MCP3909-I/SS Microchip Technology, MCP3909-I/SS Datasheet - Page 28

• Manufacturer Part Number: MCP3909-I/SS
• Description: IC POWER METERING-1 PHASE 24SSOP
• Manufacturer: Microchip Technology

Specifications of MCP3909-I/SS

• Package / Case: 24-SSOP (0.200", 5.30mm Width)
• Input Impedance: 390 KOhm
• Measurement Error: 0.1%
• Voltage - I/o High: 2.4V
• Voltage - I/o Low: 0.85V
• Current - Supply: 2.3mA
• Voltage - Supply: 4.5 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Meter Type: Single Phase
• Operating Temperature Range: - 40 C to + 85 C
• Mounting Style: SMD/SMT
• Supply Voltage Range: 4.5V To 5.5V
• Digital Ic Case Style: SSOP
• No. Of Pins: 24
• Interface Type: Serial, SPI
• Supply Voltage Max: 5.5V
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: MCP3909EV-MCU16 - EVALUATION BOARD FOR MCP3909MCP3909RD-3PH1 - REF DESIGN MCP3909 3PH ENGY MTR
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

MCP3909 / dsPIC33F 3-Phase Energy Meter Reference Design
DS51723A-page 28
After system power-up, the MCU enters the initialization process, which includes
proper configuration of the I/O ports and on-chip peripherals (such as timer, UART, SPI
and IC). At the same time, the system control parameters can be loaded from the
external EEPROM and variables are all initialized.
Since most tasks of this system are accomplished through interrupts, only three tasks
are carried out in the system main loop, which are interpreting/processing UART
communication protocol, calculating parameters, and detecting neutral current. The
UART communication is performed in function UART_process(), the executing
frequency of which depends on the polling frequency of the upper computer.
Parameters are calculated by the function Calculation(), which is executed once every
3 cycles of the power grid. Neutral current is detected by function ComputeNeutral-
Current(), and computing is performed once every 16 cycles of the power grid.
© 2009 Microchip Technology Inc.