Microchip Technology MCP3421 Weight Scale Demo Board User guide

MCP3421

Weight Scale Demo Board

User’s Guide

 2010 Microchip Technology Inc. DS51918A

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DS51918A-page 2  2010 Microchip Technology Inc.

MCP3421 WEIGHT SCALE

DEMO BOARD USER’S GUIDE

Table of Contents

Preface ........................................................................................................................... 5

Chapter 1. Product Overview

1.1 Overview ............. ........................................................................................... 9

1.2 Analog Input Configuration Options ........................ .................... .................10

1.3 Load Cell ......................................................................................................11

1.4 Universal Serial Bus (USB) and PIC18F4550 Microcontroller .... .................12

1.5 What the MCP3421 Weight Scale Kit Contains ...........................................12

Chapter 2. Installation and Operation

2.1 MCP3421 Configuration Bit Settings and Data Acquisition ..........................13

2.2 USB Commu n ic a tio n ................................................................ .................... 13

Chapter 3. Weight Scale PC Software Tool

3.1 Software In stallation .............................................................................. ....... 15

3.2 Software Ove r view ....... .. ........................... .. .. ............................................... 15

3.3 Weight Scale Calibration ........................................ ...................................... 16

Appendix A. Schematics and Layouts

A.1 Introduction ..................................................................................................17

A.2 Board – Schematic ... .................................................................... ................ 18

A.3 Board – Top Copper and Pads ....................................................................19

A.4 Board – Top Pads and Silk ...................... .................... .. .................... .. ........20

A.5 Board – Top Copper, Pads and Silk ... ......................... .. ............................ ..21

A.6 Board – Bottom Copper and Pads ...............................................................22

Appendix B. Bill of Materials

Worldwide Sales and Service .................................................................................... 26

 2010 Microchip Technology Inc. DS51918A-page 3

MCP3421 Weight Scale Demo Board User’s Guide

NOTES:

DS51918A-page 4  2010 Microchip Technology Inc.

MCP3421 WEIGHT SCALE

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.

For the most up-to-date information on development tools, see the MPLAB
Select the Help menu, and then Topics to open a list of available on-line help files.

®

IDE online help.

INTRODUCTION

This chapter contains general information that will be useful to know before using the
MCP3421 Weight Scale 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 MCP3421 Weight Scale Demo Board as a
development tool to emulate and debug firmware on a target board. The manual layout
is as follows:

• Chapter 1. “Product Overview” – Provides important information about the
MCP3421 Weight Scale Demo Board hardware.

• Chapter 2. “Installation and Operation” – Describes the MCP3421 Weight
Scale Demo Board firmware.

• Chapter 3. “Weight Scale PC Software Tool” – Provides detailed information
about the board’s PC software tool.

• Appendix A. “Schematics and Layouts” – Shows the schematic and board
layouts for the MCP3421 Weight Scale Demo Board.

• Appendix B. “Bill of Materials” – Lists the parts used to build the MCP3421
Weight Scale Demo Board.

 2010 Microchip Technology Inc. DS51918A-page 5

MCP3421 Weight Scale Demo Board User’s Guide

CONVENTIONS USED IN THIS GUIDE

This manual uses the following docum entat io n conven tion s:

DOCUMENTATION CONVENTIONS

Description Represents Examples

Arial font:

Italic chara c ters Referenced books MPLAB

Emphasized text ...is the only compiler...

Initial caps A window the Output window

A dialog the Settings dialog
A menu selection select Enable Programmer

Quotes A field name in a window or

dialog

Underlined, italic text with
right angle bracket

Bold characters A dialog button Click OK

N‘Rnnnn A number in verilog format,

Text in angle brac kets < > A key on the keyboard Press <Enter>, <F1>

Courier New font:

Plain Courier New Sample source code #define START

Italic Courier New A variable argument file.o, where file can be

Square brackets [ ] Optional arguments mcc18 [options] file

Curly brackets and pipe
character: { | }

Ellipses... Replaces r epeated text var_name [,

A menu path File>Save

A tab Click the Power tab

where N is the tota l number of
digits, R is th e radi x and n is a
digit.

Filenames autoexec.bat
File paths c:\mcc18\h
Keywords _asm, _endasm, static
Command-line options -Opa+, -Opa-
Bit values 0, 1
Constants 0xFF, ‘A’

Choice of mut ually exclus ive
arguments; an OR selection

Represents code supplied by
user

“Save project before build”

4‘b0010, 2‘hF1

any valid filename

[options]
errorlevel {0|1}

var_name...]
void main (void)

{ ...
}

®

IDE User’s Guide

DS51918A-page 6  2010 Microchip Technology Inc.

RECOMMENDED READING

This user’s guide describes how to use MCP3421 Weight Scale Demo Board. Other
useful documents are listed below. The following Microchip documents are available
and recommended as supplemental reference resources:

• MCP3421 Data Sheet – 18-Bit Analog-to-Digital Converter with I
Interface and On-Board Reference (DS22003)

• MCP3422/3/4 Data Sheet – 18-Bit, Multi-Channel ΔΣ Analog-to-Digital
Converter with I

• MCP6V07 Data Sheet – 300 µA, Auto-Zeroed Op Amps (DS22093)

• PIC18F4550 Data Sheet – 28/40/44-Pin, High-Performance, Enhanced Flash,
USB Microcontrollers with nanoWatt Technology (DS39632)

• AN1030 – Weigh Scale Applications for the MCP3551 (DS01030)

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

2

C™ Interface and On-Board Reference (DS22088)

Preface

2

C™

CUSTOMER SUPPORT

Users of Microchip products can receive assistance through several channels:

• Distributor or Representative

• Local Sales Office

• Field Application Engineer (FAE)

• Technical Support

Customers should contact their distributor, representative or field application engineer
(FAE) 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 A (November 2010)

• Initial Release of this Document.

 2010 Microchip Technology Inc. DS51918 A-page 7

MCP3421 Weight Scale Demo Board User’s Guide

NOTES:

DS51918A-page 8  2010 Microchip Technology Inc.

1.1 OVERVIEW

The MCP3421 Weight Scale Demo Board works with the LabVIEW™ Graphical User
Interface (GUI) PC Software. This demo board demonstrates how to use the MCP3421
18-bit Delta-Sigma ADC for weight scale applications. It uses the PIC18F4550 micro­controller for data processing and USB communication with PC. This board also dem­onstrates the changes in the system performance by adjusting the parameters of the
sensor signal conditioning circuits using the MCP6V07 auto-zeroed op amp.

1.1.1 Feature Highlights

• The LCD displays the user’s selected option and the ADC output code or the

• The user can select the signal averaging factor (1 or 4) by pressing the S3 button.

• System performance analysis using PC GUI: the interface allows various

• Hardware PCB design examples: this demo board utilizes a robust grounding

• Signal conditioning examples using MCP6V07: the low-noise op amp is used to

• 2 Kg load cell with 1 mV/V sensitivity.

MCP3421 WEIGHT SCALE

DEMO BOARD USER’S GUIDE

Chapter 1. Product Overview

calculated results.

The selected option is displayed on the LCD.

interactive post signal processing, such as standard deviations and histogram.

method of analog circuits in PCB design. It also demonstrates how to split analog
and digital ground planes.

boost input signal levels.

FIGURE 1-1: MCP3421 Weight Scale Demo Board.

 2010 Microchip Technology Inc. DS51918A-page 9

MCP3421 Weight Scale Demo Board User’s Guide

1.2 ANALOG INPUT CONFIGURATION OPTIONS

The MCP3421 Weight Scale Demo Board has an MCP6V07 auto-zeroed op amp, to
investigate different signal conditioning configuration.

As shown in Figure 1-2, the user can configure the input signal chain with the following
three options, combining the jumpers:

a) Bypassing the MCP6V07: the MCP3421 input pins are directly connected to the

sensor output. In this case, the PGA of the MCP3421 is set to a gain of 8. The
jumpers must be set as follows: J4 and J5 are on the left position. J10 and J13
are ON, while J8, J9, J11 and J12 are OFF (see Figure 1-3a).

b) Extra gain is added by the low-noise, auto-zeroed op amp MCP6V07, before the

ADC. The added gain is 50x, and the ADC’s PGA is 2x. For this option the jump­ers must be set as follows: J4 and J5 are on the right position; J9, J11 and J12
are ON, while J8, J10 and J13 are OFF (see Figure 1-3b).

c) PGA = 1x, but uses the MCP6V07 to add high gain. Extra gain is added by the

low-noise, auto-zeroed op amp MCP6V07, before the ADC. The added gain is
250x, and the ADC’s PGA is 1x. For this option the jumpers must be set as fol­lows: J4 and J5 are on the right position; J8, J11 and J12 are ON, while J9, J10
and J13 are OFF (see Figure 1-3c).

d) Table 1-1 shows the jumper positions and their results.

FIGURE 1-2: Signal Conditioning and ADC on the MCP3421 Weight Scale Demo Board.

DS51918A-page 10  2010 Microchip Technology Inc.

Product Overview

TABLE 1-1: JUMPERS POSITIONS VS. FUNCTION

Symbol Jumpers Positions Function

(1)

xPGA

xGLo

xGHi

Note 1: x indicates the selected averaging factor (1 or 4).

J4 and J5 connected to J19
J10 and J13 are ON
J8, J9, J11 and J12 are disconnected (

(1)

J4 and J5 connected to GND
J9, J11 and J12 are ON
J8, J10 and J13 are disconnected (

(1)

J4 and J5 connected to GND
J8, J11 and J12 are ON
J9, J10 and J13 are disconnected (

Figure 1-3a)

Figure 1-3b)

Figure 1-3c)

This combination evaluates the ADC perfor­mance. The on-board op amp is bypassed.

This combination evaluates the influence of the
extra gain added by the MCP6V07 device.

This combination evaluates the influence of the
extra gain added by the MCP6V07 device, but
with higher extra gain.

FIGURE 1-3: Gain Selection Options on MCP3421 Weight Scale Demo Board.

1.3 LOAD CELL

The MCP3421 device with a maximum PGA gain setting (8x) can detect an input signal
level as low as 2 µV. Therefore, it can detect the input with an accuracy of 1g. When
measuring such a low input signal level, to control the noise level at the input pins is
very important. Therefore, using low-noise op amp at the signal conditioning circuit is
necessary. In this demo board, MCP6V07 auto-zeroed op amp is used. This op amp
has the offset voltage less than ±2 µV, and drifts less than ±50 nV/C.

Additional improvement in signal-to-noise ratio can be achieved by doing more averag­ing in digital domain. The user can tell the difference by selecting the data average
options 1 or 4. The results are shown in the PC GUI.

Note: This demo board uses a low-cost load cell for demonstration purposes. The

load cell can measure up to 2 Kg with 1 mV/V sensitivity. The load cell
output is connected to the demo board PCB through J18 and J19
connectors. The user can also connect their own load cell instead.

 2010 Microchip Technology Inc. DS51918A-page 11

MCP3421 Weight Scale Demo Board User’s Guide

1.4 UNIVERSAL SERIAL BUS (USB) AND PIC18F4550 MICROCONTROLLER

The MCP3421 Weight Scale Demo Board has a USB connector to communicate with
the PC GUI. The PC GUI allows various user options, such as calibrations and perfor­mance evaluation of the system.

The USB communication with the PC is done by the on-board microcontroller.
PIC18F4550 is also communicating with the ADC, and controls the LCD.

The four button switches on the board have the following functions:

• S5 is the Reset pin

• S2 is used to change the LCD indication from “Weight” to “ADC code”, “ADC out­put”, or “Calibration”

• S3 is used in parallel with the configuration of the signal conditioning chain. By
pressing this button, the LCD indication will change from 1PGA to 1GLo, 1GHi,
4PGA, 4GLo or 4GHi. PGA means that the ADCs PGA only is used at highest
gain. GLo means that the external op amp is being used with low gain, GHi means
that external op amp is used with high gain. The 1 and 4 before the letters indicate
the numbers of averages – no averaging, or averaging on four samples

• S4 is doing the zero calibration. By pressing this button, the “Weight” indication
will go to a value closer to 0g.

1.5 WHAT THE MCP3421 WEIGHT SCALE KIT CONTAINS

The MCP3421 Weight Scale Demo Board kit includes:

• MCP3421 Weight Scale Demo Board, 102-00250

• Important Information Sheet

DS51918A-page 12  2010 Microchip Technology Inc.

MCP3421 WEIGHT SCALE

DEMO BOARD USER’S GUIDE

Chapter 2. Installation and Operation

2.1 MCP3421 CONFIGURATION BIT SETTINGS AND DATA ACQUISITION

The communication with the ADC is done through I2C, but the I2C peripheral port of the
MCU is not being used. Instead, two pins (RA4, RA5) are being controlled from the firm­ware.

The MCU is changing the setup of the ADC each time S3 is pressed, to change the
PGA gain: 8x for PGA, 2x for GLo and 1x for GHi. The ADC always operates in 18-bit
mode.

The data received from the MCP3421 device is scaled to a value expressed in grams
by the compute() function, in order to be displayed on the LCD.

There are two calibration steps: offset subtraction and gain scaling. The two values, the
offset and the gain constants, are stored in EEPROM during the calibration, and read
out at Reset, or when the S3 is pressed.

2.2 USB COMMUNICATION

The Microchip USB Firmware Framework is a software library developed by Microchip
Technology Inc., that can be used to create new USB applications. It can be
considered as a reference design project, containing the necessary firmware code for
USB operation, also providing a placeholder for user’s code. The whole code project
is contained within one single root project directory, with many subdirectories for
source code organization.

®

Microchip provides a general purpose Windows
dows applications, to interface with a custom class USB device. The driver will not be
used in all USB applications, one of the exceptions being the USB HID class devices,
which would normally use built-in HID class drivers distributed with the OS.

For USB applications that do not easily fit within the constraints of these other device
class options, Microchip’s general purpose driver may be used. Windows applications
can access the USB devices either by directly interfacing with the driver
(mchpusb.sys), or indirectly use the driver through a pre-compiled library.

A custom class Windows application using the Microchip general purpose USB driver
may interface directly with the driver (mchpusb.sys). By doing so, it requires more
effort and more learning time than using a pre-compiled library that exposes a simple
to use API, including basic functions like open(), read(), write() and close().

The MPUSBAPI.DLL file is a library which provides a number of functions, including the
basic ones needed for reading and writing to an USB device. A list of the functions
available and the calling conventions for those functions is currently documented in the
form of in-line comments in the source code for the DLL file. The DLL is compiled using
Borland
in the <System Driver>:

®

C++ Builder™ 6 development environment, and the source code is provided

\MCHPFSUSB\Pc\Mpusbapi\Dll\Borland_C\Source directory.

driver which can be used with Win-

 2010 Microchip Technology Inc. DS51918A-page 13

MCP3421 Weight Scale Demo Board User’s Guide

A load time linking and a run time linking example, showing how to use the DLL, are
included in the System Driver:\MCHPFSUSB\Pc\Mpusbapi\Example Applications
directory.

Note: For running this project, the USB Microchip Stack must be installed on the

user’s machine.

The MCP3421 Weight Scale Demo Board firmware is mainly based on the USB stack
example: “Device – MCHPUSB – Generic Driver Demo”. Most of the firmware changes
of the MPLAB MCP3421 Weight Scale Demo Board project are done in the user v7
eeprom.c file. This project is downloadable from Microchip’s MCP3421 product page
web site: http://www.microchip.com/wwwproducts/Devices.aspx?dDoc­Name=en520011.

The input offset error voltage is computed when S4 is being pressed. The gain constant
is computed by the PC software and transmitted to the MCU via USB on the OUT-
Packet._byte[2] to OUTPacket._byte[7].

The weight scale is sending to the PC software the following values: weight, ADC code,
ADC output, zero calibration and gain calibration, represented by six characters using
INPacket._byte[0] to INPacket._byte[31].

DS51918A-page 14  2010 Microchip Technology Inc.

Chapter 3. Weight Scale PC Software Tool

3.1 SOFTWARE INSTALLATION

The Weight Scale PC software is an executable file that does not require installation.
But, to enable running the software, the user must first install two additional programs,
in the following order:

- NI LabVIEW Run-Time Engine

- NI-VISA Run-Time Engine

These programs can be downloaded from www.ni.com

3.2 SOFTWARE OVERVIEW

The MCP3421 Weight Scale Demo Board includes a PC graphical user interface (GUI),
that can be used to evaluate the weight scale accuracy and weight scale calibration.

This board is communicating with the software via USB port.
The following figure shows a sample of the software’s GUI in Measurement mode:

MCP3421 WEIGHT SCALE

DEMO BOARD USER’S GUIDE

.

FIGURE 3-1: MCP3421 Weight Scale Demo Board Software – Measurement Mode.

The user can control the size of the X axis by writing the desired figure in buffer length.
Several series of statistical analysis are performed on this buffer, the most important
being displayed on the screen, under the Measurement Standard Deviation. This
deviation is measured in grams and represents the RMS noise value of the weight
scale. The actual accuracy of the weight scale can be defined in many ways, but most
commonly it is 10 times the standard deviation.

 2010 Microchip Technology Inc. DS51918A-page 15

MCP3421 Weight Scale Demo Board User’s Guide

3.3 WEIGHT SCALE CALIBRATION

The MCP3421 Weight Scale Demo Board requires a two points calibration: one at 0g,
to remove the weight scale offset, and another at a known point, for gain calibration.

To perform the complete weight scale calibration the user must follow the next steps:

1. Connect the weight scale to the PC and run the software.

2. Press S3 button to select the desired option (xPGA, xGLo or xGHi).

3. Press S4 to remove the offset. The weight indication does not reach 0 in all

cases. This is a normal behavior, since calibration is not completed at this step.

4. Place a known weight on the scale’s platform.

5. Write the weight value in the “Calibration Weight (g)” field on the GUI.

6. Press Calibrate button from the GUI, or F4 on the keyboard. This last step will

perform the gain calibration.

The offset calibration may be required more often than the gain calibration, for precision
reasons. Once the complete weight scale calibration done, the offset calibration can be
performed at any time, by pressing S4.

It is important to perform complete calibrations for all six signal conditioning options.
The calibration constants are being stored in the MCU EEPROM.

FIGURE 3-2: MCP3421 Weight Scale Demo Board Software – Calibration mode.

DS51918A-page 16  2010 Microchip Technology Inc.

Appendix A. Schematics and Layouts

A.1 INTRODUCTION

This appendix contains the following schematics and layouts for the MCP3421 Weight
Scale Demo Board:

• Board – Schematic

• Board – Top Copper and Pads

• Board – Top Pads and Silk

• Board – Top Copper, Pads and Silk

• Board – Bottom Copper and Pads

MCP3421 WEIGHT SCALE

DEMO BOARD USER’S GUIDE

 2010 Microchip Technology Inc. DS51918A-page 17

MCP3421 Weight Scale Demo Board User’s Guide

R24

523

+5V

R25

4.7K

V

DD

LCD1

LCD_2X16_COG

+5V

MCP1702

RD2

RD1

RD0

DB0

DB1

DB2

DB3

DB4

DB5

DB6

DB7

E

R/W

RS

V

EE

Vcc

GND

GND1

3

2

1

14

131215

11

10

9

8

7

546

4550_RA0

4550_RA1

4550_RA2

4550_RA3

VOUT

U4

V

IN

GND

D5

1N914

2

3

1

C7

0.1

UF

P

OWER ON

D6

R19

1.5K

BAT1

9V

9V DC Battery

* SEE NOTE 1

BELOW

C6

0.33uF

2

3

1

9V

J1

9V AC Power Supply

* Note 1:

Use 9V power supply or 9V battery, but

not both at the same time.

J18

1

2

+5V_A

EXCITATION

LC1

LOAD

CELL

LC2

LOAD

CELL

INPUT –

J4

J19

1

2

OUTPUT

INPUT +

J5

R38

1k

Extra Gain Lo

J9

R37

220

J8

Extra Gain Hi

R31 220

PGA

J10

C10

10nF

C18

1uF

C17

10nF

R35

220

MCP6V07

R30

2.2K

Extra Gain

J11

Extra Gain

J12

PGA

J13

1K

R39

1K

R36

10K

R17

+5V

C70

47uF

L5

10uH

10uH

L6

C69

47uF

D11

R27

1.5K

+5V

Reset

PIC18F4550

U2

44 Pin TQFP

20 MHz

X1

D12

D13

R32

R33

R34

1.5K 1.5K

1.5K

+5V

+5V

+5V

R21

24.9

R22

24.9

Pin 3

Pin 2

C4

0.1uF

D14

C11

0.1uF

C12

0.1uF

U5

R29

2.2K

47K

R28

R26

47K

C19

1uF

C20

1uF

MCP3421 A0

R18

10K

+5V +5V +5V

D7

D8

D9

RB0

RB1

RB2

S2 S3

S4

1.5K

1.5K

1.5K

R13

R14

R15

SSL–LX15IC

D3

R20

332

C8

C14

10uF

10uF

C13

0.1uF

L1

10uH

None

R23

C15

18pF

GND GND

C16

18pF

C9

0.1uF

J_MINI_USB_HRS_UX60_MBM5ST

USB1

MINI USB

NC

NC

RB4/CSSPP

RB6

RB7

MCLR

RA1

RA2

RB5

RA3

RA0

RC6

RC5/D+

RC4/D–

RD3/SPP3

RD2/SPP2

RD1/SPP1

RD0/SPP0

VUSB

RC2

RC1

NC

RC7

RD4/SPP4

RD5/SPP5

RD6/SPP6

RD7/SPP7

V

SS

VDD

RB0

RB1

RB2

RB3

NC

RC0

OSC2

OSC1

V

DD

VSS

RE2/OESPP

RE1/CK2SPP

RE0/CK1SPP

RA5

RA4

A.2 BOARD – SCHEMATIC

DS51918A-page 18  2010 Microchip Technology Inc.

A.3 BOARD – TOP COPPER AND PADS

Schematics and Layouts

 2010 Microchip Technology Inc. DS51918A-page 19

MCP3421 Weight Scale Demo Board User’s Guide

BOARD EDGE

A.4 BOARD – TOP PADS AND SILK

DS51918A-page 20  2010 Microchip Technology Inc.

Schematics and Layouts

BOARD EDGE

A.5 BOARD – TOP COPPER, PADS AND SILK

 2010 Microchip Technology Inc. DS51918A-page 21

MCP3421 Weight Scale Demo Board User’s Guide

A.6 BOARD – BOTTOM COPPER AND PADS

DS51918A-page 22  2010 Microchip Technology Inc.

MCP3421 WEIGHT SCALE

DEMO BOARD USER’S GUIDE

Appendix B. Bill of Mater ials

TABLE B-1: BILL OF MATERIALS (BOM)

Qty Reference Description Manufacturer Part Number

6 C4, C7, C9,

C11, C12,
C13

1 C6 CAP .33UF 6.3V CERAMIC X5R

2 C8, C14 CAP CER 10UF 6.3V X5R 0603 Murata Manufacturing

2 C10, C17 CAP CER 10000PF 50V 10% X7R

2 C15, C16 CAP CER 18PF 50V 5% C0G 0603 Murata Manufacturing

3 C18, C19,

C20

2 C69, C70 CAP TANTALUM 47UF 6.3V 10%

1 D3 DO NOT POPULATE — —
1 D5 DIODE SS HI COND100V 200MA

4 D6, D7, D8,

D9, D11,
D12, D13,
D14,

1 J1 CONN POWERJACK MINI .08" R/A

2 J4, J5 CONN HEADER VERT 2POS .100

6 J8, J9, J10,

J1 1 , J 12, J1 3
2 J18, J19 CONN TERM BLOCK 2.54MM 2POS Phoenix Contact 1725656
2 L5, L6 INDUCTOR 10UH 450MA 1210 Murata Manufacturing

1 LC1 DO NOT POPULATE — —
1 LC2 Load cell AMA–2kg Xiamen Kuanyi Electronic

1 LCD1 16X2 LCD Character Display Fema Electronics

1 P2 6w ay pins MCU pr ogramming Tyco Elect ronics 3-644456-6
1 PCB RoHS Compliant Bare PCB,

Note 1: The components listed in this Bill of Materials are representative of the PCB assembly. The

released BOM used in manufacturing uses all RoHS-compliant components.

CAP X2Y CER .1UF X7R 6.3V 0603 Johanson Dielectrics Inc 6R3X14W104MV4T

Panasonic

0603

Co., Ltd.
Murata Manufacturing

0603

CAP CER 1.0UF 6.3V 10% X5R 0603 Murata Manufacturing

SMD

DO-35
LED GREEN CLEAR THIN 0805

SMD

T/H

TIN
CONN HEADER VERT 2POS .100

TIN

MCP3421 Weight Scale Demo Board

Co., Ltd.

Co., Ltd.

Co., Ltd.
Kemet B45196H1476K209

Fairchild Semiconductor
Inc.

Lite-On

Switchcraft

Tyco Electronics 3-644695-3

Tyco Electronics 3-644695-2

Co., Ltd.

Technology Co., Ltd.

Corporation

— 104-00250

®

– ECG ECJ-1VB0J334K

GRM188R60J106ME47D

GRM188R71H103KA01D

GRM1885C1H180JA01D

GRM188R60J105KA01D

1N914BTR

®

, Inc. LTST-C171GKT

®,

Inc. RAPC722X

LQH32CN100K53L

AMA-2

CG1626-SGR1

 2010 Microchip Technology Inc. DS51918A-page 23

MCP3421 Weight Scale Demo Board User’s Guide

TABLE B-1: BILL OF MATERIALS (BOM) (CONTINUED)

Qty Reference Description Manufacturer Part Number

8 R13, R14,

R15, R19,
R27, R32,
R33, R34

2 R17, R18 RES 10.0K OHM 1/10W 1% 0603

1 R20 RES 332 OHM 1/10W 1% 0603 SMD Panasonic – ECG ERJ-3EKF3320V
2 R21, R22 RES 24.9 OHM 1/10W 1% 0603 SMD Panasonic – ECG ERJ-3EKF24R9V
1 R23 DO NOT POPULATE — —
1 R24 RES 523 OHM 1/10W 1% 0603 SMD Panasonic – ECG ERJ-3EKF5230V
1 R25 RES 4.70K OHM 1/10W 1% 0603

2 R26, R28 RES 47.0K OHM 1/10W 1% 0603

2 R29, R30 RES 2.20K OHM 1/10W 1% 0603

3 R31, R35,

R37

3 R36, R38,

R39

4 S2, S3, S4, S5SWITCH LT TOUCH 6X3.5 100GF

1 U1 MCP3421 SOT-23_6L A0 Microchip Technology

1 U2 PIC18F4550 TQFP44 Microchip Technology

1 U4 MCP1702 SOT23A 5V CMOS low

1 U5 MCP6V02 SOIC8 Linear High Preci-

1 USB1 CONN RECEPT MINI USB2.0 5POS Hirose Electric Co., Ltd. UX60-MB-5ST
1 X1 CRYSTAL 20MHZ METAL CASE

Note 1: The components listed in this Bill of Materials are representative of the PCB assembly. The

released BOM used in manufacturing uses all RoHS-compliant components.

RES 1.50K OHM 1/10W 1% 0603
SMD

SMD

SMD

SMD

SMD
RES 220 OHM 1/10W 1% 0603 SMD Panasonic – ECG ERJ-3EKF2200V

RES 1.00K OHM 1/10W 1% 0603
SMD

SMD

dropout positive voltage regulator

sion Op Amps-Auto Zero

SMD

Yageo Corporation RC0603FR-071K5L

Panasonic – ECG ERJ-3EKF1002V

Panasonic – ECG ERJ-3EKF4701V

Panasonic – ECG ERJ-3EKF4702V

Panasonic – ECG ERJ-3EKF2201V

Panasonic – ECG ERJ-3EKF1001V

Panasonic – ECG EVQ-PJS04K

MCP3421A0T-E/CH

Inc.

PIC18F4550-I/PT

Inc.
Microchip Technology

Inc.
Microchip Technology

Inc.

Connor-Winfield XM-1-20.0000

MCP1701T-5002I/CB

MCP6V07-E/SN

DS51918A-page 24  2010 Microchip Technology Inc.

NOTES:

MCP3421 Weight Scale Demo Board User’s Guide

 2010 Microchip Technology Inc. DS51918A-page 25

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08/04/10

DS51918A-page 26  2010 Microchip Technology Inc.