Datasheet

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
N L
SCK
SDI
SDO
CS
CLKIN
CH0+
CH0-
CH1+
CH1-
AV
DD
,DV
DD
A
GND
,D
GND
MCP3909
RC3/SCK
RC5/SDO
RC4/SDI
RA0/ANO
GND
PIC MCU
40 MHZ
RC1/CCP2
RX/RC6
TX/RC7
RB0 RB7
...
LCD
kW
kWhr
kVAhr
A
V
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