Microchip Technology MCP3901EV-MCU16 User Manual
MCP3901 ADC Evaluation Board for 16-Bit MCUs User’s Guide
DS51845B-page 12
2010 Microchip Technology Inc.
1.3
MCP3901 DELTA-SIGMA SAMPLING/MCLK OPTIONS
The MCP3901 device is an ADC with a second order modulator and a third order sync
filter. This Delta-Sigma A/D converter has an adjustable oversampling ratio. The CLKIN
pin of the MCP3901 is the oversampling clock (MCLK) input. The MCP3901 ADC
Evaluation Board for 16-Bit MCUs offers two different options for the MCP3901 master
clock (MCLK).
filter. This Delta-Sigma A/D converter has an adjustable oversampling ratio. The CLKIN
pin of the MCP3901 is the oversampling clock (MCLK) input. The MCP3901 ADC
Evaluation Board for 16-Bit MCUs offers two different options for the MCP3901 master
clock (MCLK).
1.3.1
Using the Crystal X2
The MCP3901 ADC Evaluation Board for 16-Bit MCUs is populated with a 3.58 MHz
crystal, which is used as a clock source by placing jumpers in the following position on
the MCP3901 Digital I/O header block:
crystal, which is used as a clock source by placing jumpers in the following position on
the MCP3901 Digital I/O header block:
FIGURE 1-3:
ADC Clock Selection Jumpers – External Crystal.
1.3.2
Driving the Clock with the PIM Module
The PIC MCU can be used to generate the CLKIN (MCLK) signal for the MCP3901,
setting the ADC sample rate through the use of the output compare module OC1. To
use this, make the following jumper change to the MCP3901 Digital I/O header block:
setting the ADC sample rate through the use of the output compare module OC1. To
use this, make the following jumper change to the MCP3901 Digital I/O header block:
FIGURE 1-4:
ADC Clock Selection Jumpers – Clock from MCU.
The frequency of the OC1 output is based on the PR1 bits settings in the firmware
(for both PIC24 and dsPIC33 PIM modules supplied with this system). The signal
frequency from OC1 can be changed by the user from the PS software by changing the
value in the sampling rate control box. A low number will generate a high frequency sig-
nal. The value of the sampling rate, which is directly proportional with the clock
frequency from OC1, is indicated in the sampling speed indicator box in the PC
software (see Figure 3-1).
(for both PIC24 and dsPIC33 PIM modules supplied with this system). The signal
frequency from OC1 can be changed by the user from the PS software by changing the
value in the sampling rate control box. A low number will generate a high frequency sig-
nal. The value of the sampling rate, which is directly proportional with the clock
frequency from OC1, is indicated in the sampling speed indicator box in the PC
software (see Figure 3-1).
XTAL
XTAL
XTAL
PIM OC1
CLKIN
CLKIN
CLKOUT
XTAL
XTAL
XTAL
PIM OC1
CLKIN
CLKIN
CLKOUT