MCP3909T(2006) データシートの表示（PDF） - Microchip Technology

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MCP3909T
(Rev.:2006)

Energy Metering IC with SPI Interface and Active Power Pulse Output

Microchip Technology 

MCP3909

N

L

Resistor Divider

CH0+

CH0-

CH1+

CH1-

AVDD,DVDD CLKIN

MCP3909

AGND,DGND

SCK

SDI

SDO

CS

Power Supply

Circuitry

PHA_W:16

ENERGY_W:64

ENERGY_VA_GLSB:16

PHA_I_RMS:16

PHA_V_RMS:16

kW

kWhr

kVAhr

A

V

LCD

RC1/CCP2

RC3/SCK

RC5/SDO

RC4/SDI

RA0/ANO

...

OSC1

OSC2

GND

RX/RC6

TX/RC7

RS-232

To PC or

Calibration

Equipment

FIGURE 6-3:

Simplified MCU Based Energy Meter.

6.3 Meter Calibration

To achieve meter calibration the MCP3909 waveform

samples are adjusted during the power calculations on

the PIC MCU. In Figure 6-3, this interface is shown via

RS-232 on the PIC microcontroller. This process is

streamlined using calibration software available from

Microchip’s web site.

6.4 Analog Meter Design Tips

For analog design tips and PCB layout recommenda-

tions, refer to AN994, "IEC Compliant Active Energy

Meter Design Using The MCP390X” (DS00994). This

application note includes all required energy meter

design information, including the following:

• Meter rating and current sense choices

• Shunt design

• PGA selection

• F2, F1, F0 selection

• Meter calibration

• Anti-aliasing filter design

• Compensation for parasitic shunt inductance

• EMC design

• Power supply design

• No-Load threshold

• Start-up current

• Accuracy Testing Results from MCP390X-based

meter

• EMC Testing Results from MCP390X-based

meter

DS22025A-page 32

© 2006 Microchip Technology Inc.

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