Microchip Technology MCP3905A, Справочный проект, Страница: 14 / 24

MCP3905A/06A Energy Meter Reference Design
DS51565B-page 10
©
2009 Microchip Technology Inc.
FIGURE 2-3: MCP3905A/06A Energy Meter Reference Design Block Diagram.
2.5 FRONT-SIDE OF PCB DETAILED DESCRIPTION
2.5.1 Shunts for Gain and FC Selection (J11-J15)
Positions for both logic-high and logic-low are here for all gain and frequency constant
selections. The logic-high positions are labeled “J1H” and the logic-low positions are
labeled “J1L” (Jumper 1 used here as an example). Do not short both the high and the
low positions for any one jumper.
2.5.2 Calibration Jumpers (J1-J10)
Calibration resistors for each of these jumper locations are located directly beneath the
associated jumper. When a shorting resistor or jumper is in place, the associated
calibration resistor is shorted and bypassed.
2.5.3 Output Connections for Mechanical Counter and Calibration
(JP5-JP7)
JP5 and JP6 are the differential output drive for the mechanical counter.
JP7 is the calibration or microcontroller output that is connected to HF
OUT
on the
MCP3905A/06A devices. A LED is supplied to assist in any optical calibration
schemes.
2.5.4 Connection to Current-Sensing Element (JP1,JP2)
These two connections lead directly through LRC filtering into Channel 0 of the
MCP3905A/06A. The schematic in Appendix A uses a low-cost shunt as the
current-sensing element. The shunt resistance should be placed in parallel with these
two connections, between JP1 and JP2.
FRONT
Power Supply
Ground Plane
Analog
Ground Plane
BACK
DC Power
Supply
(U1)
Opto.
Isolator (U3)
MOV1
Power Supply
Ground Plane
Analog
Ground Plane
Voltage Conn.
(JP3,JP4)
Current Conn.
(JP1,JP2)
Calibration
Jumpers (J1-J10)
Shunts for Gain,
FC and HPF
Selection (J11-J15)
Output Connections (JP5-JP7)
MCP3905A