tcn75a Microchip Technology Inc., tcn75a Datasheet - Page 10

• Manufacturer Part Number: tcn75a
• Description: 2-wire Serial Temperature Sensor
• Manufacturer: Microchip Technology Inc.

TCN75A
5.0
The TCN75A temperature sensor consists of a band-
gap type temperature sensor, a ΣΔ Analog-to-Digital
Converter (ADC), user-programmable registers and a
2-wire I
FIGURE 5-1:
DS21935C-page 10
Register
Pointer
2
C protocol-compatible serial interface.
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
Interface
I
2
C™
Temperature
Band-Gap
0.0625°C
ΣΔ ADC
0.125°C
Sensor
0.25°C
0.5°C
5.1
The TCN75A 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 5-1.
EQUATION 5-1:
5.2
A Sigma-Delta ADC is used to convert ΔV
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
Section 5.3.2
(CONFIG)” and Section 5.3.4.7 “ΣΔ ADC Resolution”
for details.
Where:
IC
1
and IC
Temperature Sensor
ΣΔ Analog-to-Digital Converter
ΔV
BE
Δ
T = temperature in kelvin
q = electron charge
k = Boltzmann's constant
2
V
BE
“Sensor
= change in diode base-emitter
= currents with n:1 ratio
1
to IC
=
voltage
⎛
⎝
kT
----- -
q
© 2006 Microchip Technology Inc.
2
. With this method, the ΔV
⎞
⎠
×
Configuration
ln IC
(
1
⁄
IC
2
)
BE
to a digital
Register
BE