Other Parts Discussed in Thread: TPS82130,
We've been having a lot of trouble with the TPS82130 power supply. We currently use it on 4 of our PCBs for a 3.3V supply and on several of our boards, it seems to work ok in terms of providing a steady 3.3V line. However, when we attempted to use the exact same circuit on another one of our boards, the power supply was completely unstable and blew itself upon power up.
We're hoping to use bode analysis and step load response to characterize the stability of our power supply circuits something we have not attempted to do as part of our standard PCB functionality testing until just recently) so that we can figure out whats going on and apply a fix . We first wanted to start by characterizing the stability of the TPS82130 evaluation module (TPS82130EVM-720) so that we would know what to expect from a well-designed, stable power supply circuit. We have started by first analyzing the load step response using the Richtek load transient tool (https://www.richtek.com/Design%20Support/Reference%20Design/RD0004). We first apply a static load to ensure the power supply is not in PSM mode, then the load step response tool switches on and off an external load. The results we are seeing are not as expected. We are seeing the power supply fail to recover back to it's original level before the extra load was switched on. There appears to be about a 27mV offset. From the data sheet, load regulation is suppose to be 0.12%, so I believe we should only expect a max 1.7mV change.
Any advice or explanation would be much appreciated
Set up:
Dynamic load is 2.2ohm for 1.8V (818mA draw)
Static load is 1.8 ohm for 1.8V (1A draw)
Oscilloscope channels:
1 - Green - Voltage at the Switching Node
2 - Pink - Step load
3 - Yellow - V_out
