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| AMC1204_1108 Datasheet, PDF (21/30 Pages) Texas Instruments – 20MHz, Second-Order, Isolated Delta-Sigma Modulator for Current-Shunt Measurement | |||
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AMC1204
www.ti.com
SBAS512B â APRIL 2011 â REVISED AUGUST 2011
APPLICATION INFORMATION
A typical operation of the AMC1204 in a motor control application is shown in Figure 50. Measurement of the
motor phase current is done via the shunt resistor RSHUNT (in this case, a two-terminal shunt). For better
performance, the differential signal is filtered using RC filters (components R2, R3, and C2). Optionally, C3 and C4
can be used to reduce charge dumping from the inputs. In this case, care should be taken when choosing the
quality of these capacitorsâmismatch in values of these capacitors leads to a common-mode error at the input of
the modulator.
The high-side power supply for the AMC1204 (AVDD) is derived from the power supply of the upper gate driver.
For lowest cost, a zener diode can be used to limit the voltage to 5V ±10%. A decoupling capacitor of 0.1µF is
recommended for filtering this power-supply path. This capacitor (C1 in Figure 50) should be placed as close as
possible to the AVDD pin for best performance. If better filtering is required, an additional 1µF to 10µF capacitor
can be used. The floating ground reference AGND is derived from the end of the shunt resistor, which is
connected to the negative input of the AMC1204 (VINN). If a four-terminal shunt is used, the inputs of AMC1204
are connected to the inner leads, while AGND is connected to one of the outer leads of the shunt. Both digital
signals, CLKIN and DATA, can be directly connected to a digital filter (for example, the AMC1210); see
Figure 51.
HV+
Floating
Power Supply
Isolation
Barrier
To Load
RSHUNT
Gated
Drive
Circuit
Power
Supply
R1
D1
R2
5.1V 12W
R3
12W
C2
330pF
C3
10pF
(optional)
C4
10pF
(optional)
AMC1204
C1(1)
0.1mF
AVDD
VINP
DVDD
DATA
VINN CLKIN
AGND DGND
Gated
Drive
Circuit
HV-
(1) Place C1 close to the AMC1204.
Figure 50. Typical Application Diagram
Copyright © 2011, Texas Instruments Incorporated
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