TPS543C20: TPS543C20 start-up problem

Peter Jancso

Intellectual 310 points

Part Number: TPS543C20
Other Parts Discussed in Thread: UCD9090A

We have received our boards, where we use TPS543C20 to generate core voltage for an FPGA (0.9V).

On boards, where the FPGA is no soldered in, the power supply works well, the switching starts 4 ms

after the rising edge of the enable signal, just as we set by pin strap resistor.

Meanwhile on the other board, which assembled with this FPGA the TPS does not seem to start at all. No signal

on the switching node. What problem can possibly block TPS start-up? We have investigated further by breaking the

sense line, or grounding the output capacitors...both in these cases TPS started switching.

thank you in advance.

Peter

over 6 years ago

0 Peter Jancso over 6 years ago

Intellectual 310 points

The further investigation (breaking up sense line, etc.) was done on the board without the FPGA.

0 Newey Yakamna over 6 years ago in reply to Peter Jancso

TI__Intellectual 1520 points

Hi Peter,
I just want to clarify when the further investigation was performed, was it performed on the board with or without the FPGA? Also, when you break the sense line, did you modify to sense the VOUT locally (not at FPGA)?

Would you please send the schematic and the layout directly to my e-mail address?
ayakamna@ti.com

Thanks,
Amnat

0 Peter Jancso over 6 years ago in reply to Newey Yakamna

Intellectual 310 points

In order to summarize what we experienced:

We synchronize this power supply to a clock, which is being generated by a power supervisor (UCD9090A). While this circuit generates

3.3V clock on the board with no FPGA, it turned out the voltage is only 1 V on the board with the FPGA, thus the TPS could not start (Vih = 2V).

After breaking up the SYNC TPS543C20 could start in RT mode.

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TPS543C20: TPS543C20 start-up problem