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LM5170EVM-BIDIR: Output voltage changes followed with input voltage change in boost mode

Part Number: LM5170EVM-BIDIR
Other Parts Discussed in Thread: LM5170


I want to use LM5170EVM-BIDIR for 20-30V battery to 48V motor application, when the motor brakes, I want the brake energy go back to the battery.

I changed R75 to 41.2k, R77 to 2k, R78 to 2k, R18 to 0, R15 to 47k, R17 to 64.9k. Pads at bottom layer near D3 short,

J34 to 37, J2, J3, J4, J8, J25 short.

J21 pin1,2 short.

The board worked good with buck mode, I change the input voltage at HV side, LV side could remain stable 29.6V voltage.

But in boost mode, when there is no load, 11V input at LV and 48V output appeared at HV, if I increase the input voltage to 13V or above, OVP will be triggered, the output voltage will oscillate between 45V and 55V. If I remove one of J34 - J37, output voltage oscillated even at 11V input voltage.

Then I tried to applied 0.1A load at HV side, at this situation, 11V input generates 44V HV output, increase the input to 30V would also increase HV output to 48V.