The subject part number is being used in a low power application. So quite large pull-ups are being used on the resetn line. 750k in this case pulling up to 3.3V. It has been observed that about half of the units behave as expected and about half do not. The main difference observed is voltage on the output. On units that function properly, ~3.1V is observed which is exactly what we expect. Units that fail, we observe anywhere between 2.6V and 2.9V. Furthermore, if resistance across the pullup is measured in circuit, ~745 - 750kohm is observed on passing units. On failing units, anywhere from ~400k to ~720k is observed.
1. Is this an issue due to output resistance of the LP3470A? Can it vary this wildly?
2. Can this be fixed by using a lower pullup resistor (100k is referenced in datasheet)?
Or if the output resistance is consistent from part to part, then they may be getting damaged in assembly/soldering or testing (inputs to device are connected to lab power supplies). Before I make that claim, I need to make sure the design is not suspect.
3. Any other thoughts?
