DS28EA00U+ Maxim Integrated Products, DS28EA00U+ Datasheet - Page 22

• 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

1-Wire Digital Thermometer with
Sequence Detect and PIO
The DS28EA00 requires strict protocols to ensure data
integrity. The protocol consists of four types of signaling
on one line: reset sequence with reset pulse and pres-
ence pulse, write-zero, write-one, and read-data.
Except for the presence pulse, the bus master initiates
all falling edges. The DS28EA00 can communicate at
two different speeds, standard speed and overdrive
speed. If not explicitly set into the overdrive mode, the
DS28EA00 communicates at standard speed. While in
overdrive mode the fast timing applies to all waveforms.
To get from idle to active, the voltage on the 1-Wire line
needs to fall from V
from active to idle, the voltage needs to rise from
V
voltage to make this rise is seen in Figure 12 as “ε” and
its duration depends on the pullup resistor (R
and the capacitance of the 1-Wire network attached.
The voltage V
determining a logical level, not triggering any events.
Figure 12 shows the initialization sequence required to
begin any communication with the DS28EA00. A reset
pulse followed by a presence pulse indicates the
DS28EA00 is ready to receive data, given the correct
ROM and control function command. If the bus master
uses slew-rate control on the falling edge, it must pull
down the line for t
A t
mode, returning the device to standard speed. If the
DS28EA00 is in overdrive mode and t
than 80µs, the device remains in overdrive mode. If the
Figure 12. Initialization Procedure “Reset and Presence Pulses”
22
ILMAX
RSTL
______________________________________________________________________________________
past the threshold V
duration of 480µs or longer exits the overdrive
V
IHMASTER
V
ILMAX
V
ILMAX
V
PUP
V
0V
TH
TL
RSTL
PUP
is relevant for the DS28EA00 when
+ t
t
below the threshold V
F
F
to compensate for the edge.
MASTER Tx "RESET PULSE"
TH
1-Wire Signaling
RESISTOR
. The time it takes for the
RSTL
t
RSTL
is no longer
PUP
TL
. To get
) used
ε
MASTER
device is in overdrive mode and t
and 480µs, the device resets, but the communication
speed is undetermined.
After the bus master has released the line, it goes into
receive mode. Now the 1-Wire bus is pulled to V
through the pullup resistor, or in the case of a DS2482-
x00 or DS2480B driver, by active circuitry. When the
threshold V
and then transmits a presence pulse by pulling the line
low for t
must test the logical state of the 1-Wire line at t
The t
t
expired, the DS28EA00 is ready for data communica-
tion. In a mixed population network, t
extended to minimum 480µs at standard speed and
48µs at overdrive speed to accommodate other 1-Wire
devices.
Data communication with the DS28EA00 takes place in
time slots, which carry a single bit each. Write time slots
transport data from bus master to slave. Read time
slots transfer data from slave to master. Figure 13 illus-
trates the definitions of the write and read time slots.
All communication begins with the master pulling the
data line low. As the voltage on the 1-Wire line falls
below the threshold V
nal timing generator that determines when the data line
is sampled during a write time slot and how long data is
valid during a read time slot.
PDLMAX
t
PDH
RSTH
t
MSP
PDL
, and t
MASTER Rx "PRESENCE PULSE"
window must be at least the sum of t
TH
t
PDL
. To detect a presence pulse, the master
t
is crossed, the DS28EA00 waits for t
RSTH
RECMIN
TL
, the DS28EA00 starts its inter-
. Immediately after t
t
REC
Read/Write Time Slots
DS28EA00
RSTL
is between 80µs
RSTH
should be
MSP
PDHMAX
RSTH
.
PDH
PUP
is
,