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BENEFITS AND FEATURES
• Guaranteed Unique 64-Bit ROM ID Chip for
Absolute Traceability
o Unique, Factory-Lasered and Tested
64-Bit Registration Number (8-Bit Family
Code +48-Bit Serial Number + 8-Bit CRC
Tester)
o 8-Bit Family Code Specifies DS2401
Communications Requirements to Reader
• Minimalist 1-Wire® Interface Lowers Cost
and Interface Complexity
o Multiple DS2401 Devices Can Reside on
a Common 1-Wire Net
o Built-In Multidrop Controller Ensures
Compatibility with Other 1-Wire Net
Products
o Reduces Control, Address, Data, and
Power to a Single Pin and Communicates
at Up to 16.3kbps
o Presence Pulse Acknowledges When the
Reader First Applies Voltage
o Low-Cost TO-92, SOT-223, and TSOC
Surface-Mount Packages
o TO-92 Tape-and-Reel Version with Leads
Bent to 100-mil Spacing (Default) or with
Straight Leads (DS2401-SL)
Wide Voltage and Temperature Operating
Ranges Enables Robust System Performance
o Extended 2.8V to 6.0V Range
o Zero Standby Power Required
o -40°C to +85°C Industrial Temperature
Range
APPLICATIONS
P CB Ide ntification
Network Node ID
Equipment Registration
PIN CONFIGURATIONS
1 2
01rrd
Flip Chip, Top View
with Laser Mark,
Contacts Not Visible.
“rrd” = Revision/Date
A
B
+
TOP VIEW
WLP
DS2401
1
2
2
1
PIN DES CRIPTIONS
NAME
PIN
TO-92
SOT-
223
TSOC
FLIP-
CHIP
WLP
DATA
(DQ)
2 2 2 1 A1, B1
GROUND
1
1, 4
1
2
A2, B2
N.C. (No
Connect)
3 3 3–6 — —
DS2401
Silicon Serial Number
TOP VIEW
TOP VIEW
BOTTO M VIEW
TO-92
DS2401
2
3
1
1 2 3
1-Wire is a registered trademark of Maxim Integrated Products, Inc.
19-5860; Rev 12/16
TSOC
DS2401
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ORDERING INFORMATION
PART
TEMP RANGE
PIN-PACKAGE
DS2401+
-40°C to +85°C
3 TO-92
DS2401+T&R
-40°C to +85°C
3 TO-92 (formed leads)
DS2401-SL+T&R
-40°C to +85°C
3 TO-92 (straight leads)
DS2401P+
-40°C to +85°C
6 TSOC
DS2401P+T&R
-40°C to +85°C
6 TSOC
DS2401Z+
-40°C to +85°C
4 SOT-223
DS2401Z+T&R
-40°C to +85°C
4 SOT-223
DS2401X1-S#T
-40°C to +85°C
2 Flip Chip (2.5k pieces)
DS2401X-S+T
-40°C to +85°C
4 WLP
+Den ot e s a lead( Pb)-free/RoHS-compliant package.
T&R/T = Tape and r eel.
SL = Straight leads.
#Denote s a RoHS-compliant device that may include lead that is exempt u n der the RoHS requir em ents .
DESCRIPTION
The DS2401 enhanced silicon serial number is a low-cost, electronic registration number that provides an
absolutely unique identity which can be determined with a minimal electronic interface (typically, a
single port pin of a microcontroller). The DS2401 consists of a factor y-lasered, 64-bit ROM that includes
a unique 48-bit serial number, an 8-bit CRC, and an 8-bit Famil y Code (01h). Data i s transferr ed serial ly
via the 1-Wire protocol that requires only a single data lead and a ground return. Power for reading and
writing the device is derived from the data line itself with no need for an external power source. The
DS2401 is an upgrade to the DS2400. The DS2401 is fully reverse-compatible with the DS2400 but
provides the additional multi-drop capability that enables many devices to reside on a single data line.
The familiar TO-92, SOT-223 or TSOC package provides a compact enclosure that allows standard
assembly equipment to handle the device easily.
OPERATION
The DS2401’s internal ROM is accessed via a single data line. The 48-bit serial number, 8-bit family
code and 8-bit CRC are retrieved using the Maxim 1-Wire protocol. This protocol defines bus
transactions in terms of the bus state during specified time slots that are initiated on the falling edge of
sync pulses from the bus master. All data is read and written least significant bit first.
1-Wire BUS SYSTEM
The 1-Wire bus is a system which has a single bus master system and one or more slaves. In all instances,
the DS2401 is a slave device. The bus master is typically a microcontroller. The discussion of this bus
system is broken down into three topics: hardware configuration, transaction sequence, and 1-Wire
signaling (signal type and timing).
Hardware Configuration
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 an
open-drain connection or 3-state outputs. The DS2401 is an open-drain part with an internal circuit
equivalent to that shown in Fi gure 2. The bus mas ter can be the same equi valent circuit. If a bidirect ional
pin is not available, separate output and input pins can be tied together. The bus master requires a pullup
resistor at the master end of the bus, with the bus m aster circuit equivalent to the one shown in Figure 3.
The value of the pullup resistor should be approximately 5kΩ for short line lengths. A multidrop bus
consists of a 1-Wire bus with multiple slaves attached. The 1-Wire bus has a maximum data rate of
16.3kbits per second.
DS2401
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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
for more than 120µs, one or more of the devices on the bus may be reset.
DS2401 ME MORY MAP Figure 1
8-Bit CRC Code 48-Bit Serial Number 8-Bit Family Code (01h)
MSB LSB MSB LSB MSB LSB
DS2401 E Q UIVALENT CIRCUI T Figure 2
BUS MASTER CIRCUIT Figure 3 A) Open Drain
Note:
Depending on the 1-Wire communication speed and the bus load characteristics, the optimal pullup
resistor (RPU) value will be in the 1.5kΩ to 5kΩ range.
To data connection
of DS2401
B) Standard TTL
To data connection
of DS2401
See note
See note
VPUP
VPUP
DS2401
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TRANS ACTIO N SEQ UE NCE
The sequence for accessing the DS2401 via the 1-Wire port is as follows:
Initialization
ROM Function Command
Read Data
INITIALIZATION
All transactions on the 1-Wire bus begin with an initialization sequence. The initialization sequence
consists of a reset pulse transmitted by the bus master followed by a Pres ence Pul se(s) tr ansmitt ed by the
slave(s).
The Presence Pulse lets the bus master know that the DS2401 is on the bus and is ready to operate. For
more details, see the 1-Wire Signaling section.
ROM FUNCTION COMMA NDS
Once the bus master has detected a presence, it can issue one of the four ROM function commands. All
ROM function commands are 8 bits long. A list o f these commands follows (refer to flowchart in F igure
4).
Read ROM [3 3 h] or [ 0 Fh]
This command allows the bus master to read the DS2401’s 8-bit family code, unique 48-bit serial
number, and 8-bit CRC. This command can only be used if there is a single DS2401 on the bus. If more
than one slave is present on the bus, a data collision will occur when all slaves try to transmit at the same
time (open drain will produce a wired-AND result). The DS2401 Read ROM function will occur with a
command byte of either 33h or 0Fh in order to ensure compatibility with the DS2400, which will only
respond to a 0Fh command word with its 64-bit ROM data.
Match ROM [55h] / Sk ip ROM [CCh]
The complete 1-Wire protocol for all Maxim iButtons® contains a Match ROM and a Skip ROM
command. Since the DS2401 contains only the 64-bit ROM with no additional data fields, the Match
ROM and Skip ROM are not applicable and will cause no further a ctivity on the 1-Wir e bus if ex ecuted.
The DS2401 does not interfere with other 1-Wire parts on a multidrop bus that do respond to a Match
ROM or Skip ROM (for example, a DS2401 and DS1994 on the same bus).
Search ROM [F0h]
When a system is initially brought up, the bus master might not know the number of devices on the
1-Wire bus or their 64-bit ROM co des . Th e search RO M com m and al l ows the bu s m ast er to us e a pro cess
of elimination to identify the 64-bit ROM codes of all slave devices on the bus. The ROM sea rch process
is the repetition of a simple 3-step routine: read a bit, read the complement of the bit, then write the
desired value of that bit. The bus master performs this simple 3-step routine on each bit of the ROM.
After one complete pass, the bus master knows the contents of the ROM in one device. The remaining
number of devices and their ROM codes may be identified by additional passes. Refer to Application
Note 187: 1-Wire Search Algorithm for a comprehensive discussion of a ROM search , i ncl udi n g an act ual
example.
iButton is a registered trademark of Maxim Integrated Products, Inc.
DS2401
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1-Wire SIGNALING
The DS2401 requires a strict protocol to ensure data integrity. The protocol consists of four types of
signali ng on o ne lin e: reset s equence wi th R eset Pu lse and Presen ce Puls e, writ e 0, writ e 1, and read data.
All these signals except Presence Pulse are initiated by the bus master.
The initialization sequence required to begin any communication with the DS2401 is shown in Figure 5.
A reset pulse followed by a Presence Pulse indicates the DS2401 is ready to send or receive data given
the correct ROM command.
The bus master transmits (TX ) a reset pulse (tRSTL , minimum 480µs). The bus master then releases the
line and goes i nt o recei v e m od e (RX ). The 1-Wire bus is pulled to a high state via the 5kΩ pullup resistor.
After detecting the rising edge on the data pin, the DS2401 waits (tPDH, 15-60µs) and then transmits the
Presence Pulse (tPDL, 60-240µs). The 1-Wire bus requires a pullup resistor range of 1.5kΩ to 5kΩ,
depending on bus load characteristics.
READ/WRITE TIME SLOTS
The definitions of write and read time slots are illustrated in Figure 6. All time slots are initiated by the
master driving the data line low. The falling edge of the data line synchronizes the DS2401 to the master
b y trig g ering a delay circuit in the DS2401. During write time slots, the delay circuit determines when the
DS2401 will sample the data line. For a read data time slot, if a “0” is to be transmitted, the delay circuit
determines how long the DS2401 will hold the data line low overriding the “1” generat ed by the master.
If the data bit is a 1, the DS2401 will leave the read data time slot unchanged.
DS2401
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ROM FUNCTI O NS FLOW CHART Figure 4
DS2401
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INITIALIZATION PROCE DURE “RESET AND PRESENCE PULSE S” Figure 5
480µs ≤ tRSTL < ∞ *
480µs ≤ tRSTH < ∞ (includes recovery time)
15µs ≤ tPDH < 60µs
60µs ≤ tPDL < 240µs
∗ In order not to mask interrupt signaling by other devices on the 1-Wire bus, tRSTL + tR should always
be less than 960µs.
READ/WRITE TIMING DIAGRAM Figure 6
Write-One Time Slot
60µs ≤ tSLOT < 120µs
1µs ≤ tLOW1 < 15µs
1µs ≤ tREC < ∞
RESISTOR
MASTER
RESISTOR
MASTER
DS2401
DS2401
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READ/WRITE TIMING DIAGRAM (cont’d) Figure 6
Write-zero Time Slot
60µs ≤ tLOW0 < tSLOT < 120µs
1µs ≤ tREC < ∞
Read-data Tim e Slot
60µs ≤ tSLOT < 120µs
1µs ≤ tLOWR < 15µs
0 ≤ tRELEASE < 45µs
1µs ≤ tREC < ∞
tRDV = 15µs
tSU < 1µs
CRC GENER ATIO N
To validate the data transmitted from the DS2401, the bus master may generate a CRC value from the
data as it is received. This generated value is compared to the value stored in the last 8 bits of the
DS2401. If the two CRC values match, the transmission is error-free.
The equivalent polynomial function of this CRC is: CRC = x8 + x5 + x4 + 1. Additional information about
the Maxim 1-Wire CRC is available in Application Note 27.
CUSTOM DS 2 4 0 1
Customization of a portion of the unique 48-bit serial number by the customer is available. Maxim will
register and assign a specific customer ID in the 12 most significant bits of the 48-bit field. The next most
significant bits are selectable by the customer as a starting value, and the least significant bits are non-
selectable and will be automatically incremented by one. Certain quantities and conditions apply for these
custom parts. Contact your Maxim sales representative for more information.
RESISTOR
MASTER
DS2401
DS2401
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ABSOLUTE MAXIMUM RATINGS
Voltage Range on Any Pin Relative to Ground -0.5V to +7.0V
Operating Temperature Range -40°C to +85°C
Storage Temperature Range -55°C to +125°C
Lead Temperature (TO-92, TSOC, SOT-223 only; soldering, 10s) +300°C
Soldering Temperature (reflow)
TO-92 +250°C
TSOC, SOT-223, WLP +260°C
Flip Chip +240°C
This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation sections of this
specification is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliabili ty.
DC ELECTRICAL CHARACTERIS TICS
(TA = -40°C to +85°C, unless otherwise noted.)
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS
NOTES
Pullup Voltage
VPUP
2.8
6.0
V
2
Logic 1
VIH
2.2
V
1, 6
Logic 0
VIL
-0.3
+0.3
V
1
Output Logic-Low at 4mA
VOL
0.4
V
1
Input Load Current
IL
5
µA
3
Operating Charge
QOP
30
nC
7, 8
CAPACITANCE
(TA = +25°C, unless otherwise noted.)
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS
NOTES
I/O ( 1 -Wire)
CIN/OUT
800
pF
9
AC ELECTRICAL CHARACTERIS TICS
(TA = -40°C to +85°C, unless otherwise noted.)
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS
NOTES
Time Slot
tSLOT
60
120
µs
Write 1 Low Time
tLOW1
1
15
µs
12
Write 0 Low Time
tLOW0
60
120
µs
Read Data Valid
tRDV
15
µs
11
Release Time
tRELEASE
0
15
45
µs
Read Data Setup
tSU
1
µs
5
Recovery Time
tREC
1
µs
Reset Time High
tRSTH
480
µs
4
Reset Time Low
tRSTL
480
960
µs
10
Presence Detect High
tPDH
15
60
µs
Presence Det e ct Low
tPDL
60
240
µs
DS2401
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NOTES:
1) All voltages are referenced to ground.
2) VPUP = external pullup voltage.
3) Input load is to ground.
4) An additional reset or communication sequence cannot begin until the reset high time has expired.
5) Read data setup time refers to the time the host must pull the 1-Wire bus low to read a bit. Data is
guaranteed to be valid wi thin 1µs of this falling edge and will remain valid for 14µs minimum (15µs
total from falling edge on 1-Wire bus).
6) VIH is a function of the external pullup resistor and VPUP.
7) 30 nanocoulombs per 72 time slots at 5.0V.
8) At VPUP = 5.0V with a 5kΩ pullup to VPUP and a maximum time slot of 120µs.
9) Capacitance on the I/O pin could be 800pF when power is first applied. If a 5kΩ resistor is used to
pullup the I/O line to VPUP, 5µs after power has been applied the parasite capacitance will not affect
normal communications.
10) The reset low time (tRSTL) should be restricted to a maximum of 960µs, to allow interrupt signaling,
otherwise it could mask or conceal interrupt puls es if this device is used in parallel wit h a DS2404 or
DS1994.
11) The optimal sampling point for the master is as close as possible to the end time of the tRDV period
without exceeding tRDV. For the cas e of a Read-One Time slot, this maximizes the amount of time for
the pullup resistor to recover to a high level. For a Read-Zero Time slot, it ensures that a read will
occur before the fastest 1-Wire device(s) releases the line.
12) The duration of the low pulse sent by the master should be a minimum of 1μs with a maximum value
as short as possible to allow time for the pullup resistor to recover the line to a high level before the
1-Wire dev ice samples in the case of a Wri te-One Time or b efore the mas ter samples in the case of a
Read-One Time.
PACK AGE INFO RMATION
For the latest pac kage outline infor mation a nd land pa tterns (footprints), go to www.maxim-ic.com/packages. Note that a “+”,
“#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the
drawing pertains to the package regardless of RoHS status.
PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO.
3 TO-92
(straight leads)
Q3+1 21-0248 —
3 TO-92
(formed leads)
Q3+4 21-0250 —
6 TSOC D6+1 21-0382 90-0321
4 SOT-223 K3+1 21-0264 —
2 Flip Chip BF211#1 21-0378 21-0378
4 WLP N40B1+1 21-0605
Refer to
Application Note 1891
DS2401
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Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim
reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 160 Rio Robles, San Jose, CA 94134 408-601-1000
© 2016 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.
REVIS IO N HISTO RY
REVISION
DATE
DESCRIPTION
PAGES
CHANGED
040601
Changed MicroLAN to 1-Wire Net; updated ordering information for
tape and reel
1
Changed soldering temperature from 260°C for 10 seconds to See J-STD-
020A Specification
9
022202
Below Figure 3, added a note on the optimal R
PUP
range; added a similar
note before the Read/Write Time Slots section
3, 6
Added notes 11 to 13 to the EC table
9, 10
122106
Added flip chip package; added lead-free ordering information
1, 2
References to the Book of iButton Standards replaced with references to
corresponding application notes
Various
V
ILMAX
changed from 0.8V to 0.3V, EC table note 11 deleted
9, 10
5/11
Deleted standard (Pb) parts from ordering information; changed flip chip
part number from DS2401X1 to DS2401X1-S#T
2
Deleted V
OH
from the EC table; moved V
PUP
from the EC table header
into the EC table; changed soldering temperature from J-STD-020A
reference to explicit package specific numbers
9
Added Package Information and Revision History sections
10, 11
3/15
Revised Benefits and Features section
1
12/16
Added WLP package to Pin Configurations, Pin Descriptions, Ordering
Information, Absolute Maximum Ratings, and Package Information
sections
1, 2, 9, 10
