Datasheet

Detailed Description
Measuring Temperature
The DS75LV measures temperature using a bandgap
temperature sensing architecture. An on-board delta-sig-
ma analog-to-digital converter (ADC) converts the mea-
sured temperature to a digital value that is calibrated in
degrees centigrade; for Fahrenheit applications a lookup
table or conversion routine must be used. The DS75LV is
factory-calibrated and requires no external components to
measure temperature.
At power-up the DS75LV immediately begins convert-
ing temperature to a digital value. The resolution of the
digital output data is user-configurable to 9, 10, 11, or 12
bits, corresponding to temperature increments of 0.5°C,
0.25°C, 0.125°C, and 0.0625°C, respectively, with 9-bit
default resolution at power-up. The resolution is controlled
via the R0 and R1 bits in the configuration register as
explained in the Configuration Register section of this
data sheet. Note that the conversion time doubles for
each additional bit of resolution.
After each temperature measurement and analog-to-
digital conversion, the DS75LV stores the temperature as
a 16-bit two’s complement number in the 2-byte tempera-
ture register (see Figure 3). The sign bit (S) indicates if the
temperature is positive or negative: for positive numbers
S = 0 and for negative numbers S = 1. The most recently
converted digital measurement can be read from the tem-
perature register at any time. Since temperature conver-
sions are performed in the background, reading the tem-
perature register does not affect the operation in progress.
Bits 3 through 0 of the temperature register are hardwired
to 0. When the DS75LV is configured for 12-bit resolution,
the 12 MSbs (bits 15 through 4) of the temperature reg-
ister contain temperature data. For 11 bit resolution, the
11 MSbs (bits 15 through 5) of the temperature register
contain data, and bit 4 reads out as 0. Likewise, for 10-bit
resolution, the 10 MSbs (bits 15 through 6) contain data,
and for 9-bit the 9 MSbs (bits 15 through 7) contain data,
and all unused LSbs contain 0s. Table 1 gives examples
of 12-bit resolution digital output data and the correspond-
ing temperatures.
Table 1. 12-Bit Resolution Temperature/
Data Relationship
Figure 3. Temperature, T
OS
, and T
HYST
Register Format
TEMPERATURE
(°C)
DIGITAL OUTPUT
(BINARY)
DIGITAL
OUTPUT
(HEX)
[phone] 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 2
6
2
5
2
4
2
3
2
2
2
1
2
0
bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0
LS Byte 2
-1
2
-2
2
-3
2
-4
0 0 0 0
DS75LV Digital Thermometer and Thermostat
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