DS28EA00U+ Maxim Integrated Products, DS28EA00U+ Datasheet - Page 10

• 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 power-on default chain state is OFF, where PIOA
and PIOB are solely controlled through the PIO Access
Read and Write commands. In the chain ON state,
PIOA is pulled high to the device’s internal V
through an approximately 40kΩ resistor, applying a
logic 1 to the PIOB (EN) pin of the next device. Only in
the ON state does a DS28EA00 respond to the
Conditional Read ROM command, provided its EN is at
logic 0. After a device’s ROM registration number is
read, it is put into the chain DONE state, which enables
the next device in the chain to respond to the
Conditional Read ROM command.
At the beginning of the sequence discovery process, all
devices are put into the chain ON state. As the discov-
ery progresses, one device after another is transitioned
into the DONE state until all devices are identified.
Finally, all devices are put into the chain OFF state,
which releases the PIO pins and restores their power-
on default state.
Figure 9 shows the protocols necessary for measuring
temperatures, accessing the memory and PIO pins,
and changing the chain state. Examples on how to use
these and other functions are included at the end of this
document. The communication between master and
DS28EA00 takes place either at standard speed
(default, OD = 0) or at overdrive speed (OD = 1). If not
explicitly set into the overdrive mode after power-up,
the DS28EA00 communicates at standard speed.
This command allows the master to write 3 bytes of
data to the scratchpad of the DS28EA00. The first data
byte is associated with the TH register (byte address
2), the second byte is associated with the TL register
(byte address 3), and the third byte is associated with
the Configuration register (byte address 4). Data must
be transmitted least significant bit first. All 3 bytes must
be written before the master issues a reset, or the data
can be corrupted.
This command allows the master to read the contents
of the scratchpad. The data transfer starts with the least
significant bit of the Temperature Readout register at
byte address 0 and continues through the remaining 7
bytes of the scratchpad. If the master continues read-
ing, it gets a ninth byte, which is an 8-bit CRC of all the
data in the scratchpad. This CRC is generated by the
DS28EA00 and uses the same polynomial function as is
10
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Control Function Commands
Write Scratchpad [4Eh]
Read Scratchpad [BEh]
DD
supply
used with the ROM registration number. The CRC is
transmitted in its true (noninverted) form. The master
can issue a reset to terminate the reading early if only
part of the scratchpad data is needed.
This command copies the contents of the scratchpad
byte addresses 2 to 4 (TH, TL, and Configuration regis-
ters) to the backup EEPROM. If the device has no V
power, the master must enable a strong pullup on the
1-Wire bus for the duration of t
after this command is issued. If the device is powered
through the V
slots to monitor the copy process. Copy is completed
when the master reads 1 bits instead of 0 bits.
This command initiates a temperature conversion.
Following the conversion, the resulting thermal data is
found in the Temperature Readout register in the
scratchpad and the DS28EA00 returns to its low-power
idle state. If the device has no V
must enable a strong pullup on the 1-Wire bus for the
duration of the applicable resolution-dependent
t
the device is powered through the V
can generate read time slots to monitor the conversion
process. The conversion is completed when the master
reads 1 bits instead of 0 bits.
For Copy Scratchpad and Convert Temperature, the
master needs to know whether the DS28EA00 has V
power available. The Read Power Mode command is
implemented to provide the master with this informa-
tion. After the command code, master issues read time
slots. If the master reads 1s, the device is powered
through the V
the 1-Wire line, the master read 0s. The power-supply
sensor samples the state of the V
slot that the master generates after the command code.
This command recalls the TH and TL alarm trigger val-
ues and configuration data from backup EEPROM into
their respective locations in the scratchpad. After hav-
ing transmitted the command code, the master can
issue read time slots to monitor the completion of the
recall process. Recall is completed when the master
reads 1 bits instead of 0 bits. The recall occurs auto-
matically at power-up, not requiring any activity by the
master.
CONVMAX
within 10µs after this command is issued. If
DD
DD
pin, the master can generate read time
pin. If the device is powered through
Convert Temperature [44h]
Read Power Mode [B4h]
Copy Scratchpad [48h]
Recall EEPROM [B8h]
PROGMAX
DD
DD
DD
power, the master
pin for every time
pin, the master
within 10µs
DD
DD