TPS259827LEVM: The output voltage rises slowly when starting

Justin zhuang

Part Number: TPS259827LEVM
Other Parts Discussed in Thread: TPS25982

Tool/software:

Such as Figure1. When the Vin voltage is stable, if you turn on the Enable pin at this time, you will see that the Vout voltage slowly rising. What will happen in this situation?

And why is this caused? TPS2421 does not have this situation. thanks.

Figure1. TPS259827LEVM (startup)

Figure2. TPS2421-1DDAR (startup)

2 months ago

0 Arush Gupta 2 months ago

TI__Mastermind 24895 points

Hi Justin,

It looks like TPS25982 is doing multiple restarts to charge the output cap. These restarts are happening due to high inrush current. Please refer to this FAQ.

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1368578/faq-tps25983-how-to-set-dvdt-cap-and-auto-retries-for-very-large-output-capacitor?tisearch=e2e-sitesearch&keymatch=faq%3Atrue

Best Regards,
Arush

0 Justin zhuang 2 months ago in reply to Arush Gupta

Prodigy 30 points

Hi , Arush

If I want to shorten the rising time (Tr<200ms), can I adjust it through dvdt and it can startup successfully?

such as figure2. It can achieve very short rising.

Figure1. TPS259827(startup pass)

Figure2. TPS2421-1DDAR (startup)

+1 Arush Gupta 2 months ago in reply to Justin zhuang

TI__Mastermind 24895 points

Hi Justin,

Can you share your schematic or use the design calculator to find the minimum dvdt value such that startup is glitch free. https://www.ti.com/tool/download/SLVC779

If dvdt is very small, startup will be very fast and result in high inrush and thermal shutdown. (what you are seeing).

If dvdt is increased, the startup will slow down resulting in less inrush current.

Best Regards,
Arush

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TPS259827LEVM: The output voltage rises slowly when starting