9 Detailed Description

9.1 Overview

The REF34xx is family of 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 REF34xx showing

basic band-gap topology.

9.2 Functional Block Diagram

Bandgap

core

Buffer

Digital

Enable

Blocks

Inrush

EN

IN

GNDF

OUTS

Current

Vdd

GNDS

OUTF

Limit

9.3 Feature Description

9.3.1 Supply Voltage

The REF34xx family of references features an extremely low dropout voltage. For loaded conditions, a typical

dropout voltage versus load is shown on the front page. The REF34xx features a low quiescent current that

is extremely stable over changes in both temperature and supply. The typical room temperature quiescent

current is 72 μA, and the maximum quiescent current over temperature is just 95 μA. Supply voltages below the

specified levels can cause the REF34xx to momentarily draw currents greater than the typical quiescent current.

Use a power supply with a fast rising edge and low output impedance to easily prevent this issue.

9.3.2 Low Temperature Drift

The REF34xx is designed for minimal drift error, which is defined as the change in output voltage over

temperature. The drift is calculated using the box method, as described by Equation 3. For this equation, VREF is

VOUT which is the output voltage seen at the junction of OUT_F and OUT_S.

REF(MAX)

REF(MIN)

6

REF(25 C)

V

V

Drift

10

V

Temperature Range

q

§

·

u

¨

¸

¨

¸

u

©

¹

(3)

9.3.3 Load Current

The REF34xx family is specified to deliver a current load of ±10 mA per output. The device temperature

increases according to Equation 4:

J

A

D

JA

T

T

P

R

T

u

(4)

where

• TJ = junction temperature (°C),

• TA = ambient temperature (°C),

• PD = power dissipated (W), and

• RθJA = junction-to-ambient thermal resistance (°C/W)

The REF34xx maximum junction temperature must not exceed the absolute maximum rating of 150°C.

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REF3425, REF3430, REF3433, REF3440, REF3450

SBAS804F – SEPTEMBER 2017 – REVISED JUNE 2021

Copyright © 2021 Texas Instruments Incorporated

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Product Folder Links: REF3425 REF3430 REF3433 REF3440 REF3450