A708

A708 ADDTEK | Alldatasheet

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www.addmtek.com Copyright © 2007 ADDtek Corp. 1 DD076_A -- AUGUST 2007 A708

3 C HANNELS 20mA

ADV ANCED C URRENT R EGULATOR DESCRIPTION FEATURES 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% effici ency 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. „ 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 APPLICATIONS „ Small Size Color LCD Backlights. „ Mobile Phone, Smart Phone. „ LED Backlight for Portable DVD, NB, Monitors, and UMPC. PACKAGE PIN OUT Enable A708 EN LED2 VDD GND LED1 LED3 VDD VLED+ CIN CBP A708 TSOT-26 LED1 VDD GND LED3 3 4 LED2 5 EN A708 ORDER INFORMATION Plastic TSOT-26 TA (°C) Y 6-pin -40 ~ 85 A708YFT Note: The letter ”F” is marked for Lead Free process, and letter “T” is marked for Tape & Reel.

Copyright © 2007 ADDtek Corp. 2 DD076_A -- AUGUST 2007 ABSOLUTE MAXIMUM RATINGS (Note) Input Voltage, VDD -0.3V to 13.2V Output Sustaining Voltage, VLEDn -0.3V to 17V Voltage at all other pins -0.3V to 12V Maximum Junction Temperature, TJ 150 O C Storage Temperature Range -40 O C to 150°C Lead Temperature (soldering, 10 seconds) 260 O C 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. POWER DISSIPATION TABLE Package θJA (°C / W ) Derating factor ( mW/°C ) TA≧25 O C TA≦25°C Power rating (mW) TA=70 Power rating (mW) TA= 85°C Power rating (mW) Y 220 4.5 568 363 295 Note : Junction Temperature Calculation: T J = 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 VDDI EN VDD GND LED1Driving Stage LED2 Driving Stage LED3 Driving Stage Control Logic A708 Reference Current

Copyright © 2007 ADDtek Corp. 3 DD076_A -- AUGUST 2007 PIN DESCRIPTION Pin Name Pin Function LED1 ~ LED3 Output pins; connect to LED’s cathode. EN Enable control pin. Pulling this pin high w ill enable the device. Pulling this pin to GND will disable the device. VDD Power supply GND Ground PGND Power ground RECOMMENDED OPERATING CONDITIONS Parameter Symbol Min Typ Max Unit Supply Voltage V DD 2.7 12 V Output Sink current I LED 25 mA Operating free-air temperature range T A -40 +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 V IL 0 0.4 V “High” Input Voltage V IH 1.7 V DD V “Low” Input Current I IL -5.0 +5.0 µA “High” Input Current I IH -5.0 +5.0 µA EN LED Dropout Voltage V LEDL Note 1 75 90 mV Rank A 19 20 21 LED Sink Current I LED 18 20 22 mA LED Sink Current Deviation △ILEDn Note 2 ±3 % Load Regulation V LEDn=0.15~3V ±3 % Line Regulation V DD=2.7~12V, VLEDn=0.15V ±3 % LEDn Supply Current I DD 300 600 uA Standby Supply Current I DDSTBY 0.1 uA VDD Note 1: LED Dropout Voltage: 90% × I LEDn @ VLEDn=150mV Note 2: ILEDn(max)-ILEDn(average) and ILEDn(average)-ILEDn(min)

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

Copyright © 2007 ADDtek Corp. 5 DD076_A -- AUGUST 2007

APPLICATION INFORMATION

Pulling the EN pin to high will enable the device sinki ng constant current on LED pins. Pulling the EN pin to ground will shutdown the device. This pin should not be left floating and need to be terminated. LED Number in the String Driven by Each Channel The breakdown voltage of LEDn pin is 17V so that each ch annel can drive up to 9 pcs of LEDs in series. When the chip is disabled, the forward voltage of the LED may drop to half of the ra ted value because of the extremely small leakage current. LED Brightness Control The LED sink current was fixed at 20mA. Apply PWM signal to EN pin and control the duty that could control the LED brightness from 0% to maximum. Enable A708 EN LED2 VDD GND LED1 LED3 VDD VIN CIN CBP Efficiency The ACR (Advanced Current Regulator) architecture offers ultra low output dropout that significantly improves the efficiency compared to In ductive Boost type or Capacitor Charge Pump type LED driver. The system efficiency, defined as the ratio between the LEDs power and the input supplied power, is: Efficiency = (VF1 × I LED1 + VF2 × I LED2 + VF3 × I LED3 ) / ( VDD × I DD ) Where, VF is the forward voltage of LED.

Copyright © 2007 ADDtek Corp. 6 DD076_A -- AUGUST 2007 Li-ion Battery Voltage Supply The A708 can work with Li-ion battery. The supply voltage of Li-ion battery ranges from 4.5V down to lower than 3V while the white/blue LED forward voltage (V F) is in the range of 2.9V to 3.5V at 20mA current. The supply voltage range and LED forward voltage can be set to fully utilize Li-ion battery energy. For example, if the forward voltage of white LED is 3.2V at 20mA, the Li-ion battery can discharge until ou tput voltage reaches 3.275V (normally around 1% ~ 3% power left in the battery). When Li-ion battery voltage is lower than the 3.275V, the LED current (brightness) will start to decrease. Enable A708 EN LED2 VDD GND LED1 LED3 VDD Li-ion Battery

Copyright © 2007 ADDtek Corp. 7 DD076_A -- AUGUST 2007 PACKAGE Surface Mount TSOT-26 MILLIMETERS SYMBOLS MIN TYP MAX A --- --- 1.00 A1 0.00 0.05 0.10 A2 0.84 0.87 0.90 b 0.35 0.40 0.50 C 0.10 0.125 0.15 D 2.70 2.90 3.10 E 2.60 2.80 3.00 E1 1.40 1.60 1.80 e --- 0.95 --- e1 --- 1.90 --- L 0.30 0.40 0.60 L1 0.5 0.6 0.7 θ 0° 4° 8° θ1 4° 10° 12° C 4xθ1 L D A2 A A1 4xθ1 E1E e b θ

Copyright © 2007 ADDtek Corp. 8 DD076_A -- AUGUST 2007 IMPORTANT NOTICE ADDtek reserves the right to make changes to its products or to discontinue any integrated circuit product or service without notice, and advises its customers to obtain the latest version of relevant information to verify, before placing orders, that the information being relied on is current. A few applications using integrated circuit products may invo lve potential risks of death, personal injury, or severe property or environmental damage. ADDtek integrated circuit products are not designed, intended, authorized, or warranted to be suitable for use in life- support applications, devices or systems or other critical applications. Use of ADDtek products in such applications is understood to be fully at the risk of the customer. In order to minimize risks associated with the customer’s applications, the customer should provide adequate design and operating safeguards. ADDtek assumes to no liability to customer product design or application support. ADDtek warrants the performance of its products to the specifications applicable at the time of sale. ADDtek Corp. 9F, No. 20, Sec. 3, Bade Rd., Taipei, Taiwan, 105 TEL: 2-25700299 FAX: 2-25700196