LTC7001 TS pin voltage issue when the INP signal is low

Hi ADIExpert

I have a BMS application usng LTC7001 as a high side switch as below schematic

the issue is when I turn the U64/U65 off by asserting INP low (Vcc is still supplied with a 5V)

I can still get a voltage (around )4.5V at V4_Pack+ node

it looks like the voltage from internal charge pump circuit

the only way I can get 0V at the V4_Pack+ node is to turn off VCC voltage when I try to shut the mosfet off

May I know it's normal for LTC7001 ?  Any suggestion to solve this issue without shutting off the Vcc?PDF

Note: CURRENT4_BAT+ connects to Battery set and V4_Pack+  is the positive node of the pack

thank you

Ken

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  • +1
    •  Analog Employees 
    on Jan 7, 2021 7:00 PM

    Hi Ken,

    This is normal to have some voltage at TS pin and V4_Pack+ node due to the internal charge pump operation and no load at the output.  Output load impedance of 10K to 100Kohm is enough to bring the output voltage close to zero.  You can try putting 10K to 100Kohm and a FET across the output to pull down the output voltage close to zero.  With the FET, you can disconnect the 10K to 100K load when not needed.

Reply
  • +1
    •  Analog Employees 
    on Jan 7, 2021 7:00 PM

    Hi Ken,

    This is normal to have some voltage at TS pin and V4_Pack+ node due to the internal charge pump operation and no load at the output.  Output load impedance of 10K to 100Kohm is enough to bring the output voltage close to zero.  You can try putting 10K to 100Kohm and a FET across the output to pull down the output voltage close to zero.  With the FET, you can disconnect the 10K to 100K load when not needed.

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