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L6226Q broken when Vs pin is rapidly switched on and off ?

Question asked by masmoudi.mahmoud on Apr 13, 2016

I am using the eval board EVAL6226QR that has the dual full bridge driver L6226Q on it.
I am using it to drive a 40kHz train of pulses from IN1A to OUT1A (and IN2A to OUT2A).
To minimize current consumption, I am controlling the Vs pin (that has 32V on it) by a window that goes HIGH for 500 microseconds, and LOW for 30 milliseconds.
After few tests (sometimes, that happens after few days of proper operation), the HBRIDGE breaks down ! (there are high current peaks detected on my voltage generator higher than 1Amp !)
This is the fifth EVAL6226QR that breaks down now !
Feeding Vs with continuous voltage does not cause the hbridge to break down (but it consumes 120mA which is too high)

I looked carefully into the datasheet of the eval board and that of the chip, and I found only frequency characteristics for IN pins only (Vs is supposed to have a constant voltage apparently)

Does it mean that it is not meant to have its Vs pin fed with AC voltage ?
Can anyone suggest a solution for this please ?

PS : I don't want to feed this window signal to ENA pin because when LOW, outputs go high impedance and not low state