DS1721U/T&R+W Maxim Integrated Products, DS1721U/T&R+W Datasheet - Page 6

• Manufacturer Part Number: DS1721U/T&R+W
• Description: Board Mount Temperature Sensors Digital Thermometer & Thermostat
• Manufacturer: Maxim Integrated Products

Specifications of DS1721U/T&R+W

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

R0, R1 = Thermometer Resolution Bits. Table 3 below defines the resolution of the digital thermometer,
based on the settings of these two bits. There is a direct tradeoff between resolution and conversion time,
as depicted in the DC Electrical Characteristics: Digital Thermometer table. The designer has read/write
access to R0 and R1, and the default state is R0="1" and R1="1" (12-bit conversions).
THERMOMETER RESOLUTION CONFIGURATION Table 3
X = Undefined. These bits are used internally by the DS1721.
DONE = Temperature Conversion Status Bit. "1" = conversion complete and "0" = conversion in
progress. The DONE bit is read-only, and the power-up state is "1". In the continuous conversion mode,
DONE = "0".
Thermostat Setpoints Programming
The thermostat registers (TH and TL) define the setpoints for operation of the TCOM output. The
respective register can be accessed over the 2-wire bus via the Access TH (A1h) or Access TL (A2h)
commands. Reading from or writing to the respective register is controlled by the state of the R/
the 2-wire control byte (See “2-Wire Serial Data Bus” section).
The format of the TH and TL registers is a 12-bit 2’s complement representation of the temperature in °C.
The user can program the number of bits (9, 10, 11, or 12) for each TH and TL that correspond to the
thermometer resolution configuration chosen. If the 9-bit mode is chosen, for example, the 3 least
significant bits of TH and TL will be ignored by the thermostat comparator. The format for both TH and
TL is shown in Figure 4. The power-up default of TH is 80°C and that for TL is 75°C.
TEMPERATURE/DATA RELATIONSHIPS Figure 4
MSb
2
S
-1
R1
-25.0625°C
+10.125°C
-10.125°C
0
0
1
1
TEMP
+0.5°C
-0.5°C
+80°C
+75°C
-55°C
+0°C
2
2
-2
6
2
2
-3
5
R0
0
1
0
1
2
2
(UNIT = °C)
-4
4
DIGITAL OUTPUT
0101 0000 0000 0000
0100 1011 0000 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
6 of 17
(Binary)
2
0
3
THERMOMETER
RESOLUTION
10-BIT
11-BIT
12-BIT
9-BIT
2
0
2
2
0
1
DIGITAL OUTPUT
CONVERSION
0A20h
4B00h
FF80h
F5E0h
E6F0h
C900h
5000h
0080h
0000h
(Hex)
LSb
2
0
93.75ms
187.5ms
0
TIME
375ms
750ms
MAX
W
MSB
LSB
bit in