Can the SRAM of LPC213x be battery backed?

[techie]

There is an internal RTC with battery switchover circuit in LPC21xx controllers. These controllers also have an SRAM. Is the VBAT pin coonected to SRAM also. If not, is there a way to battery back this internal SRAM. I have seen some controllers like the ST uPSD which do that.

 

[robert_from_philips]

The internal SRAM can be preserved but not throught eh Vbat on the LPC213x and LPC214x.
On the LPC2103 (much smaller) the SRAM can be preserved through Vbat.
Another way to preserve the SRAM is to put the micro into power down mode and power the Vdd from the battery as well.
Will drain the battery faster but it is the only way I can think of.

Robert

 

[movingbait]

you can use the fact that there is a diode on each pin, so power the device via a resistor; conduction will begin when pin voltage is higher than that of supply

you need to seperate micro from supply incase it does not have protection diode and not try to power the whole power rail with the battery.

 

[techie]

Robert, there is no difference in the data-sheet portion of LPC213x and LPC2103 as far as the VBAT is concerned. In the block diagram the VBAT only connects to RTC, not SRAM. There is no mention anywhere if VBAT powers the SRAM also.

Are you sure that the SRAM of LPC2013 gets power from VBAT in LPC2103. I have to order these chips and want to know for sure about this feature.