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BQ25505EVM-218: Can a low impedance on VIN damage the BQ25505 part?

Rob Meades
Prodigy 55 points

Part Number: BQ25505EVM-218

I have a BQ25505EVM-218 board and have made sure that it works by connecting a button cell (4 Volts) on VBAT_SEC/J8 and an LED with a 1k series resistor on VOR/J15; the LED lights, as you would expect.

I then disconnected the button cell and connected my intended energy source, a small wind turbine, to VIN_DC/J2, with the turbine not rotating.  I reconnected the button cell on VBAT_SEC/J8 but now I cannot get my LED on VOR/J15 to light under any circumstances, even disconnecting everything and recreating the conditions of my first paragraph.  VBAT_SEC/J8 still shows 4 Volts, VB_SEC_ON is still low but VSTOR and VOR/J15 never have any Volts on them.

Could I have damaged the BQ25505 part? The coils of my wind turbine measure 56 Ohms: could a low impedance on VIN_DC have caused damage?  I can't see anything in the datasheet about this except a mention that if VIN_DC is higher than VSTOR and VSTOR is higher than VBAT_OV (which has never been the case here) then VIN_DC should be higher than 20 Ohms.

  • 0
    TI__Prodigy 670 points

    BQ25505 could not so easy to be damaged, this issue should be due to the hot-plugging the storage element. If VIN is absent,  the VSTOR node should be discharged to ground before attaching a storage element. Hot-plugging a storage element that is charged and with the VSTOR node more than 100 mV above ground results in the PFET between VSTOR and VBAT_SEC remaining off until the VIN is attached.

  • 0 in reply to Robin Tang
    Prodigy 55 points

    Thanks for the explanation: I found that I had to short VSTOR to ground and also short VIN to ground, just to make sure that everything was off, then it all came back to life.

    I'll stop worrying now :-).