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DS1821S+T Datasheet

Download or read online Maxim Integrated DS1821S+T Programmable Digital Thermostat and Thermometer pdf datasheet.



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Programmable Digital Thermostat and Thermometer
FEATURES
 Requires no external components
®
 Unique 1-Wire
interface requires only one
port pin for communication
 Operates over a -55°C to +125°C (-67°F to
+257°F) temperature range
 Functions as a standalone thermostat with
user-definable trip-points
 Provides 8-bit (1°C resolution) centigrade
temperature measurements
 Accuracy is ±1°C over 0°C to +85°C range
 Converts temperature to a digital word in
1 second (max)
 Available in 3-pin TO92 and 8-pin SO
packages
 Applications include thermostatic controls,
industrial systems, consumer products,
thermometers, or any thermally sensitive
system
1-Wire is a registered trademark of Maxim Integrated
Products, Inc.
DESCRIPTION
The DS1821 can function as a standalone thermostat with user-programmable trip-points or as 8-bit
temperature sensor with a 1-Wire digital interface. The thermostat trip-points are stored in nonvolatile
memory, so DS1821 units can be programmed prior to system insertion for true standalone operation.
The DS1821 has an operating temperature range of –55°C to +125°C and is accurate to ±1°C over a range
of 0°C to +85°C. Communication with the DS1821 is accomplished through the open-drain DQ pin; this
pin also serves as the thermostat output.
PIN ASSIGNMENT
DS1821
GND
1 2 3
1
2 3
(BOTTOM VIEW)
TO92
(DS1821C)
PIN DESCRIPTION
GND
- Ground
DQ
- Data In/Out and Thermostat Output
V
- Power Supply Voltage
DD
NC
- No Connect
1 of 19
DS1821
DQ
V
8
1
DD
7
2
NC
NC
6
NC
3
NC
NC
4
5
8-pin 208-mil SO
(DS1821S)

Summary of Contents

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... Applications include thermostatic controls, industrial systems, consumer products, thermometers, or any thermally sensitive system 1-Wire is a registered trademark of Maxim Integrated Products, Inc. DESCRIPTION The DS1821 can function as a standalone thermostat with user-programmable trip-points or as 8-bit temperature sensor with a 1-Wire digital interface. The thermostat trip-points are stored in nonvolatile memory, so DS1821 units can be programmed prior to system insertion for true standalone operation. The DS1821 has an operating temperature range of – ...

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... ORDERING INFORMATION PART DS1821C DS1821S DS1821ST&R Denotes a lead(Pb)-free/RoHS-compliant package. T&R Tape and reel. DETAILED PIN DESCRIPTIONS Table 1 TO92 8-PIN SYMBOL SO GND All pins not specified in this table are No Connect pins. OVERVIEW Figure 1 shows a block diagram of the DS1821 and pin descriptions are given in Table 1. The DS1821 can operate as a standalone thermostat with user-programmable trip-points or as 8-bit temperature sensor with a 1-Wire digital interface ...

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DS1821 BLOCK DIAGRAM Figure 1 DS1821 V DD 4.7K DQ POWER V SUPPLY DD SENSE GND TEMPERATURE SENSOR FUNCTIONALITY The core functionality of the DS1821 is its proprietary direct-to-digital temperature sensor, which provides 8-bit (1°C increment) centigrade temperature readings over ...

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TEMPERATURE MEASURING CIRCUITRY Figure 2 PRESET LOW TEMPERATURE COEFFICIENT OSCILLATOR HIGH TEMPERATURE COEFFICIENT OSCILLATOR OPERATING MODES The DS1821 has two operating modes: 1-Wire mode and thermostat mode. The power-up operating mode is determined by the user-programmable T/R ¯ bit in ...

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Nonvolatile write status can be monitored by reading the NVB bit in the status/configuration register: NVB 1 a write to EEPROM memory is in progress, NVB 0 nonvolatile memory is idle. THERMOSTAT MODE In thermostat mode ...

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TEMPERATURE/DATA RELATIONSHIP Table 2 TEMPERATURE 125°C 85°C 25°C 0°C -1°C -25°C -55°C HIGH-RESOLUTION TEMPERATURE READINGS The user can calculate temperature values with higher than 8-bit resolution using the data remaining in the counter and slope accumulator when the temperature conversion ...

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OPERATION THERMOSTAT When the DS1821 is in thermostat mode (T/R ¯ the status/configuration register), temperature conversions are performed continuously beginning at power-up (regardless of the value of the 1SHOT bit), and the DQ pin serves as ...

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CONFIGURATION REGISTER BIT DESCRIPTIONS Table 3 Bit Name (User Access) DONE Temperature Conversion Done (Read Only) NVB Non-volatile Memory Busy (Read Only) THF Temperature High Flag (Read/Write) TLF Temperature Low Flag (Read/Write) T/R ¯ ...

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BUS SYSTEM The 1-Wire bus system uses a single bus master (i.e., a microprocessor) to control slave devices. The DS1821 functions as a slave device when it is used in 1-Wire mode; however, since the DS1821 is not addressable ...

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INITIALIZATION All transactions on the 1-Wire bus begin with an initialization sequence. The initialization sequence consists of a reset pulse transmitted by the bus master followed by a presence pulse transmitted by the DS1821. The presence pulse lets the bus ...

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DS1821 FUNCTION COMMAND SET Table 4 Command TEMPERATURE CONVERSION COMMANDS Read Reads last converted temperature Temperature value from temperature register. Start Convert T Initiates temperature conversions. Stop Convert T Halts temperature conversions. THERMOSTAT and STATUS/CONFIGURATION COMMANDS Write TH Writes data ...

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INITIALIZATION TIMING Figure 7 MASTER T 480 µs minimum V DD 1-WIRE BUS GND READ/WRITE TIME SLOTS The bus master writes data to the DS1821 during write time slots and reads data from the DS1821 during read time slots. One ...

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Figure 9 illustrates that the sum of T Figure 10 shows that system timing margin is maximized by keeping T and by locating the master sample time during read time slots towards the end of the 15 µs period. READ/WRITE ...

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DS1821 OPERATION EXAMPLE In this example, the master device programs the DS1821 with T that the data has been saved correctly. The master then programs the status/configuration register so that the device will power-up in thermostat mode (T/R ¯ ...

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ABSOLUTE MAXIMUM RATINGS Voltage on Any Pin Relative to ground Operating Temperature Range Storage Temperature Range Soldering Temperature (reflow, SO) (wave, TO92) Lead Temperature (soldering, 10s) These are stress ratings only and functional operation of the device at these or ...

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AC ELECTRICAL CHARACTERISTICS: PARAMETER Temperature Conversion Time EEPROM Write Time 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 V Low to ...

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TYPICAL PERFORMANCE CURVE Figure 11 MODE TOGGLE TIMING WHEN T/R ¯ Figure ...

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TIMING DIAGRAMS Figure 13 PACKAGE INFORMATION For the latest package outline information and land patterns (footprints www.maxim-ic.com/packages. Note that a , #, or - in the package code indicates RoHS status only. Package drawings may show a different ...

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... Maxim Integrated Products DESCRIPTION Replaced the PR35 package with the TO92 package; updated the Ordering Information table; updated the soldering information in the Absolute Maximum Ratings section Maxim is a registered trademark of Maxim Integrated Products, Inc. DS1821 PAGES CHANGED ...

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