7 Detailed Description

7.1 Overview

The AMC3302 is a fully differential, precision, isolated amplifier with a fully integrated DC/DC converter that can

supply the device from a single 3.3-V or 5-V voltage supply 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 an internal voltage reference and clock generator to convert the analog input signal to a digital bitstream.

The drivers (termed TX in Section 7.2) transfer the output of the modulator across the isolation barrier that

separates the high-side and low-side voltage domains. As shown in Section 7.2, 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

The signal path is isolated by a double capacitive silicon dioxide (SiO2) insuation barrier, whereas power

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

AMC3302

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

DCDC_OUT

DCDC_HGND

HLDO_IN

INP

INN

7.3 Feature Description

7.3.1 Analog Input

The differential amplifier input stage of the AMC3302 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 Section 7.3.2.

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

HGND – 6 V to HLDO_OUT + 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.

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AMC3302

SBASA11 – AUGUST 2020

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