LM75BD,112【PDF 7/37 页】IC TEMP SENSOR DIGITAL 8-SOIC

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Sheet目录41

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LM75B

All information provided in this document is subject to legal disclaimers.

Product data sheet

Rev. 5 22 January 2014

7 of 37

NXP Semiconductors

LM75B

Digital temperature sensor and thermal watchdog

7.2 I

C-bus serial interface

The LM75B can be connected to a compatible 2-wire serial interface I

C-bus as a slave

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

device through the SDA terminal. Notice that if the I

C-bus common pull-up resistors have

not been installed as required for I

C-bus, then an external pull-up resistor, about 10 kW,

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

If the SDA line is held LOW for longer than t

(75 ms minimum / 13.3 Hz; guaranteed at

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

The LM75B slave address on the I

C-bus is partially defined by the logic applied to the

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

logic 0, or to V

for logic 1. These pins represent the three LSB bits of the device 7-bit

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

inside the LM75B. Table 4

shows the devices 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 5

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

are also shown in Table 5

Table 4.

Address table

1 = HIGH; 0 = LOW.

MSB

LSB

Table 5.

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

overtemperature shutdown T

th(ots)

limit;

default = 80 癈.

Thyst

02h

R/W

4B00h

Hysteresis register: contains two 8-bit data bytes;

to store the hysteresis T

hys

limit; default = 75 癈.

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