AMC1200-Q1_16 Datasheet, PDF (16/30 Pages) Texas Instruments – Fully-Differential Isolation Amplifier

AMC1200-Q1
SBAS585A – SEPTEMBER 2012 – REVISED JANUARY 2016
Typical Applications (continued)
8.2.1.1 Design Requirements
Table 3 lists the parameters for the typical application in Figure 32.
Table 3. Design Requirements
PARAMETER
High-side supply voltage
Low-side supply voltage
Voltage drop across shunt for linear response
VALUE
5V
3 V, or 3.3 V, or 5 V
±250 mV (max)
www.ti.com
8.2.1.2 Detailed Design Procedure
The high-side power supply (VDD1) for the AMC1200-Q1 is derived from the power supply of the upper gate
driver. Further details are provided in the Power Supply Recommendations section.
The floating ground reference (GND1) is derived from one of the ends of the shunt resistor that is connected to
the negative input of the AMC1200-Q1 (VINN). If a four-pin shunt is used, the inputs of the AMC1200-Q1 are
connected to the inner leads and GND1 is connected to one of the outer shunt leads.
Use Ohm's Law to calculate the voltage drop across the shunt resistor (V_SHUNT) for the desired current to be
measured: V_SHUNT = I × R_SHUNT.
Consider the following two restrictions to choose the proper value of the shunt resistor R_SHUNT:
• The voltage drop caused by the nominal current range must not exceed the recommended differential input
voltage range: V_SHUNT ≤ ±250 mV
• The voltage drop caused by the maximum allowed overcurrent must not exceed the input voltage that causes
a clipping output: V_SHUNT ≤ V_Clipping
For best performance, use an RC filter (components R₂, R₃, and C₂ in Figure 32) to limit the noise bandwidth of
the differential input signal. Limiting the value of resistors R₂ and R₃ to less than 24 Ω is recommended to avoid
incomplete settling of the AMC1200-Q1 input circuitry (see Analog Input).
Optionally, the common-mode capacitors C₃ and C₄ can be used to reduce charge dumping from the inputs.
Mismatch in values of C₃ and C₄ leads to a common-mode error at the modulator input. In this case, choose the
value of the differential filter capacitor C₂ to be at least 10 times larger than the values of C₃ and C₄ to limit the
effect of the common-mode error. NP0-type capacitors are recommended to be used for C₂, C₃ and C₄.
The differential output of the AMC1200-Q1 can either directly drive an analog-to-digital converter (ADC) input or
can be further filtered before being processed by an ADC. For more information on the general procedure to
design the filtering and driving stages for SAR ADCs, consult the TI Precision Designs 18 bit, 1Msps Data
Acquisition Block Optimized for Lowest Distortion and Noise (SLAU515), and 18 bit Data Acquisition Block
Optimized for Lowest Power (SLAU513) available for download at www.ti.com.
16
Submit Documentation Feedback
Copyright © 2012–2016, Texas Instruments Incorporated
Product Folder Links: AMC1200-Q1