DS1922L ...........................................................-40°C to +85°C
DS1922T ............................................................0°C to +125°C
*Storage
or operation above +50°C significantly reduces battery life.
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.
Junction Temperature ......................................................+150°C
Storage Temperature Range*
DS1922L..........................................................-40°C to +85°C*
DS1922T ...........................................................0°C to +125°C*
Electrical Characteristics
(V
PUP
= +3.0V to +5.25V.)
PARAMETER
Operating Temperature
IO PIN: GENERAL DATA
1-Wire Pullup Resistance
Input Capacitance
Input Load Current
High-to-Low Switching Threshold
Input Low Voltage
Low-to-High Switching Threshold
Switching Hysteresis
Output Low Voltage
R
PUP
C
IO
I
L
V
TL
V
IL
V
TH
V
HY
V
OL
(Notes 2, 3)
(Note 4)
IO pin at V
PUP
(Notes 5, 6)
(Notes 2, 7)
(Notes 5, 8)
(Note 9)
At 4mA (Note 10)
Standard speed, R
PUP
= 2.2k
Recovery Time (Note 2)
t
REC
Overdrive speed, R
PUP
= 2.2k
Overdrive speed, directly prior to reset
pulse; R
PUP
= 2.2k
(Note 11)
Standard speed
Time-Slot Duration (Note 2)
t
SLOT
Overdrive speed, V
PUP
> 4.5V
Overdrive speed (Note 12)
IO PIN: 1-Wire RESET, PRESENCE-DETECT CYCLE
Standard speed, V
PUP
> 4.5V
Reset Low Time (Note 2)
t
RSTL
Standard speed (Note 12)
Overdrive speed, V
PUP
> 4.5V
Overdrive speed (Note 12)
Standard speed, V
PUP
> 4.5V
Standard speed (Note 12)
Overdrive speed (Note 12)
Presence-Detect Fall Time
(Note 13)
t
FPD
Standard speed, V
PUP
> 4.5V
Standard speed
Overdrive speed
480
690
48
70
15
15
2
1.5
1.5
0.15
720
720
80
80
60
63.5
7
5
8
1
μs
μs
μs
5
2
5
0.6
65
8
9.5
μs
2.0
μs
μs
0.7
0.09
0.4
100
6
2.2
800
10
3.2
0.3
3.4
N/A
0.4
k
pF
μA
V
V
V
V
V
SYMBOL
T
A
CONDITIONS
DS1922L (Note 1)
DS1922T (Note 1)
MIN
-40
0
TYP
MAX
+85
+125
UNITS
°C
Rising-Edge Hold-Off Time
t
REH
Presence-Detect High Time
t
PDH
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Maxim Integrated | 2
DS1922L/DS1922T
iButton Temperature Loggers
with 8KB Datalog Memory
Electrical Characteristics (continued)
(V
PUP
= +3.0V to +5.25V.)
PARAMETER
SYMBOL
CONDITIONS
Standard speed, V
PUP
> 4.5V
Standard speed (Note 12)
Overdrive speed, V
PUP
> 4.5V (Note 12)
Overdrive speed (Note 12)
Standard speed, V
PUP
> 4.5V
t
MSP
Standard speed
Overdrive speed
IO PIN: 1-Wire WRITE
Standard speed
Write-Zero Low Time
(Notes 2, 14)
Write-One Low Time
(Notes 2, 14)
IO PIN: 1-Wire READ
Read Low Time
(Notes 2, 15)
Read Sample Time
(Notes 2, 15)
REAL-TIME CLOCK
Accuracy
Frequency Deviation
TEMPERATURE CONVERTER
Conversion Time
(Note 16)
Thermal Response Time
Constant (Note 17)
Conversion Error Without
Software Correction
Conversion Error with Software
Correction
t
CONV
RESP
MIN
60
60
7
7
65
71.5
8
60
6
7.5
5
1
5
1
t
RL
+
t
RL
+
TYP
MAX
240
287
24
28
75
75
9
120
12
12
15
1.95
15 -
1.95 -
15
1.95
UNITS
Presence-Detect Low Time
t
PDL
μs
Presence-Detect Sample Time
(Note 2)
μs
t
W0L
Overdrive Speed, V
PUP
> 4.5V (Note 12)
Overdrive speed (Note 12)
Standard speed
Overdrive speed
Standard speed
Overdrive speed
Standard speed
Overdrive speed
μs
t
W1L
μs
t
RL
t
MSR
μs
μs
See RTC Accuracy
graphs
-40°C to +85°C
F
min/
month
PPM
-300
-600
30
240
130
+60
+60
75
600
0°C to +125°C
8-bit mode
16-bit mode (11 bits)
Can package
(Notes 18, 19)
(Notes 19, 20)
ms
s
°C
°C
See Temperature
Accuracy graphs
See Temperature
Accuracy graphs
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
Note 6:
Guaranteed by design, not production tested to -40°C or +125°C.
System requirement.
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 recovery times. For
more heavily loaded systems, an active pullup such as that found in the DS2480B may be required.
Capacitance on the data pin could be 800pF when V
PUP
is first applied. If a 2.2kΩ resistor is used to pull up the data line,
2.5µs after V
PUP
has been applied, the parasite capacitance does not affect normal communications.
V
TL
and V
TH
are functions of the internal supply voltage, which is a function of V
PUP
and the 1-Wire recovery times. The
V
TH
and V
TL
maximum specifications are valid at V
PUP
= 5.25V. In any case, V
TL
< V
TH
< V
PUP
.
Voltage below which, during a falling edge on IO, a logic 0 is detected.
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Maxim Integrated | 3
DS1922L/DS1922T
iButton Temperature Loggers
with 8KB Datalog Memory
Electrical Characteristics (continued)
(V
PUP
= +3.0V to +5.25V.)
Note 7:
Note 8:
Note 9:
Note 10:
Note 11:
Note 12:
Note 13:
Note 14:
Note 15:
Note 16:
Note 17:
Note 18:
Note 19:
The voltage on IO must be less than or equal to V
ILMAX
whenever the master drives the line low.
Voltage above which, during a rising edge on IO, a logic 1 is detected.
After V
TH
is crossed during a rising edge on IO, the voltage on IO must drop by V
HY
to be detected as logic 0.
The I-V characteristic is linear for voltages less than 1V.
The earliest recognition of a negative edge is possible at t
REH
after V
TH
has been previously reached.
Numbers in
bold
are
not
in compliance with the published iButton device standards. See the
Comparison Table.
Interval during the negative edge on IO at the beginning of a presence-detect pulse between the time at which the voltage
is 90% of V
PUP
and the time at which the voltage is 10% of V
PUP
.
ε
in Figure 13 represents the time required for the pullup circuitry to pull the voltage on IO up from V
IL
to V
TH
. The actual
maximum duration for the master to pull the line low is t
W1LMAX
+ t
F
-
ε
and t
W0LMAX
+ t
F
-
ε,
respectively.
δ
in Figure 13 represents the time required for the pullup circuitry to pull the voltage on IO up from V
IL
to the input-high
threshold of the bus master. The actual maximum duration for the master to pull the line low is t
RLMAX
+ t
F
.
To conserve battery power, use 8-bit temperature logging whenever possible.
This number was derived from a test conducted by Cemagref in Antony, France, in July 2000:
www.cemagref.fr/English/index.htm Test Report No. E42.
Includes +0.1/-0.2°C calibration chamber measurement uncertainty.
Warning:
Maxim data-logger products are 100% tested and calibrated at time of manufacture to ensure that they meet all
data sheet parameters, including temperature accuracy. As with any sensor-based product, user shall be responsible for
occasionally rechecking the temperature accuracy of the product to ensure it is still operating properly. Furthermore, as
with all products of this type, when deployed in the field and subjected to handling, harsh environments, or other hazards/
use conditions, there may be some extremely small but nonzero logger failure rate. In applications where the failure of any
logger is a concern, user shall assure that redundant (or other primary) methods of testing and determining the handling
methods, quality, and fitness of the articles and products are implemented to further mitigate any risk.
Assumes using calibration memory with calibration equations for error compensation. Includes +0.1/-0.2°C calibration
chamber measurement uncertainty. Guaranteed by design.
Note 20:
Comparison Table
LEGACY VALUES
PARAMETER
STANDARD SPEED
(μs)
MIN
t
SLOT
(including t
REC
)
t
RSTL
t
PDH
t
PDL
t
W0L
61
480
15
60
60
MAX
(undefined)
(undefined)
60
240
120
OVERDRIVE SPEED
(μs)
MIN
7
48
2
8
6
MAX
(undefined)
80
6
24
16
DS1922L/DS1922T VALUES
STANDARD SPEED
(μs)
MIN
65
*
OVERDRIVE SPEED
(μs)
MIN
9.5
70
2
7
7.5
MAX
(undefined)
80
7
28
12
MAX
(undefined)
720
63.5
287
120
690
15
60
60
*Intentional
change; longer recovery time requirement due to modified 1-Wire front-end.
Note:
Numbers in
bold
are
not
in compliance with the published iButton device standards.
iButton Can Physical Specification
SIZE
WEIGHT
See the
Package Information
section.
Ca. 3.3 grams
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Maxim Integrated | 4
DS1922L/DS1922T
iButton Temperature Loggers
with 8KB Datalog Memory
DS1922L Minimum Product Lifetime vs. Temperature, Slow Sampling
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