A708 ADVANCED www.addmtek.com DESCRIPTION 3 CHANNELS 20mA CURRENT REGULATOR 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% 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. 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 V LED+ C BP Small Size Color LCD Backlights. Mobile Phone, Smart Phone. LED Backlight for Portable DVD, NB, Monitors, and UMPC. PACKAGE PIN OUT V DD LED2 LED3 GND 2 VDD C IN EN 3 A708 EN Enable A708 VDD 1 LED1 6 LED1 5 LED2 4 LED3 A708 TSOT-26 GND ORDER INFORMATION TA (°C) Y -40 ~ 85 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 A708 ABSOLUTE MAXIMUM RATINGS (Note) -0.3V to 13.2V -0.3V to 17V -0.3V to 12V 150OC -40OC to 150°C 260OC 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: 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 Y TA=70 °C TA= 85°C θJA Derating factor ( mW/°C ) TA≦25°C Power rating (mW) Power rating (mW) Power rating (mW) (°C / W ) TA≧25 OC 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 VDDI EN Control Logic A708 Driving Stage Driving Stage Driving Stage Reference Current Copyright © 2007 ADDtek Corp. LED1 LED2 LED3 GND 2 DD076_A -- AUGUST 2007 A708 PIN DESCRIPTION Pin Name Pin Function LED1 ~ LED3 Output pins; connect to LED’s cathode. EN Enable control pin. Pulling this pin high will 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 Supply Voltage VDD 2.7 Output Sink current ILED Operating free-air temperature range TA -40 Max 12 25 +85 Unit V mA °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 “Low” Input Voltage VIL 0 0.4 V “High” Input Voltage VIH 1.7 VDD V “Low” Input Current IIL -5.0 +5.0 µA “High” Input Current IIH -5.0 +5.0 µA LED Dropout Voltage VLEDL 75 90 mV 19 20 21 18 20 22 LED Sink Current ILED △ILEDn Note 1 Rank A ±3 % Load Regulation VLEDn=0.15~3V ±3 % Line Regulation VDD=2.7~12V, VLEDn=0.15V ±3 % 600 uA Supply Current Standby Supply Current IDD 300 IDDSTBY 0.1 EN mA Note 2 LED Sink Current Deviation Apply Pin uA LEDn VDD Note 1: LED Dropout Voltage: 90% × ILEDn @ VLEDn=150mV Note 2: ILEDn(max)-ILEDn(average) and ILEDn(average)-ILEDn(min) Copyright © 2007 ADDtek Corp. 3 DD076_A -- AUGUST 2007 A708 CHARACTERISTIC CURVES Output Current vs. Supply Voltage Output Current vs. Temperature 21.0 Output Current (mA) Output Current (mA) 21.00 20.50 20.00 V EN=3.3V V DROP =0.2V TA =25℃ 19.50 19.00 0.0 5.0 10.0 Supply Voltage (V) 20.5 20.0 19.5 19.0 -50 15.0 Output Current vs. Dropout Voltage 50 Temperature ( ℃ ) 100 150 10 Max. Allowable Dropout (mV) Output Current (mA) 0 Max. Allowable VDrop vs. Ambient Temp. 25.00 20.00 15.00 10.00 V DD=3.7V V EN=3.3V TA=25℃ 5.00 0.00 10 V DD=3.7V V EN=3.3V V DROP =0.2V 100 1,000 Dropout Voltage (mV) Copyright © 2007 ADDtek Corp. 6 4 2 0 10 10,000 4 V DD=3.7V V EN=3.3V TJ,MAX =125℃ ILED,T otal =60mA 8 30 50 70 90 Ambient Temperature (°C) DD076_A 110 -- AUGUST 2007 A708 APPLICATION INFORMATION Enable Pulling the EN pin to high will enable the device sinking 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 channel 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 rated 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. V IN C BP LED1 LED2 LED3 VDD V DD C IN A708 EN Enable GND Efficiency The ACR (Advanced Current Regulator) architecture offers ultra low output dropout that significantly improves the efficiency compared to Inductive 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 × ILED1 + VF2 × ILED2 + VF3 × ILED3 ) / ( VDD × IDD ) Where, VF is the forward voltage of LED. Copyright © 2007 ADDtek Corp. 5 DD076_A -- AUGUST 2007 A708 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 (VF) 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 output 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. V DD LED1 Li-ion Battery LED2 LED3 VDD A708 EN Enable GND Copyright © 2007 ADDtek Corp. 6 DD076_A -- AUGUST 2007 A708 PACKAGE Surface Mount TSOT-26 C D SYMBOLS b L E E1 e θ e1 4xθ1 A A2 A1 Copyright © 2007 ADDtek Corp. 4xθ1 7 L1 MILLIMETERS 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° DD076_A -- AUGUST 2007 A708 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 involve 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 Copyright © 2007 ADDtek Corp. 8 DD076_A -- AUGUST 2007