MCP3901EV-MCU16 Microchip Technology, MCP3901EV-MCU16 Datasheet - Page 22

• 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

MCP3901 ADC Evaluation Board for 16-Bit MCUs User’s Guide
3.2
3.3
3.4
3.5
DS51845A-page 18
SETTING THE CONFIGURATION OF THE ADC
CONNECTIVITY AND RECORDING LENGTH
SCOPE PLOT WINDOW - TIME DOMAIN ANALYSIS
HISTOGRAM WINDOW - NOISE ANALYSIS
The MCP3901 Data View is able to set up the configuration registers of the MCP3901
by putting the desired value on the “Write Registers” tab. Usually, it takes a few seconds
to update the MCP3901 configuration. If the user wants to know the configuration of the
MCP3901 without changing it, then he can click the “Read Registers” tab and the same
image as in “Write Registers” will be found. The difference is that the controls are now
in fact indicators, and the user can't change the values, he can only read the setup of
the MCP3901.
The PC is connected to the MCP3901 ADC Evaluation Board for 16-Bit MCUs through
the RS232 cable. It is important to have a COM port on the PC. It is possible to use a
USB to RS232 adaptor cable, in this case being necessary to write the number of the
virtual COM port. To do this, right-click on My computer > Manage > Device Manager
> Port (COM and LPT), and read the number in parenthesis after the device name.
The COM port number must be selected in the “VISA Resource Name” field.
The MCU sends a big package of data to the PC. If the user needs to see only a small
part of the buffer, he will write the desired buffer length in the “Buffer length” field. The
maximum length is 512 samples.
The average control can be used to see the impact of averaging over the ADC
accuracy. The number of points in the waveform graph will be less than the number
written in the “Buffer Length” control by a ratio equal with the value of the average. A
value equal to zero will cause an error. The value 1 means that no averaging is done.
When the program is opened for the first time, the value from the controls will have
some default values. The user must set up the communication port before starting the
acquisition, by pressing the START button. To stop the acquisition, it is necessary to
press the STOP button. The MCP3901 Data View application can be closed by clicking
the X button in the upper right corner of the window.
The recorded samples from a buffer are indicated on the “Waveform Graphs” screens.
The size of the X axis is given by the number written in the “Buffer Length” field.
On the Y axis, the LSBs are indicated.
To scale the time axis, it is necessary to modify either the buffer length (the number of
points indicated in the waveform graph), or to change the sampling rate of the ADC.
The sampling rate of the ADC can be changed from the “Sampling Speed Control” box.
Writing a small value there, a high sampling rate will be obtained. The correct value of
the sampling rate is indicated in the “Sampling Speed Indicator”. The highest sampling
speed that can be obtained is 55 ksps by setting: OSR=32, Addr Loop = ALL and
Sampling Speed Control = 5.
For the evaluation of the Effective Number Of Bits (ENOB), the GUI will compute a few
statistical parameters: the “mean” value, “standard deviation”, and “variance” for each
channel. These parameters can be seen at the bottom of the GUI, under the Histogram
Graph screens. The formula used for the ENOB in the case of a DC signal is as follows,
if the application indicates the acquired data on 16 bits:
© 2009 Microchip Technology Inc.