AMC1304L05DW datasheet(22/46 Pages) TI2

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û -Modulator

1.25-V

Reference

DOUT

CLKIN

DVDD

DGND

AGND

AINP

AINN

VCAP

BUF

AMC1304

DOUT_N (AMC1304Lx only)

CLKIN_N (AMC1304Lx only)

Voltage Regulator

(LDO)

LDOIN

AMC1304L05, AMC1304L25, AMC1304M05, AMC1304M25

SBAS655F – SEPTEMBER 2014 – REVISED JANUARY 2020

www.ti.com

Product Folder Links: AMC1304L05 AMC1304L25 AMC1304M05 AMC1304M25

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8 Detailed Description

8.1 Overview

The differential analog input (AINP and AINN) of the AMC1304 is a fully-differential amplifier feeding the

switched-capacitor input of a second-order, delta-sigma (ΔΣ) modulator stage that digitizes the input signal into a

1-bit output stream. The isolated data output (DOUT and DOUT_N) of the converter provides a stream of digital

ones and zeros that is synchronous to the externally-provided clock source at the CLKIN pin with a frequency in

the range of 5 MHz to 20.1 MHz. The time average of this serial bit-stream output is proportional to the analog

input voltage.

The Functional Block Diagram section shows a detailed block diagram of the AMC1304. The analog input range

is tailored to directly accommodate a voltage drop across a shunt resistor used for current sensing. The SiO2-

based capacitive isolation barrier supports a high level of magnetic field immunity as described in the ISO72x

Digital Isolator Magnetic-Field Immunity application report (SLLA181A), available for download at www.ti.com.

The external clock input simplifies the synchronization of multiple current-sensing channels on the system level.

The extended frequency range of up to 20 MHz supports higher performance levels compared to the other

solutions available on the market.

8.2 Functional Block Diagram

8.3 Feature Description

8.3.1 Analog Input

The AMC1304 incorporates a front-end circuitry that contains a differential amplifier and sampling stage, followed

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

devices with a specified input voltage range of ±250 mV (this value is for the AMC1304x25), or to a factor of 20

in devices with a ±50-mV input voltage range (for the AMC1304x05), resulting in a differential input impedance of

5 kΩ (for the AMC1304x05) or 25 kΩ (for the AMC1304x25).

Consider the input impedance of the AMC1304 in designs with high-impedance signal sources that can cause

degradation of gain and offset specifications. The importance of this effect, however, depends on the desired

system performance. Additionally, the input bias current caused by the internal common-mode voltage at the

output of the differential amplifier causes an offset that is dependent on the actual amplitude of the input signal.

See the Isolated Voltage Sensing section for more details on reducing these effects.

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

range AGND – 6 V to 3.7 V, the input current must be limited to 10 mA because the device input electrostatic

discharge (ESD) diodes turn on. In addition, the linearity and noise performance of the device are ensured only

when the differential analog input voltage remains within the specified linear full-scale range (FSR), that is

±250 mV (for the AMC1304x25) or ±50 mV (for the AMC1304x05), and within the specified input common-mode

range.

AMC1304L05DW Datasheet(PDF) 22 Page - Texas Instruments

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