Carl Norman

How to reduce MCF52259 VSTBY  current draw

Discussion created by Carl Norman on Apr 11, 2011
Latest reply on May 5, 2011 by Mark Butcher



I am just after some clarification of current draw from VSTBY on the MCF52259. Is there a way to reduce the standby current draw from 20uA down to around 1uA (Which is what it is when VCC is on)? Is it possible to 'turn off' some features to get the current draw down? i.e. stop VSTBY from supplying SRAM in standby  and just runt the RTC?


It seems strange to draw nearly 20uA to run a RTC, even 1uA is a big much really... I did some initial testing a couple of years ago and noted it was drawing 1.5uA at 3.3V in standby, however, I now realize that if you power it up and then down (initialize RTC etc), it jumps to nearly 20uA which is just to much for our application.


The smallest viable lion battery (CR1220) doesn't even make 100 days standby before it dies!  CR2450's etc are just way to big to run something as light weight as a RTC, in cost and space...