MP1521 High Efficiency White LED Driver Monolithic Power Systems General Description Features The MP1521 is a constant-current Boost Regulator. This IC has three individual current-sensing feedbacks, which are ideal for driving multiple strings of series connected LEDs. The OLS pin is designed for detecting loose or open LED connections. The IC uses a peak current, constant minimum off-time architecture. The feedback pins measure voltage across sense resistors in series with the LED strings. When supplying a bias current of 20mA, the voltage drop across the sense resistor is only 0.4V to minimize power loss. Either a DC voltage or a PWM signal at the BRT/PWM input can control the LED brightness. The MP1521 has an on board power MOSFET switch that is protected by current limit, open load shutdown, thermal shutdown, and under voltage lockout. Applications Ordering Information Part Number Package Temperature MP1521EK MSOP10 -20 to +85C MP1521EQ QFN16 (3x3) -20 to +85C EV0005 MP1521EK Evaluation Board EV0021 MP1521EQ Evaluation Board On Board Power MOSFET Drive 9 White LEDs from 2.7V Input Drive 15 White LEDs from 5V Input Up to 90% Efficiency Over 80mA Output Current Capacity Open Load Shutdown Low Current Sensing Feedback Voltage Up to 3 String Current Sensing Feedback Analog and Digital PWM Brightness Control UVLO, Thermal Shutdown Soft Start Internal Current Limit Available in Compact MSOP10 and Tiny 3 mm x 3 mm QFN16 Package Evaluation Boards Available Handheld Computers, Cell phones, PDAs, Digital and Video Cameras, Small LCD Displays Li Ion and NiMH Battery Applications For Tape & Reel, add suffix -Z (i.e., MP1521EK-Z) For Lead Free, add suffix -LF (i.e., MP1521EK-LF-Z) Typical Application Circuit (One String of Six (6) LEDs) IN OFF SW 10 EN BRT/ PWM 2 EN GND 9 OLS 8 3 REF 4 BRT/PWM FB1 7 FB3 FB2 6 5 CIN 100 GND COUT MP1521 White LEDs Efficiency (%) 1 ON Efficiency vs LED current, 1 string of 6 Using Toko D62CB 47H Inductor VIN L1 D1 90 VIN = 5V 80 VIN = 4V 70 VIN = 3V 60 50 5 10 15 20 25 LED Current (mA) MP1521 Rev 2.7 10/06/04 www.monolithicpower.com 1 MP1521 High Efficiency White LED Driver Monolithic Power Systems Absolute Maximum Ratings Supply Voltage (VIN) Switch Voltage to GND VEN, VREF, VBRT, VFB1, VFB2, VFB3 Storage Temperature Recommended Operating Conditions 28V -0.5V to 28V -0.3V to 6V -55C to +150C Supply Voltage (VIN) Operating Temperature Switch Voltage to GND 2.7V to 25V -20C to +85C -0.5V to 25V Package Thermal Characteristics Thermal Resistance, JA (MSOP10) Thermal Resistance, JA (QFN16) 150C/W 60C/W Electrical Characteristics (VIN = 5.0V, TA = 25C unless specified otherwise) Parameters Supply Current (shutdown) Supply Current (quiescent) Minimum Off Time, normal operation Minimum Off Time, start-up (Note 1) UVLO Symbol IIN (OFF) IIN (ON) tOFF (NORMAL) tOFF (START) Under Voltage Lockout Enable Threshold Hysterisis Leakage Current Open Load Shutdown Threshold Leakage Current Reference Output Voltage Load Regulation Line Regulation Feedback Comparator Threshold Hysterisis (Note 2) FB Input Bias Current PWM Mode Output-Off Threshold BRT Input Bias BRT Full Scale Threshold (Note 3) Output Switch Switch On Resistance (Note 2) RON Switch Current Limit Leakage Current Thermal Shutdown (Note 2) Condition Min VEN<0.4V VEN >1.5V, VBRT=0V, VFB=0V VEN >1.5V, VBRT =0.6V 400 VFB =0 VEN >1.5V, VBRT =0.6V, 1.5 VFB =0V VIN RISING VIN FALLING Typ 1 550 Max 3 700 Units A A 500 700 nS 2.4 S 2.6 2.4 V V 2.0 1 V mV A 45 29 1 70 V A A 2.1 1.9 0.8 1.0 60 VEN=3V Measured at OLS Pin VOLS=15V VOLS=25V 26 IREF=0A IREF=0 to 100A VIN =3 to 15V, IREF=0A 1.20 1.235 2.5 2.5 1.27 5 5 V mV mV VBRT =1.2V VBRT =1.2V VFB=0.2V 380 420 -150 400 30 -50 0 mV mV nA VBRT=0.6V 0.18 -100 -30 0.26 0 V nA 1.2 V 0.6 mA A C VIN=5.0V 300 0.5 400 VSW=25V 5 160 Notes: 1) First 64 pulses after EN switches high. 2) Guaranteed by design. 3) The output current is off when BRT is driven below the output-off threshold and full-scale when driven above the full-scale threshold. To PWM the output drive BRT above and below these thresholds. MP1521 Rev 2.7 10/06/04 www.monolithicpower.com 2