Tool/software:
Hello, I'm using the DRV8412 in parallel mode to drive a thermoelectric unit. It's mostly working but has some issues. It needs to power a TEC module at 5A. I'm testing with a 24V power supply and electronic load. It works for smaller loads, like a few amps. But when I turn it on with a 5A load straight to 100% then the output is only 7V (should be ~22V) and then it gets too hot.
Also, running the DRV8412 at 50% will cause it to overheat (assert OTW) and the output inductors are quite hot.
I can drive a 5A load on it but only under the following conditions:
1) configure output load to be 1A
2) Turn on TEC to 100%
3) Stepwise increase load to 5A.
In this case the output inductors don't get as hot as the chip does.
Schematic was copied from TI reference design. See attached image.
Heatsinks are on the inductors, the DRV8412 top, and on the PCBA beneath the DRV8412.
Output inductors are TDK FLS6045EX-4R7M (4.7uH, 0.035Ohm, Isat=5.8A) (link - ESR on these is pretty flat up to 1MHz. They're about 1cm from the chip.
Output caps are Samsung CL32B106KBJNNWE (10uF 20%,1210 imperial size, 50V). The larger ones are Kemet A768EB476M1VLAE042 (47uF 20% 35V Poly) - link
PWM frequency (set duty cycle to 50%) is 95kHz. Measured on pulse of 5250nSec and off pulse of same at 50%. I can change this to whatever, up to the part's maximum of 500kHz of course. Firmware monitors both OTW and FAULT: if OTW then it turns off the PWM to the DRV8412, waits 5 seconds, then if OTW no longer asserted then it slowly ramps back up the output. If FAULT then it disables the DRV8412 completely.
Maximum output is 99%, at which point off pulse is 208nSec.
