Shutdown Mode

For power-sensitive applications, the DS75 offers a low-

power shutdown mode. The SD bit in the configuration

register controls shutdown mode. When SD is changed

to 1, the conversion in progress will be completed and

the result stored in the temperature register after which

the DS75 will go into a low-power standby state. The

O.S. output will be cleared if the thermostat is operating

in interrupt mode and O.S will remain unchanged in com-

parator mode. The 2-wire interface remains operational in

shutdown mode, and writing a 0 to the SD bit returns the

DS75 to normal operation.

Operation–Thermostat

The DS75 thermostat has two operating modes, com-

parator mode and interrupt mode, which activate and

deactivate the open-drain thermostat output (O.S.) based

The DS75 powers up with the thermostat in comparator

mode with active-low O.S. polarity and with the over-

power-up settings are compatible with the application, the

DS75 can be used as a standalone thermostat (i.e., no

2–wire communication required). If interrupt mode opera-

values are desired, they must be programmed after pow-

erup, so standalone operation is not possible.

In both operating modes, the user can program the ther-

mostat fault tolerance, which sets how many consecutive

temperature readings (1, 2, 4, or 6) must fall outside of

the thermostat limits before the thermostat output is trig-

gered. The fault tolerance is set by the F1 and F0 bits in

the configuration and at power-up the fault tolerance is 1.

identical to that of the temperature register (Figure 3),

i.e., a two-byte two’s complement representation of the

trip-point temperature in degrees centigrade with bits 3

through 0 hardwired to 0. After every temperature con-

version, the measured temperature is compared to the

is updated based on the result of the comparison and

used during the thermostat comparison is equal to the

conversion resolution set by the R1 and R0 bits in the

configuration register. For example, it the resolution is 9

the thermostat comparator.

The active state of the O.S. output can be changed via the

POL bit in the configuration register. The power-up default

is active low.

If the user does not wish to use the thermostat capabilities

of the DS75, the O.S. output should be left floating. Note

registers can be used for general storage of system data.

Table 3. 12-Bit Resolution Temperature/Data Relationship

TEMPERATURE (°C)

DIGITAL OUTPUT (BINARY)

DIGITAL OUTPUT (HEX)

+125

0111 1101 0000 0000

7D00h

+25.0625

0001 1001 0001 0000

1910h

+10.125

0000 1010 0010 0000

0A20h

+0.5

0000 0000 1000 0000

0080h

0

0000 0000 0000 0000

0000h

-0.5

1111 1111 1000 0000

FF80h

-10.125

1111 0101 1110 0000

F5E0h

-25.0625

1110 0110 1111 0000

E6F0h

-55

1100 1001 0000 0000

C900h

bit 15

bit 14

bit 13

bit 12

bit 11

bit 10

bit 9

bit 8

MS Byte

S

bit 7

bit 6

bit 5

bit 4

bit 3

bit 2

bit 1

bit 0

LS Byte

0

0

0

0

DS75

Digital Thermometer and Thermostat

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