SBAS949A February   2020  – February 2021

PRODUCTION DATA

1. Features
2. Applications
3. Description
4. Revision History
5. Pin Configuration and Functions
6. Specifications
7. Parameter Measurement Information
8. Detailed Description
1. 8.1 Overview
2. 8.2 Functional Block Diagram
3. 8.3 Feature Description
4. 8.4 Device Functional Modes
1. 8.4.1 Power-Up and Reset
2. 8.4.2 Fast Startup Behavior
3. 8.4.3 Conversion Modes
4. 8.4.4 Power Modes
5. 8.4.5 Standby Mode
6. 8.4.6 Current-Detect Mode
5. 8.5 Programming
1. 8.5.1 Interface
2. 8.5.2 Synchronization
6. 8.6 Registers
9. Application and Implementation
1. 9.1 Application Information
2. 9.2 Typical Application
1. 9.2.1 Design Requirements
2. 9.2.2 Detailed Design Procedure
3. 9.2.3 Application Curves
10. 10Power Supply Recommendations
11. 11Layout
12. 12Device and Documentation Support
13. 13Mechanical, Packaging, and Orderable Information

• PBS|32
• RSN|32
• PBS|32
• RSN|32

#### 9.2.2.1 Voltage Measurement Front-End

The nominal voltage from the mains is from 100 V – 240 V so this voltage must be scaled down to be sensed by an ADC. Figure 9-6 shows the analog front-end used for this voltage scaling.

Figure 9-6 Voltage Measurement Front-End

The analog front-end for voltage consists of a spike protection varistor (RV), a voltage divider network (RHI and RLO), and an RC low-pass filter (RFILT and CFILT).

Equation 11 shows how to calculate the range of differential voltages fed to the voltage ADC channel for a given mains voltage and the selected voltage divider resistor values.

Equation 11.

RHI is 300 kΩ and RLO is 750 Ω in this design. For a mains voltage of 240 V (as measured between the line and neutral), the input signal to the voltage ADC has a voltage swing of ±256 mV (182 mVRMS) based on Equation 11 and the selected resistor values. This voltage is well within the ±1.2-V input voltage range that can be sensed by the ADS131M06 for the selected PGA gain value of 1 that is used for the voltage channels.