AMC1301-Q1 Datasheet, PDF (17/34 Pages) Texas Instruments – Precision, 250-mV Input, Delay, Reinforced Isolated Amplifier

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8 Detailed Description
AMC1301-Q1
SBAS792A – APRIL 2017 – REVISED APRIL 2017
8.1 Overview
The AMC1301-Q1 device is a fully-differential, precision, isolated amplifier. 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.
The SiO₂-based, double-capacitive isolation barrier supports a high level of magnetic field immunity, as described
in ISO72x Digital Isolator Magnetic-Field Immunity. The digital modulation used in the AMC1301-Q1 device and
the isolation barrier characteristics result in high reliability and common-mode transient immunity.
8.2 Functional Block Diagram
AMC1301-Q1
VDD1
Band-Gap
Reference
Isolation
Barrier
VDD2
Band-Gap
Reference
VINP
+
±
VINN
û -Modulator
Data
TX
Retiming and
4^th-Order
VOUTP
RX
Active
Low-Pass
Filter
VOUTN
CLK _RX
TX
Oscillator
GND1
GND2
Copyright © 2016, Texas Instruments Incorporated
8.3 Feature Description
8.3.1 Analog Input
The AMC1301-Q1 device incorporates front-end circuitry that contains a fully-differential amplifier followed by a
ΔΣ modulator sampling stage. 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. Consider the input impedance of the AMC1301-Q1 device in
designs with high-impedance signal sources that may 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 this effect.
There are two restrictions on the analog input signals (VINP and VINN). First, if the input voltage exceeds the
range GND1 – 6 V to VDD1 + 0.5 V, then the input current must be limited to 10 mA because the device input
electrostatic discharge (ESD) protection 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.
Copyright © 2017, Texas Instruments Incorporated
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