Rainbow Electronics DS1631 - Manual (Page 3)

DS1631
3 of 14
OVERVIEW
The DS1631 measures temperature using a bandgap-based temperature sensor. A delta-sigma analog-to-
digital converter (ADC) converts the measured temperature to a 9-, 10-, 11-, or 12-bit (user-selectable)
digital value that is calibrated in degrees centigrade; for Fahrenheit applications a lookup table or
conversion routine must be used. The DS1631 also provides thermostat capability with user-
programmable NV trip-point registers. Communication with the DS1631 is achieved through a standard
2-wire serial interface.
Detailed DS1631 pin descriptions are provided in Table 1 and user-accessible registers are summarized in
Table 2.
Note: The DS1631 is software- and pin-compatible with DS1621. This compatibility covers all
functions/commands described in the DS1621 data sheet including access to the Count_Remain and
Count_Per_C registers for high-resolution temperature calculations based on the legacy dual-oscillator
architecture. Refer to Application Note 176 Using the DS1631 in DS1621 Applications for more
information.
OPERATION—MEASURING TEMPERATURE
The DS1631 can be programmed to take continuous temperature measurements (continuous conversion
mode) or to take single temperature measurements on command (one-shot mode). The measurement
mode is programmed through the 1SHOT bit in the configuration register: 1SHOT = 1—one-shot mode;
1SHOT = 0—continuous conversion mode. The 1SHOT bit is stored in NV EEPROM, so it can be
programmed prior to installation if desired. In continuous conversion mode, when a Start Convert T
command is issued, the DS1631 will perform consecutive temperature measurements until a Stop Convert
T command is issued. In one-shot mode, the Start Convert T command causes one temperature
measurement to be taken, then the DS1631 returns to a low-power idle state. One-shot mode is
recommended for use in power-sensitive applications.
The resolution of the DS1631 digital temperature 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. The
default resolution at power-up is 12 bits, and it can be changed through 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 DS1631 stores the temperature
as a 16-bit two’s complement number in the 2-byte temperature register (see Figure 2). The sign bit (S)
indicates if the temperature is positive or negative: for positive numbers S = 0 and for negative numbers S
= 1. The Read Temperature command provides user access to the temperature register.
Bits 3 through 0 of the temperature register are hardwired to 0. When the DS1631 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.