TK11850L WHITE LED DRIVER FEATURES APPLICATIONS n Very High Speed Adjustable OSC (Max 800 kHz) n Very Wide Operating Voltage Range (2.3 V to 10 V) n Low Loss Detector (Low Reference Voltage: n LED Backlighting and Frontlighting n LED Flashlights n Step-up DC-DC Converters n n n n n n V REF = 0.5 V) Operates with Toko D31FU Miniature Coil (Current Limited by Input Current Sensor) Internal Switching Transistor Internal Diode Active High On / Off Control Available Intensity Control Using EN Pin with PWM Signal Very Small SOT23L-8 Surface Mount Package voltage increase or the inrush current as start-up) that flows through the coil. The ON /OFF control is built-in and the circuit current can be decreased when the EN pin is low (standby mode). The white LEDs can be dimmed by applying a PWM signal to the EN (ON/OFF control) pin. With this method, the white LED brightness is still controlled by constant current resulting in constant chromaticity. The TK11850L is available in the SOT23L-8 surface mount package. DESCRIPTION The TK11850L is a pulse skipping step-up DC-DC converter IC designed for White LED driver applications with the following built in: a very high current switching transistor (400 mA peak), an inductor current limit detector, low voltage reference (Vref = 0.5 V), high speed oscillator, an error comparator, a rectifier diode (for small power output) and an ON/OFF control. The IC works with a very wide operating supply range (2.3 V to 10 V) and the adjustable output voltage can be set as high as 20 V. The device is in the ON state when the EN pin is pulled to a high level. Using the very small TK11850L and a few external components, battery powered systems with LCD displays such as digital cameras and cellular phones can be effectively backlit with white LEDs. The white LEDs are connected in series and driven at a constant current resulting in uniform brightness and high efficiency. This IC has an oscillator, which allows the designer to set the operating frequency by an external capacitor with the output controlled by pulse skipping. The reference voltage is a very low 0.5 V, achieving high efficiency operation with the constant current output. A small coil can be used because the inductor current limit detector circuit limits the peak current (caused by an input TK11850 VIN 8 EN IS 7 CX EXT GND VOUT VFB BLOCK DIAGRAM 0.1 V VIN IS COMP BAND GAP REFERENCE + 8 EN OSC 0.86 V CX IS 7 CX 0.3 V CLK CLK ORDERING INFORMATION TK11850L EXT GND S Tape/Reel Code Q R ERROR COMP + VOUT VFB VREF 0.525 V TAPE/REEL CODE TL: Tape Left May 2001 TOKO, Inc. Page 1 TK11850L ABSOLUTE MAXIMUM RATINGS Supply Voltage ........................................................ 20 V Switching Voltage .................................................... 20 V Operating Voltage Range ............................... 2.3 to 10 V Power Dissipation (Note 1) ................................. 400 mW Storage Temperature Range ..................... -55 to +150 °C Operating Temperature Range ..................... -30 to +85 °C Switching Peak Current ....................................... 400 mA Diode Current ........................................................ 10 mA Maximum Frequency ...................................... ~ 800 kHz TK11850 ELECTRICAL CHARACTERISTICS Test Conditions: VIN = 3 V, VIS =VEN = VIN, VEXT = Open, VFB = GND, CX = 100 pF, TA = 25 °C, unless otherwise specified. SYMBOL PARAMETER TEST CONDITIONS MIN TYP MAX UNITS OSCILLATOR SECTION (CX PIN) ICHG CX Charging Current VCX = 0.1 V 16 22 30 mA IDIS CX Discharging Current VCX = 1.0 V 35 49 65 mA IDIS / ICHG Charge and Discharge Current Ratio VCX (HIGH) CX Threshold Voltage + VCX at ICHG = 0mA 810 860 910 mV VCX (LOW) CX Threshold Voltage - VCX at IDIS = 0mA 260 300 340 mV VOSC CX Oscillation Voltage (Vth +) - (Vth -) 520 560 600 mV 2.2 CURRENT LIMITING COMPARATOR SECTION (IS PIN) VLIMIT Current Limit Sense Voltage VLIMIT = VIN - VIS 72 77 82 mV IIsIn IS Pin Bias Current VIN = VIS = 3 V 5 10 15 mA OUTPUT SWITCH SECTION (EXT PIN) VSW, Sat Output Transistor Saturation Voltage VCX = 0 V, ISW = 200 mA 0.2 0.4 V ISW, Off Output Transistor Off Leakage Current VFB = 1 V, VEXT = 20 V 0.01 2 mA 0.505 0.525 0.545 V -2 -0.3 FEEDBACK COMPARATOR SECTION (VFB PIN) VREF IFBIn Reference Voltage VFB Pin Output Current VFB = 0.4 V mA Note 1: Power dissipation is 400 mW when mounted. Derate at 3.2 mW / °C for operation above 25 °C. Page 2 May 2001 TOKO, Inc. TK11850L TK11850 ELECTRICAL CHARACTERISTICS (CONT) Test Conditions: VIN = 3 V, VIS =VEN = VIN, VEXT = Open, VFB = GND, CX = 100 pF, TA = 25 °C, unless otherwise specified. SYMBOL PARAMETER TEST CONDITIONS MIN TYP MAX UNITS 2 V SHUTDOWN SECTION (EN PIN) VEN (HIGH) EN Threshold Voltage + On Mode VEN (LOW) EN Threshold Voltage - Shutdown Mode 0.6 IENIn EN Pin Bias Current VIN = VEN = 3 V 2 V 5 8 mA DIODE SECTION (EXT PIN - VOUT PIN) VF Forward Voltage ID = 10 mA 0.75 V VIN SECTION (VIN PIN) VIN (LOW) Low Voltage Stop 1.7 2.0 2.3 V VIN (HIGH) High Voltage Output Stop 11 12.5 14 V ICC (Off) Shutdown Supply Current VEN = 0 v 0.01 1 mA ICC (On) Quiescent Supply Current VFB = 1 V 1.5 2 mA 1 Reference Value η Efficiency ILOAD = 20 mA, VOUT = 16.5 V, VIN = 3.6 V (Note 2) 78 % Note 2: This value is different depending on the components used, circuit conditions, etc. Thus, this is reference data only. Refer to Reference data test circuit. May 2001 TOKO, Inc. Page 3 TK11850L TEST CIRCUIT ICC IEN VIN EN 8 VEN V VIN VIN V 10 µF IDIS ICHG IIS IS CX 7 VCX VIS V V 100 pF IEXT GND VOUT VFB VEXT V IVOUT V EXT IFB VFB V VVOUT REFERENCE DATA TEST CIRCUIT RSC 0.22Ω ICC VIN 3.6 V V ILOAD L 15µ D 2200p VOUT 20 mA COUT 47µ CIN 47µ VIN IS VOUT EXT 620k 8 EN TK11850L VFB L = 15 mH D52LC (A914BYW - 150M) Toko D - SB07 - 03C Sanyo 7 CX GND 20k CX 56 pF Page 4 May 2001 TOKO, Inc. TK11850L TYPICAL PERFORMANCE CHARACTERISTICS TA = 25 °C, unless otherwise specified. OSC PERIOD vs. CX OSC FREQUENCY vs. TEMPERATURE 300 0 100 200 CX CAPACITANCE (pF) 280 VIN = 10 V 260 240 220 VIS = VEN =VIN CX = 100 pF 200 180 300 -30 INDUCTOR CURRENT-LIMIT SENSE VOLTAGE (mV) 85 °C 300 200 VIN = 3 V VIS = VEN = VIN VFB = 0 V VCX = 0 V 100 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 SWITCH SATURATION VOLTAGE (V) 100 90 528 526 VIS = VEN = VIN 522 520 518 80 85 °C 70 60 Vlimit = VIS - VIN VEN = VIN 50 40 30 20 10 0 2 4 6 8 10 SUPPLY VOLTAGE (V) 2 4 6 8 SUPPLY VOLTAGE (V) May 2001 TOKO, Inc. 10 -20 °C 25 °C 85 °C 80 70 60 50 40 30 20 VIN = VEN = VIS VFB = 1 V 10 0 0 2 4 6 8 10 12 14 16 18 20 IS VOLTAGE (V) SUPPLY CURRENT vs. EN VOLTAGE 10 9 VIN = 3 V VIS = VEN = VIN 528 1000 vs. IS VOLTAGE 12 526 524 522 520 518 8 -20 °C 25 °C 85 °C 7 6 5 4 3 VIN = 3 V VIS = VIN VFB = 0 V CX = 100 pF 2 1 0 516 516 100 OSC FREQUENCY (kHz) IS INPUT BIAS CURRENT 530 REFERENCE VOLTAGE (mV) REFERENCE VOLTAGE (mV) 10 REFERENCE VOLTAGE vs. TEMPERATURE 530 0 70 100 90 -20 °C 25 °C REFERENCE VOLTAGE vs. SUPPLY VOLTAGE 524 75 65 90 SUPPLY CURRENT (mA) SWITCHING CURRENT (mA) -20 °C 25 °C -10 10 30 50 70 TEMPERATURE (°C) VIN = 3 V VIS = VEN = VIN VFB = 0 V INDUCTOR CURRENT-LIMIT SENSE VOLTAGE vs. SUPPLY VOLTAGE 500 400 80 VIN = 3 V VIN = 5 V MAXIMUM DUTY CYCLE (%) VIN = 3 V VIS = VEN = VIN SWITCHING CURRENT vs. SWITCH SATURATION VOLTAGE 0 MAXIMUM DUTY CYCLE vs. OSC FREQUENCY IS INPUT BIAS CURRENT (µA) 12 11 10 9 8 7 6 5 4 3 2 1 0 OSC FREQUENCY (kHz) OSC PERIOD (µS) CAPACITANCE -30 -10 10 30 50 70 TEMPERATURE (°C) 90 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 EN VOLTAGE (V) Page 5 TK11850L TYPICAL PERFORMANCE CHARACTERISTICS (CONT.) TA = 25 °C, unless otherwise specified. SUPPLY CURRENT vs. EN INPUT BIAS CURRENT 8 7 6 VIN = 3 V VIS = VIN VFB = 0 V CX = 100 pF 5 4 3 2 -20 °C 25 °C 1 0 85 °C EN INPUT BIAS CURRENT (µA) SUPPLY CURRENT (mA) 10 9 EN INPUT BIAS CURRENT vs. EN VOLTAGE 100 90 -20 °C 25 °C 85 °C 80 70 60 50 40 30 20 VIN = 3 V VIS = VIN 10 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 EN INPUT BIAS CURRENT (µA) 0 2 DIODE CURRENT vs. DIODE FORWARD VOLTAGE 2 1.8 8 SUPPLY CURRENT (mA) DIODE CURRENT (mA) 6 8 10 12 14 16 18 20 EN VOLTAGE (V) SUPPLY CURRENT vs. SUPPLY VOLTAGE 10 VIS = VEN = VIN 6 4 2 1.6 1.4 1.2 1 VIS = VEN = VIN VFB = 1 V CX = 100 pF 0.8 0.6 0.4 -20 °C 25 °C 0.2 0 4 300 400 500 600 700 800 DIODE FORWARD VOLTAGE (mV) 0 85 °C 0 1 2 3 4 5 6 7 8 9 SUPPLY VOLTAGE (V) 10 SUPPLY CURRENT vs. SUPPLY VOLTAGE (SHUTDOWN MODE) SUPPLY CURRENT (µA) 10 9 -20 °C 25 °C 85 °C 8 VIS = VIN VEN = 0.6 V 7 6 5 4 3 2 1 0 Page 6 0 2 4 6 8 10 12 14 16 18 20 SUPPLY VOLTAGE (V) May 2001 TOKO, Inc. TK11850L APPLICATION CIRCUIT (2 LEDs in Series) VIN VIN 0.1 V IS COMP EN BAND GAP REFERENCE + CIN 4.7 µF ON/OFF 8 - RSC 0.39 Ω OSC 0.86 V IS GND CX CX 7 0.3 V CLK CLK L 33 uH D31FU TOKO CX 100 pF GND EXT • Input Voltage: 2.7 V • LED Current : 20 mA • On/Off: Pin Number 8 (EN Pin) S SB07-03C SANYO VOUT Q ERROR COMP VFB + R RLED 27 Ω VREF 0.525 V LED Current (ILED) is set by RLED. ILED doesn’t depend on VIN because ILED is controlled by the feedback circuit. COUT 2.2 uF VLED ILED TYPICAL PERFORMANCE CHARACTERISTICS TA = 25 °C, unless otherwise specified. LED Current and Efficiency Characteristics VIN (V) IIN (mA) VLED (V) ILED (mA) EF LED (%) 2.7 71.3 7.01 18.81 68.6 3.0 62.9 7.01 18.85 70.0 3.5 52.8 7.02 18.95 71.9 4.5 39.9 7.02 19.10 74.8 L: D31FU, 33 mH Toko Part Number: 888FU-330M EF LED (%) = 100 * VLED * ILED / VIN * IIN EF LED vs. VIN ILED vs. VIN 80 18 ILED (mA) 20 EF LED (%) 100 60 40 20 0 16 14 12 0 2 4 VIN (V) May 2001 TOKO, Inc. 6 10 0 2 4 6 VIN (V) Page 7 TK11850L APPLICATION CIRCUIT (3 LEDs in Series) VIN VIN 0.1 V IS COMP EN BAND GAP REFERENCE + CIN 4.7 µF ON/OFF 8 - RSC 0.27 Ω OSC 0.86 V IS GND Cx CX 7 0.3 V CLK CLK L 22 uH D31FU TOKO • Input Voltage: 2.7 V • LED Current: 20 mA • On/Off: Pin Number 8 (EN Pin) CX 82 pF GND EXT SB07-03C SANYO S LED Current (ILED) is set by RLED. ILED doesn’t depend on VIN because ILED is controlled by the feedback circuit. VOUT Q ERROR COMP VFB RLED 27 Ω + R VREF 0.525 V COUT 2.2 uF VLED ILED TYPICAL PERFORMANCE CHARACTERISTICS (CONT.) TA = 25 °C, unless otherwise specified. LED Current and Efficiency Characteristics VIN (V) IIN (mA) VLED (V) ILED (mA) EF LED (%) 2.5 115.9 10.38 19.41 69.52 2.7 106.9 10.38 19.49 70.09 L: D31FU, 22 mH Toko Part Number: 888FU-220M EF LED (%) = 100 * VLED * ILED / VIN* IIN 3.0 95.4 10.38 19.52 70.83 3.5 79.1 10.38 19.52 73.19 4.5 59.2 10.39 19.56 76.26 6.0 42.9 10.39 19.60 79.04 EF LED vs. VIN ILED vs. VIN 80 18 ILED (mA) 20 EF LED (%) 100 60 40 20 0 Page 8 16 14 12 0 2 4 VIN (V) 6 8 10 0 2 4 VIN (V) 6 8 May 2001 TOKO, Inc. TK11850L APPLICATION CIRCUIT (4 LEDs in Series) VIN VIN 0.1 V IS COMP EN BAND GAP REFERENCE + CIN 4.7 µF ON/OFF 8 - RSC 0.22 Ω OSC 0.86 V IS GND CX CX 7 0.3 V CLK CLK L 15 uH D52LC TOKO • Input Voltage: 2.7 V • LED Current: 20 mA • On/Off: Pin Number 8 (EN Pin) CX 56 pF GND EXT SB07-03C SANYO LED Current (ILED) is set by RLED. ILED doesn’t depend on VIN because ILED is controlled by the feedback circuit. S VOUT Q ERROR COMP VFB RLED 27 Ω + R VREF 0.525 V COUT 2.2 uF VLED ILED TYPICAL PERFORMANCE CHARACTERISTICS (CONT.) TA = 25 °C, unless otherwise specified. LED Current and Efficiency Characteristics VIN (V) IIN (mA) VLED (V) ILED (mA) EF LED (%) 2.5 144.4 13.68 19.32 73.30 2.7 132.2 13.68 19.30 73.97 L: D52LC, 15 mH Toko Part Number: A914BYNW - 150M EF LED (%) = 100 * VLED * ILED / VIN * IIN 3.0 117.9 13.68 19.27 74.44 3.5 99.0 13.68 19.28 76.07 4.5 75.3 13.68 19.35 78.06 6.0 55.3 13.68 19.34 79.71 EF LED vs. VIN ILED vs. VIN 80 18 ILED (mA) 20 EF LED (%) 100 60 40 20 0 16 14 12 0 May 2001 TOKO, Inc. 2 4 VIN (V) 6 8 10 0 2 4 VIN (V) 6 8 Page 9 TK11850L DIMMING The following are 3 kinds of dimming methods. 1. Dimming by RLED The current of the LED (ILED) is determined by RLED,which can be set by switches such as transistors. Example of 3 LEDs with a 4 brightness level circuit: VIN VIN 0.1 V IS COMP EN BAND GAP REFERENCE + CIN ON/OFF 8 - RSC OSC 0.86 V IS GND Cx ILED = CX 7 0.3 V CLK VREF RLED CLK L CX RLED: Total value of Resistors VREF = 0.525 V (typ) VFB Voltage = 0.525 V (typ) CLK GND EXT D S VOUT Q ERROR COMP VFB + R VREF 0.525 V COUT VLED ILED RLED2 RLED1 SW1 CONTROL SIGNAL 1 RLED3 CONTROL SIGNAL 2 SW2 ILED vs. RLED RLED (9) ILED (mA) 24 21.9 LED CURRENT (ILED) vs. TOTAL RESISTANCE (RLED) 20 18 19.5 36 14.6 51 10.4 ILED (mA) 27 16 14 12 10 8 6 4 100 5.4 510 1.1 2 0 Page 10 10 100 RLED (Ω) 1000 May 2001 TOKO, Inc. TK11850L DIMMING (CONT) 2. PWM Dimming Apply the PWM signal to the EN Terminal (Pin no. 8). In this case, a signal frequency of approximately120 Hz is adequate. The average current of the LED changes due to the On/Off cycle of the IC, which follows the duty cycle of the PWM signal. Set the PWM signal at a high level over 2 V and a low level under 0.6 V, with a driving current over 2 mA. VIN VIN 0.1 V IS COMP EN BAND GAP REFERENCE + CIN ON/OFF 8 - RSC OSC 0.86 V IS GND Cx CX 7 0.3 V LED CURRENT CURVE vs. PWM SIGNAL CURVE CLK CLK L LED SETTING CURRENT CX LED CURRENT CLK GND EXT D Ton S VOUT Q ERROR COMP Toff VFB + R 2.0 V VREF 0.525 V PWM SIGNAL 0.6 V (Applied to On/Off pin.) fdim = 1 / T = 120 Hz Duty (%) = (Ton * 100) / T T COUT VLED ILED RLED (LED CURRENT) The PWM dimming LED current follows the PWM signal. (As shown above) The average LED current is obtained from the formula below. The graph below shows an example with ILED(MAX) (20 mA) at a Duty Cycle up to 100%. ILED(AVG) = ILED(MAX) * Duty ILED vs. DUTY 100 DUTY (%) ILED (mA) 100 20.0 90 18.0 80 16.0 70 14.0 18 60 12.0 14 50 10.0 40 8.0 30 6.0 20 4.0 LED CURRENT (ILED) vs. DUTY CYCLE OF INPUT PWM SIGNAL 20 ILED (mA) 16 12 10 8 6 4 2 10 May 2001 TOKO, Inc. 2.0 0 0 20 40 60 DUTY CYCLE (%) 80 100 Page 11 TK11850L Input PWM signal curve vs. LED current curve (ex. Three LEDs, Output current 20 mA) LED CURRENT 10 mA/Div (1) Duty Cycle = 80% 2.0 mSec/Div PWM SIGNAL 1.0 V/Div (Applied to On/Off pin.) 2.0 mSec/Div LED CURRENT 10 mA/Div (2) Duty Cycle = 50% 2.0 mSec/Div PWM SIGNAL 1.0 V/Div (Applied to On/Off pin.) 2.0 mSec/Div LED CURRENT 10 mA/Div (3) Duty Cycle = 20% 2.0 mSec/Div PWM SIGNAL 1.0 V/Div (Applied to On/Off pin.) 2.0 mSec/Div Page 12 May 2001 TOKO, Inc. TK11850L DIMMING (CONT) 3. Dimming by DAC (D/A Converter) output Dimming is achievable by applying a DAC output to the VFB terminal with the addition of RDAC1 and RDAC2. VIN VIN 0.1 V IS COMP EN BAND GAP REFERENCE + CIN ON/OFF 8 - RSC OSC 0.86 V IS GND Cx CX 7 0.3 V CLK CLK L CX CLK GND EXT D S VOUT Q ERROR COMP VFB + R DAC OUTPUT RDAC1 VREF 0.525 V RDAC2 COUT VLED RLED 1 ILED Example Conditions: RDAC1 = RDAC2 RLED = 49 W ILED vs. VDAC DAC VOLTAGE (V) LED CURRENT (mA) 0.1 19.58 0.2 17.45 0.3 15.32 0.4 13.21 0.5 11.08 LED CURRENT (ILED) vs. DAC VOLTAGE (VDAC) 20 18 16 0.6 8.95 0.7 6.84 0.8 4.71 0.9 2.6 1 0.5 ILED (mA) 14 12 10 8 6 4 2 May 2001 TOKO, Inc. 0 0 0.2 0.4 0.6 VDAC (V) 0.8 1 Page 13 TK11850L PACKAGE OUTLINE Marking Information SOT23L-8 Marking 0.45 TK11850L 5 1.0 8 1850 e1 3.0 Marking e 0.8 1 4 Recommended Mount Pad +0.15 e 0.8 0.3 - 0.05 3.5 0.1 Çl +0.3 - 0.1 2.2 15 max 1.2 +0.15 - 0.15 0.15 0.1 0 - 0.1 1.4max (0.3) (3.4) 0.4 3.3 + 0.3 Dimensions are shown in millimeters Tolerance: x.x = ± 0.2 mm (unless otherwise specified) Toko America, Inc. Headquarters 1250 Feehanville Drive, Mount Prospect, Illinois 60056 Tel: (847) 297-0070 Fax: (847) 699-7864 TOKOAMERICAREGIONALOFFICES Midwest Regional Office Toko America, Inc. 1250 Feehanville Drive Mount Prospect, IL 60056 Tel: (847) 297-0070 Fax: (847) 699-7864 Western Regional Office Toko America, Inc. 2480 North First Street , Suite 260 San Jose, CA 95131 Tel: (408) 432-8281 Fax: (408) 943-9790 Semiconductor Technical Support Toko Design Center 4755 Forge Road Colorado Springs, CO 80907 Tel: (719) 528-2200 Fax: (719) 528-2375 Visit our Internet site at http://www.tokoam.com The information furnished by TOKO, Inc. is believed to be accurate and reliable. However, TOKO reserves the right to make changes or improvements in the design, specification or manufacture of its products without further notice. TOKO does not assume any liability arising from the application or use of any product or circuit described herein, nor for any infringements of patents or other rights of third parties which may result from the use of its products. No license is granted by implication or otherwise under any patent or patent rights of TOKO, Inc. Page 14 © 1999 Toko, Inc. All Rights Reserved May 2001 TOKO, Inc. IC-XXX-TKXXXXX 0798O0.0K Printed in the USA