AMC1204_12 Datasheet, PDF (21/32 Pages) Texas Instruments – 20MHz, Second-Order, Isolated Delta-Sigma Modulator for Current-Shunt Measurement

AMC1204
AMC1204B
www.ti.com
SBAS512C – APRIL 2011 – REVISED AUGUST 2012
APPLICATION INFORMATION
A typical operation of the AMC1204 and AMC1204B in a motor control application is shown in Figure 50.
Measurement of the motor phase current is done via the shunt resistor R_SHUNT (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 capacitors—mismatch in values of these capacitors leads to a common-mode
error at the input of the modulator.
The high-side power supply (AVDD) for the AMC1204 and AMC1204B 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 (VINN) of the AMC1204 and AMC1204B. If a four-terminal
shunt is used, the inputs of AMC1204 and AMC1204B 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.
Floating
HV+ ^{Power Supply}
Isolation
Barrier
To Load
R_SHUNT
Gated
Drive
Circuit
Power
Supply
R₁
D₁
R₂
5.1V 12W
R₃
12W
C₂
330pF
C₃
10pF
(optional)
C₄
10pF
(optional)
C₁₍₁₎
0.1mF
AMC1204
AMC1204B
AVDD DVDD
VINP DATA
VINN CLKIN
AGND DGND
Gated
Drive
Circuit
HV-
(1) Place C₁ close to the AMC1204 and AMC1204B.
Figure 50. Typical Application Diagram
Copyright © 2011–2012, Texas Instruments Incorporated
Product Folder Links: AMC1204 AMC1204B
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