TPS1685: TPS1685 startup waveforms and AOA

Alex Kucherov

Part Number: TPS1685

Hello,

Please see attached startup waveforms for the TPS1685 on our PCB.

Curve F2 is the hotswap's VDS (mathematical function CH1-CH2).

Can you please confirm the behaviour is as expected? And how can I make sure the plot is not violating the AOA curve?

Thank you in advance,

Alex

0 Amrit Jit 7 months ago

Hello Alex,

TPS1685 has self-protected AOA feature. VDS looks fine.

IIN current reaching more than device start-up current limit that's why it's going into thermal foldback and limiting the start-up current.

What's your COUT value and dvdt cap.

Thanks
Amrit

0 Alex Kucherov 7 months ago in reply to Amrit Jit

Hello Amrit,

Cout =~260uF.

Cdvdt = 22nF.

Is the start-up current internally limited to 0.5A?

Thanks,

Alex

0 Alex Kucherov 7 months ago in reply to Alex Kucherov

Hello Amrit,

Any update?

Do you see any issue in the provided plots?

Thanks,

Alex

0 Rakesh 6 months ago in reply to Alex Kucherov

Hi Alex,

sorry for the delay.

The max current you can get during startup is 0.5A (typ). Considering device to device variation, the startup current can be lower.

If you don't have aggressive startup time need, you can increase the Cdvdt to 47nF.

Also, use PG output of TPS1685 to enable the downstream so that the device see only capacitive load during startup.

Best Regards

Rakesh

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