TMP401

SBOS371B – AUGUST 2006 – REVISED OCTOBER 2014

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7.3 Feature Description

7.3.1 Standard and Extended Temperature Measurement Range

Temperature measurement data are taken over a default range of 0°C to +127°C for both local and remote

locations. Measurements from –55°C to +150°C can be made both locally and remotely by reconfiguring the

TMP401 for the extended temperature range. To change the TMP401 configuration from the standard to the

extended temperature range, switch bit 2 (RANGE) of the configuration register from low to high.

Temperature data resulting from conversions within the default measurement range are represented in binary

form, as shown in Table 1 (see the Standard Binary column). Note that any temperature below 0°C results in a

data value of zero (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 of the 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 Table 1 (see the Extended Binary column). This

configuration allows measurement of temperatures below 0°C. Note that binary values corresponding to

temperatures as low as –64°C, and as high as +191°C are possible; however, most temperature-sensing diodes

only measure with the range of –55°C to +150°C. Additionally, the TMP401 is rated only for ambient

temperatures ranging from –40°C to +125°C. Parameters in the Absolute Maximum Ratings table must be

followed.

Table 1. Temperature Data Format (Local and Remote Temperature High Bytes)

LOCAL, REMOTE TEMPERATURE REGISTER HIGH BYTE VALUE (+1°C Resolution)

TEMPERATURE (°C)

STANDARD BINARY

EXTENDED BINARY

BINARY

HEX

BINARY

HEX

–64

0000 0000

00

0000 0000

00

–50

0000 0000

00

0000 1110

0E

–25

0000 0000

00

0010 0111

27

0

0000 0000

00

0100 0000

40

1

0000 0001

01

0100 0001

41

5

0000 0101

05

0100 0101

45

10

0000 1010

0A

0100 1010

4A

25

0001 1001

19

0101 1001

59

50

0011 0010

32

0111 0010

72

75

0100 1011

4B

1000 1011

8B

100

0110 0100

64

1010 0100

A4

125

0111 1101

7D

1011 1101

BD

127

0111 1111

7F

1011 1111

BF

150

0111 1111

7F

1101 0110

D6

175

0111 1111

7F

1110 1111

EF

191

0111 1111

7F

1111 1111

FF

NOTE

Whenever changing between standard and extended temperature ranges, be aware that

the temperatures stored in the temperature limit registers are NOT automatically

reformatted to correspond to the new temperature range format. These temperature limit

values must be reprogrammed in the appropriate binary or extended binary format.

Both local and remote temperature data use two bytes for data storage. The high byte stores the temperature

with 1°C resolution. The second or low byte stores the decimal fraction value of the temperature and allows a

higher measurement resolution; see Table 2. The measurement resolution for the remote channel is 0.0625°C,

and is not adjustable. The measurement resolution for the local channel is adjustable and can be set for 0.5°C,

0.25°C, 0.125°C, or 0.0625°C by setting the RES1 and RES0 bits of the resolution register; see the Resolution

Register section.

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