8 Application and Implementation

Note

Information in the following applications sections is not part of the TI component specification,

and TI does not warrant its accuracy or completeness. TI’s customers are responsible for

determining suitability of components for their purposes, as well as validating and testing their design

implementation to confirm system functionality.

8.1 Application Information

Isolated amplifiers are widely used for voltage measurements in high-voltage applications that must be isolated

from a low-voltage domain. A typical application is the sensing of the DC link voltage in a frequency inverter.

The high input impedance, low input bias current, low temperature drift, and high DC accuracy make the

AMC3311 a high-performance solution for applications where isolated voltage measurements are required.

8.2 Typical Application

Figure 8-1 shows a simplified schematic of the AMC3311 in a typical motor drive application. The DC link voltage

is divided down to an approximate 2-V level across the bottom two sense resistors (RSNS1 + RSNS2) of a

high-impedance resistive divider. This voltage is sensed by the AMC3311. The AMC3311 digitizes the analog

input signal on the high-side, transfers the data across the isolation barrier to the low-side, and reconstructs an

analog signal that is presented as a differential voltage on the output pins OUTN and OUTP.

2.2 µF

100 nF

VDD1

GND1

IN

REF

AMC23C11

VDD2

LATCH

OUT

GND2

to MCU

from MCU

100 nF

1 nF

100 nF

1 nF

100 nF

100 pF

FB1

FB2

RSNS1

DCDC_OUT

DCDC_HGND

HLDO_IN

HLDO_OUT

HGND

IN

HGND

NC

AMC3311

100 nF

4.7 k

DCDC_IN

LDO_OUT

VDD

OUTP

OUTN

GND

DIAG

DCDC_GND

5 V supply

RREF

1 nF

1 nF

1 nF

RSNS2

DC-link +

DC-link –

Number of unit resistors depends

on design requirements.

See design examples for details.

power module

ICROSS

M

3~

RX1

RX2

ADC

Figure 8-1. The AMC3311 in a Motor Drive Application

The AMC3311 integrates an isolated power supply for the high-voltage side and therefore is particularly easy to

use in applications that do not have a high-side supply readily available. In this example, the integrated power

supply of the AMC3311 is also used to power an AMC23C11 isolated, high-speed comparator that is used for

low-latency overvoltage detection on the DC link.

The AMC23C11 isolated comparator senses the voltage across the bottom resistor (RSNS2) of the resistive

divider and compares that value against an adjustable reference voltage (VREF). The isolated comparator pulls

down the open-drain output on the low-side whenever the input voltage exceeds the reference value. For a

detailed description of the isolated comparator, see the AMC23C11 data sheet available for download at ti.com.

AMC3311

SBASAQ5A – JUNE 2023 – REVISED AUGUST 2023

www.ti.com

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