SE95_7

© NXP B.V. 2009. All rights reserved.

Product data sheet

Rev. 07 — 2 September 2009

11 of 27

NXP Semiconductors

SE95

Ultra high accuracy digital temperature sensor and thermal watchdog

Obviously, for 9-bit Temp data application in replacing the industry standard LM75, just

use only 9 MSB bits of the two bytes and disregard 7 LSB of the LSByte. The 9-bit Temp

data with 0.5

°C resolution of the SE95 is defined exactly in the same way as for the

standard LM75 and it is here similar to the Tos and Thyst registers.

8.6 Overtemperature shutdown threshold and hysteresis registers

These two registers, are write/read registers, and also called set-point registers. They are

used to store the user-defined temperature limits, called overtemperature shutdown

threshold (Tos) and hysteresis temperature (Thyst), for the device watchdog operation. At

the end of each conversion the Temp data will be compared with the data stored in these

two registers in order to set the state of the device OS output; see Section 7.1.

Each of the set-point registers contains two 8-bit data bytes consisting of one MSByte and

one LSByte the same as register Temp. However, only 9 bits of the two bytes are used to

store the set-point data in two’s complement format with the resolution of 0.5

°C. Table 12

and Table 13 show the bit arrangement of the Tos data and Thyst data in the data bytes.

Notice that because only 9-bit data are used in the set-point registers, the device uses

only the 9 MSB of the Temp data for data comparison.

When a set-point register is read, all 16 bits are provided to the bus and must be collected

by the controller to complete the bus operation. However, only the 9 most significant bits

should be used and the 7 LSB of the LSByte are equal to zero and should be ignored.

Table 14 shows examples of the limit data and value.

Table 12.

Tos register

MSByte

LSByte

7654321076543210

D8

D7

D6

D5

D4

D3

D2

D1

D0

XXXXXXX

Table 13.

Thyst register

MSByte

LSByte

7654321076543210

D8

D7

D6

D5

D4

D3

D2

D1

D0

XXXXXXX

Table 14.

Tos and Thyst register

11-bit binary

(two’s complement)

Hexadecimal value

Decimal value

Value

0 1111 1010

0FA

250

125.0

°C

0 0011 0010

032

50

25.0

°C

0 0000 0001

001

1

0.5

°C

0 0000 0000

000

0

0.0

°C

1 1111 1111

1FF

−1

−0.5 °C

1 1100 1110

1CE

−50

−25.0 °C

1 1001 0010

192

−110

−55.0 °C