LM75B_2

© NXP B.V. 2008. All rights reserved.

Product data sheet

Rev. 02 — 9 December 2008

6 of 29

NXP Semiconductors

LM75B

Digital temperature sensor and thermal watchdog

device under the control of a controller or master device, using two device terminals, SCL

and SDA. The controller must provide the SCL clock signal and write/read data to/from the

Ω,

is needed for each of these two terminals. The bus communication protocols are

described in Section 7.10.

7.2.1 Bus fault time-out

50 ms minimum / 20 Hz), the LM75B will reset to the idle state (SDA released) and wait

for a new START condition. This ensures that the LM75B will never hang up the bus

should there be conflict in the transmission sequence.

7.3 Slave address

device address pins A2, A1 and A0. Each of them is typically connected either to GND for

address. The other four MSB bits of the address data are preset to ‘1001’ by hard wiring

inside the LM75B. Table 3 shows the device’s complete address and indicates that up to

8 devices can be connected to the same bus without address conflict. Because the input

pins, SCL, SDA and A2 to A0, are not internally biased, it is important that they should not

be left floating in any application.

7.4 Register list

The LM75B contains four data registers beside the pointer register as listed in Table 4.

The pointer value, read/write capability and default content at power-up of the registers

are also shown in Table 4.

Table 3.

Address table

1 = HIGH; 0 = LOW.

MSB

LSB

1001A2

A1

A0

Table 4.

Register table

Register

name

Pointer

value

R/W

POR

state

Description

Conf

01h

R/W

00h

Configuration register: contains a single 8-bit data

byte; to set the device operating condition; default = 0.

Temp

00h

read only

n/a

Temperature register: contains two 8-bit data bytes;

to store the measured Temp data.

Tos

03h

R/W

5000h

Overtemperature shutdown threshold register:

contains two 8-bit data bytes; to store the

default = 80

°C.

Thyst

02h

R/W

4B00h

Hysteresis register: contains two 8-bit data bytes;