MCP9802 Microchip Technology Inc., MCP9802 Datasheet - Page 8

• Manufacturer Part Number: MCP9802
• Description: 2-wire High-accuracy Temperature Sensor
• Manufacturer: Microchip Technology Inc.

MCP9800/1/2/3
4.0
The MCP9800/1/2/3 family of temperature sensors
consists of a band-gap type temperature sensor, a
Analog-to-Digital Converter (ADC), user-programmable
registers and a 2-wire I
serial interface.
FIGURE 4-1:
DS21909B-page 8
Register
Pointer
FUNCTIONAL DESCRIPTION
Configuration
Temperature
Register
Register
Register
Register
T
T
HYST
SET
Alert Comp/Int
Alert Polarity
Fault Queue
Resolution
Functional Block Diagram.
Shutdown
One-Shot
2
C/SMBus protocol compatible
I
2
C™/SMBus
Interface
Temperature
Band-Gap
Sensor
10-Bit
11-Bit
12-Bit
9-Bit
ADC
4.1
The MCP9800/1/2/3 uses the difference in the base-
emitter voltage of a transistor while its collector current
is changed from IC
depends only on the ratio of the two currents and the
ambient temperature, as shown in Equation 4-1.
EQUATION 4-1:
4.2
A sigma-delta analog-to-digital converter is used to
convert V
transistor
adjustable resolution from 9-bits (at 30 ms conversion
time) to 12-bits (at 240 ms conversion time). Thus, it
allows the user to make trade-offs between resolution
and conversion time. Refer to Section 4.3.4 “Sensor
Configuration
Section 4.3.4.7 “
Where:
IC
1
Temperature Sensor
and IC
BE
temperature.
V
Analog-to-Digital Converter
BE
to a digital word that corresponds to the
V
T = temperature in kelvin
k = Boltzmann's constant
q = electron charge
BE
2
= change in diode base-emitter
= currents with n:1 ratio
1
=
Register
to IC
voltage
ADC Resolution” for details.


kT
----- -
q
 2004 Microchip Technology Inc.
2


. With this method, the V
The
ln IC
converter
(CONFIG)”
1
IC
2
has
and
an
BE