ST Sitronix ST1208 3-Channel White LED Driver ! Features " " " " " " " " " " " " " High Efficiency Operation ( PLEDs / PBATT ) -- Extends battery life -- Peak efficiency over 88 % 1 / 1.5x Fractional Charge Pump Circuits -- extends voltage operate range Range of LED Driver Power -- 2.7 to 5.0V Drivability 30 mA/LED with Li-Ion Battery Operating Range Shutdown Mode Draws Less Than 1 uA Regulated to ± 3 % Output Current Matching Soft-Start Function To Limit Inrush Current Dimming Control by Logic or PWM No external Schottky Diode and Inductor Required Low Input Ripple and EMI Short Circuit and Over-Temperature Protection 2KV ESD Rating Thin QFN ( 4 mm X 4 mm ), Small TSSOP-16L Packages and Bare Chip ! Ordering Information Ordering No. ST1208-Q ST1208-T ST1208-B Package QFN-16 TSSOP-16L Bare Chip ! Description The ST1208 is a versatile change pump designed for use in battery operated power supply application. The wide input range is matched for Li-Ion battery applications. The ST1208 LED drivers feature a fractional change pump implementation with efficiency comparable to a switching regulator without costly inductors. Only four tiny ceramic capacitors are required, and no external inductor is required for operation that provides a reduced-EMI solution. Proprietary low noise mode switching circuit and constant output current allow the use of extremely small input and output capacitor. The ST1208 contains a thermal management circuit to protect the device under continuous output short circuit condition. ! Applications " Cellular phones " PDAs " Portable communication devices " LED/Display backlight driver " Digital Cameras " Handheld Electronics " Flash LED driver V1.1 1/12 2004/10/27 ST1208 ! Block Diagram V1.1 2/12 2004/10/27 ST1208 ! Pin Description Name GND IN OUT SET EN1 EN2 LED1 LED2 LED3 C1P C1N C2P C2N Function Ground Supply voltage input pin (2.7 ~ 5.0 V). Bypass IN to GND with a ceramic capacitor. Charge pump output pin. Bypass to GND with a ceramic capacitor. Connect to the anodes of all the LEDs. OUT is high impedance during shutdown. Variable output current pin by changing the resistant value. Connect a resistor from SET to GND to set the LED bias current. ISET = 0.6V / RSET Enable, Dimming Control Input. EN1 and EN2 control shutdown and the LED current. See the Applications Information section for brightness control. LED cathode connection and charge-pump feedback. The charge pump regulates to the lowest voltage on the LED1. Therefore, LED1 must be used at least. LED cathode connection. Connect LEDx to the cathode of one output LED. Let the LEDx floating if this LED is not populated. Charge Pump Capacitor 1 positive connection. Charge Pump Capacitor 1 negative connection. Charge Pump Capacitor 2 positive connection. Charge Pump Capacitor 2 negative connection. ! Pin Assignment Pin ( Pad ) Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 TSSOP-16 LED1 LED2 LED3 GND GND C1P C2P C1N VOUT C2N IN IN EN1 EN2 SET NC Pin ( Pad ) Name QFN-16 Bare Chip C2N LED1 VDD LED2 VDD LED3 EN1 GND EN2 GND SET C1P NC C2P LED1 C1N LED2 VOUT LED3 C2N GND IN GND IN C1P EN1 C1N EN2 C2P SET VOUT NC TSSOP-16 QFN-16 V1.1 3/12 2004/10/27 ST1208 ! Bare Chip Pad Arrangement ! Bare Chip Pad Location Coordinates V1.1 Pad No. Function X Y 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 LED1 LED2 LED3 GND GND C1P C2P C1N VOUT C2N IN IN EN1 EN2 SET NC -641.5 -641.5 -641.5 -641.5 -641.5 -641.5 -641.5 -641.5 609.5 609.5 640.5 640.5 640.5 640.5 103.5 -189.5 718 386 163 28 -72 -318 -750 -900 -777.3 -546 9 109 320 547 769 903 4/12 2004/10/27 ST1208 ! Function Description The ST1208 is a complete charge-pump buck-boost converter which is requiring only four small ceramic capacitors. In order to regulated constant current for uniform intensity, the ST1208 utilizes a proprietary 1x/1.5x fractional charge-pump topology to drive up three white LEDs. While two digital inputs control on/off and provide brightness control, an external resistor (RSET) programs the full-scale LED current. The ST1208 operates with a 1MHz fixed frequency. the IC cools by approximately 20°C. Output Regulation The ST1208 operates in 1x mode until just above dropout. Then the ST1208 switches to 1.5x charge pump mode to regulate the LED1 to 300mV and maintain constant LED brightness even at very low battery voltages. Using this topology, there is no LED brightness change from 1x to 1.5x. which guarantees no flicker on the display. The 1x mode produces almost no ripple, while the 1.5x mode regulates the output voltage by controlling the rate at which the charge pump capacitors are charged. In this way, the switching frequency remains constant for reduced input ripple and stable noise spectrum. SET control the LED bias current. Current into LED1, LED2 and LED3 is a multiple of the current flowing out of SET. Set the output current as follows: ILEDx = K X ( 0.6 / RSET ) Where K = 160, 48 or 16 ( depending upon EN1 and EN2. see Table1 ), and RSET is the resistor connected between SET and GND. Soft Start Shutdown Mode When EN1 and EN2 are grounded, the ST1208 is in shutdown. The shutdown current is less than 1uA. ST1208 which is out of shutdown will be operated in 1x mode while the input voltage is higher than output voltage. Thermal Shutdown The ST1208 includes a thermal-limit circuit that shutdown the IC at about +160°C. Turn-on occurs after V1.1 Setting the Output Current 5/12 The ST1208 includes soft-start circuitry to limit inrush current at turn-on. When starting up with an output voltage that is not near the input voltage, the output capacitor is charged directly from the input with a ramped current source until the output voltage is near the input voltage. Once this occurs, the charge pump determines if 1x or 1.5x mode is required. In the case of 1x mode, the soft start is terminated and normal operation begins. In the case of 1.5x mode, soft-start operates until the LED1 reaches regulation. 2004/10/27 ST1208 ! Applications Information Dimming Using EN1 and EN2 ( See Figure 1. ) Input Ripple ( See Figure 4. ) Use EN1 and EN2 inputs as a digital 2-bit number to control on/off, 1/10, 3/10 and full current ( see Table1 ). RSET programs the full current level ( see the Setting the Output Current section ). For LED drivers, input ripple is more important than output ripple. Input ripple depends on the source supply’s impedance. Adding a lowpass filter to the input further reduce input ripple. Figure 4 shows a C-R-C filter used to reduce input ripple to less than 2mVp-p when driving a heavy load or flash LED. EN1 0 0 1 1 EN2 0 1 0 1 BRIGHTNESS LED CURRENT Shutdown ILED = 0 1/10 Brightness ILED = 16 X ISET 3/10 Brightness ILED = 48 X ISET Full Brightness ILED = 160 X ISET Table 1. Brightness Control Dimming Using PWM into EN1 ( See Figure 2. ) Use EN2 for shutdown and drive EN1 with a PWM signal. Current can be varied from 1/10 to full. The maximum frequency of PWM is 10 KHz. ILED = K·ISET· ( 0.9·PWM + 0.1 ) Where K = 160, PWM = 0% ~ 100%. Dimming Using a Filtered PWM Signal ( See Figure 3. ) Use a high-frequency PWM signal to drive an R-C-R filter on the SET pin. A 0% PWM duty cycle corresponds to 20mA/LED, while a 100% PWM duty cycle corresponds to 0mA/LED. At PWM frequencies above 5 KHz, C may be reduced. Figure 1. Typical Operating Circuit V1.1 PCB Layout and Routing The ST1208 is a high-frequency switched-capacitor voltage regulator. For best circuit performance, use a solid ground plane and place CIN and COUT as close to the ST1208 as possible. Also, place their ground pads close together and as close as possible to GND. Making the bias current clear can enhance stability of the LED output current, Component Selection For high efficiency performance, how to choose the component is the most important. Low ESR capacitor can reduce the output voltage ripple and increase the voltage of charge pump. The ceramic capacitor with an X5R or X7R is the best. The efficiency of 1x mode is over 15% higher than 1.5x mode. Therefore, higher input voltages or the low forward voltage of LED can make the ST1208 switch to 1x mode. Figure 2. Dimming Using PWM Signal into EN1 6/12 2004/10/27 ST1208 ! Applications Information………………………………. ( Continued ) Figure 3. Dimming Using Filtered PWM Signal Figure 4. C-R-C Filter Reduces Input Ripple V1.1 7/12 2004/10/27 ST1208 ! Absolute Maximum Ratings IN, OUT, EN1, EN2 to GND ........……..…....... -0.3V to + 6.0V SET, LED1, LED2, LED3 to GND ….… -0.3V to ( VIN + 0.3V ) C1N, C2N to GND .........................…..... -0.3V to ( VIN + 1V ) C1P, C2P to GND ...........................……... -0.3V to greater of .................................................. ....(VOUT + 1V) or (VIN + 1V) Continuous Power Dissipation (TA = +70°C) 16-Pin QFN ( de-rate 17 mW/°C above +70°C ) 1350 mW 16-Pin TSSOP ( de-rate 18 mW/°C above +70°C ) 1500 mW Operating Temperature Range ...….................-40°C to +85°C Storage Temperature Range .…....................-40°C to +125°C ! Electrical Characteristics Condition: VIN = VEN1 = VEN2 = 3.6 V, CIN = C1 = C2 = COUT = 1 uf, dropout current is 60 mA. ( 20 mA / LED X 3 ), LED Vf = 3.3 V, ISET = 125 uA, Charge pump switching ( TA = +25℃) Symbol Parameter VIN IIN IOUT IN Operating Voltage Power Supply Current Maximum OUT Current ILED Maximum LEDx Sink Current IINS ILSS Shutdown Supply Current SET Leakage in Shutdown ILLS ISET VIH VIL IEN LED Leakage in Shutdown SET Current Range EN1, EN2 Logic High Voltage EN1, EN2 Logic Low Voltage EN1, EN2 Input Current LEDx Minimum Regulation Voltage (1.5x Mode) LEDx Dropout Voltage VLED VDP Test Condition Switching, no load VIN >=3.6 V, EN1 = EN2 = IN VIN >=3.3 V, ISET = 190 uA, EN1 = EN2 = IN EN1 = EN2 = GND EN1 = EN2 = GND, TA = 25℃ EN1 = EN2 = GND, TA = 25℃ VIN=2.7 V to 5.0 V VIN=2.7 V to 5.0 V VENx = GND or 5.0 V, TA = 25℃ EN1 = EN2 = IN, ISET = 125 uA ISET = 125 uA 1x mode ( 1 X VIN - VOUT ) / IOUT @ VIN = 4.2 V, IOUT = 60 mA ROUT Open-Loop OUT Resistance 1.5x mode ( 1.5 X VIN - VOUT ) / IOUT @ VIN = 3.6 V, IOUT = 60 mA ± 20% fSW Switching Frequency 20℃ hysteresis TTS Thermal-Shutdown Threshold VUV Undervoltage Lockout Threshold VIN rising or falling, 0.25V hysteresis EN1 = EN2 = IN SET to LEDx Current Ratio K ISET= 125 uA EN1 = IN, EN2 = GND ( ILED / ISET ) EN1 = GND, EN2 = IN EN1 = EN2 = IN, RSET = 4.8KOhm, A LEDx Current Accuracy TA = 0℃ ~ 85℃ EN1 = EN2 = IN, ISET = 125 uA, M LEDx Current Matching TA = 0℃ ~ 85℃ ( Note 1 ) η Peak efficiency in 1x mode IOUT = 60 mA, PLEDs / PIN X 100 % Note1: LEDx current matching is define as : ( ILEDX - IAVG ) / IAVG X 100 %. V1.1 8/12 Min. Typ. Max. Unit 2.7 100 2.0 5.0 4.0 - V mA mA 28 30 - mA - 1 0.01 3 0.1 uA uA 30 0.7 VIN 0 - 0.01 0.5 0.1 200 VIN 0.2 VIN 1.0 uA uA V V uA 200 300 400 mV - 20 30 mV - 7 10 - 11 15 0.8 130 2.2 145 43 14 1.0 160 2.3 160 48 16 1.2 190 2.6 175 52 17 MHz ℃ V - ±3 - % - ±3 - % 80 88 - % Ohm A/A 2004/10/27 ST1208 ! Typical Operating Characteristics Condition: VIN = VEN1 = VEN2 = 3.6 V, CIN = C1 = C2 = COUT = 1 uf, dropout current is 60 mA. ( 20 mA / LED X 3 ), LED forward voltage Vf = 3.3 V, ISET = 125 uA EFFICIENCY ( PLEDs / PBATT ) vs. Li + BATTERY DISCHARGE 90 EFFICIENCY ( % 80 45mA 70 60mA 60 90mA 100mA 50 40 4.2 4.1 4.0 3.9 3.8 3.7 3.6 3.5 3.4 Li+ BATTERY VOLTAGE, TIME-WEIGHTED ( V ) LED CURRENT vs. SUPPLY VOLTAGE Under-Voltage Protection IIN ( mA ) 19 60 40 LED CURRENT ( mA Increase Reduce 50 30 20 10 18 17 16 LED1 LED2 LED3 15 14 13 12 0 2.1 2.3 2.5 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5 2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3 3.1 3.2 3.3 VIN ( V ) SUPPLY VOLTAGE ( V ) ILED vs. ISET ILED ( mA ) 50 VIN > 3.3 V 40 VIN = 3.0 V ILED = 30 mA @ Iset = 190 30 VIN = 2.7 V 20 10 0 10 30 60 90 0 12 0 15 0 18 0 21 0 24 ISET ( uA ) VIN = 2.7 V VIN = 3.6 V V1.1 VIN = 3.0 V VIN = 4.2 V 9/12 VIN = 3.3 V VIN = 5.0 V 2004/10/27 ST1208 ! Package Information TSSOP-16L NOTE: 1. CONTROLLING DIMENSION : mm 2. LEAD FRAME MATERIAL : OLIN C7025/EFTEC 64T 3. DIMENSION “D” DOES NOT INCLUDE MOLD FLASH, TIE BAR BURRS AND GATE BURRS. MOLD FLASH, TIE BAR BURRS AND GATE BURRS SHALL NOT EXCEED 0.006” [0.15mm] PER END DIMENSION “E1” DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010” [0.25mm] PER SIDE. 4. DIMENSION “b” DOES NOT INCLUDE DAMBAR PROTRUSION. ALLOWABLE DAMBAR PROTRUSION SHALL BE 0.003” [0.08mm] TOTAL IN EXCESS OF THE “b” DIMENSION AT MAXIMUM MATERIAL CONDITION. DAMBAR CANNOT BE LOCATED ON THE LOWER RADIUS OR THE FOOT. MINIMUM SPACE BETWEEN PROTRUSION AND AN ADJACENT LEAD TO BE 0.0028 “ [0.07mm] 5. TOLERANCE: +/- 0.010” [0.25mm] UNLESS OTHERWISE SPECIFIED. 6. OTHERWISE DIMENSION FOLLOW ACCEPTABLE SPEC. 7. REFERENCE DOCUMENT : JEDEC SPEC MO-153 V1.1 10/12 SYMBOLS A A1 A2 b C D DIMENSIONS IN MILLIMETERS MIN NOM MAX 1.05 1.10 1.20 0.05 0.10 0.15 1.00 1.05 0.20 0.25 0.28 0.127 4.90 5.075 5.10 E E1 e L y th 6.20 4.30 0.50 0˚ 6.40 4.40 0.65 0.60 4˚ 6.60 4.50 0.70 0.076 8˚ DIMENSIONS IN INCHES MIN NOM MAX 0.041 0.043 0.047 0.002 0.004 0.006 0.039 0.041 0.008 0.010 0.011 0.005 0.193 0.1998 0.200 ( *1 ) 0.244 0.252 0.260 0.170 0.173 0.177 0.026 0.020 0.024 0.028 0.003 0˚ 4˚ 8˚ 2004/10/27 ST1208 ! Package Information……………………………………. ( Continued ) QFN-16 ° ° ° DIM. A A1 A2 A3 b c D D1 E E1 e J K L R V1.1 MIN. 0.8 0 0.65 0.25 0.24 2.37 2.37 0.3 0.685 NOM. 0.02 0.203 REF 0.3 0.42 4 BSC 3.75 BSC 4 BSC 3.75 BSC 0.65 BSC 2.47 2.47 0.4 0.785 MAX. 0.9 0.05 0.69 0.35 0.6 2.57 2.57 0.5 0.885 NOTES 1. DIE THICKNESS ALLOWABLE IS 0.305mm MAXIMUM ( .012 INCHES MAXIMUM ). 2. DIMENSION APPLIES TO PLATED TERMINAL AND IS MEASURED BETWEEN 0.2 AND 0.25 mm FROM TERMINAL TIP. 3. THE PIN #1 IDENTIFIER MUST BE EXISTED ON THE TOP SURFACE OF THE PACKAGE BY USING INDENTATION MARK OR OTHER FEATURE OF PACKAGE BODY. 4. EXACT SHAPE AND SIZE OF THIS FEATURE IS OPTIONAL. 5. APPLIED FOR EXPOSED PAD AND TERMINALS. EXCLUDE EMBEDDING PART OF EXPOSED PAD FROM MEASURING. 6. APPLIED ONLY THE TERMINALS. 7. EXACT SHAPE OF EACH CORNER IS OPTIONAL UNIT DIMENSION AND TOLERANCES REFERENCE DOCUMENT MM ASME Y14.5M 98A0016PN004 11/12 2004/10/27 ST1208 ST1208 Serial Specification Revision History Version Date 0.2c 2004/05/05 1. Take off PHO function. 2. Release TBD value. 0.2e 2004/07/26 1. Add the drawing of QFN package. 2. Adjust the characteristic for ST1208. 1.0 2004/08/19 1. a-site release. ( Ver0.2e # Ver1.0 ) 1.1 2004/10/27 1. Add the bare chip information. V1.1 Revision Description 12/12 2004/10/27