AMC1305L25 Datasheet, PDF (23/39 Pages) Texas Instruments – AMC1305x High-Precision, Reinforced Isolated Delta-Sigma Modulators

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AMC1305L25, AMC1305M05, AMC1305M25
SBAS654C – JUNE 2014 – REVISED DECEMBER 2014
10.2 Typical Applications
10.2.1 Frequency Inverter Application
Because to their high ac and dc performance, isolated ΔΣ modulators are being widely used in new generation
frequency inverter designs. Frequency inverters are critical parts of industrial motor drives, photovoltaic inverters
(string and central inverters), uninterruptible power supplies (UPS), electrical and hybrid electrical vehicles, and
other industrial applications. The input structure of the AMC1305 is optimized for use with low-impedance shunt
resistors and is therefore tailored for isolated current sensing using shunts.
DC link
Gate Driver
Gate Driver
Gate Driver
RSHUNT
RSHUNT
RSHUNT
Gate Driver
5.0 V
AMC1305
AVDD DVDD
AINP DOUT
AINN CLKIN
AGND DGND
3.3 V
Gate Driver
5.0 V
AMC1305
AVDD DVDD
AINP DOUT
AINN CLKIN
AGND DGND
3.3 V
Gate Driver
5.0 V
AMC1305
AVDD DVDD
AINP DOUT
AINN CLKIN
AGND DGND
3.3 V
5.0 V
AMC1305
AVDD DVDD
AINP DOUT
AINN CLKIN
AGND DGND
3.3 V
TMS320F2837x
SD-D1
SD-C1
SD-D2
SD-C3
SD-D4
SD-C4
SD-D5
SD-C5
Figure 51. The AMC1305 in a Frequency Inverter Application
10.2.1.1 Design Requirements
A typical operation of the device in a frequency inverter application is shown in Figure 51. When the inverter
stage is part of a motor drive system, measurement of the motor phase current is done via the shunt resistors
(R_SHUNT). Depending on the system design, either all three or only two phase currents are sensed.
In this example, an additional fourth AMC1305 is used to support isolated voltage sensing of the dc link. This
high voltage is reduced using a high-impedance resistive divider before being sensed by the device across a
smaller resistor. The value of this resistor can degrade the performance of the measurement, as described in the
Isolated Voltage Sensing section.
10.2.1.2 Detailed Design Procedure
The usually recommended RC filter in front of a ΔΣ modulator to improve signal-to-noise performance of the
signal path, is not required for the AMC1305. By design, the input bandwidth of the analog front-end of the
device is limited to 1 MHz.
For modulator output bit-stream filtering, a device from TI's TMS320F2837x family of dual-core MCUs is
recommended. This family supports up to eight channels of dedicated hardwired filter structures that significantly
simplify system level design by offering two filtering paths per channel: one providing high accuracy results for
the control loop and one fast response path for overcurrent detection.
Copyright © 2014, Texas Instruments Incorporated
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