RTC Feature disable

manish bhatt1

Intellectual 785 points

Other Parts Discussed in Thread: AM3352

Hello

I want to use AM3352 with RTC feature disable.

What we have to do with following Pins

RTC_PWRRSTn

CAP_VDD_RTC

Can we keep these pins floating.

Manish

over 12 years ago

0 Biser Gatchev-XID over 12 years ago

TI__Guru**** 393215 points

Hi Manish,

No, you should not. VDDS_RTC supply must be present.

The CAP_VDD_RTC terminal operates as a power input to the RTC core voltage domain when the RTC_KLDO_ENn terminal is high. In the case where you are not using RTC, this terminal can be connected to VDD_CORE and a dedicated capacitor is not required.

The CAP_VDD_RTC terminal provides a passive connection to an external de-coupling capacitor when the RTC_KLDO_ENn terminal is low. In this case, the internal regulator is sourcing the RTC core voltage domain, CAP_VDD_RTC terminal should have 1uF capacitor connected to it, and RTC_KLDO_ENn should be pulled down with 10kOhm.

For the RTC_PWRONRSTn please check section 8.1.7.9 of the TRM. It says it needs to be shorted with PORz, but be aware that they are on different voltage domains. I would interpret this as "they should be driven from the same source".

Best Regards

Biser

0 manish bhatt1 over 12 years ago in reply to Biser Gatchev-XID

Intellectual 785 points

Dear Biser

In my design RTC_PWRONRSTn and PORz are in different power domain VDDS_RTC(1.8v) and VDDSHV6 (3.3V).

So we can't tie both togeather.

What we need to do with RTC_PWRONRSTn .

Manish

0 Biser Gatchev-XID over 12 years ago in reply to manish bhatt1

TI__Guru**** 393215 points

Buffer it, with buffer supply from VDDS_RTC, and buffer input from same source as PORz.

Biser

0 peaves over 12 years ago in reply to Biser Gatchev-XID

TI__Guru 63125 points

This buffer must have a fail-safe input if you are going to input a voltage higher that the supply voltage. I'm mentioning this because many CMOS devices have an maximum input voltage limit of (VDD + 0.3 volts).

Regards,
Paul

0 Javad Memariani over 12 years ago in reply to Biser Gatchev-XID

Prodigy 50 points

If we disable RTC as mentioned above, what about power consumption? using or not using RTC consumes same energy?

I am asking this because for some applications we do not need RTC and the energy consumption is critical.

0 Biser Gatchev-XID over 12 years ago in reply to Javad Memariani

TI__Guru**** 393215 points

Hi Javad,

Please check this thread: http://e2e.ti.com/support/dsp/sitara_arm174_microprocessors/f/791/t/226304.aspx

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RTC Feature disable