DS75U Datasheet, PDF (6/14 Pages) Maxim Integrated Products – Digital Thermometer and Thermostat

DS75
Figure 2. TIMING DIAGRAM
Note: The DS75 does not delay the SDA line internally with respect to SCL for any length of time.
OPERATION–MEASURING TEMPERATURE
The DS75 measures temperature using a bandgap temperature sensing architecture. An on-board delta-
sigma analog-to-digital converter (ADC) converts the measured temperature to a digital value that is
calibrated in degrees centigrade; for Fahrenheit applications a lookup table or conversion routine must be
used. The DS75 is factory-calibrated and requires no external components to measure temperature.
At power-up the DS75 immediately begins measuring the temperature and converting the 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 DS75 stores the temperature as
a 16-bit two’s complement number in the 2-byte temperature 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 temperature register at any
time. Since temperature conversions are performed in the background, reading the temperature register
does not affect the operation in progress.
Bits 3 through 0 of the temperature register are hardwired to 0. When the DS75 is configured for 12-bit
resolution, the 12 MSbs (bits 15 through 4) of the temperature register will contain temperature data. For
11-bit resolution, the 11 MSbs (bits 15 through 5) of the temperature register will contain data, and bit 4
will read out as 0. Likewise, for 10-bit resolution, the 10 MSbs (bits 15 through 6) will contain data, and
for 9-bit the 9 MSbs (bits 15 through 7) will contain data, and all unused LSbs will contain 0s. Table 3
gives examples of 12-bit resolution digital output data and the corresponding temperatures.
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