9.2.1.1 Design Requirements

A detailed design procedure is based on a design example. For this design example, use the parameters listed

in Table 9-2 as the input parameters.

Table 9-2. Design Example Parameters

DESIGN PARAMETER

VALUE

Input voltage VIN

3 V

Input capacitor

0.1-µF

Output capacitor

10-µF

9.2.1.2 Detailed Design Procedure

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 9-2. REF54250CDR Startup Response(CL=10 uF)

REF54

SNVSCN7 – NOVEMBER 2023

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