Linux/AM3352: Battery discharge issue

yang yang2

Part Number: AM3352
Other Parts Discussed in Thread: TPS65910A

Tool/software: Linux

Hi, there

MS920SE-FL27E(11mAh) is used as backup power like reference design provided by TI. But it is out of charge after one day or two, in a word it is out of charge very soon. Is that the same in TI's reference board?

Thanks

Yang

over 8 years ago

0 Biser Gatchev-XID over 8 years ago

TI__Guru**** 393215 points

Hi,

Which TI design are you referring? Are you talking about RTC-only mode?

0 yang yang2 over 8 years ago in reply to Biser Gatchev-XID

Expert 1420 points

Hi, Biser

Sorry I mean am335x_reference_design. When the main battery is power down, the backup battery functions. I am not sure whether this is RTC-only mode.

0 Biser Gatchev-XID over 8 years ago in reply to yang yang2

TI__Guru**** 393215 points

I still do not understand which "am335x_reference_design"? There are several - GP EVM, Starter Kit, ICEv2, Beaglebone Black. Which one of them? If you don't know please point to the web link.

0 yang yang2 over 8 years ago in reply to Biser Gatchev-XID

Expert 1420 points

Hi, Biser

I mean www.ti.com/.../tmdxevm3358

0 Biser Gatchev-XID over 8 years ago in reply to yang yang2

TI__Guru**** 393215 points

OK, this is the GP EVM. The coin cell (BT1 in the schematic) was initially meant to provide VRTC in RTC-only mode, however you should see that R53 is not installed on the EVM and VRTC is provided instead by an external LDO (U5). During AM335x device characterization it was found that the VDDS_RTC current is rather high in RTC-only mode (see processors.wiki.ti.com/.../AM335x_Power_Consumption_Summary ) and a coin cell will be drained very quickly. A rechargeable battery could be used instead, because the PMIC has the ability to charge the backup battery. You will find details in the TPS65910A datasheet.

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Linux/AM3352: Battery discharge issue