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I'm ultimately trying to make a BLDC motor driver, but in the meantime I'm trying to get the IRS2301 MOSFET driver I intend to use working as expected. I built an H-bridge test circuit with a 1K resistor as my simulated load (shown below), and started with both drivers' HIN and LIN pins grounded, when I do this, the gate and source on both high side FETs read 10V, but are not shorted when do a connectivity test. The low side gates read 0V, as expected, but I cannot seem to get the high side gates to operate correctly with the driver. I've modeled my circuit based on AN-978, and cannot figure out why even the most basic operation isn't working, so any advice would be appreciated.

H-Bridge

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  • \$\begingroup\$ Pin 4 of your drivers does not appear to go to GND \$\endgroup\$
    – Matthew
    Nov 21, 2016 at 23:39
  • \$\begingroup\$ That's just an oversight on the schematic, it actually does. I'll update and post a new picture \$\endgroup\$ Nov 21, 2016 at 23:44

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It is the bias current for the pulse generator circuitry in the high side part of the driver causing the DC voltage reading, as with the bottom FETs turned off there is no path to GND, other than the 100k resistors. Turn the bottom FETs on and I believe the problem will go away.

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  • \$\begingroup\$ Thanks, I'll give it a shot, I was being overly cautious with this one after frying some earlier circuitry. Why would the 100k resistors not be sufficient as a path to ground though, out of curiosity? \$\endgroup\$ Nov 22, 2016 at 0:18
  • \$\begingroup\$ The quiescent current for Vbs is 160uA @ 15V, which results in around 16V across a 100k resistor, so I would expect a reasonable voltage across them. \$\endgroup\$
    – Matthew
    Nov 22, 2016 at 5:45
  • \$\begingroup\$ Circuit works as is, that's what I get for being scared of it. Thanks for the info though! \$\endgroup\$ Nov 24, 2016 at 1:02
  • \$\begingroup\$ No problem. Best to be thorough and understand it than to replace broken parts! \$\endgroup\$
    – Matthew
    Nov 24, 2016 at 7:59

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