10.2.2 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 the Input and Output Capacitors 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

0.1 μF

0.1 μF

Figure 10-2. Basic Reference Connection

10.2.2.1 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

Input voltage range VIN

0 V - 5 V

Output resolution

12-bit

REF35 input capacitor

1 µF

REF35 output capacitor

10 µF

10.2.2.2 Detailed Design Procedure

10.2.2.2.1 Selection of Reference

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

current while offering ±0.05% initial accuracy and very low noise. 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.

10.2.2.2.2 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.

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REF35

SNAS809A – DECEMBER 2021 – REVISED AUGUST 2022

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