AHK3292
2 Channel LED DriverPowerLinearTM
PRODUCT DATASHEET
3292.2009.06.1.2 1
www.analogictech.com
General Description
The AHK3292 is a linear current-sink LED driver, capable
of driving one or two LEDs up to 30.2mA each. Featuring
individual low resistance, low drop-out voltage current
sinks, the AHK3292 allows the LEDs to be regulated
directly from a Lithium Ion/Polymer battery without the
need for an additional step-up power supply, thereby
reducing the external component count, eliminating
switching noise and maximizing efficiency.
AnalogicTech’s Simple Serial Control™ (S2Cwire™) inter-
face is used to enable, disable, and set the LED drive
current for 32-level linear scale LED brightness control.
For maximum flexibility the LED current can be set, up
to a maximum of 30.2mA per channel, using an external
RSET resistor.
The AHK3292 is packaged in a Pb-free 6-pin SOT23
package and is available over a -40 to +85OC tempera-
ture range.
Features
• 2.7V to 5.5V Input Supply Range
• Drives up to 2 LEDs at up to 30.2mA each
• Low Resistance Current Sinks
Low Dropout, Typically 40.5mV at Full Scale
• Linear LED Output Current Control
S2Cwire Interface
• Single-wire
• 32 Steps
• ±10% LED Output Current Accuracy
• ±3% LED Output Current Matching
• Low Current Shutdown Mode
• Low Cost 6-pin SOT23 Package
Applications
• Entry Level Mobile Phones
• Indicator LEDs
• Keyboard Backlight
• MP3 Players
Typical Application Circuit
Input Voltage
2.7V to 5.5V
IN
EN
D1
D2
RSET
RSET
9.53kΩ
AHK3292
EN/SET
S2Cwire
Interface
CIN
GND
AHK3292
2 Channel LED DriverPowerLinearTM
PRODUCT DATASHEET
2 3292.2009.06.1.2
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Pin Descriptions
Pin # Symbol Function Description
1EN I
S2Cwire serial input. EN is used for ON/OFF control. EN is also the data input for the S2Cwire
interface used to control the 32 levels of LED brightness according to the current set by RSET.
2 GND I/O Ground. Connect this pin to the system ground.
3IN I
Input power pin. Connect IN to the power source, typically the battery. Bypass IN to GND with
a 1F or larger ceramic capacitor.
4D2 O
Backlight LED 2 current sink output. Connect the cathode of LED 2 to D2. If not used, connect
D2 to IN.
5 RSET I
Connect resistor from this pin to GND to set the maximum LED current level. For optimal LED
output current accuracy and matching in the AHK3292, use a 9.53k 1% resistor to set each
full-scale output current to 30.2mA maximum.
6D1 O
Backlight LED 1 current sink output. Connect the cathode of LED 1 to D1. If not used, connect
D1 to IN.
Pin Configuration
SOT23-6
(Top View)
GND
D1
RSET
D2
IN
EN
1
2
34
5
6
AHK3292
2 Channel LED DriverPowerLinearTM
PRODUCT DATASHEET
3292.2009.06.1.2 3
www.analogictech.com
Absolute Maximum Ratings1
TA = 25OC unless otherwise noted.
Symbol Description Value Units
VNIN, D1, D2, and RSET to GND -0.3 to 6.0 V
VEN VEN to GND -0.3 to VIN +0.3
Thermal Information2
Symbol Description Value Units
ΘJA Thermal Resistance3150 OC/W
PDMaximum Power Dissipation 667 mW
TJOperating Junction Temperature Range -40 to 150 °C
TLEAD Maximum Soldering Temperature (at Leads) 300
1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at conditions other than the operating conditions
specified is not implied. Only one Absolute Maximum Rating should be applied at any one time.
2. Mounted on an FR4 board.
3. Derate 5.3mW/°C above 25°C.
AHK3292
2 Channel LED DriverPowerLinearTM
PRODUCT DATASHEET
4 3292.2009.06.1.2
www.analogictech.com
Electrical Characteristics1
IN = EN = 3.6V, CIN = 1F, R SET = 9.53k; TA = -40oC to 85oC unless otherwise noted. Typical values are at TA =
25oC.
Symbol Description Conditions Min Typ Max Units
Power Supply
VIN Input Voltage Range 2.7 5.5 V
IIN Input Operating Current ID1 = ID2 = 30.2mA (DATA 1), excluding ID1 and ID2 1.8 mA
IIN(SHDN) Input Shutdown Current IN = 5.5V; EN = GND 1 A
VDO Current Sink Dropout Voltage2ID1 = ID2 = 30.2mA (DATA 1) 40.5 125 mV
ID1 = ID2 = 15.2mA (DATA 16) 36 85
LED Current Sink Outputs
ID(MAX) D1, D2 Current Accuracy ID1 = ID2 = 30.2mA (DATA 1) 27.18 30.2 33.22 mA
ID(MAX) D1, D2 Current Matching ID1 = ID2 = 30.2mA (DATA 1) ±3 %
tSStart-up Period EN = IN 150 s
ISET Current Set Ratio ISINK/IRSET 240 A/A
VSET RSET Pin Voltage 1.2 V
EN and S2Cwire Control
VEN(L) EN Input Low Threshold 0.4 V
VEN(H) EN Input High Threshold 1.4 V
IEN EN Input Leakage Current EN = IN = 5V -1 1 A
TEN(LOW) EN Serial Interface Low Time 0.3 75 s
TEN(HI_ MIN) Minimum EN high Time 50 ns
TEN(HI_ MAX) Maximum EN High Time 75 s
TEN(OFF) EN Off Timeout 500 s
TEN(LAT) EN Latch Timeout 500 s
1. The AHK3292 is guaranteed to meet the performance specifications over the -40°C to +85°C operating temperature range and is assured by design, characterization and cor-
relation with statistical process controls.
2. The current sink drop-out voltage is defined as when the current at D1 or D2 drops to 90% of its nominal value.
AHK3292
2 Channel LED DriverPowerLinearTM
PRODUCT DATASHEET
3292.2009.06.1.2 5
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Typical Characteristics
Quiescent Current vs. Input Voltage
Input Voltage (V)
Quiescent Current (mA)
2.7 3.0 3.3 3.5 3.8 4.1 4.4 4.7 4.9 5.2 5.5
0.60
0.80
1.00
1.20
1.40
1.60
1.80
2.00
2.20
85°C
25°C
-40°C
Shutdown Current vs. Temperature
Temperature (°C)
IIN(SHDN) (µA)
-40 -15 10 35 60 85
-0.010
0.000
0.010
0.020
0.030
0.040
0.050
0.060
0.070
0.080
0.090 VIN = 5.5V
VIN = 2.7V
Line Regulation
(30.2mA/ch)
Input Voltage (V)
LED Current (mA)
2.7 3.0 3.3 3.5 3.8 4.1 4.4 4.7 4.9 5.2 5.5 4.7 4.9 5.2 5.5
59.0
59.5
60.0
60.5
61.0
Efficiency vs. Input Voltage
(30.2mA/ch)
Input Voltage (V)
Efficiency (%)
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
60
65
70
75
80
85
90
95
100
105
D1, D2 Current Matching
Temperature (°C)
Sink Current (mA)
-40 -15 10 35 60 85
28.5
29
29.5
30
30.5
31
31.5
ID1
ID2
AHK3292
2 Channel LED DriverPowerLinearTM
PRODUCT DATASHEET
6 3292.2009.06.1.2
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Typical Characteristics
Turn On
(VIN = 3.6V; 30.2mA/ch)
Time (100µs/div)
EN/SET
(2V/div)
VF
(2V/div)
IIN
(50mA/div)
Turn Off
(VIN = 3.6V; 30.2mA/ch)
Time (100µs/div)
EN/SET
(2V/div)
VF
(2V/div)
IIN
(50mA/div)
EN Input HighThreshold vs. Input Voltage
VIN (V)
VIH (V)
2.7 2.98 3.26 3.54 3.82 4.1 4.38 4.66 4.94 5.22 5.5
0
0.2
0.4
0.6
0.8
1
1.2
85°C
25°C
-40°C
EN Input Low Threshold vs. Input Voltage
VIN (V)
VIL (V)
2.7 2.98 3.26 3.54 3.82 4.1 4.38 4.66 4.94 5.22 5.5
0
0.2
0.4
0.6
0.8
1
1.2
85°C
25°C
-40°C
EN Input Latch Timeout vs. Input Voltage
VIN (V)
TLAT (µs)
4.9
2.9 3.12.7 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 5.1 5.3 5.5
100
150
200
250
300
350
85°C
25°C
-40°C
EN Input OFF Timeout vs. Input Voltage
VIN (V)
TOFF (µs)
4.9
2.9 3.12.7 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 5.1 5.3 5.5
100
150
200
250
300
350
85°C
25°C
-40°C
AHK3292
2 Channel LED DriverPowerLinearTM
PRODUCT DATASHEET
3292.2009.06.1.2 7
www.analogictech.com
Functional Description
The AHK3292 is an entry level driver IC, designed to drive
up to two white LEDs. The AHK3292 operates directly
from a 2.7V to 5.5V power source and enables and con-
trols the currents to the diodes. Both channels are indi-
vidually controlled through integrated current sinks pow-
ered from an external power supply. Low resistance and
low-dropout voltage current sinks allow the LEDs to oper-
ate very close to the input supply voltage, eliminating the
need for an additional boost power supply.
The AHK3292 requires only two external components:
one 1F ceramic input capacitor (CIN), and a resistor
(RSET) to set the maximum LED current. The AHK3292
can drive two constant output sinks, D1 and D2, up to
30.2mA maximum current each. AnalogicTech’s S2Cwire
serial interface enables the AHK3292 and changes the
current sink magnitude through the EN pin.
S2Cwire Serial Interface
The LED output current of the AHK3292 is controlled by
AnalogicTech’s S2Cwire serial interface. Since the LED
current is programmable, no PWM or additional control
circuitry is needed to control LED brightness. This fea-
ture greatly reduces the burden on a microcontroller or
system IC to manage LED or display brightness, allowing
the user to “set it and forget it.” With its high-speed
serial interface (1MHz data rate), the LED current can
be changed quickly and easily. Also the non-pulsating
LED current reduces system noise and improves LED
reliability.
The S2Cwire interface relies on the number of rising
edges to the EN/SET pin to set the register. A typical
write protocol is a burst of EN rising edges, followed by
a pause with EN held high for at least tLAT (500s). The
programmed current is then seen at the current sink
outputs. When EN is held low for an amount of time lon-
ger than tOFF (500s), the AHK3292 enters into shutdown
mode and draws less than 1A from the input and the
internal data register is reset to zero.
The AHK3292 serial interface reduces the LED current on
each rising pulse of the enable input. If the AHK3292 is
in shutdown, the first rising edge of the EN input turns
on the LED driver to the maximum current. Successive
rising edges decrease the LED current according to Table
1 and Figure 2.
Functional Block Diagram
GND
IN
D2
D1
S2Cwire
Control DAC
EN RSET
IREF
2
AHK3292
2 Channel LED DriverPowerLinearTM
PRODUCT DATASHEET
8 3292.2009.06.1.2
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S2C Interface Data Code
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 2930 31 32
S2C Interface Data Code
DX Current (mA)
Figure 2: AHK3292 Current Profile.
Constant Current Control
Using External RSET
The AHK3292's maximum current is programmed by an
external resistor connected to the RSET pin. The full-
scale LED current can be set between 30.2mA and
0.5mA as shown on Figure 2. Table 2 shows RSET resistor
values for various full-scale current levels. For maximum
accuracy, a 1% tolerance resistor is recommended.
ILED (mA) RSET(kΩ)
30.2 9.53
25 11.5
20.1 14.3
18.2 15.8
15.1 19.1
10 28.7
Table 2: Maximum LED Current vs. RSET Resistor
Values (1% Resistor Tolerance).
1
EN/SET
2n-1 n ≤ 32
Data Reg 0 n-1 0
THI
TLO TLAT TOFF
Figure 1: S2Cwire Serial Interface Timing.
Data EN Rising Edges
D1- D2 Output
Current (mA) Data EN Rising Edges
D1-D2 Output
Current (mA)
1 1 30.2 17 17 14.6
2 2 29.2 18 18 13.6
3 3 28.3 19 19 12.7
4 4 27.3 20 20 11.7
5 5 26.3 21 21 10.7
6 6 25.3 22 22 9.7
7 7 24.4 23 23 8.8
8 8 23.4 24 24 7.8
9 9 22.4 25 25 6.8
10 10 21.4 26 26 5.8
11 11 20.5 27 27 4.9
12 12 19.5 28 28 3.9
13 13 18.5 29 29 2.9
14 14 17.5 30 30 1.9
15 15 16.6 31 31 1.0
16 16 15.6 32 32 0.5
Table 1: AHK3292 LED Current Settings.
AHK3292
2 Channel LED DriverPowerLinearTM
PRODUCT DATASHEET
3292.2009.06.1.2 9
www.analogictech.com
Applications Information
LED Selection
The AHK3292 is specifically intended for driving white
LEDs. However, the device design will allow the AHK3292
to drive most types of LEDs with forward voltage specifi-
cations typically ranging from 2.2V to 4.7V depending
upon supply voltage. LED applications may include mixed
arrangements for display backlighting, keypad display,
and any other application that needs a constant current
sink generated from a varying input voltage. Since the
D1 to D2 constant current sinks are matched within 3%
with negligible supply voltage dependence, the constant
current channels will be matched regardless of the spe-
cific LED forward voltage (VF) levels. The low dropout
current sinks in the AHK3292 maximize performance and
make it capable of driving LEDs with high forward volt-
ages. The two channels can be combined to obtain a
higher LED drive current without complication.
Shutdown
Since the current switches are the only power supplies
for all loads, there is no leakage current when all sink
switches are disabled. To activate the shutdown opera-
tion, the EN input for the AHK3292 should be strobed low
for longer than tOFF (500s). In this state, the AHK3292
typically draws less than 1A from the input. Registers
are reset to 0 in shutdown.
Additional Applications
The current sinks of the AHK3292 can be combined to
drive higher current levels through a single LED. As an
example, a single LED can typically be driven at 60.4mA
total by combining together the D1-D2 outputs as shown
in Figure 3.
Capacitor Selection
Careful selection of the external capacitor CIN is impor-
tant because it will affect turn-on time and transient
performance. Optimum performance will be obtained
when low equivalent series resistance (ESR) ceramic
capacitor is used; in general, low ESR may be defined as
less than 100m. A value of 1F for the input capacitor
is a good starting point when choosing it. If the constant
current sinks are only programmed for light current lev-
els, then the input capacitor size may be decreased.
Capacitor Characteristics
Ceramic composition capacitor is highly recommended
over all other types of capacitors for use with the
AHK3292. Ceramic capacitors offer many advantages
over their tantalum and aluminum electrolytic counter-
parts. A ceramic capacitor typically has very low ESR, is
lower cost, has a smaller PCB footprint, and is non-
polarized. Since ceramic capacitors are non-polarized,
they are not prone to incorrect connection damage.
VIN
IN
EN
D1
D2
RSET
RSET
9.53kΩ
AHK3292
EN/SET
CIN
1μF
GND
Figure 3: Higher Current Single LED Application.
AHK3292
2 Channel LED DriverPowerLinearTM
PRODUCT DATASHEET
10 3292.2009.06.1.2
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Equivalent Series Resistance
ESR is an important characteristic to consider when
selecting a capacitor. ESR is a resistance internal to a
capacitor that is caused by the leads, internal connec-
tions, size or area, material composition, and ambient
temperature. Capacitor ESR is typically measured in mil-
liohms for ceramic capacitors and can range to more
than several ohms for tantalum or aluminum electrolytic
capacitors.
Ceramic Capacitor Materials
Ceramic capacitors less than 0.1F are typically made
from NPO or C0G materials. NPO and C0G materials gen-
erally have tight tolerance and are very stable over tem-
perature. Larger capacitor values are usually composed
of X7R, X5R, Z5U, or Y5V dielectric materials. Large
ceramic capacitors (i.e., larger than 2.2F) are often
available in low cost Y5V and Z5U dielectrics, but capac-
itors larger than 1F are not typically required for
AHK3292 applications. Capacitor area is another con-
tributor to ESR. Capacitors that are physically large will
have a lower ESR when compared to an equivalent
material smaller capacitor. These larger devices can
improve circuit transient response when compared to an
equal value capacitor in a smaller package size.
Evaluation Board User Interface
The user interface for the AHK3292 evaluation board is
provided by three buttons and two connection terminals.
The board is operated by supplying external power and
pressing individual buttons or button combinations.
Table 3 indicates the function of each button or button
combination.
To power-on the evaluation board, connect a power sup-
ply or battery to the DC- and DC+ terminals. A red LED
indicates that power is applied. The evaluation board is
made flexible so that the user can disconnect the enable
line from the microcontroller and apply external enable
signal. External enable signal must be applied to the EN
pin.
When applying external enable signal, consideration
must be given to the voltage levels. The externally
applied voltage should not exceed the supply voltage
that is applied to the IN pins of the device (DC+).
User Interface Functionality
Button(s) Pushed Description
UP [Push/Release once] D1 and D2 are turned on with 0.5mA per channel. With every push/release the
current is increased according to Table 1.
DOWN [Push/Release once] D1 and D2 are turned on with 30.2mA per channel. With every push/release the
current is decreased according to Table 1.
CYCLE [Push/Release together] Auto cycling up and down.
Table 3: AHK3292 Evaluation Board User Interface.
AHK3292
2 Channel LED DriverPowerLinearTM
PRODUCT DATASHEET
3292.2009.06.1.2 11
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VDD
1
GP5
GP4
GP3
VSS
GP0
GP1
GP2
2
3
4 5
6
7
8
U2 PIC12F675
C1
1µF
C2
1µF
1
23
45
0
DOWN SW1
1
23
45
0
UP SW2
1
23
45
0
CYCLE SW3
VIN
VR4
POT10K
LED1
GRN
LED2
RED
R6
330
R5
330
J2 R7
100K
R4
1K
R3
1K
R2
1K
R1
9.53k
D1 D2
GND 2
IN 3
EN 1
RSET
5
D2
4
D1
6
U1 AHK3292
1 2 3
J1
VINGND
IN
JP1
JP3
JP2
Figure 4: AHK3292 Evaluation Board Schematic.
AHK3292
2 Channel LED DriverPowerLinearTM
PRODUCT DATASHEET
12 3292.2009.06.1.2
www.analogictech.com
Figure 5: AHK3292 Evaluation Board Figure 6: AHK3292 Evaluation Board
Top Side Layout. Bottom Side Layout.
AAT3292 EVAL Component Listing
Component Part Number Description Manufacturer
U1 AHK3292IGU Two Channel LED driver; SOT23-6 package AnalogicTech
U2 PIC12F675 8-bit CMOS, FLASH-based C; 8-pin PDIP package Microchip
CYCLE, UP, DOWN PTS645TL50 Switch Tact, SPST, 5mm ITT Industries
R1 Chip Resistor 9.53k, 1%, 1/4W; 0603 Vishay
R5, R6 Chip Resistor 330, 1%, 1/4W; 0603 Vishay
R7 Chip Resistor 100K, 5%, 1/4W; 0603 Vishay
R2, R3, R4 Chip Resistor 1K, 5%, 1/4W; 0603 Vishay
C1, C2 GRM185R60J105KE21 1F, 6.3V, X7R, 10%, 0603 Murata
LED1 CMD15-21VGC/TR8 Green LED; 0603 Chicago Miniature Lamp
LED2 CMD15-21SRC/TR8 Red LED; 0603 Chicago Miniature Lamp
J1, J2 PRPN401PAEN Conn. Header, 2mm zip Sullins Electronics
JP1, JP2 Chip Resistor 0, 5%, 1/4W; 0603 Vishay
JP3 Chip Resistor 0, 5%, 1/2W; 0805 Vishay
D1, D2 LW M673 Mini TOPLED White LED; SMD OSRAM
Table 4: AHK3292 Evaluation Board Bill of Materials (BOM)
AHK3292
2 Channel LED DriverPowerLinearTM
PRODUCT DATASHEET
3292.2009.06.1.2 13
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Advanced Analogic Technologies, Inc.
3230 Scott Boulevard, Santa Clara, CA 95054
Phone (408) 737-4600
Fax (408) 737-4611
© Advanced Analogic Technologies, Inc.
AnalogicTech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AnalogicTech product. No circuit patent licenses, copyrights, mask work rights, or other intellectual
property rights are implied. AnalogicTech reserves the right to make changes to their products or specifi cations or to discontinue any product or service without notice. Except as provided in AnalogicTech’s terms and
conditions of sale, AnalogicTech assumes no liability whatsoever, and AnalogicTech disclaims any express or implied warranty relating to the sale and/or use of AnalogicTech products including liability or warranties
relating to fi tness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right. In order to minimize risks associated with the customer’s applications, adequate
design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards. Testing and other quality control techniques are utilized to the extent AnalogicTech deems necessary to
support this warranty. Specifi c testing of all parameters of each device is not necessarily performed. AnalogicTech and the AnalogicTech logo are trademarks of Advanced Analogic Technologies Incorporated. All other
brand and product names appearing in this document are registered trademarks or trademarks of their respective holders.
1. XYY = assembly and date code.
2. Sample stock is generally held on part numbers listed in BOLD.
Ordering Information
Package Part Marking1Part Number (Tape and Reel)2
SOT23-6 7MXYY AHK3292IGU-T1
All AnalogicTech products are offered in Pb-free packaging. The term “Pb-free” means semiconductor
products that are in compliance with current RoHS standards, including the requirement that lead not exceed
0.1% by weight in homogeneous materials. For more information, please visit our website at
http://www.analogictech.com/about/quality.aspx.
Package Information
SOT23-6
1.90 BSC
0.95 BSC
0.45
±
0.15 0.10 BSC
2
.
85
±
0
.
15
0.075
±
0.075
0.40
±
0.10
×
6
1.575
±
0.125
1.20
±
0.25
1.10
±
0.20
2.80
±
0.20
4
°
±
4
°
10
°
±
5
°
0.15
±
0.07
GAUGE PLANE
0.60 REF
All dimensions in millimeters.
