MCP6SX2 PGA Thermistor
PICtail™ Demo Board
User’s Guide
© 2006 Microchip Technology Inc.
DS51517B
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FanSense, FlexROM, fuzzyLAB, In-Circuit Serial
Programming, ICSP, ICEPIC, Linear Active Thermistor, Mindi,
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DS51517B-page ii
© 2006 Microchip Technology Inc.
MCP6SX2 PGA THERMISTOR PICtail™
DEMO BOARD USER’S GUIDE
Table of Contents
Preface ........................................................................................................................... 1
Introduction............................................................................................................ 1
Document Layout .................................................................................................. 1
Conventions Used in this Guide ............................................................................ 2
Recommended Reading........................................................................................ 3
The Microchip Web Site ........................................................................................ 3
Customer Support ................................................................................................. 4
Document Revision History ................................................................................... 4
Chapter 1. Product Overview ....................................................................................... 5
1.1 Introduction ..................................................................................................... 5
1.2 What is thE MCP6SX2 PGA Thermistor PICtail™ Demo Board? .................. 5
1.3 What the MCP6SX2 PGA Thermistor PICtail™ Demo Board Kit Includes .... 5
1.4 Associated Tools ............................................................................................ 6
Chapter 2. Setup and Installation ................................................................................ 9
2.1 Introduction ..................................................................................................... 9
2.2 Required Tools ............................................................................................... 9
2.3 Connecting The MCP6SX2 PGA Thermistor PICtail™ Demo Board ............. 9
Chapter 3. Using the MCP6SX2 PGA Thermistor PICtail™ Demo Board ............... 11
3.1 Introduction ................................................................................................... 11
3.2 Configuring Board ........................................................................................ 11
Appendix A. Schematic and Layouts ........................................................................ 19
A.1 Introduction .................................................................................................. 19
A.2 Demonstration Board Description ................................................................ 19
A.3 Additional Comments ................................................................................... 20
A.4 Board Schematic ........................................................................................ 21
A.5 Board - Top Silk-Screen And Metal Layers ................................................ 22
A.6 Board - Top Metal Layer ............................................................................ 23
A.7 Board - Bottom Metal Layer ...................................................................... 24
Appendix B. Bill Of Materials (BOM) ......................................................................... 25
B.1 Components Installed on PCB ..................................................................... 25
B.2 Separately Packaged Components ............................................................. 26
Worldwide Sales and Service .................................................................................... 28
© 2006 Microchip Technology Inc.
DS51517B-page iii
MCP6SX2 PGA Thermistor PICtail™ Demo Board User’s Guide
NOTES:
DS51517B-page iv
© 2006 Microchip Technology Inc.
MCP6SX2 PGA THERMISTOR PICtail™
DEMO BOARD USER’S GUIDE
Preface
NOTICE TO CUSTOMERS
All documentation becomes dated, and this manual is no exception. Microchip tools and
documentation are constantly evolving to meet customer needs, so some actual dialogs
and/or tool descriptions may differ from those in this document. Please refer to our web site
(www.microchip.com) to obtain the latest documentation available.
Documents are identified with a “DS” number. This number is located on the bottom of each
page, in front of the page number. The numbering convention for the DS number is
“DSXXXXXA”, where “XXXXX” is the document number and “A” is the revision level of the
document.
INTRODUCTION
This chapter contains general information that will be useful to know before using the
MCP6SX2 PGA Thermistor PICtail™ Demo Board. Items discussed in this chapter
include:
•
•
•
•
•
•
Document Layout
Conventions Used in this Guide
Recommended Reading
The Microchip Web Site
Customer Support
Document Revision History
DOCUMENT LAYOUT
This document describes how to use the MCP6SX2 PGA Thermistor PICtail™ Demo
Board as a development tool. The manual layout is as follows:
• Chapter 1. “Product Overview” – An introduction to the MCP6SX2 PGA
Thermistor PICtail™ Demo Board. It covers the kit contents, associated tools and
how they work together.
• Chapter 2. “Setup and Installation” – Covers the initial set-up of the MCP6SX2
PGA Thermistor PICtail™ Demo Board. It lists the required tools, shows how to
connect this board and demonstates how to verify the set-up.
• Chapter 3. “Using the MCP6SX2 PGA Thermistor PICtail™ Demo Board” –
Discusses different light sources, using the Signal Analysis PC application and
setting up the board as a stand-alone.
• Appendix A. “Schematic and Layouts” – Gives detailed information on the
MCP6SX2 PGA Thermistor PICtail™ Demo Board. Includes detailed circuit
explanation, schematic and board layouts.
• Appendix B. “Bill Of Materials (BOM)” – List the parts used to build the
MCP6SX2 PGA Thermistor PICtail™ Demo Board.
© 2006 Microchip Technology Inc.
DS51517B-page 1
MCP6SX2 PGA Thermistor PICtail™ Demo Board User’s Guide
CONVENTIONS USED IN THIS GUIDE
This manual uses the following documentation conventions:
DOCUMENTATION CONVENTIONS
Description
Arial font:
Italic characters
Represents
Referenced books
Emphasized text
A window
A dialog
A menu selection
A field name in a window or
dialog
A menu path
MPLAB® IDE User’s Guide
...is the only compiler...
the Output window
the Settings dialog
select Enable Programmer
“Save project before build”
A dialog button
A tab
A number in verilog format,
where N is the total number of
digits, R is the radix and n is a
digit.
A key on the keyboard
Click OK
Click the Power tab
4‘b0010, 2‘hF1
Italic Courier New
Sample source code
Filenames
File paths
Keywords
Command-line options
Bit values
Constants
A variable argument
Square brackets [ ]
Optional arguments
Curly brackets and pipe
character: { | }
Ellipses...
Choice of mutually exclusive
arguments; an OR selection
Replaces repeated text
#define START
autoexec.bat
c:\mcc18\h
_asm, _endasm, static
-Opa+, -Opa0, 1
0xFF, ‘A’
file.o, where file can be
any valid filename
mcc18 [options] file
[options]
errorlevel {0|1}
Initial caps
Quotes
Underlined, italic text with
right angle bracket
Bold characters
N‘Rnnnn
Text in angle brackets < >
Courier New font:
Plain Courier New
Represents code supplied by
user
DS51517B-page 2
Examples
File>Save
Press <Enter>, <F1>
var_name [,
var_name...]
void main (void)
{ ...
}
© 2006 Microchip Technology Inc.
Preface
RECOMMENDED READING
This user's guide describes how to use the MCP6SX2 PGA Thermistor PICtail™ Demo
Board. Other useful documents are listed below. The following Microchip documents
are available and recommended as supplemental reference resources.
PICkit™ 1 Flash Starter Kit User’s Guide (DS40051)
Contains instructions on how to use the PICkit 1 Flash Starter Kit hardware and
software.
Signal Analysis PICtail™ Daughter Board User’s Guide (DS51476)
Contains instructions on how to use the Signal Analysis PICtail™ Daughter Board’s
hardware and software.
AN897, “Thermistor Temperature Sensing with MCP6SX2 PGAs” (DS00897)
Explains the functionality and design of this board’s circuit. Contains measurement
results.
MCP6S21/2/6/8 Data Sheet (DS21117)
Gives detailed information on the MCP6S21/2/3/6/8 Programmable Gain Amplifiers
(PGA).
MCP6S91/2/3 Data Sheet (DS21908)
Gives detailed information on the MCP6S91/2/3 PGAs.
PIC16F684 Data Sheet (DS41202)
Gives detailed information on the PICmicro microcontroller used on the Signal Analysis
PICtail Daughter Board.
PIC16C745/765 Data Sheet (DS41124)
Gives detailed information on the PICmicro® microcontroller used on the PICkit 1 Flash
Starter Kit.
THE MICROCHIP WEB SITE
Microchip provides online support via our web site at www.microchip.com. This web
site is used as a means to make files and information easily available to customers.
Accessible by using your favorite Internet browser, the web site contains the following
information:
• Product Support – Data sheets and errata, application notes and sample
programs, design resources, user’s guides and hardware support documents,
latest software releases and archived software
• General Technical Support – Frequently Asked Questions (FAQs), technical
support requests, online discussion groups, Microchip consultant program
member listing
• Business of Microchip – Product selector and ordering guides, latest Microchip
press releases, listing of seminars and events, listings of Microchip sales offices,
distributors and factory representatives
© 2006 Microchip Technology Inc.
DS51517B-page 3
MCP6SX2 PGA Thermistor PICtail™ Demo Board User’s Guide
CUSTOMER SUPPORT
Users of Microchip products can receive assistance through several channels:
•
•
•
•
•
Distributor or Representative
Local Sales Office
Field Application Engineer (FAE)
Technical Support
Development Systems Information Line
Customers should contact their distributor, representative or field application engineer
for support. Local sales offices are also available to help customers. A listing of sales
offices and locations is included in the back of this document.
Technical support is available through the web site at: http://support.microchip.com
DOCUMENT REVISION HISTORY
Revision B (May 2006)
• Updated Bill of Materials (BOM) to show RoHS-compliant part numbers.
• Updated title of this document to match web site board name.
Revision A (October 2004)
• Initial Release of this Document.
DS51517B-page 4
© 2006 Microchip Technology Inc.
MCP6SX2 PGA THERMISTOR PICtail™
DEMO BOARD USER’S GUIDE
Chapter 1. Product Overview
1.1
INTRODUCTION
The following name and assembly number are found on the MCP6SX2 PGA Thermistor PICtail™ Demo Board’s Printed Circuit Board (PCB):
• MCP6SX2DM-PICTLTH
• 102-00028
This PCB goes by the following title:
• MCP6SX2 PGA Thermistor PICtail™ Demo Board
This board is supported by AN897, “Thermistor Temperature-Sensing with MCP6SX2
PGAs”, (DS00897). It uses a BC Components® 2322 640 55103 NTC thermistor to
detect temperature. The circuit also includes a voltage divider and a MCP6S22
Programmable Gain Amplifier (PGA).
•
•
•
•
1.2
Kit Contents
MCP6SX2 PGA Thermistor PICtail™ Demo Board
Associated Tools
Initial Set-up
WHAT IS THE MCP6SX2 PGA THERMISTOR PICTAIL™ DEMO BOARD?
The MCP6SX2 PGA Thermistor PICtail™ Demo Board contains the analog circuitry
represented in Figure 1-1. It uses BC Components’ 2322 640 55103 NTC thermistor to
convert temperature to resistance. The thermistor is placed in a voltage divider which
converts resistance to voltage. This voltage is filtered and placed at the MCP6S22
Programmable Gain Amplifier’s (PGA) CH0 input. The PGA gains and buffers this
output, which is sent off board (VOUT). Board power is applied at the +5V and GND
inputs. The SPI bus makes it possible to control the PGA; its gain and input channel
can be set, as desired, from the software.
1.3
WHAT THE MCP6SX2 PGA THERMISTOR PICTAIL™ DEMO BOARD KIT
INCLUDES
• MCP6SX2 PGA Thermistor PICtail™ Demo Board – An assembled and tested
PCB (102-00028)
• PICkit™ 1 CD-ROM (DS40049) – Contains the files and literature mentioned in
this user’s guide
• Stand-off, screw and an additional PGA (MCP6S92) provided in an anti-static bag
© 2006 Microchip Technology Inc.
DS51517B-page 5
MCP6SX2 PGA Thermistor PICtail™ Demo Board User’s Guide
Thermistor
Temperature
MCP6SX2 PGA Thermistor
PICtail™ Demo Board
Thermistor
+5V
Test Point
GND
Test Point
+5V
Voltage
Divider
GND
CH0 Input
Test Point
CH1 Input
Test Point
FIGURE 1-1:
Diagram.
4
MCP6S22
PGA
SPI™ Bus
VOUT
MCP6SX2 PGA Thermistor PICtail™ Demo Board Block
The test points make it easier to test key points in the circuit, change the input signals,
and to use this as a stand-alone board.
• GND Test Point – Connected to the ground plane, it is a convenient ground point
for any lab equipment
• +5V Test Point – Allows measurement of the positive supply voltage and provides
a means to power this board with a laboratory power supply
• CH0 Test Point – The place to measure the voltage divider’s output (also the
PGA’s CH0 input)
• CH1 Test Point – Makes it possible to send any desired signal to the PGA
More details on the circuit and its design can be found in Appendix A. “Schematic
and Layouts” and in AN897 (DS00897).
1.4
ASSOCIATED TOOLS
Figure 1-2 shows the block diagram of the hardware and software tools that the
MCP6SX2 PGA Thermistor PICtail™ Demo Board is designed to work with. More information on these tools can be found in the “Recommended Reading” section.
Hardware
PC
Software
PICkit™ 1 Signal Analysis
PC Program
USB
PICkit™ 1
Flash Starter Kit
PICkit™ 1
Firmware
14
Signal Analysis
PICtail™ Daughter Board
PICA2Dlab.hex
Firmware
14
MCP6SX2 PGA Thermistor
PICtail™ Demo Board
FIGURE 1-2:
DS51517B-page 6
Measurement Set-up Block Diagram.
© 2006 Microchip Technology Inc.
Product Overview
1.4.1
PC Platform
The Personal Computer (PC) shown in Figure 1-2 needs to run on Windows® 98 SE or
later. It provides a convenient interface for the user, communicates with the other
boards and provides power through the USB connection.
1.4.2
PICkit™ 1 Signal Analysis PC Program
The PICkit™ 1 Signal Analysis PC program configures and programs the PIC16F684
PICmicro® microcontroller on the Signal Analysis PICtail Daughter Board through the
USB port on the PICkit 1 Flash Starter Kit. It also imports data through the same
connection and displays the data in strip-chart, histogram, FFT plot and oscilloscope
plot formats. Data can be output in CSV format for importing into a spreadsheet
program.
1.4.3
PICkit 1 Flash Starter Kit
The PICkit 1 Flash Starter Kit (DV164101) programs PICmicro microcontrollers. It uses
the PIC16C745’s USB port to communicate with the PICkit 1 Signal Analysis PC
program. It connects to the Signal Analysis PICtail Daughter Board via a header (see
Figure 2-1).
This board provides a single +5V supply voltage for the daughter boards. It can drive
up to 5 µF on the supply; a larger capacitance may interfere with program timing.
1.4.4
PICkit 1 Firmware
This software resides on the PICkit 1 Flash Starter Kit’s PIC16C745 microcontroller.
Use version 2.0.2 or later.
1.4.5
Signal Analysis PICtail Daughter Board
This board is Microchip Development Tool AC164120. It connects to the PICkit 1 Flash
Starter Kit, which it uses for both power and as a communications link to the PC. The
on-board PIC16F684 has a 10-bit ADC which converts the MCP6SX2 PGA Thermistor
PICtail™ Demo Board’s output voltage. The results are temporarily stored on the
board’s 25LC640 serial EEPROM chips.
The +5V single supply voltage from the PICkit 1 Flash Starter Kit board is bypassed
with a bulk 1 µF capacitor and local 0.1 µF capacitors for each IC.
1.4.6
Firmware for the Signal Analysis PICtail Daughter Board
PICA2Dlab.hex is the standard file that supports the PICkit™ 1 Signal Analysis PC
program. The PGA and 10-bit ADC configuration are selected in the Signal Analysis
PC program and written to the PIC16F684. The PIC16F684 then sends the
command(s) over the SPI™ bus to the PGA. It displays the ADC code on the strip chart.
Therm_PGA1.hex implements the first design in AN897. It supports the PICkit™ 1
Signal Analysis PC program, but with reduced functionality; its output can be viewed
on the strip chart only. The results need to be manually converted to commonly-seen
temperature (codes 0 to 1023 convert to 0.0°C to 102.3°C).
Therm_PGA2.hex implements the second design in AN897. It supports the PICkit™ 1
Signal Analysis PC program, but with reduced functionality; its output can be viewed
on the strip chart only. The results need to be manually converted to commonly-seen
temperature (codes 0 to 1023 convert to 0.0°C to 102.3°C).
© 2006 Microchip Technology Inc.
DS51517B-page 7
MCP6SX2 PGA Thermistor PICtail™ Demo Board User’s Guide
1.4.7
Interface Details
A more detailed look at how the MCP6SX2 PGA Thermistor PICtail™ Demo Board
interfaces with the other boards is shown in Figure 1-3.
Thermistor
Temperature
MCP6SX2 PGA Thermistor
PICtail™ Demo Board
PICkit™ 1
Flash Starter Kit
Signal Analysis
PICtail™ Daughter Board
Thermistor
+5V
Test Point
GND
Test Point
Voltage
Divider
GND
4
4
PGA
MCP6S22
SPI Bus
VOUT
FIGURE 1-3:
DS51517B-page 8
+5V
GND
SPI™ Bus
CH0 Input
Test Point
CH1 Input
Test Point
Serial
EEPROM
+5V
PIC16F684
2
PIC16F745
USB
to PC
ADC
Detailed Interface Diagram.
© 2006 Microchip Technology Inc.
MCP6SX2 PGA THERMISTOR PICtail™
DEMO BOARD USER’S GUIDE
Chapter 2. Setup and Installation
2.1
INTRODUCTION
This chapter shows how to set up the MCP6SX2 PGA Thermistor PICtail™ Demo
Board. This chapter discusses:
• Required Tools
• Connecting the MCP6SX2 PGA Thermistor PICtail™ Demo Board
• Set-up Verification
2.2
REQUIRED TOOLS
The PICkit™ 1 Flash Starter Kit User’s Guide explains how to set up the PC and the
PICkit™ 1 Flash Starter Kit. Use firmware version 2.0.2 or later.
The Signal Analysis PICtail™ Daughter Board User’s Guide shows how to install the
PICkit 1 Signal Analysis PC Program on the PC and set up the Signal Analysis PICtail
Daughter Board. It also covers the features of the PICkit 1 Signal Analysis PC program.
The PICkit 1 CD-ROM (DS40049) contains many of the necessary files.
2.3
CONNECTING THE MCP6SX2 PGA THERMISTOR PICTAIL™ DEMO BOARD
An exploded view of how the different boards connect is shown in Figure 2-1.
MCP6SX2 PGA Thermistor
PICtail™ Demo Board
Mounting hole for
screw and standoff
Signal Analysis
PICtail™ Daughter Board
USB Cable
Expansion
Header (J3)
Remove PICmicro® MCU
from Evaluation Socket
PICkit™ 1 Flash Starter Kit
PIC16C745 Firmware
Version 2.0.2 or later
FIGURE 2-1:
© 2006 Microchip Technology Inc.
Board Connections.
DS51517B-page 9
MCP6SX2 PGA Thermistor PICtail™ Demo Board User’s Guide
2.3.1
PCB Standoff
The standoff and screw listed in Table B-2 are installed at the mounting hole shown in
Figure 2-1. The standoff goes on bottom, and the screw on top.
2.3.2
PICkit 1 Flash Starter Kit
1. Remove any PICmicro microcontroller that may be in the evaluation socket.
2. Connect the USB cable to the PC and the PICkit 1 Flash Starter Kit board. The
status LEDs (green POWER and yellow BUSY in the LED array) should light up.
It is easiest to use this board when it lays directly on a bench top.
2.3.3
Signal Analysis PICtail Daughter Board
This board plugs into the PICkit 1 Flash Starter Kit’s expansion header J3 and must not
cover the LED array. There should be no change in the status LEDs on the PICkit 1
Flash Starter Kit board after it is plugged in.
2.3.4
MCP6SX2 PGA Thermistor PICtail™ Demo Board
If you would rather use the MCP6S92 PGA, take it out of the anti-static bag and replace
the already installed MCP6S22 PGA.
1. Plug this board into, and directly above, the Signal Analysis PICtail Daughter
Board. There should be no change in the status LEDs on the PICkit 1 Flash
Starter Kit board after it is plugged in.
2.3.4
Set-up Verification
1.
2.
3.
4.
Select the Real Time Mode radio button.
Click on the Strip Chart button.
Change the sample speed to 20 Sample/Secs.
Click on the green GO button; the strip chart will show the measured output of
the MCP6SX2 PGA Thermistor PICtail™ Demo Board.
5. Change the switch positions (SW1 and SW2) and verify that the strip chart
changes. Figure 2-2 shows the result when RA was set to 10 kΩ and Rvar to 0Ω,
then 12.8 kΩ, and then 217.6 kΩ (see Section 3.2 “Configuring Board”).
FIGURE 2-2:
DS51517B-page 10
Strip Chart.
© 2006 Microchip Technology Inc.
MCP6SX2 PGA THERMISTOR PICtail™
DEMO BOARD USER’S GUIDE
Chapter 3. Using the MCP6SX2 PGA Thermistor PICtail™
Demo Board
3.1
INTRODUCTION
This demonstration board makes it easy to explore the operation of two thermistor
applications using the MCP6S22 PGA. Items discussed in this chapter include:
• Configuring the Board
• Using the Signal Analysis PC Program for This Board
• Stand-Alone Board Set-up
3.2
CONFIGURING BOARD
3.2.1
Configuring Jumper JMP1 (select Thermistor or Rvar)
Figure 3-1 shows how jumper JMP1 configures the circuit. When the shorting bar is on
the right side of jumper JMP1, the thermistor RTH is connected to the circuit. When it is
on the left side of jumper JMP1, the thermistor emulator Rvar is connected to the circuit.
Refer to Figure A.4 for the complete schematic.
VDD = 5.0V
RA
Thermistor
Rvar
To filter and PGA’s CH0 input
JMP1
Rvar
FIGURE 3-1:
© 2006 Microchip Technology Inc.
RTH
Simplified Jumper Circuit.
Draft
DS51517B-page 11
MCP6SX2 PGA Thermistor PICtail™ Demo Board User’s Guide
3.2.2
Configuring DIP Switch SW1 (RA)
DIP switch SW1 and resistors R1 – R7 in Figure 3-2 emulate the voltage divider resistor
(RA in Figure 3-1). R1 is placed in series with the others to prevent shorting the supplies
together. These resistors produce a binary sequence of values between 0.5 kΩ and
32.0 kΩ.
Refer to Figure A.4 for the complete schematic.
+5V
R1
499
500
SW1
500
1,000
2,000
4,000
8,000
16,000
FIGURE 3-2:
R2 499Ω
R3 1.00 kΩ
R4 2.00 kΩ
R5 4.02 kΩ
R6 8.06 kΩ
R7 16.0 kΩ
RA Emulator.
Each resistor with its switch (in SW1) pointing to the right, away from the silk screen
resistor values, is not added into the total for RA (it shorts that resistor).
Each resistor with its switch (in SW1) pointing to the left, towards the silk screen resistor
values, is added into the total for RA.
As an example, if the top four switches are to the right, and the bottom two are to the
left, then RA is calculated as 500 + 0 + 0 + 0 + 0 + 8,000 + 16,000 = 24,500Ω.
3.2.3
Using the Thermistor (RTH)
R21 in Section A.4 “Board Schematic” is the thermistor (RTH in Figure 3-1). The
resistance changes depending on temperature; see AN897, “Thermistor Temperature
Sensing with MCP6SX2 PGAs” (DS00897).
DS51517B-page 12
Draft
© 2006 Microchip Technology Inc.
Using the MCP6SX2 PGA Thermistor PICtail™ Demo Board
3.2.4
Configuring DIP Switch SW2 (RTH Emulator, Rvar)
DIP switch SW2 and resistors R8 – R19 in Figure 3-3 comprise the thermistor emulator
(Rvar in Figure 3-1). Rvar produces a binary sequence of resistances between 0Ω and
409.5 kΩ.
Refer to Figure A.4 for the complete schematic.
SW2
100
200
400
800
1,600
3,200
6,400
12,800
25,600
51,200
102,400
204,800
FIGURE 3-3:
R8
R9
R10
R11
R12
R13
R14
R15
R16
R17
R18
R19
100Ω
200Ω
402Ω
806Ω
1.6 kΩ
3.24 kΩ
6.49 kΩ
12.7 kΩ
25.5 kΩ
51.1 kΩ
102 kΩ
205 kΩ
RTH Emulator (Rvar).
Each resistor with its switch (in SW2) pointing to the right, away from the silk screen
resistor values, is not added into the total for RA (it shorts that resistor).
Each resistor with its switch (in SW2) pointing to the left, towards the silk screen resistor
values, is added into the total for RA.
As an example, if the top ten switches are to the right, and the bottom two are to the
left, then Rvar is calculated as 0 + 0 + ... + 0 + 102,400 + 204,800 = 307,200Ω.
AN897, “Thermistor Temperature Sensing with MCP6SX2 PGAs” (DS00897) contains
information on converting this resistance to the equivalent, nominal thermistor
temperature, and visa-versa.
3.2.5
Using the Signal Analysis PC Application for This Board
See “Chapter 2. Using the PICkit™ Signal Analysis PC Application” of the “Signal
Analysis PICtail™ Daughter Board User’s Guide” (DS51476) for details on displaying
measured results. The possible formats include: oscilloscope, FFT, histogram and
strip-chart.
The measured results can then be interpreted as temperature; see AN897, “Thermistor
Temperature Sensing with MCP6SX2 PGAs” (DS00897).
© 2006 Microchip Technology Inc.
Draft
DS51517B-page 13
MCP6SX2 PGA Thermistor PICtail™ Demo Board User’s Guide
3.2.6
Choosing Firmware for the Signal Analysis PICtail Daughter
Board
Use the standard PICA2Dlab.hex file to measure and analyze the PGA’s output
voltage. This file supports all of the display functionality of the PICkit 1 Signal Analysis
PC application program.
Use Therm_PGA1.hex to implement the first design shown in AN897, “Thermistor
Temperature Sensing with MCP6SX2 PGAs” (DS00897). Its output can only be viewed
on the strip chart. The results need to be manually converted to commonly-seen
temperatures (codes 0 to 1023 convert to 0.0°C to 102.3°C).
Use Therm_PGA2.hex to implement the second design in AN897, “Thermistor
Temperature Sensing with MCP6SX2 PGAs” (DS00897). Its output can only be viewed
on the strip chart. The results need to be manually converted to commonly-seen
temperatures (codes 0 to 1023 convert to 0.0°C to 102.3°C).
DS51517B-page 14
Draft
© 2006 Microchip Technology Inc.
Using the MCP6SX2 PGA Thermistor PICtail™ Demo Board
3.2.7
Configure the PGA
The PICkit 1 Signal Analysis PC program can configure the PGA; see Figure 3-4. The
MCP6S22 PGA defaults to a gain of 1 and CH0.
Note:
The MCP6S92 PGA powers up to a random state; it must have its gain and
input written to it before it will operate as expected.
1. Open the PGA window by clicking the External Devices button.
2. Select the correct PGA from the indicated pull-down list.
3. Select the desired PGA input. Usually the selection will be CH0 for the thermistor
output, but it can be CH1 when another input source is provided at the CH1 test
point (Figure 1-1).
a. Select Write to Register from the indicated pull-down list. (Figure 3-4, #5)
b. Set A0 = 1. (Figure 3-4, #6)
c. Set C2:C0 to all zeros. (Figure 3-4, #7)
d. Execute the command by clicking on the Write to PGA button. (Figure 3-4,
#8)
4. Select the desired PGA gain.
a. Select Write to Register from the indicated pull-down list. (Figure 3-4, #5)
b. Set A0 = 0. (Figure 3-4, #6)
c. Select PGA gain from the pull-down list. (Figure 3-4, #4))
d. Execute the command by clicking on the Write to PGA button.
(Figure 3-4, #8)
3. Select Channel
5. Select Operation 8. Execute
2. Select PGA
1. Open PGA Window
6. Set Register Pointer
4. Select Gain
7. Set Input Channel
FIGURE 3-4:
© 2006 Microchip Technology Inc.
PGA Configuration.
Draft
DS51517B-page 15
MCP6SX2 PGA Thermistor PICtail™ Demo Board User’s Guide
3.2.8
Configure the ADC
The ADC is automatically setup by the PICkit 1 Signal Analysis PC program. The two
possible inputs are shown in Figure 3-5.
1. If in the Real Time Mode of operation (Strip Chart), select the Number of
Samples from the first pull-down list.
2. Select the Sample Rate from the second pull-down list.
1. Select Number of Samples
2. Select Sample Rate
FIGURE 3-5:
Standard ADC Options.
The PICkit 1 Signal Analysis PC program allows the user to manually configure the
ADC.
1. Clicking the ADC button (see Figure 3-6) opens the ADC configuration window.
This window starts at the power-on default conditions for the ADC; therefore, it
must be configured before use.
See the PIC16F684 data sheet (DS41202) for more information on configuring the
registers.
2. ADC Window
FIGURE 3-6:
DS51517B-page 16
1. Select ADC window
Manual ADC Configuration.
Draft
© 2006 Microchip Technology Inc.
Using the MCP6SX2 PGA Thermistor PICtail™ Demo Board
3.2.9
Measurement Example
Jumper JMP1 was configured to select the thermistor, R21 (RTH in Figure 3-1). RA was
set at 10 kΩ (Design # 1). The thermistor was at room temperature. The MCP6S22
PGA was at its default settings, input CH0 and gain = 1. The results using the
PICA2Dlab.hex file (Section 3.2.6 “Choosing Firmware for the Signal Analysis
PICtail Daughter Board”) are shown in Figure 3-7. The output voltage is 2.568V.
FIGURE 3-7:
Measurement Results.
The output voltage was used to calculate RTH ≈ 10.56 kΩ and TTH ≈ 23.5°C (74.3°F).
See AN897, “Thermistor Temperature Sensing with MCP6SX2 PGAs” (DS00897).
© 2006 Microchip Technology Inc.
Draft
DS51517B-page 17
MCP6SX2 PGA Thermistor PICtail™ Demo Board User’s Guide
3.2.10 Stand-Alone Board Setup
Figure 3-8 shows one possible method for using the MCP6SX2 PGA Thermistor
PICtail™ Demo Board as a stand-alone (without the accompanying tools shown in
Figure 1-2). Most of the probes from the lab equipment (on the left) connect to the test
points. The oscilloscope (O-Scope) probe to VOUT connects to header J2’s pin # 10
(labeled RC0).
Power
Supply
+5V
Test Point
O-Scope
Function
Generator
FIGURE 3-8:
Diagram.
GND
Test Point
CH0 Input
Test Point
CH1 Input
Test Point
MCP6SX2 PGA Thermistor
PICtail™ Demo Board
Thermistor
Temperature
4
SPI Bus
VOUT
MCP6SX2 PGA Thermistor PICtail™ Demo Board Block
The PGAs’ power supply range is between 2.5V and 5.5V. The SPI bus needs to be
connected to a microcontroller with the appropriate firmware. The MCP6S22 PGA
powers up to input CH0 and 1 V/V gain. The MCP6S92 needs to be initialized after
power-up.
DS51517B-page 18
Draft
© 2006 Microchip Technology Inc.
MCP6SX2 PGA THERMISTOR PICtail™
DEMO BOARD USER’S GUIDE
Appendix A. Schematic and Layouts
A.1
INTRODUCTION
This appendix contains the schematics and layouts for the MCP6SX2 PGA Thermistor
PICtail™ Demo Board.
The MCP6SX2-PICTLTH demonstration board is constructed using a two-layer Printed
Circuit Board (PCB). The top layer is for components and traces, while the bottom layer
is the ground plane.
Information on this board includes:
•
•
•
•
A.2
Board Schematic
Board - Top Silk-Screen And Metal Layers
Board - Top Metal Layer
Board - Bottom Metal Layer
DEMONSTRATION BOARD DESCRIPTION
A simplified block diagram of this board is shown in Figure 1-1. The detailed schematic
is given in Figure A.4.
DIP switch SW1 and resistors R1 – R7 emulate the voltage divider’s series resistor (RA
in Figure 3-1). R1 is placed in series with the others to prevent shorting the supplies
together. Resistors R1 – R7 produce a binary sequence of values between 0.5 kΩ and
32.0 kΩ.
R21 is the thermistor (RTH in Figure 3-1).
DIP switch SW2 and resistors R8 – R19 (labeled Rvar in top silk screen) emulate the
thermistor. Rvar produces a binary sequence between 0Ω and 409.5 kΩ.
The jumper JMP1 selects either the thermistor or its emulator Rvar. R20 and C1 are the
low-pass analog filters used to minimize noise. They also act as anti-aliasing filters for
the ADC.
U1 is either the MCP6S22 or the MCP6S92 Programmable Gain Amplifier (PGA). The
PGA buffers the transimpedance amplifier output and makes it possible to gain up
weak signals before conversion by the ADC. J2 connects this board to the Signal
Analysis board. C2 and C3 are bypass capacitors that minimize power supply noise.
The demonstration board includes test points for convenience on the bench. The +5V
and GND test points connect to the board’s supply voltages. The CH0 test point
connects to the PGA’s CH0 input; it is also connected to the voltage divider’s output
(with filtering). The CH1 test point allows the user to place any desired signal at the
PGA’s CH1 input.
Note:
© 2006 Microchip Technology Inc.
While headers J1, J2, and J3 are shown together in the schematic (see
Figure A.4), J2 is installed (see Table B-1), while J1 and J3 are not. J2 and
J3 are placeholders only.
DS51517B-page 19
MCP6SX2 PGA Thermistor PICtail™ Demo Board User’s Guide
A.3
ADDITIONAL COMMENTS
The demonstration board includes test points for convenience on the bench. The +5V
and GND test points connect to the board’s supply voltages. The CH0 test point
connects to the PGA’s CH0 input; it is also connected to the voltage divider’s output
(with filtering). The CH1 test point allows the user to place any desired signal at the
PGA’s CH1 input.
The PIC16F684 (and 10-bit ADC) are not part of the demo board schematic; see
Figure 1-3 instead.
The PICkit 1 Flash Starter Kit provides a +5V single supply voltage. It can drive up to
5 µF on the supply; a larger capacitive load causes current loading and timing issues.
The PICkit 1 Flash Starter Kit Signal Analysis PICtail Daughter Board uses the +5V
single supply voltage. It has 0.1 µF local bypass capacitors for each IC, and a 1 µF bulk
bypass capacitor for the entire board.
This demonstration board also uses the +5V single supply voltage. It has a 0.1 µF local
bypass capacitor for the PGA, and a 1 µF bulk bypass capacitor for the entire board. A
solid ground plane provides a good ground for the PGA.
High-frequency design practices are used to minimize digital interference:
•
•
•
•
DS51517B-page 20
Solid ground plane
Surface-mount devices
Separate digital and analog lines and sections
Straight and short lines to the PGA
© 2006 Microchip Technology Inc.
Schematic and Layouts
BOARD SCHEMATIC
M
A.4
© 2006 Microchip Technology Inc.
DS51517B-page 21
MCP6SX2 PGA Thermistor PICtail™ Demo Board User’s Guide
A.5
BOARD - TOP SILK SCREEN AND METAL LAYERS
DS51517B-page 22
© 2006 Microchip Technology Inc.
Schematic and Layouts
A.6
BOARD - TOP METAL LAYER
© 2006 Microchip Technology Inc.
DS51517B-page 23
MCP6SX2 PGA Thermistor PICtail™ Demo Board User’s Guide
A.7
BOARD - BOTTOM METAL LAYER
DS51517B-page 24
© 2006 Microchip Technology Inc.
MCP6SX2 PGA THERMISTOR PICtail™
DEMO BOARD USER’S GUIDE
Appendix B. Bill Of Materials (BOM)
B.1
COMPONENTS INSTALLED ON PCB
Table B-1 shows the Bill of Materials for the MCP6SX2 PGA Thermistor PICtail™
Demo Board as it comes from Microchip.
TABLE B-1:
BILL OF MATERIALS
Qty Reference
Description
Manufacturer
Part Number
2
C1,C3
1.0 µF, 16V, 10%, X7R, 0805 SMD, Ceramic
Kemet®
C0805C105K4RACTU
1
C2
0.1 µF, 25V, 10%, X7R, 0805 SMD, Ceramic
Panasonic® - ECG
ECJ-2VB1E104K
1
J2
Header, 1 × 14, 0.100" Pitch, Vertical, Tin
AMP®/Tyco®
Electronics
1-640454-4
1
JMP1
Header, 1 × 3, 0.100" Pitch, Vertical, Tin
AMP/Tyco
Electronics
3-644456-3
1
(for JMP1) Shunt, 1 × 2, With Handle , Gold
AMP/Tyco
Electronics
881545-2
2
R1, R2
499Ω, 1/8W, 1%, 0805 SMD
Panasonic - ECG
ERJ-6ENF4990V
1
R3
1.00 kΩ, 1/8W, 1%, 0805 SMD
Panasonic - ECG
ERJ-6ENF1001V
1
R4
2.00 kΩ, 1/8W, 1%, 0805 SMD
Panasonic - ECG
ERJ-6ENF2001V
1
R5
4.02 kΩ, 1/8W, 1%, 0805 SMD
Panasonic - ECG
ERJ-6ENF4021V
1
R6
8.06 kΩ, 1/8W, 1%, 0805 SMD
Panasonic - ECG
ERJ-6ENF8061V
1
R7
16.2 kΩ, 1/8W, 1%, 0805 SMD
Panasonic - ECG
ERJ-6ENF1622V
1
R8
100Ω, 1/8W, 1%, 0805 SMD
Panasonic - ECG
ERJ-6ENF1000V
1
R9
200Ω, 1/8W, 1%, 0805 SMD
Panasonic - ECG
ERJ-6ENF2000V
1
R10
402Ω, 1/8W, 1%, 0805 SMD
Panasonic - ECG
ERJ-6ENF4020V
1
R11
806Ω, 1/8W, 1%, 0805 SMD
Panasonic - ECG
ERJ-6ENF8060V
1
R12
1.62 kΩ, 1/8W, 1%, 0805 SMD
Panasonic - ECG
ERJ-6ENF1621V
1
R13
3.24 kΩ, 1/8W, 1%, 0805 SMD
Panasonic - ECG
ERJ-6ENF3241V
1
R14.
6.49 kΩ, 1/8W, 1%, 0805 SMD
Panasonic - ECG
ERJ-6ENF6491V
1
R15
12.7 kΩ, 1/8W, 1%, 0805 SMD
Panasonic - ECG
ERJ-6ENF1272V
1
R16
25.5 kΩ, 1/8W, 1%, 0805 SMD
Panasonic - ECG
ERJ-6ENF2552V
1
R17
51.1 kΩ, 1/8W, 1%, 0805 SMD
Panasonic - ECG
ERJ-6ENF5112V
1
R18
102 kΩ, 1/8W, 1%, 0805 SMD
Panasonic - ECG
ERJ-6ENF1023V
1
R19
205 kΩ, 1/8W, 1%, 0805 SMD
Panasonic - ECG
ERJ-6ENF2053V
1
R20
100 kΩ, 1/8W, 1%, 0805 SMD
Panasonic - ECG
ERJ-6ENF1003V
1
R21
Thermistor, NTC, 10 kΩ, 1% tolerance at 25°C,
Leaded (Note 1)
BC Components
2381 640 55103
1
SW1
DIP Switch, 6 Position, SPST, Extended, Sealed
Grayhill, Inc
78B06ST
1
SW2
DIP Switch, 12 Position, SPST, Extended
Grayhill, Inc
78B12ST
4
CH0, CH1, PC Test Point, Compact, SMT
GND, +5V
Keystone
Electronics®
5016
Note 1:
When this thermistor is out of stock, the BC Components, 2381 640 54103 thermistor (2%), or equivalent,
will be substituted.
© 2006 Microchip Technology Inc.
DS51517B-page 25
MCP6SX2 PGA Thermistor PICtail™ Demo Board User’s Guide
TABLE B-1:
BILL OF MATERIALS (CONTINUED)
Qty Reference
Description
Manufacturer
Part Number
1
U1
MCP6S22, PGA, 10 MHz, 2 inputs, PDIP-8
Microchip
Technology Inc.
MCP6S22-I/P
1
(for U1)
IC Socket, 8-pin DIP, Tin, 0.300"
AMP/Tyco
Electronics
2-641260-1
1
PCB
Lead Free RoHS Compliant PCB
—
104-00028
0
J1, J3
Not Populated
—
—
Note 1:
B.2
When this thermistor is out of stock, the BC Components, 2381 640 54103 thermistor (2%), or equivalent,
will be substituted.
SEPARATELY PACKAGED COMPONENTS
Table B-2 lists the components that are packaged separately in an anti-static bag.
TABLE B-2:
Qty Reference
BILL OF MATERIALS – SEPARATELY PACKAGED COMPONENTS
Description
Manufacturer
Part Number
1
U1
MCP6S92, PGA, 10 MHz, 2 inputs, PDIP-8 (Note 1)
Microchip
Technology Inc.
MCP6S92-E/P
1
—
Nylon Standoff, Hex, 1.000", 4-40 Thread (Note 2)
Keystone
Electronics®
1902E
1
—
Phillips Machine Screw, 3/8", 4-40 Thread (Note 2)
Building
Fasteners
NY PMS 440 0038 PH
Note 1:
2:
Section 2.3.4 “MCP6SX2 PGA Thermistor PICtail™ Demo Board” and
Section 3.2.7 “Configure the PGA” discuss installing and using this PGA.
Section 2.3.1 “PCB Standoff” describes the installation of these parts.
DS51517B-page 26
© 2006 Microchip Technology Inc.
Bill Of Materials (BOM)
NOTES:
© 2006 Microchip Technology Inc.
DS51517B-page 27
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02/16/06
DS51517B-page 28
© 2006 Microchip Technology Inc.