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1 of 19 101107

FEATURES

 Unique 1-Wire

interface requires only one

port pin for communication

 Derives power from data line (“parasite

power”)—does not need a local power supply

 Multidrop capability simplifies distributed

temperature sensing applications

 Requires no external components

 ±2.0°C accuracy from -10°C to +85°C

 Measures temperatures from -55°C to +100°C

(-67°F to +212°F)

 Thermometer resolution is user-selectable

from 9 to 12 bits

 Converts temperature to 12-bit digital word in

750ms (max.)

 User-definable temperature alarm settings

 Alarm search command identifies and

addresses devices whose temperature is

outside of programmed limits (temperature

alarm condition)

 Software compatible with the DS18B20-PAR

 Ideal for use in remote sensing applications

(e.g., temperature probes) that do not have a

local power source

PIN ASSIGNMENT

PIN DESCRIPTION

GND - Ground

DQ - Data In/Out

NC - No Connect

DESCRIPTION

The DS1822-PAR digital thermometer provides 9- to 12-bit centigrade temperature measurements and

has an alarm function with nonvolatile (NV) user-programmable upper and lower trigger points. The

DS1822-PAR does not need an external power supply because it derives power directly from the data line

(“parasite power”). The DS1822-PAR communicates over a 1-Wire bus, which by definition requires

only one data line (and ground) for communication with a central microprocessor. It has an operating

temperature range of -55°C to +100°C and is accurate to ±2.0°C over a range of -10°C to +85°C.

Each DS1822-PAR has a unique 64-bit identification code, which allows multiple DS1822-PARs to

function on the same 1-Wire bus; thus, it is simple to use one microprocessor to control many

DS1822-PARs distributed over a large area. Applications that can benefit from this feature include

HVAC environmental controls, temperature monitoring systems inside buildings, equipment or

machinery, and process monitoring and control systems.

DS1822-PAR

Econo 1-Wire Parasite-Powe

Digital Thermomete

www.maxim

ic.

com

(

BOTTOM VIEW

)

2 3

TO-92

(

DS1822-PAR

)

DALLAS

1822P

GND

2 3

1-Wire is a registered trademark of Dallas Semiconductor.

Summary of content (19 pages)

PAGE 1
DS1822-PAR Econo 1-Wire Parasite-Power Digital Thermometer www.maxim-ic.com PIN ASSIGNMENT Unique 1-Wire® interface requires only one port pin for communication Derives power from data line (“parasite power”)—does not need a local power supply Multidrop capability simplifies distributed temperature sensing applications Requires no external components ±2.
PAGE 2
DS1822-PAR DETAILED PIN DESCRIPTIONS Table 1 PIN 1 2 SYMBOL GND DQ 3 NC DESCRIPTION Ground. Data Input/Output pin. Open-drain 1-Wire interface pin. Also provides power to the device when used in parasite power mode (see “Parasite Power” section.) No Connect. Doesn’t connect to internal circuit. OVERVIEW The DS1822-PAR uses Dallas’ exclusive 1-Wire bus protocol that implements bus communication using one control signal.
PAGE 3
DS1822-PAR PARASITE POWER The DS1822-PAR’s parasite power circuit allows the DS1822-PAR to operate without a local external power supply. This ability is especially useful for applications that require remote temperature sensing or that are very space constrained. Figure 1 shows the DS1822-PAR’s parasite-power control circuitry, which “steals” power from the 1-Wire bus via the DQ pin when the bus is high.
PAGE 4
DS1822-PAR TEMPERATURE REGISTER FORMAT Figure 3 bit 7 LS Byte MS Byte bit 6 3 2 2 bit 15 bit 14 S bit 5 2 bit 4 1 S bit 3 0 2 2 bit 13 bit 12 S bit 2 -1 2 2 2-4 2 bit 10 S bit 0 -3 2 bit 11 S bit 1 -2 bit 9 6 bit 8 5 24 2 TEMPERATURE/DATA RELATIONSHIP Table 2 TEMPERATURE DIGITAL OUTPUT (Binary) 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 10
PAGE 5
DS1822-PAR 64-BIT LASERED ROM CODE Each DS1822-PAR contains a unique 64-bit code (see Figure 5) stored in ROM. The least significant eight bits of the ROM code contain the DS1822-PAR’s 1-Wire family code: 22h. The next 48 bits contain a unique serial number. The most significant eight 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.
PAGE 6
DS1822-PAR Data is written to bytes 2, 3, and 4 of the scratchpad using the Write Scratchpad [4Eh] command, and the data must be transmitted to the DS1822-PAR starting with the least significant bit of byte 2. To verify data integrity, the scratchpad can be read (using the Read Scratchpad [BEh] command) after the data is written. When reading the scratchpad, data is transferred over the 1-Wire bus starting with the least significant bit of byte 0.
PAGE 7
DS1822-PAR proceeding if the DS1822-PAR CRC (ROM or scratchpad) does not match the value generated by the bus master. The equivalent polynomial function of the CRC (ROM or scratchpad) is: CRC = X8 + X5 + X4 + 1 The bus master can recalculate the CRC and compare it to the CRC values from the DS1822-PAR using the polynomial generator shown in Figure 8. This circuit consists of a shift register and XOR gates, and the shift register bits are initialized to 0.
PAGE 8
DS1822-PAR HARDWARE CONFIGURATION Figure 9 VPU Microprocessor VPU Strong Pullup DS1822-PAR 1-WIRE PORT 4.7k RX 1-wire bus DQ Pin RX 5μA Typ. TX 100Ω MOSFET TX RX = RECEIVE TX = TRANSMIT TRANSACTION SEQUENCE The transaction sequence for accessing the DS1822-PAR is as follows: Step 1. Initialization Step 2. ROM Command (followed by any required data exchange) Step 3.
PAGE 9
DS1822-PAR learns the ROM codes through a process of elimination that requires the master to perform a Search ROM cycle (i.e., Search ROM command followed by data exchange) as many times as necessary to identify all of the slave devices. If there is only one slave on the bus, the simpler Read ROM command (see below) can be used in place of the Search ROM process. For a detailed explanation of the Search ROM procedure, refer to the iButton® Book of Standards at www.ibutton.com/ibuttons/standard.pdf.
PAGE 10
DS1822-PAR WRITE SCRATCHPAD [4Eh] This command allows the master to write three bytes of data to the DS1822-PAR’s scratchpad. The first data byte is written into the TH register (byte 2 of the scratchpad), the second byte is written into the TL register (byte 3), and the third byte is written into the configuration register (byte 4). Data must be transmitted least significant bit first. All three bytes MUST be written before the master issues a reset, or the data may be corrupted.
PAGE 11
DS1822-PAR ROM COMMANDS FLOW CHART Figure 9 Initialization Sequence MASTER TX RESET PULSE DS1822-PAR TX PRESENCE PULSE MASTER TX ROM COMMAND 33h READ ROM COMMAND Y N 55h MATCH ROM COMMAND F0h SEARCH ROM COMMAND N Y N Y ECh ALARM SEARCH COMMAND CCh SKIP ROM COMMAND N Y Y MASTER TX BIT 0 DS1822-PAR TX BIT 0 DS1822-PAR TX BIT 0 DS1822-PAR TX BIT 0 DS1822-PAR TX BIT 0 MASTER TX BIT 0 MASTER TX BIT 0 DS1822-PAR TX FAMILY CODE 1 BYTE N BIT 0 MATCH? DS1822-PAR TX SERIAL NUMBER 6 BYTES N
PAGE 12
DS1822-PAR DS1822-PAR FUNCTION COMMANDS FLOW CHART Figure 10 44h CONVERT TEMPERATURE ? MASTER TX FUNCTION COMMAND 48h COPY SCRATCHPAD ? N Y Y MASTER ENABLES STRONG PULL-UP ON DQ MASTER ENABLES STRONG PULLUP ON DQ DATA COPIED FROM SCRATCHPAD TO EEPROM DS1822-PAR CONVERTS TEMPERATURE MASTER DISABLES STRONG PULLUP MASTER DISABLES STRONG PULLUP N B8h RECALL E2 ? BEh READ SCRATCHPAD ? N Y N Y 4Eh WRITE SCRATCHPAD ? Y MASTER TX TH BYTE TO SCRATCHPAD MASTER RX DATA BYTE FROM SCRATCHPAD MASTE
PAGE 13
DS1822-PAR 1-WIRE SIGNALING The DS1822-PAR uses a strict 1-Wire communication protocol to insure data integrity. Several signal types are defined by this protocol: reset pulse, presence pulse, write 0, write 1, read 0, and read 1. All of these signals, with the exception of the presence pulse, are initiated by the bus master.
PAGE 14
DS1822-PAR The DS1822-PAR samples the 1-Wire bus during a window that lasts from 15μs to 60μs after the master initiates the write-time slot. If the bus is high during the sampling window, a 1 is written to the DS1822PAR. If the line is low, a 0 is written to the DS1822-PAR.
PAGE 15
DS1822-PAR resister. Output data from the DS1822-PAR is valid for 15μs after the falling edge that initiated the readtime slots. Therefore, the master must release the bus and then sample the bus state within 15μs from the start of the slot. Figure 13 illustrates that the sum of TINIT, TRC, and TSAMPLE must be less than 15μs for a read-time slots.
PAGE 16
DS1822-PAR DS1822-PAR OPERATION EXAMPLE 1 In this example there are multiple DS1822-PARs on the bus. The bus master initiates a temperature conversion in a specific DS1822-PAR and then reads its scratchpad and recalculates the CRC to verify the data. MASTER MODE TX RX TX TX TX TX TX RX TX TX TX RX DATA (LSB FIRST) Reset Presence 55h 64-bit ROM code 44h DQ line held high by strong pullup Reset Presence 55h 64-bit ROM code BEh 9 data bytes COMMENTS Master issues reset pulse.
PAGE 17
DS1822-PAR ABSOLUTE MAXIMUM RATINGS* Voltage on Any Pin Relative to Ground Operating Temperature Range Storage Temperature Range Solder Dip Temperature Reflow Oven Temperature -0.5V to +6.0V -55°C to +100°C -55°C to +125°C See IPC/JEDEC J-STD-020A Specification +220°C *These are stress ratings only and functional operation of the device at these or any other conditions above those indicated in the operation sections of this specification is not implied.
PAGE 18
DS1822-PAR AC ELECTRICAL CHARACTERISTICS: PARAMETER SYMBOL Temperature Conversion tCONV Time Time to Strong Pullup On Time Slot Recovery Time Write 0 Low Time Write 1 Low Time Read Data Valid Reset Time High Reset Time Low Presence Detect High Presence Detect Low Capacitance tSPON (-55°C to +100°C; VPU = 3.0V to 5.
PAGE 19
DS1822-PAR TIMING DIAGRAMS Figure 16 19 of 19