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LM5175-Q1: Miss of the drive signal of the Boost upper bridge arm MOS when starting with load

Part Number: LM5175-Q1
Other Parts Discussed in Thread: LM5175, LM5176

Dear,

I have a customer issue, which can be summarized as:

Application Condition: LM5175-Q1 is used for charging the battery.

Problem Description: When the battery voltage is low, start the LM5175-Q1 with load, and directly enter the current limiting mode to charge the battery with a constant current. In this case, the chip does not exit the soft start state, and the driver of the upper tube Q409 of the boost bridge arm has not come out, the charging path is forced to be at the body-diode, causing the temperature of this tube to rise.

To sum up, If the LM5175-Q1 is started with load, the drive of the upper MOS of the boost side will miss. 

And we want to know, how to deal with this kind of problem?

Here gives the relevant waveforms: 

The upper waveform is the output voltage, the second upper waveform is SS pin voltage, the lowest waveform is the drive waveform of the upper MOS in the boost side.