In the schematic attached the IMON output of the TPS2493 goes to the RTN pin when there is reverse protection between the chip ground and actual ground. My question is, do you have to then differentially read the current feedback or under real conditions is the voltage differential between GND and RTN small enough or predictable enough to calculate out?
Thanks!
Hi Allen,
If reverse polarity is used with the TPS2493, then the IMON pin won't be nearly as accurate, and it won't be linear. The reason is the IMON resistor and capacitor needs to be connected to IC ground and not system ground with a reverse polarity circuit (Look below). If not, the IC could get damaged because current flows from system ground into the IMON pin.
Also, please add a Schottky Diode at the output (such as the B380-13-F). Wires inherently in nature have inductance. Which means that shutting off the FET during a circuit breaker will produce a huge voltage spike at both the input and output of the circuit. The TVS diode and Schottky will help clamp any transients and protect our IC from damage.
When C21 is connected to the p junction of D6, then the accuracy is worse and it's non-linear. The diode will have different voltage drops with different packages and this variability throws off the accuracy. I would recommend to not use the IMON pin and leave floating if reverse polarity protection is more important for this design. If the IMON pin is not going to be used, I would
If the IMON pin is not going to be used, I would recommend the LM5069. This device has all of the protection for hot-swaps like the TPS2493 (OV, UV, Short-Circuit Protection, Power Good signal). We also have an orderable EVM board with the reverse polarity circuit (http://www.ti.com/tool/lm5069evm-627), as well as an app note (http://www.ti.com/lit/an/snva683/snva683.pdf). I hope this helps :-)
Best Regards,
Aramis P. Alvarez
