TPS65910: VDD3 Diode Selection / Purpose?

TS Yang

Genius 4800 points

Part Number: WL1837MOD
Other Parts Discussed in Thread: WL1837, TPS65910

Hi,

We've got TI's schematic review as below link. (all threads are locked so I can't make any more reply to that forum.)

https://e2e.ti.com/support/wireless_connectivity/wilink_wifi_bluetooth/f/307/p/655077/2410703#2410703

Thanks to TI, we succeeded in designing WL1837 to customers' application.

They're going to use 5V for the SW3 in the PMIC.
I think the circuit is wrong and the review is not working well.
So I ask for confirmation. Is SW3 step-up?

Please also inform the following diode specifications.

thanks,

over 7 years ago

0 Eyal Reizer over 7 years ago

TI__Mastermind 20285 points

From the TPS65910 DS:

So It seems ok...

BR,

Eyal

0 TS Yang over 7 years ago in reply to Eyal Reizer

Genius 4800 points

thanks Eyal,
can you share any information about the above diode in datasheet diagram?

0 TS Yang over 7 years ago in reply to Eyal Reizer

Genius 4800 points

I can't understand your answer.

I told you that the circuit is being stepped down.

0 Josh Wyatt over 7 years ago in reply to TS Yang

TI__Guru* 91206 points

See page 3 of the TPS65910Ax Users Guide for AM335x MPUs.
www.ti.com/.../swcu093f.pdf
and schematic checklist SW3 for (page 5) here: www.ti.com/.../swca139b.pdf

they recommend a schottky for the diode (see post below) and also, they recommend the use of 4.7uH inductor to VBAT and 4.7uF cap (both of which it looks like you are missing / have wired incorrectly)

also, moving this post to the PMIC Forum

0 Kevin LaRosa over 7 years ago

TI__Genius 17380 points

Hi TS,

VDD3 is an asynchronous step-up (boost) converter. The diode is used to drive current into 5V from VBAT for the boost operation. For more information on how boost converters work, this is a good article: http://www.ti.com/lit/an/snva731/snva731.pdf

We recommend a Schottky diode for that diode. On the EVM, we use the Vishay MSS1P2L. You can find that in the EVM User's Guide in the BOM section: www.ti.com/.../swcu065f.pdf

If you want to select a different diode, a good article on the selection is: www.ti.com/.../snva762.pdf

Do not use an LED, that is a mistake in the schematic checklist that we will fix.

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TPS65910: VDD3 Diode Selection / Purpose?