We are looking at using a PTN78060H/W module on a board (there are two different configurations that require different output voltage ranges thu the two parts) but we need to be able to adjust the output voltage depending on various factors that change over time. The four choices we came up with were (and the respective major negatives)
- a JFET with high on resistance on VCR mode (most of these are going or have gone obsolete),
- Switching various fixed resistors in using MOSFETs (chews up I/O quickly)
- Digital pots (we don't have enough information to know if this is safe to do)
- Feed an external voltage/current into the node to adjust the feedback (not enough information to design the circuit)
For the digital pot one we need to know what is the highest voltage seen at the adjust pin with a 50K resistance to ground (unprogrammed resistance).
For the external voltage one we have a DAC with a 0-2.5V output available, how do we convert this to something that the converter will accept without disturbing stability. I know use an opamp to scale/sum and a resistor/opamp to convert to current if necessary but not knowing the internal proprietary circuitry this isn't an easy task.
