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AN-876
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AN-876 Replacing National’s LM75 with the Analog Devices, Inc. ADT75
by Donal McNamara
Rev. 0 | Page 1 of 4
INTRODUCTION
The ADT75 has two grades, the ADT75A and the ADT75B.
The ADT75B is a higher temperature accurate part, and the
ADT75A is designed as a second source for the LM75.
The
ADT75 is a functional and pin- and package-compatible
replacement for the LM75. No software or hardware change
is required when replacing the LM75 with the
ADT75.
SDA
1
SCL
2
OS/ALERT
3
GND
4
V
DD
8
A0
7
A1
6
A2
5
ADT75
TOP VIEW
(Not to Scale)
06439-001
Figure 1. ADT75 Pin Configuration
SDA 1
SCL 2
O.S. 3
GND
4
+V
S
8
A07
A16
A2
5
06439-002
Figure 2. LM75 Pin Configuration
TEMPERATURE ERROR PERFORMANCE OVER
TEMPERATURE
The performance capabilities of the ADT75A grade and LM75
over temperature are completely compatible. Both parts have
similar performance graphs (see
Figure 3).
Note that if more accuracy is required, the ADT75B grade is
recommended.
1.0
–1.0
–55 125
TEMPERATURE (°C)
TEMPERATURE ERROR (°C)
06439-003
0.8
0.6
0.4
0.2
0
–0.2
–0.4
–0.6
–0.8
–35 –15 5 25 45 65 85 105
V
DD
= 5V
V
DD
= 3.3V
Figure 3. ADT75 and LM75—Typical Temperature Accuracy
COMPATIBILITY
Table 1. Feature Comparison of the ADT75 and the LM75
Feature ADT75A LM75
I
2
C Interface Yes Yes
I²C Bus Address Yes Yes
8-Lead MSOP and 8-Lead SOIC Yes Yes
Identical Register Addresses
1
Yes Yes
Identical Register Content Yes Yes
Identical Temperature Accuracy Yes Yes
9-Bit Resolution Yes Yes
3.3 V and 5 V Operation Yes Yes
Similar AC/DC Parameters Yes Yes
Identical OS and Configuration Functions Yes Yes
Twos Complement Coding Yes Yes
1
The ADT75 and the LM75 have identical register content. The ADT75 contains additional register bits for one shot mode, SMBus alert enable, and extra temperature
resolution bits. The contents of all these additional registers can be ignored without having to modify LM75 software.
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