MCP3909 Microchip Technology, MCP3909 Datasheet - Page 30

• Manufacturer Part Number: MCP3909
• Description: Energy Metering IC with SPI Interface and Active Power Pulse Output
• Manufacturer: Microchip Technology

MCP3909
6.0
The following application figures represent meter
designs using the MCP3909 device. Some of these
applications ideas are available as fully function meter
reference designs and demo boards. For complete
schematic and for fully function meter designs, visit
Microchip’s web page for demo board and reference
design availability.
.
FIGURE 6-1:
are used on MCP3909 Energy Meter Reference Design.
DS22025A-page 30
CURRENT
MCP3909
VOLTAGE
ADC
ADC
APPLICATIONS INFORMATION
PIC Microcontroller
Power Calculations from Waveform sampling using PIC MCU. Register names shown
X
2
Φ
X
PHA_V_RMS_OFF:16
X
2
Σ
PHA_DELAY:8
PHA_I_RMS_OFF:16
PHA_W_OFF:32
Σ
Σ
6.1
Figure 6-1
form data based on a PIC MCU and MCP3909 device.
The PIC MCU accomplishes the following energy
meter calculation outputs per phase, per line cycle:
Output registers for the power quantities and calibra-
tion registers for phase, offset, gain, and LSB adjust-
ment are available through a serial interface to the PIC
microcontroller. See Microchip’s web page for firmware
solution and demo board.
The example signal flow here shows 4 output power
quantities and 6 calibration registers. For a 60 Hz
design that is using 128 samples per line cycle for the
power calculation the MCP3909 would have a new
data ready pulse every 130 µs. The SPI communica-
tion to gather 16-bits x 2 channels at 10 MHz is
approximately 3.2 µs, leaving ~125 µs for the power
calculations before the next sample is ready.
PHA_W_GAIN:16
- RMS Current
- RMS Voltage
- Active Power
- Apparent Power
X
Performing RMS, Apparent Power,
and Active Power using MCP3909
Waveform data
represents power calculations from wave-
X
PHA_VA_GAIN:16
© 2006 Microchip Technology Inc.
X
RMS Current
Apparent Power
Active Power
RMS Voltage