9 Detailed Description

9.1 Overview

The REF70 is family of ultra low-noise, precision bandgap voltage references that are specifically designed for

excellent initial voltage accuracy and drift. The Section 9.2 is a simplified block diagram of the REF70 showing

basic band-gap topology.

9.2 Functional Block Diagram

EN

Enable

Controller

Digital

Core

Bandgap

Core

Reference

Buffer

OUTF

+

Å

OUTS

VIN

GND

VIN

REN

9.3 Feature Description

9.3.1 EN Pin

The EN pin of the REF70 has an internal 16 MΩ pull-up resistor (REN) to VIN. This allows the EN pin of the

REF70 to be left floating. When the EN pin of the REF70 is pulled high, the device is in active mode. The device

must be in active mode for normal operation. The REF70 can be placed in shutdown mode by pulling the EN pin

low. When in shutdown mode, the output of the device becomes high impedance and the quiescent current of

the device reduces to 12 µA in shutdown mode. The EN pin must not be pulled higher than VIN supply voltage.

See the Section 7.6 for logic high and logic low voltage levels.

9.4 Device Functional Modes

9.4.1 Basic Connections

Figure 9-1 shows the typical connections for the REF70. TI recommends a supply bypass capacitor (CIN)

ranging from 0.1-μF to 10-μF. A 1-μF to 100-μF output capacitor (CL) must be connected from OUTF to GND.

The equivalent series resistance (ESR) value of CL must be 10mΩ to 400mΩ to ensure output stability.

REF7025

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GND

OUTS

OUTF

VIN

EN

AVDD

VOUT

CL

CIN

Figure 9-1. Basic Connections

9.4.2 Negative Reference Voltage

For applications requiring a negative and positive reference voltage, the REF70 and OPA211 can be used to

provide a dual-supply reference from a 5-V supply. Figure 9-2 shows the REF70 used to provide a 2.5-V supply

reference voltage and -2.5V negative reference voltage. The low noise performance of the REF70 complements

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REF70

SNAS781E – OCTOBER 2020 – REVISED JULY 2022

Copyright © 2022 Texas Instruments Incorporated

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Product Folder Links: REF70