I have come across an interesting problem using the TPS62175 as a stepdown regulator from a battery input. The situation is as follows: The TPS62175 is being fed from an 8.4V (max) lithium-ion cell pack. I am using an open-collector comparator from a selector input line connected to the EN input to determine when the output of the TPS62175 is to be active.
When the load is connected to the pack with the select lead activated (EN pulled up to the 8.4V battery input via a 100K resistor) the pack seems to go into some form of foldback current limit. However, if I disconnect the load at the end of the output cable, approximately 12 inches from the pack, and then re-connect it, the output starts normally. Output is 4.0V at 400mA. Also note that if I reduce the load to below approximately 130mA, the problem does not occur. If it were simply that the regulator was going into current limit, I would expect it to behave the same whether the load was disconnected at the pack or at the end of the cable.
Any ideas where I should look?
