Tool/software:
Hi, I have implemented the TPS922054DRRR driver in a circuit as below. It is driving 2x Cree XTEAWT-E0-0000-00000BKE1 LEDs in parallel. Vf of each LED is 2.77V. I have it set to drive the LEDs at 3A (no dimming required), providing ~1.5A per LED. Input supply rail V_Periph = 52V. Does this sound reasonable?
What I am seeing is that when I set EN/PWM high, the LEDs start to flash and never really stabilise on. On looking at the SW pin (see below), I can see the switching turn on and off in bursts so the chip is definitely turning on and off intermittently as if it is going in and out of a fault mode (?) but I'm not sure why. I didn't connect the FAULT pin unfortunately (is it OK to have left FAULT and ADIM/HD pins floating?).
Looking at the potential faults from the datasheet, during the 'on' portions:
- Vuvp = ~26V > 1V
- Vin - Vcsn = ~3V
- Vcsp - Vcsn = ~0.2V
- Temp = ~40degC (have foldback set to 120degC)
Any ideas from looking at my circuit what might be going on here? I've checked it on two separate boards and same symptom. 52V power rail is not current limited.
Thanks,
Dave
