DS1631 Datasheet, PDF (8/15 Pages) National Semiconductor (TI) – CMOS Dual Peripheral Drivers

DS1631/DS1631A/DS1731
provides user access to the temperature register. Bits 3 through 0 of the temperature register are
hardwired to 0. When the device is configured for 12-bit resolution, the 12 MSbs (bits 15 through 4) of
the temperature register contain temperature data. For 11-bit resolution, the 11 MSbs (bits 15 through 5)
of the temperature register contain data, and bit 4 is 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 4 gives examples of 12-bit resolution output data and the corresponding temperatures.
Figure 4. TEMPERATURE, T_H, AND T_L REGISTER FORMAT
bit 15
bit 14
bit 13
bit 12
bit 11
bit 10
bit 9
bit 8
MS Byte
S
2⁶
2⁵
2⁴
2³
2²
2¹
2⁰
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
Table 4. 12-BIT RESOLUTION TEMPERATURE/DATA RELATIONSHIP
TEMPERATURE
(°C)
+125
+25.0625
+10.125
+0.5
0
-0.5
-10.125
-25.0625
-55
DIGITAL OUTPUT
(BINARY)
0111 1101 0000 0000
0001 1001 0001 0000
0000 1010 0010 0000
0000 0000 1000 0000
0000 0000 0000 0000
1111 1111 1000 0000
1111 0101 1110 0000
1110 0110 1111 0000
1100 1001 0000 0000
DIGITAL OUTPUT
(HEX)
7D00h
1910h
0A20h
0080h
0000h
FF80h
F5E0h
E6F0h
C900h
OPERATION—THERMOSTAT FUNCTION
The thermostat output (T_OUT) is updated after every temperature conversion, based on a comparison
between the measured digital temperature and user-defined upper and lower thermostat trip points. T_OUT
remains at the updated value until the next conversion completes. When the measured temperature meets
or exceeds the value stored in the upper trip-point register (T_H), T_OUT becomes active and remains active
until the measured temperature falls below the value stored in the lower trip-point register (T_L) (see
Figure 5). This allows the user to program any amount of hysteresis into the output response. The active
state of T_OUT is user-programmable through the polarity bit (POL) in the configuration register.
The user-defined values in the T_H and T_L registers (see Figure 4) must be in two’s complement format
with the MSb (bit 15) containing the sign bit (S). The T_H and T_L resolution is determined by the R0 and
R1 bits in the configuration register (see Table 6), so the T_H and T_L resolution matches the output
temperature resolution. For example, for 10-bit resolution bits 5 through 0 of the T_H and T_L registers read
out as 0 (even if 1s are written to these bits), and the converted temperature is compared to the 10 MSbs
of T_H and T_L.
The T_H and T_L registers are stored in EEPROM; therefore, they are NV and can be programmed prior to
device installation. Writing to and reading from the T_H and T_L registers is achieved using the Access TH
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