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AD5725 VREFN oscillation

Thread Summary

The user is experiencing oscillation at VREFN of the AD5725 when transitioning between -10V and -5V input ranges, despite using a 0.22uF bypass capacitor. The final answer suggests that the issue is related to the ADA4077-4 buffer's response to capacitive loads and recommends adding a series resistor to stabilize the op amp, while noting that an RC snubber does not affect the ringing. The ADR01 reference IC and 4 matched resistor array are also part of the configuration.
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I'm using the AD5725 operating with the following input ranges : +/- 5V , +/-10V and any combination in between that doesn't violate the operating condition of VREF. 

Since I'm using the +/-10V reference, I placed a 0.22uF bypass capacitor at inputs. The reference IC is a precise one : ADR01 and its voltage output is configured through a 4 matched resistor array to provide the various reference voltage. The ADA4077-4 is the buffer used for VREF inputs.

However, after experimenting some transitions from -10V to -5V as an example, the added 0.22uF bypass capacitor is adding a pole that causes oscillation at VREFN. Adding a series resistor seems to prevent the op amp from oscillating, however, adding a RC snubber doesn't... Is there any explanation based on the mentioned components that would explain why the snubber doesn't affect at all the ringing observed? 

Regards,

Carl Trudeau

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