DS1822+ Maxim Integrated Products, DS1822+ Datasheet - Page 6

• 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

The use of parasite power is not recommended for temperatures above 100°C since the DS1822 may not
be able to sustain communications due to the higher leakage currents that can exist at these temperatures.
For applications in which such temperatures are likely, it is strongly recommended that the DS1822 be
powered by an external power supply.
In some situations the bus master may not know whether the DS1822s on the bus are parasite powered or
powered by external supplies. The master needs this information to determine if the strong bus pullup
should be used during temperature conversions. To get this information, the master can issue a Skip ROM
[CCh] command followed by a Read Power Supply [B4h] command followed by a “read-time slot”.
During the read time slot, parasite powered DS1822s will pull the bus low, and externally powered
DS1822s will let the bus remain high. If the bus is pulled low, the master knows that it must supply the
strong pullup on the 1-Wire bus during temperature conversions.
SUPPLYING THE PARASITE-POWERED DS1822 DURING TEMPERATURE
CONVERSIONS Figure 4
POWERING THE DS1822 WITH AN EXTERNAL SUPPLY Figure 5
64-BIT LASERED ROM CODE
Each DS1822 contains a unique 64–bit code (see Figure 6) stored in ROM. The least significant 8 bits of
the ROM code contain the DS1822’s 1-Wire family code: 22h. The next 48 bits contain a unique serial
number. The most significant 8 bits contain a cyclic redundancy check (CRC) byte that is calculated from
the first 56 bits of the ROM code. A detailed explanation of the CRC bits is provided in the CRC
GENERATION section. The 64-bit ROM code and associated ROM function control logic allow the
DS1822 to operate as a 1-Wire device using the protocol detailed in the 1-WIRE BUS SYSTEM section
of this data sheet.
64-BIT LASERED ROM CODE Figure 6
MSB
8-BIT CRC
processor
Micro-
processor
Micro-
LSB
V
PU
V
MSB
PU
4.7k
4.7k
48-BIT SERIAL NUMBER
1-Wire Bus
6 of 21
V
PU
1-Wire Bus
GND
DS1822
DQ
LSB
V
DD
GND
DS1822
MSB
8-BIT FAMILY CODE (22h)
DQ
V
DD
V
(External Supply)
DD
To Other
1-Wire Devices
To Other
1-Wire Devices
DS1822
LSB