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| MP1521 High Efficiency White LED Driver Monolithic Power Systems General Description 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. Features 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 Applications Handheld Computers, Cell phones, PDAs, Digital and Video Cameras, Small LCD Displays Li Ion and NiMH Battery Applications Ordering Information Part Number MP1521EK MP1521EQ EV0005 EV0021 Package MSOP10 QFN16 (3x3) Temperature -20 to +85C -20 to +85C MP1521EK Evaluation Board MP1521EQ Evaluation Board 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) L1 D1 1 VIN CIN Efficiency vs LED current, 1 string of 6 Using Toko D62CB 47H Inductor 100 Efficiency (%) 90 80 70 60 50 5 10 15 20 25 LED Current (mA) VIN = 5V VIN = 4V VIN = 3V IN SW 10 ON OFF MP1521 EN 2 COUT GND 9 GND EN 3 REF OLS 8 BRT/ PWM 4 BRT/PWM FB1 7 White LEDs 5 FB3 FB2 6 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 28V -0.5V to 28V -0.3V to 6V -55C to +150C Recommended Operating Conditions Supply Voltage (VIN) Operating Temperature Switch Voltage to GND 2.7V to 25V -20C to +85C -0.5V to 25V 150C/W 60C/W Package Thermal Characteristics Thermal Resistance, JA (MSOP10) Thermal Resistance, JA (QFN16) 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 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) Symbol IIN (OFF) IIN (ON) tOFF (NORMAL) tOFF (START) 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 2.1 1.9 0.8 VEN=3V Measured at OLS Pin VOLS=15V VOLS=25V IREF=0A IREF=0 to 100A VIN =3 to 15V, IREF=0A VBRT =1.2V VBRT =1.2V VFB=0.2V VBRT=0.6V 26 45 1.20 1.235 2.5 2.5 400 30 -50 -30 1.0 60 Typ 1 550 500 Max 3 700 700 2.4 2.6 2.4 2.0 1 29 1 70 1.27 5 5 420 0 0.26 0 1.2 VIN=5.0V 300 VSW=25V 160 0.5 400 0.6 5 Units A A nS S V V V mV A V A A V mV mV mV mV nA V nA V mA A C 380 -150 0.18 -100 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 |
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