0 functional description – Rainbow Electronics LM92 User Manual

Page 9

1.0 Functional Description

(Continued)

Therefore, the complete slave address is:

MSB

LSB

1.4 TEMPERATURE DATA FORMAT

Temperature data can be read from the Temperature and Set
Point registers; and written to the Set Point registers. Tem-
perature data can be read at any time, although reading
faster than the conversion time of the LM92 will prevent data
from being updated. Temperature data is represented by a
13-bit, two’s complement word with an LSB (Least Signifi-
cant Bit) equal to 0.0625 ˚C:

Temperature

Digital Output

Binary

Hex

+130˚C

0 1000 0 010 0000

08 20h

+125 ˚C

0 0111 1101 0000

07 D0h

+80 ˚C

0 0101 1010 0000

05 90h

+64 ˚C

0 0100 0000 0000

04 00h

+25 ˚C

0 0001 1001 0000

01 90h

+10 ˚C

0 0000 1010 0000

00 A0h

+2 ˚C

0 0000 0010 0000

00 20h

+0.0625 ˚C

0 0000 0000 0001

00 01h

0 ˚C

00 0000 0000

00 00h

−0.0625 ˚C

1 1111 1111 1111

1F FFh

−25 ˚C

1 1110 0111 0000

1E 70h

Temperature

Digital Output

Binary

Hex

−55 ˚C

1 1100 1001 0000

1C 90h

1.5 SHUTDOWN MODE

Shutdown mode is enabled by setting the shutdown bit in the
Configuration register via the Serial Bus. Shutdown mode re-
duces power supply current to 5 µA typical. T_CRIT_A is re-
set if previously set. Since conversions are stoped during
shutdown, T_CRIT_A and INT will not be operational. The
Serial Bus interface remains active. Activity on the clock and
data lines of the Serial Bus may slightly increase shutdown
mode quiescent current. Registers can be read from and
written to in shutdown mode. The LM92 takes miliseconds to
respond to the shutdown command.

1.6 INT AND T_CRIT_A OUTPUT

The INT and T_CRIT_A outputs are open-drain outputs and
do not have internal pull-ups. A

″

high

″

level will not be ob-

served on these pins 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 gen-
eral, the pull-up resistor should be as large as possible. This
will minimize any errors due to internal heating of the LM92.

DS101051-6

Note: Event Interrupt mode is drawn as if the user is reading the part. If the user doesn’t read, the outputs would go low and stay that way until the LM92 is read.
Comparator Interrupt Mode is drawn as if the user never reads the part. If the user does read, the outputs will go high once read instruction is executed and, if the
fault condition still exists, go low at the end of the next conversion.

FIGURE 3. Temperature Response Diagram

LM92