MicrochipPIC18F87J72單相電表參考設(shè)計

Microchip公司的PIC18F87J72是集成了雙路24位AFE,LCD驅(qū)動器的高性能微控制器,具有nanoWatt技術(shù),每路的模擬特性包括90 dB SINAD, -101 dBc THD (到35次諧波)以及103 dB SFDR,和10ppm INL,差分輸入引腳,可編程數(shù)據(jù)速率到64ksps,高增益PGA到32V/V,基準電壓源低漂移(12ppm/度C),主要用在低成本電表,電源測量和監(jiān)視,手持儀表和醫(yī)療監(jiān)視.本文介紹了PIC18F87J72主要特性,功能框圖,單相電表應(yīng)用電路圖以及PIC18F87J72單相電表參考設(shè)計主要特性,電路圖,材料清單和PCB布局圖.

This family combines the traditional advantages of all PIC18 microcontrollers – namely, high computational performance and a rich feature set – with a versatile on-chip LCD driver and a high-performance, high-accuracy analog front end. These features make the PIC18F87J72 family a logical choice for many high-performance power and metering applications where price is a primary consideration.

PIC18F87J72主要特性:

Analog Features:

 Dual-Channel, 24-Bit Analog Front End (AFE):

- 90 dB SINAD, -101 dBc THD (to 35th harmonic),103 dB SFDR for each channel

- 10 ppm INL

- Differential voltage input pins

- Low drift internal voltage reference (12 ppm/C)

- Programmable data rate to 64 ksps

- High-gain PGA on each channel (up to 32 V/V)

- Phase delay compensation between channels (1 s resolution)

12-Bit, 12-Channel SAR A/D Converter:

- Auto-acquisition

- Conversion available during Sleep

 Two Analog Comparators

 Programmable Reference Voltage for Comparators

 Charge Time Measurement Unit (CTMU):

- Capacitance measurement

- Time measurement with 1 ns typical resolution

- Temperature sensing

LCD Driver and Keypad Interface

Features:

 Direct LCD Panel Drive Capability:

- Can drive LCD panel while in Sleep mode

- Wake-up from interrupt

 Up to 33 Segments and 132 Pixels: Software Selectable

 Programmable LCD Timing module:

- Multiple LCD timing sources available

- Up to four commons: static, 1/2, 1/3 or

1/4 multiplex

- Static, 1/2 or 1/3 bias configuration

 On-Chip LCD Boost Voltage Regulator for

Contrast Control

 CTMU for Capacitive Touch Sensing

 ADC for Resistive Touch Sensing

Flexible Oscillator Structure:

 External Crystal and Clock modes, with operation

up to 48 MHz

 4x Phase Lock Loop (PLL)

 Internal Oscillator Block with PLL:

- Eight user-selectable frequencies from 31.25 kHz to 8 MHz

 Secondary Oscillator using Timer1 at 32 kHz

 Fail-Safe Clock Monitor (FSCM):

- Allows for safe shutdown if peripheral clock fails

Low-Power Features:

 Power-Managed modes:

- Run: CPU on, peripherals on

- Idle: CPU off, peripherals on

- Sleep: CPU off, peripherals off

 Two-Speed Oscillator Start-up

Peripheral Highlights:

 High-Current Sink/Source 25 mA/25 mA (PORTB and PORTC)

 Up to Four External Interrupts

 Four 8-Bit/16-Bit Timer/Counter modules

 Two Capture/Compare/PWM (CCP) modules

 Master Synchronous Serial Port (MSSP) module with

Two Modes of Operation:

- 3-wire/4-wire SPI (supports all four SPI modes)

- I2C. Master and Slave mode

 One Addressable USART module

 One Enhanced Addressable USART module:

- LIN/J2602 support

- Auto-wake-up on Start bit and Break character

- Auto-Baud Detect (ABD)

 Hardware Real-Time Clock and Calendar (RTCC) with

Clock, Calendar and Alarm Functions

Special Microcontroller Features:

 10,000 Erase/Write Cycle Flash Program Memory, Typical

 Flash Retention 20 Years, Minimum

 Self-Programmable under Software Control

 Word Write Capability for Flash Program Memory for Data EEPROM Emulators

 Priority Levels for Interrupts

 8 x 8 Single-Cycle Hardware Multiplier

 Extended Watchdog Timer (WDT):

- Programmable period from 4 ms to 131s

 Selectable Open-Drain Configuration for Serial Communication and CCP pins for Driving Outputs up to 5V

 In-Circuit Serial Programming. (ICSP.) via Two Pins

 In-Circuit Debug via Two Pins

 Operating Voltage Range: 4.5V to 5.5V (兇兠僴ADC), 2.0V to 3.6V (digital and SAR ADC)

 5.5V Tolerant Input (digital pins only)

 On-Chip 2.5V Regulator

PIC18F87J72目標應(yīng)用:

 Energy Metering

 Power Measurement and Monitoring

 Portable Instrumentation

 Medical Monitoring

圖1.PIC18F87J72功能框圖


圖2.PIC18F87J72單相電表應(yīng)用電路圖

PIC18F87J72單相電表參考設(shè)計

The PIC18F87J72 Single-Phase Energy Meter Reference Design is a fully functional single-phase meter based on the highly integrated PIC18F87J72 single-chip energy meter IC. This low-cost design does not use any transformers and requires few external components. The PIC18F87J72 directly drives the LCD, and includes both an isolated USB connection and a non-isolated RS-232 interface for meter calibration and access to the device power calculations. The system calculates active energy, active power, reactive energy, reactive power, RMS current, RMS voltage 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3.PIC18F87J72單相電表外形圖

PIC18F87J72單相電表參考設(shè)計主要特性:

? Working single phase energy meter

? Energy calculation firmware: Active/Reactive Energy; Forward/Reverse Energy; Active/Reactive/Apparent Power; RMS Current Voltage; Editable by meter designer

? GUI-assisted software calibration

? LCD display for energy

? Low cost shunt based design

? Better than IEC Class 0.5 performance

圖4.PIC18F87J72單相電表參考設(shè)計電路圖
PIC18F87J72單相電表參考設(shè)計材料清單(BOM):




圖5.PIC18F87J72單相電表PCB布局圖(頂層)(1)

圖5.PIC18F87J72單相電表PCB布局圖(頂層)(2)


圖7.PIC18F87J72單相電表PCB布局圖(底層)(1)


圖8.PIC18F87J72單相電表PCB布局圖(底層)(2)
詳情請見:
http://ww1.microchip.com/downloads/en/DeviceDoc/39979A.pdf
和
http://ww1.microchip.com/downloads/en/DeviceDoc/51931a.pdf
以及
http://ww1.microchip.com/downloads/en/DeviceDoc/103-00280-R2.pdf