MCP3909RD-3PH3 Microchip Technology, MCP3909RD-3PH3 Datasheet - Page 55

• Manufacturer Part Number: MCP3909RD-3PH3
• Description: REF DESIGN FOR MCP3909 W/18F2520
• Manufacturer: Microchip Technology

Specifications of MCP3909RD-3PH3

• Main Purpose: Power Management, Energy/Power Meter
• Utilized Ic / Part: MCP3909, PIC18F2520, PIC18F4550
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Secondary Attributes: -
• Embedded: -
• Primary Attributes: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

© 2008 Microchip Technology Inc.
5.3.9
For active power offset the following equations apply for a given phase. W1 corre-
sponds to the PHy_W_RAW register obtained during configuration C1. LINE_CYC_W1
corresponds to the LINE_CYC during this measurement.
W2 corresponds to the PHy_W_RAW register obtained during configuration C3.
LINE_CYC_W2 is the LINE_CYC during this measurement.
EQUATION 5-16:
EQUATION 5-17:
EQUATION 5-18:
EQUATION 5-19:
EQUATION 5-20:
The PHy_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:
PHY_W_OFF
LINE_CYC_NUM_1
LINE_CYC_NUM_2
Equations for Active Power Offset Calibration
Convert to 32-bit signed integer for compatibility with 18F2520 register and
firmware calculations
W2
W1
=
PHY_W_RAW @ 1/100 I
=
=
PHY_W_RAW @ I
----------------------------------------------------- -
LINE_CYC_NUM_W1
=
=
W1 100
LINE_CYC_NUM in Configuration C1
LINE_CYC_NUM in Configuration C3
⁄
B,
Configuration C1
B
, Configuration C3
–
Meter Calibration
----------------------------------------------------- -
LINE_CYC_NUM_W2
W2
DS51643B-page 51