tm TE CH Preliminary Product spec. T6311A Low-Dropout, Constant-Current White LED Bias Supply FEATURES GRNERAL DESCRIPTION • Low 200mV Dropout at 9mA • Up to 150mA LED Bias Current • 0.3% LED Current Matching • Simple LED Brightness Control • Low 40uA Supply Current • Low 0.05uA Shutdown Current • 2.5V to 5.5V Supply Voltage Range • SOP-8 and SOT23-6 Package • Output channel : SOP-8 package for four channel SOT23-6 package for three channel The T6311A low-dropout bias supply for white LEDs is a high-performance alternative to the simple ballast resistors used in conventional white LED designs. The T6311A uses a single resistor to set the bias current for four LEDs, which are matched to 0.3%. The T6311A consumes only 40uA of supply current when enabled and 0.05uA when disabled. The T6311A advantages over ballast resistors include significantly better LED to LED bias matching, much lower bias variation with supply voltage variation, significantly lower dropout voltage, and in some applications, significantly improved efficiency. The T6311A requires a 200mV dropout at a 9mA load on each output to match the LED brightness. The T6311A is available in SOP-8 and SOT23-6 package. Applications • Cellular Phones • Portable Communication Devices • Handheld Electronics • Digital Cameras • PDAs • LED/Display Back Light Driver • LEDs for Camera Flash PART NUMBER EXAMPLES PART NO. PACKAGE T6311A-D SOP-8 T6311A-X SOT23-6 TM Technology Inc. reserves the right P. 1 to change products or specifications without notice. Publication Date: JUN. 2005 Revision: C tm TE CH Preliminary Product spec. T6311A PIN ARRANGEMENT(Top view) SOT23-6 SOP-8 LED1 1 8 EN EN 1 6 LED1 LED2 2 7 GND GND 2 5 LED2 LED3 3 6 SET SET 3 4 LED3 LED4 4 5 NC PIN DESCRIPTION SYMBO L Pin no. DESCRIPTION SOP-8 SOT23-6 EN 8 1 GND 7 2 SET 6 3 NC 5 - LED4 4 - LED3 3 4 LED2 2 5 LED1 1 6 Enable Input/Power Input. Drive high (> 2.5V) to enable; drive low (< 2.2V) to disable. When disabled, SET, LED1, LED2, LED3 and LED4 are high impedance. When enabled, EN is the power input for the T6311A. Ground Bias Current Set Input. The current flowing into SET sets the bias current into each LED by ILED_= 240 x ISET. VSET is internally biased to 1.2V. SET is high impedance when EN is low. No connection. LED 4 Cathode Connection. Current flowing into LED4 is 240 times the current flowing into SET. LED4 is high impedance when EN is low. LED 3 Cathode Connection. Current flowing into LED3 is 240 times the current flowing into SET. LED3 is high impedance when EN is low. LED 2 Cathode Connection. Current flowing into LED2 is 240 times the current flowing into SET. LED2 is high impedance when EN is low. LED 1 Cathode Connection. Current flowing into LED1 is 240 times the current flowing into SET. LED1 is high impedance when EN is low. TM Technology Inc. reserves the right P.2 to change products or specifications without notice. Publication Date: JUN. 2005 Revision: C tm TE CH Preliminary Product spec. T6311A BLOCK DIAGRAM V+ LED4 current controller ON OFF EN LED3 LED2 LED1 GND REF SET + - RSET VCTRL Fig. 1 TM Technology Inc. reserves the right P.3 to change products or specifications without notice. Publication Date: JUN. 2005 Revision: C tm TE CH Preliminary Product spec. T6311A ABSOLUTE MAXIMUM RATINGS Parameter Symbol Value Unit Voltage on any pin relative to GND VIN -0.3 to 6 V Operating Temperature Rang TA -40 to +85 °C TLEAD 300 °C TS -65 to +150 °C 1 W Maximum Soldering Temperature (at leads, 10 sec) Storage Temperature Rang Continuous Power Dissipation ( TA = +70°C ) Electrical Characteristics (TA = -40 to 85°C unless otherwise noted. Typical values are at TA =25°C, VEN =3.3V, VLED1 = VLED2= VLED3= VLED4= 1V) (Note 1) Symbol Description VEN Operating voltage range ISET SET input current range VSET ILED Conditions EN is power supply input Min. Typ. Max Unit 2.5 5.5 V 5 260 uA SET to LED current ratio ILED / ISET, ISET=42uA 220 240 260 A/A SET bias voltage ISET=42uA 1.08 1.2 1.32 V SET leakage current in Shutdown EN=GND, VSET=3.3V 0.01 1 uA 5 uA TA= -40 to +25°C TA= -40 to +85°C LED to LED current matching ISET=42uA 0.3 Maximum LED sink current Each LED 100 150 mA ISET=20uA (Note 2) 100 180 mV ISET=40uA (Note 3) 200 360 mV ISET=80uA (Note 3) 230 410 mV 0.01 1 uA LED dropout voltage LED leakage current in shutdown VIH Input high voltage VLED1=VLED2=VLED3=VLED4= 3.3V, EN=GND, TA=+25°C, each LED VEN >VIH for enable 2.5 VIL Input low voltage VEN <VIL for disable IEN EN intput bias current VEN = 2.50V to 5.5V, EN is power supply input VEN = 0.4V, TA=+25°C % V 2.2 V 40 100 uA 0.05 1 uA Note 1: Limits are 100% production tested at TA = +25°C. Limits over the operating temperature range are guaranteed through correlation using statistical quality control (SQC) methods. Note 2: Dropout Voltage is defined as the LED to GND voltage at which current sink into LED drops 20% from the value at VLED = 1V. Note 3: Dropout Voltage is defined as the LED to GND voltage at which current sink into LED drops 10% from the value at VLED = 1V. TM Technology Inc. reserves the right P.4 to change products or specifications without notice. Publication Date: JUN. 2005 Revision: C tm TE CH Preliminary Product spec. T6311A Typical Operating Characteristics (VEN=+3.3V, VCTRL= 3.3V, RSET=24.9k ohm, V+=3.3V, TA=+25 ºC, unless otherwise noted.)(circuit of Fig. 1) TBD TM Technology Inc. reserves the right P.5 to change products or specifications without notice. Publication Date: JUN. 2005 Revision: C tm TE CH Preliminary Product spec. T6311A Functional Description Applications Information The T6311A provides constant current bias supply for white LED designs. The T6311A uses a single resistor to set the bias current for up to three LEDs. LED bias currents are matched to 0.3% by the T6311A current matching architecture (Fig. 1). Supply current (IEN) is a low 40uA in normal operation and 0.05uA when disabled. The T6311A offers several advantages over using ballast resistors, such as improved LED to LED brightness matching, lower bias variation with supply voltage changes, significantly lower dropout voltage, and in some applications, significantly improved efficiency. The T6311A achieves a 200mV dropout with a 9mA load on each output. For circuits requiring only one or two LEDs, leave unused LED outputs unconnected. Enable Input EN powers the input of the T6311A. Drive EN high (> 2.5V) to enable the device; drive EN low (< 2.2V) to disable the device. When driven high, EN draws 40µA to power the IC. Driving EN low forces LED1, LED2, LED3, LED4 and SET into a high-impedance state. Setting the Output Current SET controls the LED bias current. Current flowing into LED1, LED2, LED3 and LED4 is 240 times greater than the current flowing into SET. Set the output current as follows: Very Low-Cost, High-Efficiency Solution (Fig. 2). A battery (single Li+ or three NiMH cells) powers the LEDs directly. This is the least expensive and most efficient architecture. Due to the high forward voltage of white LEDs (3.3V), the LED brightness may dim slightly at the end of battery life. The T6311A current regulating architecture and low dropout greatly minimize this effect compared to using simple ballast resistors. The enable function of the T6311A turns on and off the LEDs. An existing low-dropout regulator is used as VCTRL. Brightness Adjustment Using a DAC (Fig. 3). A DAC is used as VCTRL such that the LED brightness may be dynamically adjusted to eliminate factory calibration. A battery (single Li+ or three NiMH cells) or a regulated power source drives the LEDs. ILED = 240 ( (VCTRL - VSET) / RSET ) where VSET = 1.2V, VCTRL is an external voltage between 1.8V and 5.5V, and RSET is the resistor connected between VCTRL and SET (Fig. 1). TM Technology Inc. reserves the right P.6 to change products or specifications without notice. Publication Date: JUN. 2005 Revision: C tm TE CH Preliminary Product spec. T6311A TYPICAL APPLICATION CIRCUITS V + V E x is tin g L D O C T R L T o o th e r c irc u its S E T L E D 1 L E D 2 L E D 3 L E D 4 O N E N O F F G N D Fig. 2 Very low-cost, high-efficiency solution V + D A C V C T R L SE T LE D 1 LE D 2 LE D 3 LE D 4 O N O FF E N G N D Fig. 3 Brightness adjust using DAC TM Technology Inc. reserves the right P.7 to change products or specifications without notice. Publication Date: JUN. 2005 Revision: C tm TE CH Preliminary Product spec. T6311A PACKAGE DIMENSIONS 8-LEAD SOP B B1 A1 C1 A C C2 F D Symbol A A1 B B1 C C1 C2 D E F H Min. 5.70 3.75 1.35 0.10 0.31 0.30 0.10 Dimension in mm Typ. 6.00 3.95 1.27 1.55 0.41 0.50 0.15 0~8° E H Max. 6.30 4.10 5.13 1.80 1.75 0.25 0.51 0.70 0.25 Min. 0.224 0.148 0.052 0.001 0.012 0.012 0.004 Dimension in inch Typ. 0.236 0.156 0.050 0.061 0.016 0.020 0.006 0~8° TM Technology Inc. reserves the right P.8 to change products or specifications without notice. Max. 0.248 0.164 0.202 0.071 0.069 0.004 0.020 0.028 0.010 Publication Date: JUN. 2005 Revision: C tm TE CH Preliminary Product spec. T6311A PACKAGE DIMENSIONS SOT23-6 B B 1 B 2 A 1 C 1 A C C 2 F D I Symbol A A1 B B1 B2 C C1 C2 D E F G H I Min. 2.60 1.40 2.70 0.95 0.90 0 0.30 0.08 Dimension in mm Typ. 2.80 1.575 2.85 1.90(BSC) 0.95(BSC) 1.20 1.10 0.075 0.40 0.45 0.15 0.60(REF) 0~8° 5~15° H Max. 3.00 1.60 3.00 Min. 0.102 0.055 0.106 1.45 1.30 0.150 0.037 0.035 0 0.60 0.22 0.012 0.003 G E Dimension in inch Typ. 0.110 0.062 0.112 0.075(BSC) 0.037(BSC) 0.047 0.043 0.003 0.015 0.018 0.006 TM Technology Inc. reserves the right P.9 to change products or specifications without notice. Max. 0.118 0.063 0.118 0.057 0.051 0.06 0.023 0.009 0~8° 5~15° Publication Date: JUN. 2005 Revision: C