TPS54613: TPS54613

Hi Richard,

ENA pin does not require any pull-up voltage because it has an internal current source of 5uA.

If you placed a 47nF cap on ENA/SS pin then the delay time should be 11.28ms and slow-start time of 6.58ms (refer to section 7.3.2, page 10 of the DS).

Can you share part of the circuit diagram and voltage waveform across ENA/SS?

Best regards,

Excel

Excel,

Attached is a copy of that part of the circuit.  Please let me know if you have or need any additional information.TPS54613 Circuit.pdf

Hi Richard,

Thanks for sharing the schematic diagram.

Can you provide the SS/ENA waveform with and without pullup?

Best regards,

Excel 

Sorry, I didn't realize that I had cut off the bottom of the circuit. The Cap C58 pin 2 is tied to ground.  There is no waveform associated with it.

Hi Richard,

I did the startup simulation using the PSpice model with and without SS cap and at both case the Vout was regulating properly. Refer to the figure below.

To help you better in resolving your issue, please provide the waveforms of the SS pins and VOUT at startup.

Simulation conditions: VIN = 6V, VOUT = 3.3V and Iload = 6A

Startup_no SS cap.pdf

Startup_SS cap-47nF.pdf

Best regards,

Excel