SBAS667F April   2016  – April 2020

PRODUCTION DATA.

1. Features
2. Applications
3. Description
1.     Device Images
4. Revision History
5. Device Comparison Table
6. Pin Configuration and Functions
7. Specifications
8. Parameter Measurement Information
9. Detailed Description
1. 9.1 Overview
2. 9.2 Functional Block Diagram
3. 9.3 Feature Description
4. 9.4 Device Functional Modes
10. 10Application and Implementation
1. 10.1 Application Information
2. 10.2 Typical Applications
1. 10.2.1 Frequency Inverter Application
2. 10.2.2 Isolated Voltage Sensing
3. 10.3 What To Do and What Not TO Do
11. 11Power Supply Recommendations
12. 12Layout
13. 13Device and Documentation Support
14. 14Mechanical, Packaging, and Orderable Information

• DWV|8

#### 10.2.2.2 Detailed Design Procedure

As indicated in Figure 52, the output of the integrated differential amplifier is internally biased to a common-mode voltage of 2 V. This voltage results in a bias current IIB through the resistive network R4 and R5 (or R4' and R5') used for setting the gain of the amplifier. The value of this current is specified in the Pin Configuration and Functions section. This bias current generates additional offset and gain errors that depend on the value of the resistor R3. Because the value of this bias current depends on the actual common-mode amplitude of the input signal (as shown in Figure 53), the initial system offset calibration eliminates the offset but not the gain error component. Therefore, in systems with high accuracy requirements, a series resistor is recommended to be used at the negative input (VINN) of the AMC1301 with a value equal to the shunt resistor R3 (that is, R3' = R3 in Figure 52) to eliminate the effect of the bias current.

This additional series resistor (R3') influences the gain error of the circuit. The effect is calculated using Equation 2 with R4 = R4' = 12.5 kΩ. The effect of the internal resistors R5 = R5' cancels in this calculation.

Equation 2.