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BQ24195XEVM Schematic

Somesh Modi
Prodigy 240 points
Other Parts Discussed in Thread: TIDA-00036, BQ24195, BQ25895

Hi,

Please explain functioning of MOSFET Q1 (CSD25302) in below BQ24195 EVM TIDA-00036.

As per my knowledge source drain looks in opposite direction. What is role of this 2 MOSFET (Q1 & Q3 ) circuit.


Thanks & Regards,

SOMESH

  • 0
    TI__Intellectual 1910 points
    Although PMID is the output during OTG, there internal Q1 of bq24195 is enabled hence VBUS voltage is also 5V. The external Q1 is intended to block this voltage. Q3 is ued to control the turn on/off of external Q1. When VIN is avaiable, Q3 is enabled to turn on Q1. When there is no VIN input, Q3 is disabled which would also disable Q1 and allow OTG output on PMID/VBUS pins but not Vin.
  • 0 in reply to SamW2000
    Prodigy 240 points

    Hi SamW2000,

    Thanks for your reply ,

    I want to know that , Why external Q1 Drain and source connected in reverse and how it is functioning?

    waiting for your response

    SOMESH

  • 0 in reply to Somesh Modi
    TI__Intellectual 1910 points

    I don't understand why you think external Q1 is reversed. It is intended to be off during boost mode to isolate VBUS (Boost voltage of 5V) from IN.

    BTW, you can also take a look at bq25895 which is our new generation power bank and does not require external Q1. The internal Q1 (between VBUS and PMID) is turned off during boost mode in this device.