DS1821S Maxim Integrated Products, DS1821S Datasheet - Page 11

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

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

DS1821 FUNCTION COMMAND SET Table 4
1-Wire SIGNALING
The DS1821 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.
INITIALIZATION PROCEDURE: RESET AND PRESENCE PULSES
All communication with the DS1821 begins with an initialization sequence that consists of a reset pulse
from the master followed by a presence pulse from the DS1821. This is illustrated in Figure 7. When the
DS1821 sends the presence pulse in response to the reset, it is indicating to the master that it is on the bus
and ready to operate given an appropriate function command.
During the initialization sequence the bus master transmits (T
low for a minimum of 480 μs. The bus master then releases the bus and goes into receive mode (R
When the bus is released, the 5k pullup resistor pulls the 1-Wire bus high. When the DS1821 detects this
rising edge, it waits 15–60 μs and then transmits a presence pulse by pulling the 1-Wire bus low for 60–
240 μs.
Read
Temperature
Start Convert T Initiates temperature conversions.
Stop Convert T Halts temperature conversions.
THERMOSTAT and STATUS/CONFIGURATION COMMANDS
Write TH
Write TL
Read TH
Read TL
Write Status
Read Status
HIGH-RESOLUTION COMMANDS
Read Counter
Load Counter
Command
Reads last converted temperature
value from temperature register.
Writes data to the T
Writes data to the T
Reads data from the T
Reads data from the T
Writes data to the
status/configuration register.
Reads data from the
status/configuration register.
Reads data from the counter
register
Loads slope accumulator data into
the counter register
TEMPERATURE CONVERSION COMMANDS
Description
H
L
register.
register.
H
L
register.
register.
11 of 18
Protocol
AAh
ACh
EEh
A1h
A2h
A0h
0Ch
22h
01h
02h
41h
X
) the reset pulse by pulling the 1-Wire bus
Master receives 8-bit temperature
value from DS1821.
None
None
Master transmits 8-bit T
DS1821.
Master transmits 8-bit T
DS1821.
Master receives 8-bit T
DS1821.
Master receives 8-bit T
DS1821.
Master transmits 8-bit
status/configuration value to DS1821.
Master receives 8-bit
status/configuration value from
DS1821.
Master receives 9-bit counter value
from DS1821.
None
After Command is Issued
1-Wire Bus Activity
H
L
H
L
value from
value from
value to
value to
X
).