4

active

low-pass

filter

Isolation

Barrier

OUTP

OUTN

HLDOout

AMC3301

RX

GND

Bandgap

Reference

Oscillator

INP

INN

Diagnostic

û Modulator

VDD

DCDCout

Resonator

and

Driver

LDO

Rectifier

TX

HGND

LDOout

DCDCin

DCDCgnd

TX

RX

Diagnostics

Bandgap

Reference

LDO

DCDChgnd

HLDOin

11

AMC3301

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7 Detailed Description

7.1 Overview

The AMC3301 is a fully-differential, precision, isolated amplifier with fully integrated DC/DC converter that allows

to supply the device from a single 3.3-V or 5-V voltage supply source on the low-side. The input stage of the

device consists of a fully-differential amplifier that drives a second-order, delta-sigma (ΔΣ) modulator. The

modulator uses the internal voltage reference and clock generator to convert the analog input signal to a digital

bitstream. The drivers (called TX in the Functional Block Diagram) transfer the output of the modulator across the

isolation barrier that separates the high-side and low-side voltage domains. The received bitstream and clock are

synchronized and processed by a fourth-order analog filter on the low-side and presented as a differential output

of the device, as shown in the Functional Block Diagram.

7.2 Functional Block Diagram

7.3 Feature Description

7.3.1 Analog Input

The differential amplifier input stage of the AMC3301 feeds a second-order, switched-capacitor, feed-forward ΔΣ

modulator. The gain of the differential amplifier is set by internal precision resistors to a factor of 4 with a

differential input impedance of 22 kΩ. The modulator converts the analog signal into a bitstream that is

transferred over the isolation barrier, as described in the Data Isolation Channel Signal Transmission section.

There are two restrictions on the analog input signals (INP and INN). First, if the input voltage exceeds the range

HGND – 6 V to HLDOout + 0.5 V, the input current must be limited to 10 mA because the device input

electrostatic discharge (ESD) diodes turns on. In addition, the linearity and noise performance of the device are

ensured only when the analog input voltage remains within the specified linear full-scale range (FSR) and within

the specified common-mode input voltage range.