I am using the LM3464 Eval board. I have it set up for 800ma channels, VIN=48VDC. I am using the DIM input to strobe the LEDs, completely off/on operation. The chip gets occasional faults, resulting in channels being disabled. I increased the CFLT cap by 10x, but still get faults. I then connected the FAULTb output to the EN input to reset the fault and get the channels on again, but this causes a visible disruption in the uniform LEDs strobing. Since the strobe period will vary in time, I'm not sure there is a CFLT cap that will satisfy my application. So is there a way to disable the fault timeout and/or fault circuit? Thanks.
Also note that I am not using the DHC, I am just providing the 48-50VDC to the LED string anode, and to the EVAL board Vin. I have 4 channels each has a string of 24 LEDs. Vf for each LED is 1.9V, nominal LED current is 800ma.
I strobe the LEDs nominally at 150 Hz, 20% duty cycle. The faults occur at random times, causing strings to cease operation.
Update: I noticed that the Vf of the LEDs measured to be 1.088 volts, this is less than what the LED datasheet states. So the DRx inputs are at 24 volts, which violates the DRx over-voltage protection threshold. I'm surprised that the LEDs operate at all.
The DRx pins sense for over-voltage and short fault threshold. The data sheet shows two thresholds: "Any DRx < 2.5V" and the table Min, Typ, Max (8.35, 8.4, 9.75). Which one is correct? Do I strap the DRx to VCC to disable these faults, or to a voltage above 9.75 and less that 19 ?