Datasheet

LM75A

SNOS808O –JANUARY 2000–REVISED MAY 2013

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The first data byte is the most significant byte with most significant bit first, permitting only as much data as

necessary to be read to determine temperature condition. For instance, if the first four bits of the temperature

data indicates an overtemperature condition, the host processor could immediately take action to remedy the

excessive temperatures. At the end of a read, the LM75A can accept either Acknowledge or No Acknowledge

from the Master (No Acknowledge is typically used as a signal for the slave that the Master has read its last

byte).

POINTER REGISTER (Selects which registers will be read from or written to):

P7 P6 P5 P4 P3 P2 P1 P0

0 0 0 0 0 Register Select

P0-P1: Register Select:

P2 P1 P0 Register

0 0 0 Temperature (Read only) (Power-up default)

0 0 1 Configuration (Read/Write)

0 1 0 T

HYST

(Read/Write)

0 1 1 T

(Read/Write)

1 1 1 Product ID Register

P3–P7: Must be kept zero.

TEMPERATURE REGISTER (Read Only):

D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0

MSB Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 LSB X X X X X X X

D0–D6: Undefined. D7–D15: Temperature Data. One LSB = 0.5°C. Two's complement format.

CONFIGURATION REGISTER (Read/Write):

D7 D6 D5 D4 D3 D2 D1 D0

0 0 0 Fault Queue O.S. Polarity Cmp/Int Shutdown

Power up default is with all bits “0” (zero).

D0: Shutdown: When set to 1 the LM75A goes to low power shutdown mode.

D1: Comparator/Interrupt mode: 0 is Comparator mode, 1 is Interrupt mode.

D2: O.S. Polarity: 0 is active low, 1 is active high. O.S. is an open-drain output under all conditions.

D3–D4: Fault Queue: Number of faults necessary to detect before setting O.S. output to avoid false tripping due

to noise. Faults are determine at the end of a conversion. See specified temperature conversion time in the

electrical tables.

D4 D3 Number of Faults

0 0 1 (Power-up default)

0 1 2

1 0 4

1 1 6

D5–D7: These bits are used for production testing and must be kept zero for normal operation.

Product Folder Links: LM75A