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© 2005 Microchip Technology Inc. DS00988A-page 1
AN988
INTRODUCTION
The MCP9800 is a digital CMOS silicon temperature
sensor that provides an accurate digital temperature
measurement. Data is converted from an internal
diode temperature-sensing element to a digital format
that can be directly interfaced to a PICmicro
®
microcontroller unit (MCU). The MCP9800 sensor
offers many system-level advantages, including the
integration of the sensor and signal-conditioning
circuitry in a small Integrated Circuit (IC) package. The
MCP9800 also has a One-shot Conversion mode that
performs a single temperature measurement and then
goes into power-saving Shutdown mode. The One-
shot Conversion mode makes this sensor a good
choice for power-critical, portable applications.
The MCP9800 digital temperature sensor is especially
suited for embedded systems due to its I
2
C™ interface,
which serves to provide an industry standard method of
interface to a microcontroller. This application note will
discuss system integration, firmware implementation
and Printed Circuit Board (PCB) layout techniques for
using the MCP9800 in an embedded system.
The techniques for integrating the MCP9800 into an
embedded systems environment will be demonstrated
by using the PICkit™ 1 Flash Starter Kit and a
MCP9800 PICtail™ daughter board. The MCP9800
PICtail daughter board plugs into the PICkit 1 Flash
Starter Kit expansion header J3, as shown in Figure 1.
The MCP9800 demonstration is designed to measure
and display temperature using the on-board 7-segment
LED display.
Gerber files for the PCB, source code and a hex file to
program a PIC16F684 are included in the companion
zip file, 00059R1.zip.
FIGURE 1: Block Diagram of the MCP9800 Digital Temperature Sensor Demonstration.
Author: Ezana Haile and Jim Lepkowski
Microchip Technology Inc.
V
DD
PICmicro
®
Flash
I
2
C Interface
SPI™
GND
MCU
PICkit™ 1 Flash Starter Kit
PC
USB
J3
2
+5V
J2
2
SPI Interface
I
2
C™
Alert Indicator
MCP9800 PICtail™ Demo Board
MCP9800
Thermal
Sensor
PIC16F737
Display Controller
7-Segment display
PIC16F684
Interface
Interface
Interfacing the MCP9800 I
2
C
™
Digital Temperature Sensor
to a PICmicro
®
Microcontroller
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