Other Parts Discussed in Thread: TINA-TI
Hi Ti,
We use the INA210 for current measurement ranging from 0.1 mA to 0.9 mA.
The circuit diagram is as shown below.
We have observed a 25 kHz oscillation at the output terminal (PSEQ_MON_VP12P0_MB_AMP1_ST). This oscillation occurs at the same frequency regardless of the current magnitude and only affects the common mode voltage of the output. Waveform are shown below picture, yellow signal is sense current and purple signal is INA210 output.
After removing the capacitor, we found that the oscillation disappeared.
We also simulated the INA210 using TINA-TI model and found that the gain exceeds the DC gain in certain frequency ranges. Additionally, the phase margin is worse with the capacitor compared to without the capacitor (115 degrees -> 30 degrees).
1. Could you explain why adding a capacitor causes oscillation?
2. Any design guide to prevent this issue? Like design considerations specifically for the output terminal, recommended values of Phase margin and design considerations of INA210