TPS92515-Q1: gain phase measure

Hello Kami,

I am not sure why your customer what to perform this measurement.  The TPS92515 is a hysteretic mode buck regulator which is inherently stable and regulates current on a cycle-by-cycle basis.  There is no traditional closed loop as seen on traditional voltage mode and current mode controlled regulators that have an error amplifier to close the loop and regulate.  

I am not quite sure how you would test this because you would have to break the loop going to the comparator which is a differential signal across the sense resistor, which includes the VIN pin and CSN pin.  I am not sure how the injection into VIN would affect the part.  I haven't done this measurement before due to the fact it really should be needed because of its inherent stability and pulse by pulse current limiting.  

The setup might looks something like this:

Again, I am not sure this will work correctly and I am not sure why the customer needs to perform the bode plot for gain and phase when it doesn't have a traditional control loop with an error amplifier.  

-Francis Houde