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LTC7001 output higher than input

Category: Datasheet/Specs
Product Number: LTC7001

Hi all,

im currently working on an high power switch for a battery powered device. The switch itself is made out of an NMOS with the LTC7001 as an high side driver.

No im facing the question if charging would be possible through this switch even if the LTC7001 is not supplied and the NMOS is turned off.

My first thought was that it would be fine because the body diode of the MOS would let the current flow back to the battery.

However am uncertain if the LTC7001 would survive such a procedure because the TS Pin would be driven by a voltage and the internal charge pump is not working because VCC is not supplied.

So my first question is if the LTC7001 could be used in this setting and if the current can flow through the TS pin to the bootstrap pin so that the maximum voltage rating of -0.3V from TS to BST is not exceeded?

My second question: If the LTC7001 should not be used in that way, is there an alternative to achieve this, like placing a Schottky Diode from TS to BST to limit the negative voltage difference between those pins?

best regards,

Peter

  • Hi Peter,

    I am concerned that the high side power MOSFET will get hot when charging current flow through the body diode depending on the charge current of the battery.

    To answer your question: I don't recommend putting a Schottky diode from BST to TS due to high leakage current.  You may use ultra low leakage diodes recommended in the datasheet.

    My recommendation would be to use LTC7000 with built-in LDO to power VCC pin and disable the current sense feature or use low cost LDO to supply the VCC pin from the power path.  This method would enable the internal charge pump, BST-TS voltage will be regulated at 12V (typ). The high side power MOSFET should be ON with INP pulled high to reduce power dissipation in the FET during charging.