8 Detailed Description

8.1 Overview

The REF54 is family of high precision series references that are designed for excellent initial voltage accuracy

and drift over time and temperature, and offer excellent noise while consuming low power. The Figure 8-1 is a

simplified block diagram of the REF54 showing basic band-gap topology.

8.2 Functional Block Diagram

VIN

Digital

Core

Bandgap

Core

RNR

Buffer

EN

Control

EN

GND

NR

VREF

Figure 8-1. REF54 Functional Block Diagram

8.3 Feature Description

8.3.1 EN Pin

The output of REF54 comes in active state when EN pin voltage is more than 1.6V or EN pin is left floating. The

enable feature of the REF54 is designed to achieve low quiescent current (IQ) . No current is drawn from EN pin

when EN pin is voltage is lower than VIN pin voltage. The device must be in active mode for normal operation.

The REF54 can be placed in shutdown mode by pulling the EN pin low. When in shutdown mode, the output of

the device is disabled and the quiescent current of the device reduces to 1.2 µA in shutdown mode. The EN pin

must not be pulled higher than VIN supply voltage. See the electrical table for logic high and logic low voltage

levels.

8.3.2 NR Pin

Decoupling NR pin in REF54 creates a low pass filter in combination with the internal resistance of 13 kΩ

to eliminate internal band gap noise. Unlike regular low pass filter at the output of the reference, connecting

a capacitor on NR pin doesn't affect the output impedance hence extra buffer is not needed. Leakage of the

capacitor directly impacts the accuracy and temperature drift. If NR functionality is used, choose a capacitor

which has low leakage over temperature. Please note, using the capacitor on NR pin also increases start-up

time.

REF54

SNVSCN7 – NOVEMBER 2023

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