MCP3909-ESLASHSS datasheet(34/44 Pages) MICROCHIP

34 / 44 page

MCP3909

DS22025C-page 34

 2006-2012 Microchip Technology Inc.

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

the 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

SCK

SDI

SDO

CLKIN

CH0+

CH0-

CH1+

CH1-

AVDD,DVDD

AGND,DGND

MCP3909

RC3/SCK

RC5/SDO

RC4/SDI

RA0/ANO

GND

RC1/CCP2

RX/RC6

TX/RC7

...

LCD

kWhr

kVAhr

PHA_W:16

ENERGY_W:64

ENERGY_VA_GLSB:16

PHA_I_RMS:16

PHA_V_RMS:16

RS-232

To PC or

Calibration

Equipment

OSC1

OSC2

Resistor Divider

Power Supply

Circuitry

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