next-generation PMU discussion
andy at openmoko.com
Sun Apr 20 10:46:23 CEST 2008
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Somebody in the thread at some point said:
| [ Context: we're looking for a PMU for GTA04 and beyond. One possible
| choice is to use NXP's PCF50633 again. ]
| Andy Green wrote:
|> NXP is "the devil we know", but there is no integral codec.
| In the past, we had lots of trouble with the NXP PMUs, since their
| default settings (such as which regulators are active in what state,
| and what voltage they default to) are mask-programmed in the chip,
| However, since GTA04 will have an MPU, we're considerably better
| off there. What we still have to worry about is:
| - feeding the MPU (unfortunately, the upper end of the MSP430's
| voltage range is only 3.6V. Otherwise, we could just have
| connected it to Vsys.)
| So making the PCF50633 fit wouldn't be quite the pain it was in
Agreed... VSYS is not an ideal way though because the MSP430 is happy to
run at 1.8V if you don't want to blow the flash or 2.2V if you do.
These are really big savings over 3.6V in power terms... 1mA at 2.2V is
2.2mW while at 3.6V it is 3.6mW, over time that'll add up.
I guess if we go this way we have to examine the 50633 defaults closely
to see what the other options are if any.
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