AMC1204-Q1_15 Datasheet, PDF (21/33 Pages) Texas Instruments – 20 MHz, Second-Order, Isolated Delta-Sigma Modulator for Current-Shunt Measurement

AMC1204-Q1
www.ti.com
SLAS886B – JULY 2012 – REVISED JANUARY 2013
APPLICATION INFORMATION
A typical operation of the AMC1204-Q1 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-Q1 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 5 V ±10%. A decoupling capacitor of 0.1
µF 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 1 µF to 10 µF
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-Q1. If a four-terminal shunt is used, the inputs of
AMC1204-Q1 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)
AMC1204-Q1
C₁₍₁₎
0.1mF
AVDD
VINP
DVDD
DATA
VINN CLKIN
AGND DGND
Gated
Drive
Circuit
HV-
(1) Place C₁ close to the AMC1204-Q1.
Figure 50. Typical Application Diagram
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