MCP3909RD-1PH1 Microchip Technology, MCP3909RD-1PH1 Datasheet - Page 43

• Manufacturer Part Number: MCP3909RD-1PH1
• Description: BOARD DES MCP3909 ENERGY METER
• Manufacturer: Microchip Technology

Specifications of MCP3909RD-1PH1

• Main Purpose: Power Management, Energy/Power Meter
• Embedded: Yes, MCU, 8-Bit
• Utilized Ic / Part: MCP3909, PIC18F85J90
• Primary Attributes: Single Phase Shunt Energy Meter
• Secondary Attributes: 16 Bit ADC
• Ic Function: Single Phase Energy Measurement IC
• Supply Voltage Range: 4.5V To 5.5V
• Operating Temperature Range: -40°C To +85°C
• Digital Ic Case Style: SSOP
• No. Of Pins: 24
• Interface Type: SPI
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

© 2009 Microchip Technology Inc.
5.3.7
For active power offset, the following equations apply for a given phase. W1
corresponds to the PHA_W_RAW register obtained during configuration C1.
LINE_CYC_W1 corresponds to the LINE_CYC during this measurement.
W2 corresponds to the PHA_W_RAW register obtained during configuration C3.
LINE_CYC_W2 is the LINE_CYC during this measurement.
EQUATION 5-14:
EQUATION 5-15:
EQUATION 5-16:
EQUATION 5-17:
EQUATION 5-18:
The PHA_W_OFF registers hold a signed 32-bit value. However, the math in the
microcontroller could overflow for some values near the limits. Limit check the resulting
value to make sure the value is between -2,130,706,432 and 2,130,706,431 (inclusive).
Values less than -2,130,706,432 should be set to -2,130,706,432 while values greater
than 2,130,706,431 should be set to 2,130,706,431. If the value is limited, the user
should be aware that the meter could not completely correct the offset.
It is expected that this value will always be negative. If the value is positive, it may
indicate that the user has not provided a large enough number of line cycles for
configuration C4 (where the number of line cycles should be set to a larger value such
as 64 or 128). This may also be true if offset does not contribute a large enough
percentage to W2 (for example, 10% to 50% or more).
Note:
PHA_W_OFF
LINE_CYC_NUM_1
LINE_CYC_NUM_2
Configuration C3 Equations - P
Convert to 32-bit signed integer for compatibility with PIC18F85J90 register
and firmware calculations
W2
W1
=
PHA_W_RAW @ 1/100 I
=
=
PHA_W_RAW @ I
----------------------------------------------------- -
LINE_CYC_NUM_W1
=
=
W1 100
LINE_CYC_NUM in Configuration C1
LINE_CYC_NUM in Configuration C3
⁄
B,
A
Configuration C1
B
Offset
, Configuration C3
–
Meter Calibration
----------------------------------------------------- -
LINE_CYC_NUM_W2
W2
DS51884A-page 43