DS1821S Maxim Integrated Products, DS1821S Datasheet

IC THERMOMETER/STAT PROG 8-SOIC

DS1821S

Manufacturer Part Number
DS1821S
Description
IC THERMOMETER/STAT PROG 8-SOIC
Manufacturer
Maxim Integrated Products
Datasheet

Specifications of DS1821S

Function
Thermometer, Thermostat
Topology
Comparator, Register Bank
Sensor Type
Internal
Sensing Temperature
-55°C ~ 125°C
Output Type
Digital
Output Alarm
No
Output Fan
No
Voltage - Supply
2.7 V ~ 5.5 V
Operating Temperature
-55°C ~ 125°C
Mounting Type
Surface Mount
Package / Case
8-SOIC (5.3mm Width), 8-SOP, 8-SOEIAJ
Full Temp Accuracy
+/- 1 C
Digital Output - Bus Interface
Serial (1-Wire)
Digital Output - Number Of Bits
8 bit
Maximum Operating Temperature
+ 125 C
Minimum Operating Temperature
- 55 C
Lead Free Status / RoHS Status
Contains lead / RoHS non-compliant

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FEATURES
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.
1-Wire is a registered trademark of Dallas Semiconductor Corp.,
a wholly owned subsidiary of Maxim Integrated Products, Inc.
Requires no external components
Unique 1-Wire
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 PR35 and 8-pin SO
packages
Applications include thermostatic controls,
industrial systems, consumer products,
thermometers, or any thermally sensitive
system
ma
www.maxim-ic.com
®
interface requires only one
Programmable Digital Thermostat and
1 of 18
PIN ASSIGNMENT
PIN DESCRIPTION
GND
DQ
V
NC
DD
(BOTTOM VIEW)
(DS1821)
DS1821
DALLAS
1 2 3
1
- Ground
- Data In/Out and Thermostat Output
- Power Supply Voltage
- No Connect
PR35
2 3
GND
DQ
NC
NC
Thermometer
8-pin 208-mil SO
(DS1821S)
1
3
2
4
DS1821
071107
8
7
6
5
V
NC
NC
NC
DD

Related parts for DS1821S

DS1821S Summary of contents

Page 1

... Dallas Semiconductor Corp., a wholly owned subsidiary of Maxim Integrated Products, Inc. Programmable Digital Thermostat and PIN ASSIGNMENT DALLAS DS1821 (BOTTOM VIEW) PR35 (DS1821) PIN DESCRIPTION GND - Ground DQ - Data In/Out and Thermostat Output V - Power Supply Voltage Connect DS1821 Thermometer GND 8-pin 208-mil SO (DS1821S) 071107 ...

Page 2

... PACKAGE NUMBER MARKING DS1821 DS1821 DS1821+ DS1821 (See Note) DS1821S DS1821S DS1821S/T&R DS1821S DS1821S+ DS1821S (See Note) DS1821S+T&R DS1821S (See Note) Note: A “+” symbol will also be marked on the package. + Denotes lead-free package. DETAILED PIN DESCRIPTIONS Table 1 PR35 8-PIN SYMBOL SO GND ...

Page 3

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 ...

Page 4

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 ...

Page 5

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 ...

Page 6

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 ...

Page 7

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 ...

Page 8

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 ¯ * — ...

Page 9

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 ...

Page 10

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 ...

Page 11

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 ...

Page 12

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 ...

Page 13

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 ...

Page 14

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 ¯ = ...

Page 15

ABSOLUTE MAXIMUM RATINGS* Voltage on any pin relative to ground Operating temperature Storage temperature Soldering temperature *These are stress ratings only and functional operation of the device at these or any other conditions above those indicated in the operation sections ...

Page 16

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 ...

Page 17

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

Page 18

TIMING DIAGRAMS Figure ...

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