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INA210: oscillation issue at Vout with a 100nF capacitor

Part Number: INA210
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.

under 316 mA807 mA

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).

With C5545with C5545_Bode

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

  • Tim, 

    The oscillation can be explained by the capacitance of your C5544 capacitor (100nF). According to INA210 data sheet, the INA210 cannot drive an output capacitance over 1nF, this is what is causing the oscillation.

    We recommend staying within the data sheet parameters for best results. However, if you would like to stick with the 100nF capacitor, you could increase the resistance of your R5588 resistor to 1k ohms and that should eliminate the oscillation.