AMC1304L05_15 Datasheet, PDF (24/39 Pages) Texas Instruments – AMC1304x High-Precision,Reinforced Isolated Delta-Sigma Modulators with LDO

AMC1304L05, AMC1304L25, AMC1304M05, AMC1304M25
SBAS655C – SEPTEMBER 2014 – REVISED SEPTEMBER 2015
www.ti.com
9.2 Typical Applications
9.2.1 Frequency Inverter Application
Isolated ΔΣ modulators are being widely used in new-generation frequency inverter designs because to their high
ac and dc performance. 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 AMC1304 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
L1
RSHUNT
RSHUNT
L3
L2
Gate Driver
15 V
AMC1304
LDOIN DVDD
AINP DOUT
AINN
AGND
CLKIN
DGND
3.3 V
Gate Driver
15 V
AMC1304
LDOIN DVDD
AINP DOUT
AINN CLKIN
AGND DGND
3.3 V
Gate Driver
15 V
AMC1304
LDOIN DVDD
AINP DOUT
AINN
AGND
CLKIN
DGND
3.3 V
15 V
AMC1304
LDOIN DVDD
AINP DOUT
AINN CLKIN
AGND DGND
3.3 V
TMS320F28x7x
SD-D1
SD-C1
SD-D2
SD-C2
SD-D3
SD-C3
SD-D4
SD-C4
Figure 51. The AMC1304 in a Frequency Inverter Application
9.2.1.1 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 AMC1304 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.
9.2.1.2 Detailed Design Procedure
The typically recommended RC filter in front of a ΔΣ modulator to improve signal-to-noise performance of the
signal path is not required for the AMC1304. 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 TMS320F2807x family of low-cost microcontrollers
(MCUs) or TMS320F2837x family of dual-core MCUs is recommended. These families support 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.
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