use V18bkp to supply RTC without V33 ?

shinnlin · ‎2006-03-30

Posted on March 31, 2006 at 04:41

shinnlin · ‎2004-11-16

Posted on November 16, 2004 at 10:44

Is it possible to use V18bkp to keep RTC awake without V33 ?

This is my procedure :

1. connect V18bkp to external 1.8v source

2. set STR7 to STDBY mode

3. turn off V33

Will RTC keep alive under this situation ?

That means if I power on SRT7 later, will RTC continue working ?

hichem2 · ‎2004-11-17

Posted on November 17, 2004 at 14:08

Hi Shinn,

We have tested this and it's possible to switch off the 3.3v and keep the 1.8v on the V18BKP pin during the STANDBY mode for keeping the RTC working.

But we still validating this to inssue to assure that there is any side effect.

Best Regards

HICH ;)

hichem2 · ‎2004-11-29

Posted on November 30, 2004 at 04:51

Hi Shinn,

We continued with tests about the same subject and we concluded the following:

In Standby mode if you want to keep the RTC working you must keep necessarily the 3.3v.

Best Regards

HICH :)

dmerchez9 · ‎2005-05-16

Posted on May 16, 2005 at 13:38

Are you sure?

I saw in the ''STR71x Hardware Development Getting Started'' on page 3/18 that ''In Standby mode the low Power VR can be switched off when an external regulator provides a 1.8V supply to the chip though the V18BKP pin for use by RTC and wake up block''.

So is it possible to supply the chip by an external V18 (on V18BKP pin) to make the RTC running in standby mode?

Dam

shangdawei1 · ‎2006-03-27

Posted on March 28, 2006 at 09:19

http://www.st.com/stonline/products/literature/an/11126.pdf

Page 3:

V33 pin: is the 3.3V main power supply pin. (V33 and V33IO-PLL are internally linked).

V18 pin: must be connected to a capacitor of at least 10Î¼F (Tantalum) + 33nF (ceramic) in

order to guarantee the stability of the 1.8V supply to the core.

V18BKP pin: can be used to provide an external 1.8V supply to the backup block (RTC and

Wakeup logic) when bypassing the internal voltage regulator during the STANDBY mode.

Caution: In STANDBY mode, when using an external 1.8V on V18BKP, the V33 pin must remain

connected to the 3.3V supply.

shangshuai · ‎2006-03-30

Posted on March 31, 2006 at 00:21

How can I use rtc when str7 is turned off?

Str7 must be in standby mode and can not be turn off?

jjmicro · ‎2006-03-30

Posted on March 31, 2006 at 04:41

It is NOT a real RTC !

When Need RTC function ,It should add a RTC Controller.

The ST engineers shit head !!!