LM75B_2

© NXP B.V. 2008. All rights reserved.

Product data sheet

Rev. 02 — 9 December 2008

8 of 29

NXP Semiconductors

LM75B

Digital temperature sensor and thermal watchdog

7.4.3 Temperature register

The Temperature register (Temp) holds the digital result of temperature measurement or

monitor at the end of each analog-to-digital conversion. This register is read-only and

contains two 8-bit data bytes consisting of one Most Significant Byte (MSByte) and one

Least Significant Byte (LSByte). However, only 11 bits of those two bytes are used to store

the Temp data in 2’s complement format with the resolution of 0.125

°C. Table 8 shows the

bit arrangement of the Temp data in the data bytes.

When reading register Temp, all 16 bits of the two data bytes (MSByte and LSByte) are

provided to the bus and must be all collected by the controller to complete the bus

operation. However, only the 11 most significant bits should be used, and the 5 least

significant bits of the LSByte are zero and should be ignored. One of the ways to calculate

the Temp value in

°C from the 11-bit Temp data is:

1. If the Temp data MSByte bit D10 = 0, then the temperature is positive and Temp value

(

°C) = +(Temp data) × 0.125 °C.

2. If the Temp data MSByte bit D10 = 1, then the temperature is negative and

Temp value (

°C) = −(2’s complement of Temp data) × 0.125 °C.

Examples of the Temp data and value are shown in Table 9.

B1

OS_COMP_INT R/W

OS operation mode selection

0*

OS comparator

1

OS interrupt

B0

SHUTDOWN

R/W

device operation mode selection

0*

normal

1

shutdown

Table 7.

Legend: * = default value.

Bit

Symbol

Access Value Description

Table 8.

Temp register

MSByte

LSByte

7654321076543210

D10

D9

D8

D7

D6

D5

D4

D3

D2

D1

D0

XXXXX

Table 9.

Temp register value

11-bit binary

(2’s complement)

Hexadecimal value

Decimal value

Value

011 1111 1000

3F8

1016

+127.000

°C

011 1111 0111

3F7

1015

+126.875

°C

011 1111 0001

3F1

1009

+126.125

°C

011 1110 1000

3E8

1000

+125.000

°C

000 1100 1000

0C8

200

+25.000

°C

000 0000 0001

001

1

+0.125

°C

000 0000 0000

000

0

0.000

°C

111 1111 1111

7FF

−1

−0.125 °C