This is a reference design for a 6A step-down LED driver for a portable projector. The reference design is based on the MAX16821, a PWM HB LED driver. This circuit drives a single LED; three MAX16821 devices are required to drive RGB LEDs.
LED Driver Specifications
- Input supply voltage (VIN): 10V to 15V
- Output voltage (VLED): 4.5V to 6V
- Output current (ILED): 1.5A to 6A with analog control
- Analog control voltage: 1.1V to 2.8V for 1.5A to 6A
- Maximum LED on duty cycle: 50%
- Maximum LED current rise/fall times: < 1µs
- Maximum LED current ripple: < 15% at 6A
- VIN (J1 and J2 VIN+, J3 and J4 GND): 10V to 15V input power supply
- On/Off (J8): leave open or drive +5V to enable the driver. Short for disabling the board.
- PWM input (J7): dimming PWM input. Connect a PWM signal with 3V to 5V amplitude. The source should provide rise/fall times less than 500ns with a 300pF load so that the PWM input can drive Q1 and Q7. As output can rise/fall within 1µs, any PWM period three to four times higher than 1µs can be used.
- LED current control (J6): LED current adjust input. Apply 1.1V to 2.8V to adjust LED current from 1.5A to 5A.
- LED+ (J9, J10): connect anode of LED.
- LED- (J11, J12): connect cathode of LED.
- Inductor current output (J5): provides a signal proportional to the LED current. The voltage at OUTV will be 135x the voltage across R9.
Designed, Built, Tested
Board pictured here has been fully assembled and tested. Not available for sale.