TMP451
SBOS686 –JUNE 2013
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SERIES RESISTANCE CANCELLATION
Series resistance cancellation automatically eliminates the temperature error caused by the resistance of the
routing to the remote transistor or by the resistors of the optional external low-pass filter. A total of up to 1 kΩ of
series resistance can be cancelled by the TMP451, eliminating the need for additional characterization and
temperature offset correction. See Figure 4, Remote Temperature Error vs Series Resistance, for details on the
effects of series resistance on sensed remote temperature error.
DIFFERENTIAL INPUT CAPACITANCE
The TMP451 tolerates differential input capacitance of up to 1000 pF with minimal change in temperature error.
The effect of capacitance on sensed remote temperature error is illustrated in Figure 5, Remote Temperature
Error vs Differential Capacitance.
TEMPERATURE MEASUREMENT DATA
The local and remote temperature sensors have a resolution of 12 bits (0.0625°C). Temperature data that result
from conversions within the default measurement range are represented in binary form, as shown in the
Standard Binary column of Table 1. Any temperature below 0°C results in a data value of 0 (00h). Likewise,
temperatures above +127°C result in a value of 127 (7Fh). The device can be set to measure over an extended
temperature range by changing bit 2 (RANGE) of configuration register from low to high. The change in
measurement range and data format from standard binary to extended binary occurs at the next temperature
conversion. For data captured in the extended temperature range configuration, an offset of 64 (40h) is added to
the standard binary value, as shown in the Extended Binary column of Table 1. This configuration allows
measurement of temperatures as low as –64°C, and as high as +191°C; however, most temperature-sensing
diodes only measure with the range of –55°C to +150°C. Additionally, the TMP451 is specified only for ambient
temperatures ranging from –40°C to +125°C; parameters in the Absolute Maximum Ratings table must be
observed.
Table 1. Temperature Data Format (Local and Remote Temperature High Bytes)
LOCAL/REMOTE TEMPERATURE REGISTER
HIGH BYTE VALUE (1°C RESOLUTION)
STANDARD BINARY(1)
EXTENDED BINARY(2)
TEMPERATURE
(°C)
BINARY
HEX
00
00
00
00
01
05
0A
19
32
4B
64
7D
7F
7F
7F
7F
BINARY
HEX
00
–64
–50
–25
0
0000 0000
0000 0000
0000 0000
0000 0000
0000 0001
0000 0101
0000 1010
0001 1001
0011 0010
0100 1011
0110 0100
0111 1101
0111 1111
0111 1111
0111 1111
0111 1111
0000 0000
0000 1110
0010 0111
0100 0000
0100 0001
0100 0101
0100 1010
0101 1001
0111 0010
1000 1011
1010 0100
1011 1101
1011 1111
1101 0110
1110 1111
1111 1111
0E
27
40
1
41
5
45
10
4A
59
25
50
72
75
8B
A4
BD
BF
D6
EF
FF
100
125
127
150
175
191
(1) Resolution is 1°C/count. Negative numbers are represented in twos complement format.
(2) Resolution is 1°C/count. All values are unsigned with a –64°C offset.
8
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