Microchip公司的MCP3901是兩路模擬前端(AFE),集成了兩個同步取樣16位/24位Delta-Sigma ADC,兩個PGA,相位延遲補償的內部基準電壓,調制器輸出區塊,以及高速成速0MHz SPI兼容的串行接口.每路具 91 dB SINAD, -104 dBc THD,109dB SFDR,可編數據速率高達64ksps.主要用在電表和能量管理,汽車,手提儀表,醫療和電源監視.本文介紹了MCP3901主要特性,方框圖以及采用MCP3901和PIC18F65J90電表參考設計的數字連接框圖,PIC18F65J90計算引擎信號流程圖,參考設計電路圖,材料清單和PCB元件布局圖.
 
The MCP3901 is a dual channel Analog Front End (AFE) containing two synchronous sampling Delta-Sigma Analog-to-Digital Converters (ADC), two PGAs, phase delay compensation block internal voltage reference, modulator output block, and high-speed 20 MHz SPI compatible serial interface. The converters contain a proprietary dithering algorithm for reduced Idle tones and improved THD.

The internal register map contains 24-bit wide ADC data words, a modulator output byte, as well as six writable control registers to program gain, oversampling ratio, phase, resolution, dithering, shutdown, Reset and several communication features.

The communication is largely simplified with various Continuous Read modes that can be accessed by the Direct Memory Access (DMA) of an MCU and with a separate data ready pin that can be connected directly to an Interrupt Request (IRQ) input of an MCU.

The MCP3901 is capable of interfacing to a large variety of voltage and current sensors, including shunts, current transformers, Rogowski coils and Halleffect Sensors.

MCP3901主要特性:

• Two Synchronous Sampling 16/24-bit Resolution Delta-Sigma A/D Converters with Proprietary Multi-Bit Architecture

• 91 dB SINAD, -104 dBc Total Harmonic Distortion (THD) (up to 35th harmonic), 109 dB Spurious-free Dynamic Range (SFDR) for Each Channel

• Programmable Data Rate up to 64 ksps

• Ultra Low-Power Shutdown mode with <2 μA

• -133 dB Crosstalk Between the Two Channels

• Low Drift Internal Voltage Reference: 12 ppm/℃

• Differential Voltage Reference Input Pins

• High Gain PGA on Each Channel (up to 32 V/V)

• Phase Delay Compensation Between the Two Channels with 1 μs time Resolution

• Separate Modulator Outputs for Each Channel

• High-Speed, Addressable 20 MHz SPI Interface with Mode 0,0 and 1,1 Compatibility

• Independent Analog and Digital Power Supplies: 4.5V-5.5V AVDD, 2.7V-5.5V DVDD

• Low-Power Consumption: (14 mW typical at 5V)

• Available in Small 20-lead SSOP and QFN Packages

• Industrial Temperature Ranges:

- Industrial: -40℃ to +85℃

- Extended: -40℃ to +125℃

MCP3901應用:

• Energy Metering and Power Measurement

• Automotive

• Portable Instrumentation

• Medical and Power Monitoring


圖1.MCP3901方框圖

MCP3901和PIC18F65J90電表參考設計

The MCP3901 and PIC18F65J90 Energy Meter Reference Design is a fully functional IEC Class 0.5 compliant single-phase meter. This low-cost design does not use any transformers and requires few external components. The PIC18F65J90 directly drives the LCD, and includes both an isolated USB connection for meter calibration and access to the device power calculations. The system calculates active energy, active power, RMS current, RMS voltage, reactive energy, reactive power, apparent power and other typical power quantities.

The Microchip Energy Meter 1-Phase Software is used to calibrate and monitor the system, and can be used to create custom calibration setups. For some accuracy requirements, only a single point calibration may be needed. The energy meter software offers an automated step-by-step calibration process that can be used to quickly calibrate energy meters.


圖2.MCP3901和PIC18F65J90 單相電表外形圖

圖3.電表參考設計數字連接框圖

圖4.PIC18F65J90計算引擎信號流程圖

圖5.電表參考設計電路圖(1)

圖6.電表參考設計電路圖(2)

圖7.電表參考設計電路圖(3)
電表參考材料清單(BOM):


BILL OF MATERIALS (COMPONENTS NOT INSTALLED)


圖8.電表參考PCB元件布局圖(頂層)

圖9.電表參考PCB元件布局圖(底層)
詳情請見:
http://ww1.microchip.com/downloads/en/DeviceDoc/39770c.pdf
和
http://ww1.microchip.com/downloads/en/DeviceDoc/51968A.pdf