Reference Voltage for Low Power Comparator

[Daryl]

I see that there is a 1.2 Volt VBG reference available for the ADC but that reference doesn't seem to be available for the low power comparator. Is there any undocumented way to use this reference for VIN-?

In my application VDD is powered from a battery so that varying voltage isn't suitable for the VDD pre-scaling reference (i.e. VDD1/8, VDD2/8, etc.).

I'd like to avoid an external voltage reference IC, so I see one other possible option. Can I use the 1.2V LDO output at DEC1 as an input for AREF0? The datasheet doesn't show any specifications for the 1.2V regulator, so I don't know how accurate it is, but my application doesn't require a very precise reference.

I don't plan to use the LPCOMP as a wakeup source because I'm not sure how the 1.2V regulator behaves in the System OFF state.

[ovrebekk]

Hi Daryl

The 1.2V voltage on DEC1 is not available in system OFF mode, and in system ON it is only available if one of the peripherals is running. In active mode it is always on.

In theory you can feed this voltage back into the LPCOMP, as long as you make sure not to load the pin externally any more than it already is.

If you do this you should be able to use the DEC1 voltage as reference for the LPCOMP.

Best regards
Torbjørn

[Daryl]

Thank you Torbjørn! I recognize the limitations of using DEC1 as a voltage reference, so I will proceed with testing in my application.