10.3 Typical Application: Precision Power Supply and Reference

Figure 10-2 shows the basic configuration for the REF35 device as precision power supply to ADS7038

data converter which uses its power supply AVDD as reference. Connect bypass capacitors according to the

guidelines in Section 10.3.2.2 section.

ADS7038

GND

REF35500

-

+

1

2

3

4

6

5

10 μF

GND

1 μF

AVDD

GND

+6 V

Input

0 V to 5 V

Figure 10-2. Basic Reference Connection

10.3.1 Design Requirements

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

parameters listed in Table 10-2 as the input parameters.

Table 10-2. Design Example Parameters

DESIGN PARAMETER

VALUE

0 V - 5 V

Output resolution

12-bit

REF35 input capacitor

1 µF

REF35 output capacitor

10 µF

10.3.2 Detailed Design Procedure

10.3.2.1 Selection of Reference

REF35500 reference is selected for this design. REF35500 device operates of very low quiescent current

while offering ±0.05 % initial accuracy and very low temperature drift. These parameters help improve system

accuracy as compared to external LDO based power supply. The 5 V reference voltage supports the 0 V to 5 V

input range specification.

10.3.2.2 Input and Output Capacitors

A 1-μF to 10-μF electrolytic or ceramic capacitor can be connected to the input to improve transient response in

applications where the supply voltage may fluctuate. Connect an additional 0.1-μF ceramic capacitor in parallel

to reduce high frequency supply noise.

A ceramic capacitor of at least a 0.1 μF must be connected to the output to improve stability and help filter out

high frequency noise. Add an additional 10-μF electrolytic or ceramic capacitor in parallel to improve transient

performance in response to sudden changes in load current; however, keep in mind that doing so increases the

start-up time of the device.

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REF35

SNAS809 – DECEMBER 2021

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