EVQ1932 Boost Voltage

Reference Designs
1

I am trying to evaluate the MPQ1923 for use in a 24V motor drive half bridge. Using Vdd and Vpower @ +12V for now, the driver seems to be taking around 120mA and the boost voltage is not able to keep the top FET on for a full cycle. PWM frequency is 20kHz

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20141210201237800×600 45.8 KB

Pink = VdrvH, Yellow = VinH.

The voltage drops quickly and fails at around 50% duty. Is this expected behaviour? I have removed L1 as this better represents my application, I wouldn’t have expected that to make any difference though.

Thanks

2

I may have damaged the circuit. Would you expect resistance to be 59R between gate and source of M1 of the eval board? That seems suspicious to me and would explain the fast fall off of the boost voltage.

I have lifted the gate of M1 and the resistance of 59R persists between DRVH and SW. The path left is through the MPQ1923, so I think I have damaged the IC.