1.4 TEMPERATURE DATA FORMAT

Temperature data can be read from the Temperature, T

OS

Set Point, and T

T

data is represented by a 9-bit, two’s complement word with

an LSB (Least Significant Bit) equal to 0.5˚C:

Temperature

Digital Output

Binary

Hex

+125˚C

0 1111 1010

0FAh

+25˚C

0 0011 0010

032h

+0.5˚C

0 0000 0001

001h

0˚C

0 0000 0000

000h

−0.5˚C

1 1111 1111

1FFh

−25˚C

1 1100 1110

1CEh

−55˚C

1 1001 0010

192h

1.5 SHUTDOWN MODE

Shutdown mode is enabled by setting the shutdown bit in the

Configuration register via the I

duces power supply current to 4 µA typical. In Interrupt mode

O.S. is reset if previously set and is undefined in Comparator

mode during shutdown. The I

Activity on the clock and data lines of the I

slightly increase shutdown mode quiescent current. T

T

written to in shutdown mode.

1.6 FAULT QUEUE

A fault queue of up to 6 faults is provided to prevent false

tripping of O.S. when the LM75 is used in noisy environ-

ments. The number of faults set in the queue must occur

consecutively to set the O.S. output.

1.7 COMPARATOR/INTERRUPT MODE

As indicated in the O.S. Output Temperature Response Dia-

gram, Figure 4, the events that trigger O.S. are identical for

either Comparator or Interrupt mode. The most important

difference is that in Interrupt mode the O.S. will remain set

indefinitely once it has been set. To reset O.S. while in

Interrupt mode, perform a read from any register in the

LM75.

1.8 O.S. OUTPUT

The O.S. output is an open-drain output and does not have

an internal pull-up. A “high” level will not be observed on this

pin until pull-up current is provided from some external

source, typically a pull-up resistor. Choice of resistor value

depends on many system factors but, in general, the pull-up

resistor should be as large as possible. This will minimize

any errors due to internal heating of the LM75. The maxi-

mum resistance of the pull up, based on LM75 specification

for High Level Output Current, to provide a 2V high level, is

30 k

Ω.

1.9 O.S. POLARITY

The O.S. output can be programmed via the configuration

register to be either active low (default mode), or active high.

In active low mode the O.S. output goes low when triggered

exactly as shown on the O.S. Output Temperature Response

Diagram, Figure 4. Active high simply inverts the polarity of

the O.S. output.

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