MCP3901EV-MCU16 Microchip Technology, MCP3901EV-MCU16 Datasheet - Page 10

• Manufacturer Part Number: MCP3901EV-MCU16
• Description: BOARD EVAL FOR 2CH ADC MCP3901
• Manufacturer: Microchip Technology

Specifications of MCP3901EV-MCU16

• Number Of Adc's: 2
• Number Of Bits: 24
• Data Interface: SPI™
• Inputs Per Adc: 1 Differential
• Input Range: ±1 V
• Voltage Supply Source: Analog and Digital
• Operating Temperature: -40°C ~ 85°C
• Utilized Ic / Part: MCP3901
• Silicon Manufacturer: Microchip
• Application Sub Type: ADC
• Kit Application Type: Data Converter
• Silicon Core Number: MCP3901, PIC24F, PIC24H, DsPIC33, PIC18F86J55
• Kit Contents: Board
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

1.2
1.3
1.4
DS51915A-page 10
ANALOG INPUT CIRCUIT
POWER CIRCUIT
PIC18F25K20 MICROCONTROLLER AND LIQUID CRYSTAL DISPLAY (LCD)
The MCP3901 Low-Cost Power Monitor Reference Design uses an MCP3901 dual
ADC to acquire current and voltage samples. For best performance, the power supply
and ground must be noise free. To ensure low noise, large capacitors are located on
the lines that power the MCP3901 device, i.e., C4 and C5. Additionally, multi-layer
ceramic capacitors are located near the ADC, on the C13 and C14 pins, to ensure that
high-frequency noise is also eliminated.
The V
least one 100 nF multi-layer capacitor on the V
V
The MCP3901 Low-Cost Power Monitor is provided with a 200 µ shunt as a current
sensor. The user has the option to use the two current transformer footprints U1 and
U10 that are available on the printed circuit board (PCB). Refer to the board schematic
in the appendix, A.1 “Board Schematic – Analog and Power”.
The MCP3901 Power Monitor Reference Design does not contain a crystal – it uses
the clock signal from the output compare pin RC2/CCP1 of the PIC18F25K20 micro-
controller (MCU).
Two voltages are required for the power monitor reference design:
For this reason, two MCP1703 Low Dropout Voltage Regulators (LDOs) are placed
after the C51 capacitor, with the required voltages at the outputs.
The meter is powered from the capacitive divider, mainly C6 and U53. A parametric
regulator circuit, using Zener diode D5, limits the input voltage of the LDOs to 12V.
Rectifier diode D2 restricts the current flow to a single direction, while ripple is reduced
by C51 and the LDOs.
A PIC18F25K20 MCU is used in this application for its high speed (16 MIPS) and low
power (nanoWatt XLP technology). It also has an internal EEPROM, where the calibra-
tion constants are saved.
Because the MCU does not include an LCD driver, the LCD used in this reference
design has the driver built in. The connection between the LCD and the MCU carries
four lines of data and three lines of control.
REF
- 3.3V for the MCU
- 5V for the ADC
, a larger capacitor has been added (C77).
REF
is potentially another source of noise. Accordingly, it is mandatory to place at
REF
pin. For better noise rejection on
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