DS18B20-PAR 1-Wire Parasite-Power Digital Thermometer

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DS18B20-PARMASTER MODE DATA (LSB FIRST) COMMENTSRX 9 data bytes Master reads entire scratchpad including CRC. The masterthen recalculates the CRC of the first eight data bytes from thescratchpad and compares the calculated CRC with the readCRC (byte 9). If they match, the master continues; if not, theread operation is repeated.DS18B20-PAR OPERATION EXAMPLE 2In this example there is only one DS18B20-PAR on the bus. The master writes to the T H , T L , andconfiguration registers in the DS18B20-PAR scratchpad and then reads the scratchpad and recalculatesthe CRC to verify the data. The master then copies the scratchpad contents to EEPROM.MASTER MODE DATA (LSB FIRST) COMMENTSTX Reset Master issues reset pulse.RX Presence DS18B20-PAR responds with presence pulse.TX CCh Master issues Skip ROM command.TX 4Eh Master issues Write Scratchpad command.TX 3 data bytes Master sends three data bytes to scratchpad (T H , T L , and config).TX Reset Master issues reset pulse.RX Presence DS18B20-PAR responds with presence pulse.TX CCh Master issues Skip ROM command.TX BEh Master issues Read Scratchpad command.RX 9 data bytes Master reads entire scratchpad including CRC. The master thenrecalculates the CRC of the first eight data bytes from thescratchpad and compares the calculated CRC with the read CRC(byte 9). If they match, the master continues; if not, the readoperation is repeated.TX Reset Master issues reset pulse.RX Presence DS18B20-PAR responds with presence pulse.TX CCh Master issues Skip ROM command.TX 48h Master issues Copy Scratchpad command.TXDQ line held high bystrong pullupMaster applies strong pullup to DQ for at least 10 ms while copyoperation is in progress.16 of 19
ABSOLUTE MAXIMUM RATINGS*DS18B20-PARVoltage on any pin relative to ground –0.5V to +6.0VOperating temperature–55C to +100CStorage temperature–55C to +125CSoldering temperatureSee J-STD-020A Specification*These are stress ratings only and functional operation of the device at these or any other conditionsabove those indicated in the operation sections of this specification is not implied. Exposure to absolutemaximum rating conditions for extended periods of time may affect reliability.DC ELECTRICAL CHARACTERISTICS(-55°C to +100°C; V PU =3.0V to 5.5V)PARAMETER SYMBOL CONDITION MIN TYP MAX UNITS NOTESPullup SupplyV PU 3.0 5.5 V 1,2VoltageThermometer Error t ERR -10°C to +85°C ±½ °C 3-55°C to +100°C ±2Input Logic Low V IL -0.3 +0.8 V 1,4,5Input Logic High V IH 3.0 5.5 V 1,6Sink Current I L V I/O =0.4V 4.0 mA 1Active Current I DQA 1 1.5 mA 7DQ Input Current I DQ 5 µA 8Drift ±0.2 °C 9NOTES:1. All voltages are referenced to ground.2. The Pullup Supply Voltage specification assumes that the pullup device (resistor or transistor) isideal, and therefore the high level of the pullup is equal to V PU . In order to meet the V IH spec of theDS18B20-PAR, the actual supply rail for the strong pullup transistor must include margin for thevoltage drop across the transistor when it is turned on; thus: V PU_ACTUAL = V PU_IDEAL + V TRANSISTOR .3. See typical performance curve in Figure 16.4. Logic low voltages are specified at a sink current of 4 mA.5. To always guarantee a presence pulse under low voltage parasite power conditions, V ILMAX may haveto be reduced to as low as 0.5V.6. Logic high voltages are specified at a source current of 1 mA.7. Active current refers to supply current during active temperature conversions or EEPROM writes.8. DQ line is high (“hi-Z” state).9. Drift data is based on a 1000 hour stress test at 125°C.AC ELECTRICAL CHARACTERISTICS: NV MEMORY(-55°C to +100°C; V PU =3.0V to 5.5V)PARAMETER SYMBOL CONDITION MIN TYP MAX UNITSNV Write Cycle Time t wr 2 10 msEEPROM Writes N EEWR -55°C to +55°C 50k writesEEPROM Data Retention t EEDR -55°C to +55°C 10 years17 of 19
Page 1: FEATURES Unique 1-Wire ® interface
Page 4 and 5: DS18B20-PARresolution, bits 1 and 0
Page 6 and 7: DS18B20-PAR MEMORY MAP Figure 6DS18
Page 8 and 9: DS18B20-PARHARDWARE CONFIGURATION F
Page 10 and 11: DS18B20-PARtransmitted least signif
Page 12 and 13: DS18B20-PAR FUNCTION COMMANDS FLOW
Page 14 and 15: DS18B20-PARThe DS18B20-PAR samples
Page 18 and 19: AC ELECTRICAL CHARACTERISTICSDS18B2

DS18B20-PAR 1-Wire Parasite-Power Digital Thermometer

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