Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsSensorsTemperature sensor SMD

1 of 14 020106

FEATURES

 Requires no external components

 Supply voltage range covers from 2.7V to

5.5V

 Measures temperatures from –55°C to

+125°C in 0.5°C increments. Fahrenheit

equivalent is –67°F to +257°F in 0.9°F

increments

 Temperature is read as a 9–bit value

 Converts temperature to digital word in 1

second (max)

 Thermostatic settings are user–definable and

non–volatile

 Data is read from/written via a 3–wire serial

interface (CLK, DQ, RST )

 Applications include thermostatic controls,

industrial systems, consumer products,

thermometers, or any thermally sensitive

system

 8–pin SOIC (208 mil) package

PIN ASSIGNMENT

PIN DESCRIPTION

DQ – 3–Wire Input/Output

CLK/CONV – 3–Wire Clock Input and

Stand–alone

Convert Input

RST – 3–Wire Reset Input

GND – Ground

HIGH

– High Temperature Trigger

LOW

– Low Temperature Trigger

COM

– High/Low Combination Trigger

– Power Supply Voltage (3V-5V)

DESCRIPTION

The DS1720 Digital Thermometer and Thermostat provides 9–bit temperature readings which indicate

the temperature of the device. With three thermal alarm out-puts, the DS1720 can also act as a thermostat.

HIGH

is driven high if the DS1720’s temperature is greater than or equal to a user–defined temperature

. T

LOW

is driven high if the DS1720’s temperature is less than or equal to a user–defined temperature

. T

COM

is driven high when the temperature exceeds T

and stays high until the temperature falls below

that of TL.

User–defined temperature settings are stored in non–volatile memory, so parts can be programmed prior

to insertion in a system, as well as used in stand–alone applications without a CPU. Temperature settings

and temperature readings are all communicated to/from the DS1720 over a simple 3–wire interface.

DS1720

ECON-Digital Thermometer and

Thermostat

www.maxim-ic.com

DS1720S 8-Pin SOIC (208-mil)

CLK/CONV

RST

GND

HIGH

LOW

COM

Summary of content (14 pages)

PAGE 1
DS1720 ECON-Digital Thermometer and Thermostat www.maxim-ic.com FEATURES Requires no external components Supply voltage range covers from 2.7V to 5.5V Measures temperatures from –55°C to +125°C in 0.5°C increments. Fahrenheit equivalent is –67°F to +257°F in 0.
PAGE 2
DS1720 ORDER INFORMATION ORDERING NUMBER DS1720S+ DS1720S+T&R PACKAGE MARKING DS1720 (see note) DS1720 (see note) DESCRIPTION DS1720 in Lead-Free 208mil 8-pin SO DS1720 in Lead-Free 208mil 8-pin SO, 2500 Piece Tape-and-Reel DS1720S DS1720 DS1720 in 208mil 8-pin SO DS1720S/T&R DS1720 DS1720 in 208mil 8-pin SO, 2500 Piece Tape-and-Reel Note: A “+” symbol will also be marked on the package near the Pin 1 indicator. OPERATION–MEASURING TEMPERATURE A block diagram of the DS1720 is shown in Figure 1.
PAGE 3
DS1720 DS1720 FUNCTIONAL BLOCK DIAGRAM Figure 1 3 of 14
PAGE 4
DS1720 TEMPERATURE MEASURING CIRCUITRY Figure 2 This calculation is done inside the DS1720 to provide 0.5°C resolution. The temperature reading is provided in a 9–bit, two’s complement reading by issuing a READ TEMPERATURE command. Table 1 describes the exact relationship of output data to measured temperature. The data is transmitted serially through the 3–wire serial interface, LSB first. The DS1720 can measure temperature over the range of –55°C to +125°C in 0.5°C increments.
PAGE 5
DS1720 Higher resolutions may be obtained by reading the temperature, and truncating the 0.5°C bit (the LSB) from the read value. This value is TEMP_READ. The value left in the counter may then be read by issuing a READ COUNTER command. This value is the count remaining (COUNT_REMAIN) after the gate period has ceased. The value of the slope accumulator may be read (using the READ SLOPE command), yielding the number of counts per degree C (COUNT_PER_C) at that temperature.
PAGE 6
DS1720 THERMOSTAT OUTPUT OPERATION Figure 3 OPERATION AND CONTROL The DS1720 must have temperature settings resident in the TH and TL registers for thermostatic operation. A configuration/status register is also used to determine the method of operation that the DS1720 will use in a particular application, as well as indicating the status of the temperature conversion operation.
PAGE 7
DS1720 For typical thermostat operation, the DS1720 will operate in continuous mode. However, for applications where only one reading is needed at certain times, and to conserve power, the one–shot mode may be used. Note that the thermostat outputs (THIGH, TLOW, TCOM) will remain in the state they were in after the last valid temperature conversion cycle when operating in one–shot mode. OPERATION IN STAND–ALONE MODE In applications where the DS1720 is used as a simple thermostat, no CPU is required.
PAGE 8
DS1720 Read TH [A1h] This command reads the value of the TH (HIGH TEMPERATURE) register. After issuing this command, the next nine clock cycles clock out the 9–bit temperature limit which sets the threshold for operation of the THIGH output. Read TL [A2h] This command reads the value of the TL (LOW TEMPERATURE) register. After issuing this command, the next nine clock cycles clock out the 9–bit temperature limit which sets the threshold for operation of the TLOW output.
PAGE 9
DS1720 DS1720 COMMAND SET Table 3 3-WIRE BUS DATA AFTER ISSUING INSTRUCTION DESCRIPTION PROTOCOL PROTOCOL TEMPERATURE CONVERSION COMMANDS Read Temperature Temperature Reads last converted AAh temperature value from temperature register Read Counter Reads value of count remaining A0h from counter Read Slope Reads value of the slope A9h accumulator Start Convert T Initiates temperature conversion EEh Idle Stop Convert T Halts temperature conversion 22h Idle THERMOSTAT COMM
PAGE 10
DS1720 FUNCTION EXAMPLE Example: CPU sets up DS1720 for continuous conversion and thermostatic function.
PAGE 11
DS1720 READ DATA TRANSFER Figure 4 WRITE DATA TRANSFER Figure 5 11 of 14
PAGE 12
DS1720 ABSOLUTE MAXIMUM RATINGS* Voltage on Any Pin Relative to Ground Operating Temperature Storage Temperature Soldering Temperature –0.5V to +6.0V –55°C to +125°C –55°C to +125°C 260°C for 10 seconds *This is a stress rating 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. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability.
PAGE 13
DS1720 AC ELECTRICAL CHARACTERISTICS (-55°C to +125°C; VDD=2.7V to 5.5V) PARAMETER SYMBOL Temperature Conversion TTC Time Data to CLK Setup tDC CLK to Data Hold tCDH CLK to Data Delay tCDD CLK Low Time tCL CLK High Time tCH CLK Frequency tCLK CLK Rise and Fall tR, tF tCC RST to CLK Setup t CLK to RST Hold CCH t RST Inactive Time CWH CLK High to I/O High-Z tCDZ tRDZ RST Low to I/O High-Z Convert Pulse Width tCNV Input Capacitance CI I/O Capacitance CI/O TYP EEPROM MIN MAX 750 35 40 150 285 285 DC 1.
PAGE 14
DS1720 DS1720 TYPICAL THERMOMETER ERROR DS1720 14 of 14