Microchip公司的PIC18F87J72是集成了雙路24位AFE,LCD驅動器的高性能微控制器,具有nanoWatt技術,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,可編程數據速率到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,電源測量和監視,手持儀表和醫療監視.本文介紹了PIC18F87J72主要特性,功能框圖,單相電表應用電路圖以及PIC18F87J72單相電表參考設計主要特性,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單相電表應用電路圖
PIC18F87J72單相電表參考設計
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單相電表參考設計電路圖
PIC18F87J72單相電表參考設計材料清單(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
