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TPS61094: No Charge

Dave Pulvermacher
Intellectual 870 points
Part Number: TPS61094

Hi - we are using the TPS61094 with a coin cell and a 1F supercap. 

Vin = 3v

Vout_Target = 2.7v

ICHG = 5mA

VCHG = 2.2v

Voltage at SUP = ~200mV (though the same performance can be seen when SUP = 700mV)

The issue I am having is when a battery is installed into the system the supercap doesn't always charge.  The output turns on, but no charging takes place.  If I use a bench power supply (3v) I can get the charging to turn on if I manually reduce Vin and then raise it back to 3v.  

I have confirmed that the EN line goes high as expected.   Out of 20 boards, 7 of them exhibited this issue.  Why?  This is a consumer device where the batteries might only get changed 1x/6months.  If a user replaces the batteries and the cap does not charge, they'll have no way of knowing and the product simply won't work.  Schemo is below.  

  • 0
    TI__Genius 9046 points

    Hi Dave,

    Do you already have load on VOUT? Input voltage needs to be higher than Vout_target to enter buck_on mode. Please also share some waveform on VIN, VOUT and SUP as much as possible/.

    Also, you need to toggle MODE&EN always high to make it enter auto-buck-boost mode. If you only make EN=1 but MODE=0 when battery is unplugged, it enters forcebuck mode and not going to utilize supercapacitor's energy to supply VOUT.

    -Wenhao

  • 0 in reply to Wenhao Wu
    TI__Expert 5180 points

    Hi Dave,

    I notice it has been a long time since the reply. I will close this threat, and you can open a new one if there is any more concern. Thanks.

    Best Regards,

    Eric Yue