DS1990A-F3+ Maxim Integrated Products, DS1990A-F3+ Datasheet - Page 5

• Manufacturer Part Number: DS1990A-F3+
• Description: IC IBUTTON SERIAL NUMBER F3
• Manufacturer: Maxim Integrated Products
• Series: iButton®r
• Type: Serial Number IButtonr

Specifications of DS1990A-F3+

• Rohs Information: IButton RoHS Compliance Plan
• Memory Size: 8B
• Memory Type: ROM
• Maximum Operating Temperature: + 85 C
• Package / Case: F3 MicroCan
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Ic Function: Serial Number IButton IC
• Supply Voltage Range: 2.8V To 6V
• Operating Temperature Range: -40°C To +85°C
• Digital Ic Case Style: F3 IButton
• Termination Type: SMD
• Supply Voltage Min: 2.8V
• Rohs Compliant: Yes
• Filter Terminals: SMD
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The 1-Wire bus has only a single line by definition; it is
important that each device on the bus be able to drive
it at the appropriate time. To facilitate this, each device
attached to the 1-Wire bus must have open-drain or
three-state outputs. The 1-Wire port of the DS1990A is
open drain with an internal circuit equivalent to that
shown in Figure 4. A multidrop bus consists of a 1-Wire
bus with multiple slaves attached. At standard speed,
the 1-Wire bus has a maximum data rate of 16.3kbps.
The value of the pullup resistor primarily depends on
the network size and load conditions. For most applica-
tions, the optimal value of the pullup resistor is approxi-
mately 2.2kΩ. The idle state for the 1-Wire bus is high.
If for any reason a transaction needs to be suspended,
the bus must be left in the idle state if the transaction is
to resume. If this does not occur and the bus is left low
Figure 4. Hardware Configuration
Hardware Configuration
_______________________________________________________________________________________
Rx
Tx
SIMPLE BUS MASTER
HOST CPU
DS2480B BUS MASTER
SERIAL
PORT
OPEN-DRAIN
PORT PIN
SERIAL OUT
SERIAL IN
Tx = TRANSMIT
Rx = RECEIVE
V
V
POL
RXD
TXD
PUP
DD
R
DS2480B
PUP
for more than 120µs, one or more devices on the bus
may be reset.
The protocol for accessing the DS1990A through the
1-Wire port is as follows:
• Initialization
• ROM Function Command
All transactions on the 1-Wire bus begin with an initial-
ization sequence. The initialization sequence consists
of a reset pulse transmitted by the bus master followed
by presence pulse(s) transmitted by the slave(s). The
presence pulse lets the bus master know that the
DS1990A is on the bus and is ready to operate. For
more details, see the 1-Wire Signaling section.
Serial Number iButton
GND
N.C.
1-W
V
PP
DATA
DS1990A 1-Wire PORT
+5V
100Ω MOSFET
TO 1-Wire DATA
Transaction Sequence
Rx
Tx
Initialization
5