression.
WARNING: DO NOT select less than 3 scanned digits (there are 4 leds on the display so it
should be set to 4) otherwise excessive power dissipation will occur in the driver chip.
Scan Limit Register format
Scan Limit D7-D3 D2 D1 D0 Hex
code
Digit 0 Dont care 000X0h
Digit 0,1 Dont care 001X1h
Digit 0,1,2 Dont care 010X2h
Digit 0,1,2,3 Dont care 011X3h
Digit 0,1,2,3,4 Dont care 100X4h
Digit 0,1,2,3,4,5 Dont care 101X5h
Digit 0,1,2,3,4,5,6 Dont care 110X6h
Digit 0,1,2,3,4,5,6,7 Dont care 111X7h
Nexus Machines Ltd reserves the right to alter or withdraw the product specification and characteristics without prior notice at any time in line
with product development. Nexus Machines Ltd sole and exclusive warranty is that stated in the warranty article of the conditions of sale.
Although every effort is made to ensure this data is accurate no liability is accepted for errors or omissions that may affect the end product.
Week0802 - 7 -
LED display characteristics
The Led display provides excellent output brightness verses forward current with intensity
matching of better than 10% and a long operating life with minimal display degradation. The
LED’s on the driver PCB are termed “Internal” LED’s, whilst those that can be attached to the
driver chip via a cable (not longer than 10 inches) are termed external. Note that additional
LED displays may require greater supply decoupling. It is recommended that 10uf of capacitance
be added for every additional LED digit. A 10 volt electrolytic is suitable.
EMC: The displays are designed with slew limited drivers to ensure minimal EMC emmissions.
However the cable that is wired to the display is a large source of unwanted emissions. Care
should be taken to ensure minimal cable lengths are used where ever possible and a ferrite ring
should be added to the cable to provide additional attenuation. The LED’s draw quite a high
instantaneous current and the power supply and its wiring should be designed to carry the current
whilst providing a low impedance path. Additional capacitance may be required at the display.
The end product must be complient with the relevant criteria and the user should check that the
display is connected such that it is so.
Display LED format
Digit 7 Digit 6 Digit5 Digit 4 Digit 3 Digit 2 Digit 1 Digit 0
Ext LHS Ext LHM Ext RHM Ext RHS Int LHS Int LHM Int RHM Int RHS
LED brightness Min/Typ (mCd)
Color 14mm 20mm 25mm 38mm
Green 0.9 / 2.4 1.0 / 2.55 1.3 / 3.3 1.3 / 3.6
HE Red 0.9 / 2.4 1.0 / 2.55 1.4 / 3.6 1.4 / 3.6
Yellow 0.9 / 2.4 1.0 / 2.55 1.3 / 3.2 1.3 / 3.2
Cascading displays: The displays are cascadable by connecting the Dout pin from the first
display to the Din pin on the next display in line. The other signals (chip enable and clock) are
common to all displays. The number of data bits remains the same for each display hence if 4
displays are cascaded then 64 bits are required to alter the displayed value ON ANY DISPLAY.
The command set allows for a NO OPERATION which leaves the addressed display with the
previous register values.
MAXIMUM RATINGS: THE USER IS DIRECTED TOWARDS THE MAXIMUM VALUES
OUTLINED IN THE ELECTRICAL CHARACTERISTICS. OPERATION OUTSIDE OF
THESE LIMITS MAY AFFECT PERMANENT DAMAGE TO THE LED DISPLAY OR THE
DRIVER CHIP.
Additional Information: The user is directed towards the Maxim Integrated Products data sheet
for the MAX7219/MAX7221 for information regarding the serial interface and further display
driver commands.
All Trade marks acknowledged.
Nexus Machines Ltd reserves the right to alter or withdraw the product specification and characteristics without prior notice at any time in line
with product development. Nexus Machines Ltd sole and exclusive warranty is that stated in the warranty article of the conditions of sale.
Although every effort is made to ensure this data is accurate no liability is accepted for errors or omissions that may affect the end product.
Week0802 - 8 -
Typical Applications
Simple 4 digit display to microcontroller interface.
Cascading LED displays
Nexus Machines Ltd reserves the right to alter or withdraw the product specification and characteristics without prior notice at any time in line
with product development. Nexus Machines Ltd sole and exclusive warranty is that stated in the warranty article of the conditions of sale.
Although every effort is made to ensure this data is accurate no liability is accepted for errors or omissions that may affect the end product.
Week0802 - 9 -
Data prepared by :Nexus Machines Ltd
White Swan House
60 High Street
Godstone
Surrey
RH9 8LW
Email : sales@nexusmachines.com
Web site : www.nexusmachines.com
Technical support: 0906 558 1010
Please note that the technical support line is charged at a rate of £1 per minute.
