AMC1200_15 Datasheet, PDF (13/31 Pages) Texas Instruments – AMC1200/B Fully-Differential Isolation Amplifier

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AMC1200, AMC1200B
SBAS542D – APRIL 2011 – REVISED JULY 2015
The safety-limiting constraint is the operating virtual junction temperature range specified in the Absolute
Maximum Ratings table. The power dissipation and junction-to-air thermal impedance of the device installed in
the application hardware determine the junction temperature. The assumed junction-to-air thermal resistance in
the Thermal Information table is that of a device installed in the JESD51-3, Low Effective Thermal Conductivity
Test Board for Leaded Surface Mount Packages and is conservative. The power is the recommended maximum
input voltage times the current. The junction temperature is then the ambient temperature plus the power times
the junction-to-air thermal resistance.
7.3.6 Regulatory Information
VDE/IEC
Certified according to VDE V 0884-10
Certificate number: 40016131
UL
Recognized under 1577 component recognition program
File number: E181974
7.3.7 Isolation Amplifier
The AMC1200 device consists of a second order delta-sigma modulator input stage including an internal
reference and clock generator. The output of the modulator and clock signal are differentially transmitted over the
integrated capacitive isolation barrier that separates the high- and low-voltage domains. The received bitstream
and clock signals are synchronized and processed by a third-order analog filter with a nominal gain of 8 on the
low-side and presented as a differential output of the device, as shown in Functional Block Diagram section.
7.3.8 Analog Input
The analog input range is tailored to directly accommodate a voltage drop across a shunt resistor used for
current sensing. However, there are two restrictions on the analog input signals, VINP and VINN. If the input
voltage exceeds the range AGND – 0.5 V to AVDD + 0.5 V, the input current must be limited to 10 mA to prevent
the implemented input protection diodes from damage. In addition, the linearity and the noise performance of the
device are ensured only when the differential analog input voltage remains within ±250 mV.
The differential analog input of the AMC1200 and AMC1200B devices is a switched-capacitor circuit based on a
second-order modulator stage that digitizes the input signal into a 1-bit output stream. These devices compare
the differential input signal (V_IN = VINP – VINN) against the internal reference of 2.5 V using internal capacitors
that are continuously charged and discharged with a typical frequency of 10 MHz. With the S1 switches closed,
C_IND charges to the voltage difference across VINP and VINN. For the discharge phase, both S1 switches open
first and then both S2 switches close. C_IND discharges to approximately AGND + 0.8 V during this phase.
Figure 31 shows the simplified equivalent input circuitry.
VDD1
GND1
GND1
VINP
VINN
GND1
C_INP = 3pF
400W
S1
S1 400W
S2
C_IND = 3.6pF
S2
AGND + 0.8V
Equivalent
Circuit
AGND + 0.8V
C_INN = 3pF
GND1
R_IN
=
f_CLK
1
· C_DIFF
(f_CLK = 10MHz)
Figure 31. Equivalent Input Circuit
VINP
VINN
3pF
R_IN = 28kW
3pF
GND1
7.4 Device Functional Modes
The AMC1200 is operational when the power supplies VDD1 and VDD2 are applied as specified in the
Recommended Operating Conditions section.
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Product Folder Links: AMC1200 AMC1200B
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