Rev 2; 4/09
1-Wire Digital Thermometer with
Sequence Detect and PIO
DS28EA0
General Description
Features
♦ Digital Thermometer Measures Temperatures
The DS28EA00 is a digital thermometer with 9-bit (0.5°C)
to 12-bit (1/16°C) resolution and alarm function with non-
volatile (NV), user-programmable upper and lower trigger
points. Each DS28EA00 has its own unique 64-bit regis-
tration number that is factory programmed into the chip.
from -40°C to +85°C
♦ Thermometer Resolution is User Selectable from
9 to 12 Bits
®
Data is transferred serially through the 1-Wire protocol,
♦ Unique 1-Wire Interface Requires Only One Port
which requires only one data line and a ground reference
for communication. The improved 1-Wire front-end with
hysteresis and glitch filter enables the DS28EA00 to per-
form reliably in large 1-Wire networks. Unlike other 1-Wire
thermometers, the DS28EA00 has two additional pins to
implement a sequence-detect function. This feature
allows the user to discover the registration numbers
according to the physical device location in a chain, e.g.,
to measure the temperature in a storage tower at different
height. If the sequence-detect function is not needed,
these pins can be used as general-purpose input or out-
put. The DS28EA00 can derive the power for its operation
directly from the data line (“parasite power”), eliminating
the need for an external power supply.
Pin for Communication
♦ Each Device Has a Unique 64-Bit, Factory-
Lasered Registration Number
♦ Multidrop Capability Simplifies Distributed
Temperature-Sensing Applications
♦ Improved 1-Wire Interface with Hysteresis and
Glitch Filter
♦ User-Definable NV Alarm Threshold Settings/User
Bytes
♦ Alarm Search Command to Quickly Identify
Devices Whose Temperature is Outside of
Programmed Limits
Applications
♦ Standard and Overdrive 1-Wire Speed
Data Communication Equipment
♦ Two General-Purpose Programmable IO (PIO) Pins
Process Temperature Monitoring
HVAC Systems
♦ Chain Function Sharing the PIO Pins to Detect
Physical Sequence of Devices in Network
Ordering Information
♦ Operating Range: +3.0V to +5.5V, -40°C to +85°C
♦ Can Be Powered from Data Line
♦ 8-Pin µSOP Package
PART
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
DS28EA00U+
DS28EA00U+T&R
8 μSOP
8 μSOP
Pin Configuration appears at end of data sheet.
+Denotes a lead(Pb)-free/RoHS-compliant package.
T&R = Tape and reel.
Typical Operating Circuit
V
DD
1-Wire
MASTER
#1
#2
#3
V
DD
V
DD
V
DD
PX. Y
IO
IO
IO
DS28EA00
DS28EA00
DS28EA00
MICROCONTROLLER
PIOB
PIOA
PIOB
PIOA
PIOB
PIOA
GND
GND
GND
NOTE: SCHEMATIC SHOWS PIO PINS WIRED FOR SEQUENCE-DETECT FUNCTION.
1-Wire is a registered trademark of Maxim Integrated Products, Inc.
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.