R
2
12W
R
3
12W
R
SHUNT
AMC1200
Gated
Drive
Circuit
ToLoad
Floating
PowerSupply
HV+
Isolation
Barrier
C
2
(1)
330pF
C
3
10pF
(optional)
VDD1
VINP
VINN
GND1
VDD2
VOUTP
VOUTN
GND2
C
4
10pF
(optional)
C
1
(1)
0.1 Fm
D
1
5.1V
R
1
Gated
Drive
Circuit
Power
Supply
HV-
C
5
(1)
0.1 Fm
ADC
TMC320
C/F28xxx
AMC1200
SBAS542 –APRIL 2011
www.ti.com
APPLICATION INFORMATION
MOTOR CONTROL
A typical operation of the AMC1200 in a motor-control application is shown in Figure 32. Measurement of the
motor phase current is done through the shunt resistor, R
SHUNT
(in this case, a two-terminal shunt). For better
performance, the differential signal is filtered using RC filters (components R
2
, R
3
, and C
2
). Optionally, C
3
and C
4
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.
(1) Place these capacitors as close as possible to the AMC1200.
Figure 32. Typical Application Diagram for the AMC1200
The high-side power supply for the AMC1200 (VDD1) 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 (C
1
in Figure 32) should be placed as close as
possible to the VDD1 pin for best performance. If better filtering is required, an additional 1-µF to 10-µF capacitor
can be used. The floating ground reference (GND1) is derived from the end of the shunt resistor, which is
connected to the negative input of the AMC1200 (VINN). If a four-terminal shunt is used, the inputs of AMC1200
are connected to the inner leads, while GND1 is connected to one of the outer leads of the shunt.
The high transient immunity of the AMC1200 ensures reliable and accurate operation even in high-noise
environments such as the power stages of the motor drives.
The differential output of the AMC1200 can either directly drive an analog-to-digital converter (ADC) input or can
be further filtered before being processed by the ADC.
As shown in Figure 33, it is recommended to place the bypass and filter capacitors as close as possible to the
AMC1200 to ensure best performance.
12 Copyright © 2011, Texas Instruments Incorporated
