LM3434SQ-20AEV/NOPB Evaluation Board for the LM3434 4A to 20A LED Driver
The evaluation board is designed to provide a constant current in the range of 4A to 20A. The LM3434 requires two input voltages for operation. A positive voltage with respect to GND is required for the bias and control circuitry and a negative voltage with respect to GND is required for the main power input. This allows for the capability of using common anode LEDs so that the anodes can be tied to the ground referenced chassis. The evaluation board only requires one input voltage of -9V to -30V with respect to GND. The positive voltage is supplied by the LM5002 circuit. The LM5002 circuit also provides a UVLO function to remove the possibility of the LM3434 from drawing high currents at low input voltages during startup. Initially the output current is set at the minimum of approximately 4A with the POT P1 fully counter-clockwise. To set the desired current level a short may be connected between LED+ and LED-, then use a current probe and turn the POT clockwise until the desired current is reached. The current may be adjusted with P1 up to 18A. 20A output may be achieved either by bypassing P1 and applying an analog voltage directly to ADJ or by adjusting the values of R1 and/or R2 to get higher than 1.5V with P1 fully clockwise. PWM dimming FETs are included on-board for testing when the LED can be connected directly next to the board. A shutdown test post on J2, ENA, is included so that startup and shutdown functions can be tested using an external voltage.
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