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TPS65020: DCDC2 is turning on before DCDC2_EN V_IH(min) is reached

Ashley Luna
Prodigy 10 points
Part Number: TPS65020

Tool/software:

I am using all 3 converters on this part. While DCDC1 and DCDC3 turn on once their respective EN pins reach ~1.15V, the DCDC2 output turns on when its EN pin is at ~700mV. I realize that technically this might be considered an indeterminate state it's between the V_IH(min) =1.3V and the V_IL(max) = 0.4V, but this is repeatable across multiple boards pretty reliably. Why is the EN voltage threshold different on DCDC2 than on DCDC1/3?

DCDC2_EN (left) vs DCDC1/3_EN (right)

 DCDC2_EN and VDCDC2   

  • 0
    TI__Genius 10347 points

    Hi Ashley, 

    Thank you for reaching out on E2E. Please be aware that TPS65020 is an older device, so support may be limited. 

    I will say, I agree that this is a sort of gray area since 0.7V is above the VIL threshold, but not quite at the VIH level. 

    From what point are you measuring the voltage of the EN pin? There should be at least a 170 us delay between the enable signal assertion and the actual startup of each DCDC converter.

    Unfortunately I don't have any sort of EVM on hand to confirm this device behavior. 

    Best Regards, 
    Sarah

  • 0 in reply to Sarah Lao
    Prodigy 10 points

    Hi Sarah,

    Thanks for your reply. The EN voltage is about the same 170us prior. We will come up with an alternate solution that doesn't leave the EN voltage in an unpredictable state.

    If the TPS65020 is an older device, does TI have a recommendation for a newer replacement with similar functionality?