MCP3909-I/SS Microchip Technology, MCP3909-I/SS Datasheet - Page 96

• Manufacturer Part Number: MCP3909-I/SS
• Description: IC POWER METERING-1 PHASE 24SSOP
• Manufacturer: Microchip Technology

Specifications of MCP3909-I/SS

• Package / Case: 24-SSOP (0.200", 5.30mm Width)
• Input Impedance: 390 KOhm
• Measurement Error: 0.1%
• Voltage - I/o High: 2.4V
• Voltage - I/o Low: 0.85V
• Current - Supply: 2.3mA
• Voltage - Supply: 4.5 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Meter Type: Single Phase
• Operating Temperature Range: - 40 C to + 85 C
• Mounting Style: SMD/SMT
• Supply Voltage Range: 4.5V To 5.5V
• Digital Ic Case Style: SSOP
• No. Of Pins: 24
• Interface Type: Serial, SPI
• Supply Voltage Max: 5.5V
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: MCP3909EV-MCU16 - EVALUATION BOARD FOR MCP3909MCP3909RD-3PH1 - REF DESIGN MCP3909 3PH ENGY MTR
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

MCP3909 / dsPIC33F 3-Phase Energy Meter Reference Design
C.14 RELATIONSHIP BETWEEN ERROR AND CURRENT
DS51723A-page 96
For a given load and frequency, the absolute ratio error and angle error increase when
the primary current decreases from the rated value for un-compensated current trans-
former. The reason is that with the decrease of the secondary current, the magnetic
permeability µ of the iron core varies non-linearly, resulting in less reduction in the field
ampere turns.
Figure C-8 is a typical curve for load current and the phase lag of a CT. Generally,
phase lag of the output signal is great when the load current is small, and also
increases at a fast rate.
FIGURE C-8:
Current Load Versus CT Phase Lag.
Phase Lag
Current Load
© 2009 Microchip Technology Inc.