Other Parts Discussed in Thread: CSD17573Q5B, CSD18532Q5B
Tool/software:
Hello TI team,
have problems with my first LM5176 proto. I read now all other threads for LM5176, but will start with a bit generalized list of questions. Main requirement is Vin 24V (6-50V range) / Vout 12V / Iout - 2 to 4Amps cont., I out pulse 10A (70-200msec) or so.
1. Starting with zero load and from zero volts on 1A current protection max leads to erratic behaviour over start when 6V UVLO reached - hiccup all the time (hiccup is enabled) and out of regulation, output stay on 7-8V , seems like no damage occur.
2. Going over 12V (tested max up to 18V), never over 1A - Regulation on output 12V is good, but BUCK leg transistors get really hot in seconds and CC of 1A reached, where I switch the output power.
3. Repeat the test with 120Ohms on the output / 0.1A load - same results.
3. Schematics is very close to EVK and according to XLS calculation tool. In first assumption may be gate transistors of 22Ohms could be too high, inductor of 4.7uH value need optimization or there can be general mess I create with the layout... or all together. Buck side has 3x CSD18532Q5B NMOS and boost side has 2x CSD17573Q5B
I think this first prototype is already partitialy damaged, but I could be wrong. Will provide more detailed info, schematics and pictures later on.
Any ideas on those symptoms?
p.s. I found at least one potential problem - PGOOD was actually tight to Vin (not to VCC, pin 23) via LED and 22k (and that damage it, since it is max up to 8.5V). But even on voltages below this regulation was not really working. That somehow gets under the radar...
Thanks in advance!
