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What I've done is power a LP2980-4.5 LDO regulator from a PIC pin and read its output with an ADC pin. As long as the PIC supply is >4.5 the ADC reading is less than MAX. Once the PIC supply drops to 4.5 or lower the ADC reading is MAX.
I use this with BR type coin cells, which have a fairly flat discharge curve and then drop rapidly, to signal when the batteries need replacing.
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If you meant 'I want to monitor the Battery voltage' it will never work @4.6V
If you meant 'i want to monitor the PIC 5Volts rail' you MUST have a accurate and stable ref point somewhere. Zener will work but need too much current, voltage reference are great.
But there's certainely something i miss here. Usually i'll monitor the PSU before the regulator with high value resistor R2R network. The internal comparator allow that.
Something to try i guess Mr tomskk?
Steve
It's not a bug, it's a random feature.
There's no problem, only learning opportunities.
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