PAC1720 - Dual Positive and Negative Rail Current Monitoring

I have an application where I need to monitor the current to a device that is powered by both +12 V and -12 V. Can PAC1720 be used to monitor the current in these voltage rails?

The +12 V is straightforward, while the -12 V is not. For negative supplies, the PAC1720 (or a PAC1921), needs to have the GND pin connected to the negative supply (VEE). VDD needs to be supplied by an LDO that has its GND pin connected to VEE. This regulator needs to supply only the current for the PAC device, not the load on the negative supply.

Use a sense resistor between GND and the load. Connect the two sense inputs of one channel across this sense resistor. The Vbus is measured with respect to VEE, so it will look like a positive voltage. The SMBus/I²C pins are much more of a challenge unless you know a standard way to do this translation from signals running in a negative voltage domain.

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