AMC1200-Q1_16 Datasheet, PDF (14/30 Pages) Texas Instruments – Fully-Differential Isolation Amplifier

AMC1200-Q1
SBAS585A – SEPTEMBER 2012 – REVISED JANUARY 2016
www.ti.com
7.3.5 Analog Input
The analog input voltage range (V_IN = V_VINP – V_VINN) is tailored to directly accommodate a voltage drop across a
shunt resistor used for current sensing. Note that there are two restrictions on the analog input signals. If the
absolute input voltage on either VINP or VINN exceeds the absolute maximum range of GND1 – 0.5 V to VDD1
+ 0.5 V, the input current must be limited to 10 mA to prevent damage of the integrated input protection diodes.
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-Q1 is a switched-capacitor circuit based on a second-order
modulator stage that digitizes the input signal into a 1-bit output stream. The device compares the differential
input signal V_IN against the internal 2.5-V reference using internal capacitors that are continuously charged and
discharged with a typical frequency of 10 MHz. With the S1 switches closed, C_ID 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_ID discharges to approximately GND1 + 0.8 V during this phase. Figure 31 shows the simplified
equivalent input circuitry.
VDD1
GND1
GND1
VINP
VINN
C_INP = 3 pF
400 W
S1
S1 400 W
C_INN = 3 pF
S2
C_IND = 3.6 pF
S2
GND1 + 0.8 V
Equivalent
Circuit
VINP
GND1 + 0.8 V
VINN
3 pF
R_IN = 28 kW
3 pF
GND1
GND1
R_IN
=
f_CLK
1
x C_DIFF
(f_CLK = 10 MHz)
Figure 31. Equivalent Input Circuit
GND1
7.4 Device Functional Modes
The AMC1200-Q1 is operational when the power supplies VDD1 and VDD2 are applied as specified in the
Recommended Operating Conditions section. The AMC1200-Q1 does not have any additional functional modes.
14
Submit Documentation Feedback
Copyright © 2012–2016, Texas Instruments Incorporated
Product Folder Links: AMC1200-Q1