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A708 (ADDtek) : Total 8 Pages

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www.addmtek.com
A708
3 CHANNELS 20mA
ADVANCED CURRENT REGULATOR
DESCRIPTION
The A708 is a 3 channels 20mA advanced current
regulator for driving LEDs. Only bypass capacitor is
required and the noise is very low. The special circuit
design provides over 90% efficiency because of the very
low dropout voltage.
Target end applications are LED backlights for color
LCD display, such as mobile phone, smart phone, PDA,
notebook, and monitor, etc.
FEATURES
„ Fixed 20mA DC constant sink current.
„ Individual current sink circuit for each LED
string to prevent short / open circuit on LEDs.
„ TSOT-26 package available.
„ High efficiency.
„ Supply voltage range 2.7V ~ 12V.
„ Output sustaining voltage up to 17V.
„ 0.1uA standby current.
„ 2KV HBM ESD protection.
„ Advanced Bi-CMOS process.
TYPICAL APPLICATION CIRCUIT
VLED+
CBP
APPLICATIONS
„ Small Size Color LCD Backlights.
„ Mobile Phone, Smart Phone.
„ LED Backlight for Portable DVD, NB, Monitors,
and UMPC.
PACKAGE PIN OUT
VDD
CIN
Enable
LED1 LED2 LED3
VDD
A708
EN
GND
VDD 1
GND 2
EN 3
6 LED1
5 LED2
4 LED3
A708
TSOT-26
TA (°C)
-40 ~ 85
Y
ORDER INFORMATION
Plastic TSOT-26
6-pin
A708YFT
Note: The letter ”F” is marked for Lead Free process, and letter “T” is marked for Tape & Reel.
Copyright © 2007 ADDtek Corp.
1
DD076_A -- AUGUST 2007



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ABSOLUTE MAXIMUM RATINGS
Input Voltage, VDD
Output Sustaining Voltage, VLEDn
Voltage at all other pins
Maximum Junction Temperature, TJ
Storage Temperature Range
Lead Temperature (soldering, 10 seconds)
(Note)
Note:
Exceeding these ratings could cause damage to the device. All voltages are with respect to Ground.
Currents are positive into, negative out of the specified terminal.
A708
-0.3V to 13.2V
-0.3V to 17V
-0.3V to 12V
150OC
-40OC to 150°C
260OC
Package
Y
POWER DISSIPATION TABLE
θJA Derating factor ( mW/°C )
TA25°C
TA=70 °C
TA= 85°C
(°C / W )
TA25 OC
Power rating (mW) Power rating (mW) Power rating (mW)
220 4.5
568 363 295
Note :
Junction Temperature Calculation: TJ = TA+ (PD x θJA).
PD: Power Dissipation, TA: Ambient temperature, θJA: Thermal Resistance-Junction to Ambient
The θJA numbers are guidelines for the thermal performance of the device/PC-board system.
All of the above assume no ambient airflow.
BLOCK DIAGRAM
VDD
EN
VDDI
Control
Logic
Reference
Current
A708
Driving
Stage
Driving
Stage
Driving
Stage
LED1
LED2
LED3
GND
Copyright © 2007 ADDtek Corp. 2 DD076_A -- AUGUST 2007



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Pin Name
LED1 ~ LED3
EN
VDD
GND
PGND
A708
PIN DESCRIPTION
Pin Function
Output pins; connect to LED’s cathode.
Enable control pin. Pulling this pin high will enable the device. Pulling this pin to GND
will disable the device.
Power supply
Ground
Power ground
RECOMMENDED OPERATING CONDITIONS
Parameter
Supply Voltage
Output Sink current
Operating free-air temperature range
Symbol Min Typ Max Unit
VDD 2.7
ILED
TA -40
12 V
25 mA
+85 °C
ELECTRICAL CHARACTERISTICS
VDD=3.7V, VIH=3.3V, VIL=GND, No Load, TA=25°C, (Unless otherwise noted)
Parameter
Symbol
Condition
Min
Typ
Max
Unit
Apply
Pin
“Low” Input Voltage
VIL
0 0.4 V
“High” Input Voltage
“Low” Input Current
VIH
IIL
1.7
VDD
V
EN
-5.0 +5.0 µA
“High” Input Current
LED Dropout Voltage
IIH
VLEDL
Note 1
-5.0 +5.0 µA
75 90 mV
LED Sink Current
Rank A
ILED
LED Sink Current Deviation
Load Regulation
Line Regulation
ILEDn
Note 2
VLEDn=0.15~3V
VDD=2.7~12V, VLEDn=0.15V
19 20 21
mA
18 20 22
±3
LEDn
%
±3 %
±3 %
Supply Current
IDD
Standby Supply Current
IDDSTBY
Note 1: LED Dropout Voltage: 90% × ILEDn @ VLEDn=150mV
Note 2: ILEDn(max)-ILEDn(average) and ILEDn(average)-ILEDn(min)
300 600 uA
VDD
0.1 uA
Copyright © 2007 ADDtek Corp. 3 DD076_A -- AUGUST 2007



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CHARACTERISTIC CURVES
A708
Output Current vs. Supply Voltage
21.00
20.50
20.00
19.50
19.00
0.0
VEN=3.3V
VDROP=0.2V
TA=25
5.0 10.0
Supply Voltage (V)
15.0
Output Current vs. Temperature
21.0
20.5
VDD=3.7V
VEN=3.3V
V DROP =0.2V
20.0
19.5
19.0
-50
0 50 100
Temperature ()
150
Output Current vs. Dropout Voltage
25.00
20.00
15.00
10.00
5.00
0.00
10
VDD=3.7V
VEN=3.3V
TA=25
100 1,000
Dropout Voltage (mV)
10,000
Max. Allowable VDrop vs. Ambient Temp.
10
VDD=3.7V
8 VEN=3.3V
TJ,MAX=125
6 ILED,Total=60mA
4
2
0
10 30 50 70 90 110
Ambient Temperature (°C)
Copyright © 2007 ADDtek Corp. 4 DD076_A -- AUGUST 2007






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