Microchip 双路AFE结和PIC18F65J90 高性能超低耗电表参考设计

中心议题：
    *  MCP3901主要特性
解决方案：
    *  ＭCP3901集合PIC18F65J90的电表参考设计

Microchip公司的MCP3901是两路模拟前端(AFE),集成了两个同步取样16位/24位Delta-Sigma ADC,两个PGA,相位延迟补偿的内部基准电压,调制器输出区块,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,可编数据速率高达64ksps.主要用在电表和能量管理,汽车,手提仪表,医疗和电源监视.本文介绍了MCP3901主要特性,方框图以及采用MCP3901和PIC18F65J90电表参考设计的数字连接框图,PIC18F65J90计算引擎信号流程图,参考设计电路图,材料清单和PCB元件布局图.
 
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应用:

• Energy Metering and Power Measurement

• Automotive

• Portable Instrumentation

• Medical and Power Monitoring


图1.MCP3901方框图

MCP3901和PIC18F65J90电表参考设计

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.[member]


图2.MCP3901和PIC18F65J90 单相电表外形图

图3.电表参考设计数字连接框图

图4.PIC18F65J90计算引擎信号流程图

图5.电表参考设计电路图(1)

图6.电表参考设计电路图(2)

图7.电表参考设计电路图(3)

电表参考材料清单(BOM):


BILL OF MATERIALS (COMPONENTS NOT INSTALLED)


图8.电表参考PCB元件布局图(顶层)

图9.电表参考PCB元件布局图(底层)