DS1822+ Maxim Integrated Products, DS1822+ Datasheet - Page 4

• Manufacturer Part Number: DS1822+
• Description: Board Mount Temperature Sensors IC THERMOMETER ECONO DIG
• Manufacturer: Maxim Integrated Products

Specifications of DS1822+

• Temperature Threshold: Programmable
• Full Temp Accuracy: +/- 2 C
• Package / Case: TO-92
• Digital Output - Bus Interface: 1-Wire
• Digital Output - Number Of Bits: 9 bit to 12 bit
• Supply Voltage (max): 5.5 V
• Supply Voltage (min): 3 V
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 55 C
• Output Type: Digital
• Supply Current: 1.5 mA
• Ic Output Type: Digital
• Sensing Accuracy Range: ± 2°C
• Supply Voltage Range: 3V To 5.5V
• Resolution (bits): 12bit
• Sensor Case Style: TO-92
• No. Of Pins: 3
• Accuracy %: 2°C
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

OPERATION—MEASURING TEMPERATURE
The core functionality of the DS1822 is its direct-to-digital temperature sensor. The resolution of the
temperature sensor is user-configurable to 9, 10, 11, or 12 bits, corresponding to increments of 0.5°C,
0.25°C, 0.125°C, and 0.0625°C, respectively. The default resolution at power-up is 12 bit. The DS1822
powers-up in a low-power idle state; to initiate a temperature measurement and A-to-D conversion, the
master must issue a Convert T [44h] command. Following the conversion, the resulting thermal data is
stored in the 2-byte temperature register in the scratchpad memory and the DS1822 returns to its idle
state. If the DS1822 is powered by an external supply, the master can issue “read-time slots” (see the 1-
WIRE BUS SYSTEM section) after the Convert T command and the DS1822 will respond by
transmitting 0 while the temperature conversion is in progress and 1 when the conversion is done. If the
DS1822 is powered with parasite power, this notification technique cannot be used since the bus must be
pulled high by a strong pullup during the entire temperature conversion. The bus requirements for parasite
power are explained in detail in the POWERING THE DS1822 section of this data sheet.
The DS1822 output temperature data is calibrated in degrees centigrade; for Fahrenheit applications, a
lookup table or conversion routine must be used. The temperature data is stored as a 16-bit sign-extended
two’s complement number in the temperature register (see Figure 2). The sign bits (S) indicate if the
temperature is positive or negative: for positive numbers S = 0 and for negative numbers S = 1. If the
DS1822 is configured for 12-bit resolution, all bits in the temperature register will contain valid data. For
11-bit resolution, bit 0 is undefined. For 10-bit resolution, bits 1 and 0 are undefined, and for 9-bit
resolution bits 2, 1 and 0 are undefined. Table 2 gives examples of digital output data and the
corresponding temperature reading for 12-bit resolution conversions.
TEMPERATURE REGISTER FORMAT Figure 2
TEMPERATURE/DATA RELATIONSHIP Table 2
MS Byte
LS Byte
bit 15
bit 7
2
S
*The power on reset value of the temperature register is +85°C
3
TEMPERATURE
+25.0625°C
-25.0625°C
+10.125°C
-10.125°C
+125°C
+85°C*
+0.5°C
-0.5°C
-55°C
0°C
bit 14
bit 6
2
S
2
bit 13
bit 5
DIGITAL OUTPUT
0000 0111 1101 0000
0000 0101 0101 0000
0000 0001 1001 0001
0000 0000 1010 0010
0000 0000 0000 1000
0000 0000 0000 0000
1111 1111 1111 1000
1111 1111 0101 1110
1111 1110 0110 1111
1111 1100 1001 0000
2
S
1
(Binary)
4 of 21
bit 12
bit 4
2
S
0
bit 11
bit 3
DIGITAL OUTPUT
2
S
-1
07D0h
00A2h
FF5Eh
FE6Fh
FC90h
FFF8h
0550h
0191h
0008h
0000h
(Hex)
bit 10
bit 2
2
2
-2
6
bit 1
bit 9
2
2
-3
5
DS1822
bit 0
bit 8
2
2
-4
4