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APadm
APadm
Visitor II
February 11, 2019
Question

We are using EVALPWD13F60. We are unable to make motor turn on.

  • February 11, 2019
  • 1 reply
  • 548 views

We are using EVALPWD13F60. We are unable to make motor turn on. While we give pwm(10KHz) to HIN1 and LIN2 with different duty cycles by putting LIN1 and HIN2 as low , we getting 6 V as output. When we give HIN1 and LIN2 full time high voltage is dropping down from 24V to 0V. Given VCC1and VCC2 12V. logic level 5V and VS as 24V. Please help us

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1 reply

fabbri.fabio
fabbri.fabio
ST Employee
February 12, 2019

​The high side MOSFET (the one driven by the HVG signal, in the datasheet block diagram) can be turned on only if the bootstrap capacitor (the one between BOOT and OUT) is charged.

If HIN if kept high indefinitely, the bootstrap capacitor  get discharged and the high side MOS get then off.

The bootstrap diode architecture cannot charge the bootstrap capacitor while high side is on since the diode is interdicted.

A way to keep the bootstrap capacitor charged, if the application allows it, is to use a duty cycle <100%. This to allow the bootstrap diode to recharge and keep charged the bootstrap capacitor cycle by cycle while low side is on.

As general rule, before starting applying the PWM signal to inputs, it is recommmended to charge the bootstrap capacitor by initially turning on the low side MOS.

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