Microchip Technology MCP9800DM-DL2 Data Sheet

 2010 Microchip Technology Inc.

DS21909D-page 13

The MCP9800/1/2/3 temperature sensor consists of a
band-gap type temperature sensor, a 

 Analog-to-

Digital Converter (ADC), user-programmable registers
and a 2-wire I

2

C protocol-compatible serial interface. 

The MCP9800/1/2/3 uses the difference in the base-
emitter voltage of a transistor while its collector current
is changed from IC

1

 to IC

2

. With this method, the 

V

BE

depends only on the ratio of the two currents and the
ambient temperature, as shown in 

 Analog-to-Digital Converter

A Sigma-Delta ADC is used to convert 

V

BE

 to a digital

word that corresponds to the transistor temperature.
The converter has an adjustable resolution from 0.5°C
(at 30 ms conversion time) to 0.0625°C (at 240 ms
conversion time). Thus, it allows the user to make
trade-offs between resolution and conversion time.
Refer to 

 and 

 for details.

Resolution

0.5°C

0.25°C

0.125°C

0.0625°C

Temperature

T

HYST

 

T

SET

 

Register

Register

Register

Register

Pointer

I

2

C™

Interface

Configuration

Register

 ADC

Band-Gap

Temperature

Sensor

One-Shot

Shutdown

Fault Queue

Alert Polarity

Alert Comp/Int



------

 

  ln IC

1

2









=

Where:

T = temperature in kelvin

V

BE

= change in diode base-emitter 

voltage

k = Boltzmann's constant

q = electron charge

IC

1

 and IC

2

= currents with n:1 ratio