TPS40200-HT Start up problem

John Tolman

Other Parts Discussed in Thread: TPS40200-HT, TPS40200

My buck topology power supply design uses the TPS40200-HT. 12 Volts input, 6 volts out @ 550ma. For testing, I have a light (40ma) resistive load. The output goes to 6 volts for 40ms and then shuts down.

Things I have tried:

To eliminate the possibility of a over current condition, I have connected the ISNS pin to VDD.

I have greatly increased the soft start capacitor.

What else can cause it to shut down? Any thoughts?

over 12 years ago

0 Anthony F over 12 years ago

TI__Mastermind 35165 points

Hi John,

Nothing specific comes to mind immediately but some other possible causes are stability and layout.

Could you please share the schematic and some waveforms showing the restart? I am guessing the TPS40200 is operating in the hiccup mode where the SS cap is charged and discharged like shown in Figure 27 of the datasheet.

Best Regards,
Anthony

0 John Tolman over 12 years ago in reply to Anthony F

Prodigy 50 points

Thanks for the reply. Did you mean figure 26? It only goes once - no retries. I'm including the schematic.

0 John Tolman over 12 years ago in reply to John Tolman

Prodigy 50 points

In reading through other posts about the TPS40200, I notice that my design does not have a RC filter on the VDD pin. Without this filter could false triggers of the current limit circuit occur even if I have the VDD and ISNS pins connected?

John

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TPS40200-HT Start up problem