Other Parts Discussed in Thread: TPS82085, TPS22917
Hello,
I am considering the TPS22971 for an application where I want to use load switches instead of separate regulators to sequence power supplies that use a common voltage. For example, one regulator supplies a common 1.8V rail and the load switches sequence power to several other 1.8V rails. The load currents are low enough (combined with the TPS22971 low Rdson) that there should be no problem meeting the minimum voltage specs for the sequenced rails.
I am concerned about reverse current damaging the load switch. This part has thermal shutdown but not reverse current protection. I assume that the thermal shutdown would not react fast enough to prevent damage if there is large enough reverse current. I am hoping that I can tailor my application to avoid large reverse current.
In my application I can independently control the enables for the load switches (using a microcontroller). In a controlled powerdown scenario I can allow time for the load-switched rails to discharge before disabling the common buck regulator. However if the main power source is removed suddenly then the common regulator output might discharge faster than a given load-switched rail. In that scenario the load switch enable will be negated fairly quickly but I am not sure if this will prevent reverse current.
I can try to minimize the capacitance on the load-switched rails in order to reduce the reverse current duration, but some rails might still need up to 100uF.
Should I change to a load switch with reverse current protection for this type of application, or is my concern not justified? I should mention that board space and power efficiency are primary drivers for part selection. I was using multiple TPS82085 devices in the initial design but started looking at using load switches to save space and power.
Thanks - Jason
