A 1 μF to 10 μF bypass capacitor should be connected to the input to improve transient response in applications where the supply voltage may fluctuate. Connect an additional 0.1 μF capacitor in parallel to reduce high frequency supply noise.

A low ESR capacitor of 1 μF to 100 μF must be connected to the output to improve stability and help filter out high frequency noise. Best performance and stability is attained with low-ESR output capacitors with an ESR from 1 mΩ to 400 mΩ. For very low noise applications, special care must be taken with X7R and other MLCC capacitors due to their piezoelectric effect. Mechanical vibration can transduce to voltage via the piezoelectric effect which appears as noise in the μV range, potentially dominating the noise of the REF70. More information on how the piezoelectric effect can be explored in systems can be found in Stress-induced outbursts: Microphonics in ceramic capacitors (Part 1) and Stress-induced outbursts: Microphonics in ceramic capacitors (Part 2). It is recommended that to use film capacitors for noise sensitive applications.

The transient startup response of the REF70 is shown in Figure 10-2. The startup response of the REF70 family is dependent on the output capacitor. While larger capacitors will decrease the output noise, they will increase the startup response.