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LMR10510: Stability issue of LMR10510XMF/NOPB

Part Number: LMR10510

Stability issue reported by a TI Customer-

We came across a stability issue of switcher regulator LMR10510XMF/NOPB. As shown in the schematic below, C81P CAP 10nF was recommended by TI for Vout = 1.8V for LMR10510XMF for stability when R1611P = 20 kOhm and R71P = 10 kOhm. But LMR10510 will be unstable for Vout = 3.6V with C81P installed in this circuitry, whereas it is stable for Vout = 3.6V with C81P removed.


Could you please explain about the root cause of this stability problem of LMR10510X? Thank you very much for your help.


Please see the circuitry shown below.

A) With 10 nF capacitor installed. We clearly don’t have a constant duty cycle and the regulator appears unstable when probing at pin 1                  



B) After 10 nF chip capacitor C81P is removed. We observe a constant duty cycle and switching regulator is stable as shown in the pic below which was probed at at pin 1.