JAJSS83B November 2023 – June 2024 REF54
PRODUCTION DATA
A bulk capacitor (0.1 μF to 10 μF) must be connected to the supply to improve transient response in the applications where the supply voltage can fluctuate. Connect an additional 0.1 μF capacitor at VIN pin closer to the device to bypass high frequency supply noise.
A low ESR (maximum 1 Ω) capacitor of 1 μF to 100 μF must be connected to the output to provide stable output. For very low noise applications, special care must be taken with X7R and other MLCC capacitors due to their piezoelectric effect. Piezoelectric property of multilayer ceramic capacitors (MLCC) can introduce a μV range noise due to mechanical vibrations, potentially dominating the noise of the REF54. 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). Designer must use film capacitors for noise sensitive applications. TI recommends placing the REF54 reference as close to the load as possible to minimize IR drop due to trace resistance.
The transient startup response of the REF54 is shown in Figure 9-2. The startup response of the REF54 family is dependent on the output and NR pin capacitor. Increasing the output capacitor improves the load transient performance of the device, however this also increases the startup time. Figure 9-3 shows the startup time with CNR = 10 μF, increases to 3 seconds.