DS28EA00U+ Maxim Integrated Products, DS28EA00U+ Datasheet - Page 5

• Manufacturer Part Number: DS28EA00U+
• Description: IC THERMOMETER 1-WIRE 8-USOP
• Manufacturer: Maxim Integrated Products

Specifications of DS28EA00U+

• Function: Thermometer, Thermostat
• Topology: Register Bank, Scratchpad
• Sensor Type: Internal
• Sensing Temperature: -40°C ~ 85°C
• Output Type: Digital
• Output Alarm: Yes
• Output Fan: No
• Voltage - Supply: 3 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-MSOP, Micro8™, 8-uMAX, 8-uSOP,
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The Block Diagram shows the relationships between
the major function blocks of the DS28EA00. The device
has three main data components: 64-bit registration
number, 64-bit scratchpad, and alarm and configura-
tion registers. The 1-Wire ROM function control unit
processes the ROM function commands that allow the
device to function in a networked environment. The
device function control unit implements the device-spe-
cific control functions, such as read/write, temperature
conversion, setting the chain state for sequence detec-
tion, and PIO access. The cyclic redundancy check
(CRC) generator assists the master verifying data
integrity when reading temperatures and memory data.
In the sequence-detect process, PIOB functions as an
input, while PIOA provides the connection to the next
device. The power-supply sensor allows the master to
remotely read whether the DS28EA00 has local power
available.
Figure 1 shows the hierarchical structure of the 1-Wire
protocol. The bus master must first provide one of the
eight ROM function commands: Read ROM, Match
ROM, Search ROM, Conditional (Alarm) Search ROM,
Conditional Read ROM, Skip ROM, Overdrive-Skip
ROM, Overdrive-Match ROM.
Upon completion of an overdrive ROM command exe-
cuted at standard speed, the device enters overdrive
mode, where all subsequent communication occurs at
iButton is a registered trademark of Maxim Integrated Products, Inc.
2, 3, 5
PIN
1
4
6
7
8
PIOA (DONE)
PIOB (EN)
NAME
GND
_______________________________________________________________________________________
N.C.
V
IO
DD
Detailed Description
1-Wire Bus Interface and Parasitic Power Supply. Open-drain pin that requires external pullup
resistor.
No Connection
Ground Supply
Open-Drain PIOA Channel and Chain Output. For sequence detection, PIOA must be connected to
PIOB of the next device in the chain; leave open or connect to GND for the last device in the
chain.
Open-Drain PIOB Channel and Chain Input. For sequence detection, PIOB of the first device in the
chain must be connected to GND.
Power Supply. Must be connected to GND for operation in parasite-power mode.
1-Wire Digital Thermometer with
Sequence Detect and PIO
a higher speed. The protocol required for these ROM
function commands is described in Figure 11. After a
ROM function command is successfully executed, the
device-specific control functions become accessible
and the master can provide any one of the nine avail-
able commands. The protocol for these control function
commands is described in Figure 9. All data is read
and written least significant (LS) bit first.
Each DS28EA00 contains a unique registration number
that is 64 bits long. The first 8 bits are a 1-Wire family
code. The next 48 bits are a unique serial number. The
last 8 bits are a CRC of the first 56 bits (see Figure 2 for
details). The 1-Wire CRC is generated using a polyno-
mial generator consisting of a shift register and XOR
gates as shown in Figure 3. The polynomial is X
X
available in Application Note 27: Understanding and
Using Cyclic Redundancy Checks with Maxim iButton
Products .
The shift register bits are initialized to 0. Then starting
with the least significant bit of the family code, one bit
at a time is shifted in. After the eighth bit of the family
code has been entered, then the 48-bit serial number is
entered. After the last byte of the serial number has
been entered, the shift register contains the CRC value.
Shifting in the 8 bits of CRC returns the shift register to
all 0s.
4
+ 1. Additional information about the 1-Wire CRC is
FUNCTION
64-Bit Registration Number
Pin Description
8
+ X
5
5
®
+