DS28EA00U+ Maxim Integrated Products, DS28EA00U+ Datasheet - Page 9

• 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 functional assignments of the individual bits are
explained in the table below. Bits [4:0] and bit 7 have
Each PIO consists of an open-drain pulldown transistor
and an input path to read the pin state. The transistor is
controlled by the PIO output latch, as shown in Figure
5. The device function control unit connects the PIO
pins logically to the 1-Wire interface. PIOA has a pullup
path to internal V
function (see the Block Diagram ) in conjunction with the
Chain command; PIOB is truly an open-drain structure.
The power-on default state of the PIO output transistors
is off; high-impedance, on-chip resistors (not shown in
Figure 5) pull the PIO pins to internal V
The chain function is a feature that allows the 1-Wire
master to discover the physical sequence of devices
that are wired as a linear network (chain). This is partic-
ularly convenient for devices that are installed at equal
spacing along a long cable (e.g., to measure tempera-
tures at different locations inside a storage tower or
tank). Without chain function, the master needs a
lookup table to correlate the registration number to the
physical location.
The chain function requires two pins: an input (EN) to
enable a device to respond during the discovery and
an output (DONE) to inform the next device in the chain
that the discovery of its neighbor is done. The two gen-
Table 2. Chain States
R1, R0: Temperature
Converter Resolution
ADDRRESS
BIT DESCRIPTION
CHAIN STATE
4h
OFF (Default)
DONE
ON
BIT 7
DD
_______________________________________________________________________________________
0
to facilitate the sequence-detect
PIO (High Impedance)
EN Input
No Function
BIT(S)
[6:5]
BIT 6
R1
PIOB (
Chain Function
These bits control the resolution of the temperature converter. The codes are as follows:
R1
0
0
1
1
1-Wire Digital Thermometer with
PIO Structure
DD
.
BIT 5
)
R0
R0
0
1
0
1
Sequence Detect and PIO
10 bits
11 bits
12 bits
9 bits
PIO (High Impedance)
Pullup On
Pulldown On (DONE Logic 0)
BIT 4
1
no function and cannot be changed by the user. As a
factory default, the device operates in 12-bit resolution.
Figure 5. PIO Simplified Logic Diagram
eral-purpose ports of the DS28EA00 are reused for the
chain function. PIOB functions as an EN input and PIOA
generates the DONE signal, which is connected to the
EN input of the next device, as shown in the Typical
Operating Circuit . The EN input of the first device in the
chain needs to be hardwired to GND or logic 0 must be
applied for the duration of the sequence discovery
process. Besides the two pins, the sequence discovery
relies on the Conditional Read ROM command.
For the chain function and normal PIO operation to
coexist, the DS28EA00 distinguishes three chain states:
OFF, ON, and DONE. The transition from one chain
state to another is controlled through the Chain com-
mand. Table 2 summarizes the chain states and the
specific behavior of the PIO pins.
DEVICE BEHAVIOR
PIO OUTPUT LATCH STATE
PIOA (
BIT 3
PIO PIN STATE
1
DEFINITION
PIO CLOCK
PIO DATA
)
BIT 2
1
CLOCK
Not Recognized
Recognized if EN is 0
Not Recognized
Configuration Register
PIO OUTPUT LATCH
CONDITIONAL READ ROM
D
BIT 1
1
Q
Q
BIT 0
PIO PIN
1
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