AMC1100_15 Datasheet, PDF (18/33 Pages) Texas Instruments – AMC1100 Fully-Differential Isolation Amplifier

AMC1100
SBAS562A – APRIL 2012 – REVISED DECEMBER 2014
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Typical Applications (continued)
The analog output of the device is converted to the digital domain using the on-chip analog-to-digital converters
(ADCs) of a suitable metrology microcontroller. The architecture of the MSP430F471x7 family of ultra-low power
microcontrollers is tailored for this kind of applications. The MSP430F471x7 offers up to seven ADCs for
simultaneous sampling: six of which are used for the three phase currents and voltages whereas the seventh
channel can be used for additional voltage sensing of the neutral line for applications that require anti-tampering
measures.
8.2.2.2 Detailed Design Procedure
The high-side supply for the AMC1100 can be derived from the phase voltage using a capacitive-drop power
supply (cap-drop), as shown in Figure 37 and described in the application report SLAA552, AMC1100:
Replacement of Input Main Sensing Transformer in Inverters with Isolate Amplifier.
Phase
470 n / 400 V
220
1N4007
5.1 V
5.6V
470 µ / 10 V
Neutral
GND
Figure 37. Cap-Drop High-Side Power Supply for the AMC1100
Alternatively, the high-side power supply for each AMC1100 can also be derived from the low-side supply using
the SN6501 to drive a transformer, as proven by the TI reference design TIPD121, Isolated Current Sensing
Reference Design Solution, 5A, 2kV.
8.2.2.3 Application Curve
One of the key parameters of an e-meter is its noise performance, which is mainly influenced by the performance
of the ADC and the current sensor. When using a shunt-based approach, the sensor front-end consists of the
actual shunt resistor and the isolated amplifier. Figure 38 shows the typical output noise density of the AMC1100
as a basis for overall performance estimations.
2600
2400
2200
2000
1800
1600
1400
1200
1000
800
600
0.1
1
10
100
Frequency (kHz)
Figure 38. Output Noise Density of the AMC1100
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