DS1990A Datasheet, PDF (2/10 Pages) Dallas Semiconductor – Serial Number iButton

Serial Number iButton
ABSOLUTE MAXIMUM RATINGS
IO Voltage Range to GND .....................................-0.5V to +6.0V
IO Sink Current....................................................................20mA
Junction Temperature ......................................................+125°C
Storage Temperature Range .............................-55°C to +125°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(T_A = -40°C to +85°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN TYP MAX UNITS
IO PIN: GENERAL DATA
1-Wire Pullup Voltage
V_PUP (Notes 1, 2)
1-Wire Pullup Resistance
R_PUP (Notes 3, 4)
Input Capacitance
C_IO
(Notes 5, 6)
Input Load Current
I_L
(Note 7)
Input Low Voltage
V_IL
(Notes 1, 3, 8)
Input High Voltage
V_IH
(Notes 1, 9)
Output Low Voltage at 4mA
V_OL
(Note 1)
Operating Charge
Q_OP (Notes 6, 10)
Recovery Time
t_REC (Note 3)
Time Slot Duration
t_SLOT (Note 3)
IO PIN: 1-Wire RESET, PRESENCE-DETECT CYCLE
2.8
6.0
V
0.6
5
k

100 800
pF
0.25
μA
0.3
V
2.2
V
0.4
V
30
nC
1
μs
61
μs
Reset Low Time
Reset High Time
Presence-Detect High Time
Presence-Detect Low Time
Presence-Detect Sample Time
IO PIN: 1-Wire WRITE
t_RSTL
t_RSTH
t_PDH
t_PDL
t_MSP
(Notes 3, 11)
(Notes 3, 12)
(Note 13)
(Note 3)
480
μs
480
μs
15
60
μs
60
240
μs
60
75
μs
Write-Zero Low Time
Write-One Low Time
IO PIN: 1-Wire READ
t_W0L
t_W1L
(Notes 3, 14)
(Notes 3, 14)
60
120
μs
1
15
μs
Read Low Time
Read Sample Time
t_RL
t_MSR
(Notes 3, 15)
(Notes 3, 15)
1
t_RL + 
15 - 
μs
15
μs
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
Note 6:
Note 7:
All voltages are referenced to ground.
External pullup voltage. See Figure 4.
System requirement.
Full R_PUP range is guaranteed by design and simulation and not production tested. Production testing performed at a
fixed R_PUP value. Maximum allowable pullup resistance is a function of the number of 1-Wire devices in the system and 1-
Wire recovery times. The specified value here applies to systems with only one device and with the minimum 1-Wire recov-
ery times. For more heavily loaded systems, an active pullup such as that found in the DS2480B may be required.
Capacitance on the IO pin could be 800pF when power is first applied. If a 5kΩ resistor is used to pull up the IO line to
V_PUP, 5µs after power has been applied the parasite capacitance will not affect normal communications.
Guaranteed by design, simulation only. Not production tested.
Input load is to ground.
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