7 Detailed Description

7.1 Overview

The AMC3330 is a fully-differential, precision, isolated amplifier with high input impedance, and an integrated

DC/DC converter that allows the device to be supplied from a single 3.3-V or 5-V voltage supply source on the

low side. The input stage of the device drives a second-order, delta-sigma (ΔΣ) modulator. The modulator uses

an internal voltage reference and clock generator to convert the analog input signal to a digital bitstream. The

drivers (termed 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 analog

output.

A block diagram of the AMC3330 is shown in the Functional Block Diagram. The 1.2-GΩ differential input

impedance of the analog input stage supports low gain-error signal-sensing in high-voltage applications using

high-impedance resistor dividers.

isolation uses an on-chip transformer separated by a thin-film polymer as the insulating material.

7.2 Functional Block Diagram

Retiming and

4

Active

Low-Pass

Filter

Isolation

Barrier

AMC3330

RX

GND

û Modulator

VDD

Resonator and

Driver

LDO

Rectifier

TX

HGND

LDO_OUT

DCDC_IN

DCDC_GND

TX

RX

Diagnostics

DIAG

Oscillator

OUTP

OUTN

Bandgap

Reference

LDO

HLDO_OUT

INP

INN

DCDC_OUT

DCDC_HGND

HLDO_IN

7.3 Feature Description

7.3.1 Analog Input

The input stage of the AMC3330 feeds a second-order, switched-capacitor, feed-forward ΔΣ modulator. The

modulator converts the analog signal into a bitstream that is transferred over the isolation barrier, as described in

the Isolation Channel Signal Transmission section. The high-impedance, and low bias-current input of the

AMC3330 makes the device suitable for isolated, high-voltage-sensing applications that typically employ high-

impedance resistor dividers.

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

range specified in the Absolute Maximum Ratings table, the input current must be limited to 10 mA because the

device input electrostatic discharge (ESD) diodes turn on. Second, the linearity and noise performance of the

device are ensured only when the differential analog input voltage remains within the specified linear full-scale

Operating Conditions table.

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AMC3330

SBASA34A – JUNE 2020 – REVISED OCTOBER 2020

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Product Folder Links: AMC3330