Microchip Technology MCP6S22 PGA PICtail, User Manual

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MCP6S2X Evaluation Board (Rev. 4) User’s Guide
DS51327B-page 8

2004 Microchip Technology Inc.
1.2 EVALUATION BOARD DESCRIPTION
The single-channel MCP6S21 and six-channel MCP6S26 have been selected for this
evaluation board. The PIC16F676 microcontroller is used to program the PGAs accord-
ing to the user inputs. User inputs are selected using the on-board DIP switch settings
that are configured according to the table printed on the evaluation board. This allows
the user to program the channel, gain and shutdown of each PGA. Either PGA or both
PGAs can be shut down. The six channels of the MCP6S26 and the PGA gains of 1, 2,
4, 5, 8, 10, 16 and 32 V/V can be configured. Refer to
Appendix D.”Setup Conditions” ,
for additional information.
When the momentary READ push button switch is pressed, the microcontroller reads
the DIP switch configuration through the I/O ports. The controller determines the proper
command and data bytes to be transmitted to the PGAs and the transmits a 16 or 32-bit
word through the Serial Peripheral Interface (SPI™) port.
When the momentary
MCLR
push button switch is pressed, the microcontroller Master
Clear is activated. This resets the microcontroller to a known initial state.
The ICSP connector provides the capability of programming the PIC16F676 from a PC.
This requires additional hardware, such as MPLAB
®
ICD 2.
The two PGAs are cascaded, while the signal output of the MCP6S26 is directly
connected to the analog input of the MCP6S21. This configuration outputs a maximum
signal gain of 1024 V/V.
The digital lines of the PGA are daisy chained. The MCP6S26 has a Serial-Out (SO)
line that can be used to serially program another device. Therefore, the SO line is con-
nected to the Serial-In (SI) line of the MCP6S21. If the MCP6S26 is removed from the
socket, the MCP6S21 cannot be programmed.
The MCP6S2X family of PGAs has a reference voltage input pin to offset the output
signal. There are three reference voltage options on the board: 2.5V, adjustable refer-
ence voltage (0V to 5V) and ground. These options can be selected using the on-board
jumper (JP1).
A prototype area is available for user circuit interface. The inputs, outputs and refer-
ence voltage traces of the PGAs conveniently pass near the prototype area for ease
of connection. Test point connectors are available to interface with external circuits.
The signals V
IN_0
, V
IN_1
, V
OUT_1
and V
OUT_2
can use SMA connectors that slide hor-
izontally onto the board. 50
Ω
termination resistors can be added to V
IN_O
and V
IN_1
.
Refer to Appendix A.”Schematic and Board Layouts” and Appendix D.”Setup
Conditions” , for additional information.