DS75LX
Digital Thermometer and Thermostat
with Extended Addressing
www.maxim-ic.com
GENERAL DESCRIPTION
This low-voltage (1.7V to 3.7V) digital thermometer
and thermostat provides 9, 10, 11, or 12-bit digital
temperature readings over a -55°C to +125°C range
with
±2°C
accuracy over a -25°C to +100°C range. At
power-up, the DS75LX defaults to 9-bit resolution for
software compatibility with the LM75. Communication
with the DS75LX is achieved through a simple 2-wire
serial interface. Three tri-state address pins allow up
to 27 DS75LX devices to operate on the same 2-wire
bus, which greatly simplifies distributed temperature-
sensing applications.
The DS75LX thermostat has a dedicated open-drain
output (O.S.) and programmable fault tolerance,
which allow the user to define the number of
consecutive error conditions that must occur before
O.S. is activated. There are two thermostatic
operating modes that control thermostat operation
based on user-defined trip-points (T
OS
and T
HYST
).
FEATURES
1.7V to 3.7V Operating Range
Tri-State Address Pins Allow Up to 27 Unique
Bus Addresses
Temperature Measurements Require No
External Components
Measures Temperatures from -55°C to +125°C
(-67°F to +257°F)
±2°C
Accuracy from -25°C to +100°C
Thermometer Resolution Is User-
Configurable from 9 (Default) to 12 Bits (0.5°C
to 0.0625°C Resolution)
9-Bit Conversion Time is 25ms (max)
Thermostatic Settings are User-Definable
Data is Read/Written Through 2-Wire Serial
Interface (SDA and SCL Pins)
Data Lines Filtered Internally for Noise
Immunity (50ns Deglitch)
Bus Timeout Feature Prevents Lockup
Problems on 2-Wire Interface
Multidrop Capability Simplifies Distributed
Temperature-Sensing Applications
Pin/Software Compatible with the LM75
Available in 8-Pin
μSOP
(μMAX
®
) and SO
Packages
APPLICATIONS
Any Thermally Sensitive System
Cellular Base Stations
Telecom Switches and Routers
Servers
PIN CONFIGURATIONS
SDA
SCL
O.S.
GND
1
8
ORDERING INFORMATION
PART
TEMP RANGE
-55°C to +125°C
-55°C to +125°C
-55°C to +125°C
-55°C to +125°C
V
DD
A
0
DS75LXS+
DS75LXS+T&R
2
3
4
7
6
5
A
1
A
2
DS75LXU+
DS75LXU+T&R
SO (150 mils)
SDA
SCL
O.S.
GND
1
8
PIN
PACKAGE
8 SO
(150 mils)
8 SO
(150 mils),
2500 Piece
8 µSOP
(µMAX)
8 µSOP
(µMAX),
3000 Piece
DS75
LX
DS75
LX
V
DD
A
0
A
1
A
2
+ Denotes lead-free package.
T&R denotes tape-and-reel.
Note:
A “+” symbol will also be marked on the package near the
pin 1 indicator.
µMAX is a registered trademark of Maxim Integrated Products, Inc.
2
3
4
7
6
5
μSOP/μMAX
1 of 13
050307
DS1386/DS1386P
ABSOLUTE MAXIMUM RATINGS
Voltage Range on V
DD
, Relative to Ground
Voltage Range on Any Other Pin, Relative to Ground
Operating Temperature Range
Storage Temperature Range
Soldering Temperature
-0.3V to +4.0V
-0.3V to +6.0V
-55°C to +125°C
-55°C to +125°C
See IPC/JEDEC J-STD-020
These are stress ratings 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 reliability.
The Dallas Semiconductor DS75LX is built to the highest quality standards and manufactured for long-term
reliability. All Dallas Semiconductor devices are made using the same quality materials and manufacturing
methods. However, the DS75LX is not exposed to environmental stresses, such as burn-in, that some industrial
applications require. For specific reliability information on this product, contact the factory in Dallas at (972) 371-
4448.
DC ELECTRICAL CHARACTERISTICS
(1.7V
≤
V
DD
≤
3.7V, T
A
= -55°C to +125°C.)
PARAMETER
SYMBOL
Supply Voltage
V
DD
Thermometer Error
T
ERR
(Note 2)
Input Logic-High SDA,
V
IH
SCL
Input Logic-Low SDA,
V
IL
SCL
V
OL1
SDA Output Logic-Low
Voltage (Note 3)
V
OL2
O.S. Saturation Voltage
Input Current SDA, SCL
I/O Capacitance
Address Input Sink
Current
Address Input Source
Current
Address Voltage High
Address Voltage Low
Standby Current
Active Current
(Notes 1, 4, 5)
V
OL
C
I/O
I
LAH
I
LAL
V
AH
V
AL
I
DD1
I
DD
A0, A1, or A2 tied to V
DD
(Notes 4, 5)
A0, A1, or A2 tied to GND
(Notes 4, 5)
(Note 6)
(Note 6)
(Notes 4, 5)
Active temp conversions
Communication only
0.2
0.2
V
DD
- .04
V
SS
+ .04
13
1000
100
CONDITIONS
(Note 1)
-25°C to +100°C
-55°C to +125°C
(Note 3)
MIN
1.7
MAX
3.7
±2.0
±3.0
V
DD
+ 0.3
0.3 x V
DD
0.4
0.6
0.8
-10
+10
10
3.5
3.5
UNITS
V
°C
V
V
V
V
µA
pF
µA
µA
V
V
µA
µA
0.7 x V
DD
V
SS
- 0.3
3mA sink current
6mA sink current
4mA sink current
(Notes 2, 3)
0.4 < V
I/O
< 0.9V
DD
0
0
AC ELECTRICAL CHARACTERISTICS
(1.7V
≤
V
DD
≤
3.7V, T
A
= -55°C to +125°C.)
PARAMETER
SYMBOL
Resolution
CONDITIONS
MIN
9
TYP
MAX
12
25
50
ms
11-bit conversions
12-bit conversions
100
200
UNITS
Bits
9-bit conversions
Temperature Conversion
Time
10-bit conversions
t
CONVT
2 of 13
SCL Frequency
f
SCL
DS75LX: Digital Thermometer and Thermostat with Extended Addressing
400
kHz
AC ELECTRICAL CHARACTERISTICS (continued)
(1.7V
≤
V
DD
≤
3.7V, T
A
= -55°C to +125°C.)
PARAMETER
SYMBOL
Bus Free Time Between
t
BUF
a STOP and START
Condition
START and Repeated
t
HD:STA
START Hold Time from
Falling SCL
Low Period of SCL
t
LOW
High Period of SCL
t
HIGH
Repeated START
t
SU:STA
Condition Setup Time to
Rising SCL
Data-Out Hold Time from
t
HD:DAT
Falling SCL
Data-In Setup Time to
t
SU:DAT
Rising SCL
Rise Time of SDA and
t
R
SCL (Receive)
Fall Time of SDA and
t
F
SCL (Receive)
Spike Suppression
t
SS
Filter Time (Deglitch
Filter)
STOP Setup Time to
t
SU:STO
Rising SCL
Capacitive Load for Each
C
B
Bus Line
Input Capacitance
C
I
Serial Interface Reset
t
TIMEOUT
Time
B
CONDITIONS
(Note 7)
MIN
1.3
TYP
MAX
UNITS
µs
(Notes 7, 8)
(Note 7)
(Note 7)
(Note 7)
(Notes 7, 9)
(Note 7)
(Notes 7, 10)
(Notes 7, 10)
600
1.3
0.6
600
0
100
20 +
0.1C
B
20 +
0.1C
B
B
B
ns
µs
µs
ns
0.9
µs
ns
300
300
50
ns
ns
ns
ns
400
5
pF
pF
325
ms
0
(Note 7)
600
SDA time low
(Notes 11, 12)
75
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
Note 6:
Note 7:
Note 8:
Note 9:
Note 10:
Note 11:
Note 12:
V
DD
must be decoupled with a high-quality 0.1µF bypass capacitor. X5R or X7R ceramic surface-mount capacitors are
recommended.
Internal heating caused by O.S. loading causes the DS75LX to read approximately 0.5°C higher if O.S. is sinking the max
rated current.
All voltages are referenced to ground.
I
DD
specified with O.S. pin open and A0–A2 pins grounded.
I
DD
and address leakage specified with V
DD
at 3.0V and SDA, SCL = 3.0V at 0°C to +70°C.
Address pins A0, A1, A2 are directly connected to V
DD
, V
SS
, or floating with less than 50pF capacitive load.
See the timing diagram (Figure 1). All timing is referenced to 0.9 x V
DD
and 0.1 x V
DD
.
After this period, the first clock pulse is generated.
The DS75LX provides an internal hold time of at least 75ns on the SDA signal to bridge the undefined region of SCL's falling
edge.
For example, if C
B
= 300pF, then t
R
[min] = t
F
[min] = 50ns.
This timeout applies only when the DS75LX is holding SDA low. Other devices can hold SDA low indefinitely and the DS75LX
will not reset.
The DS75LX is available with timeout feature disabled upon special order. Contact Factory.
PIN DESCRIPTION
PIN
1
2
3
4
5
6
7
8
NAME
SDA
SCL
O.S.
GND
A
2
A
1
A
0
V
DD
FUNCTION
Data Input/Output for 2-Wire Serial Communication Port (Open Drain)
Clock Input for 2-Wire Serial Communication Port
Thermostat Output Open Drain
Ground
Address Input
Address Input
Address Input
Supply Voltage. +1.7V to +3.7V supply pin. V
DD
must have an external bypass
capacitor to GND. 0.1µF X5R or X7R ceramic SMT caps recommended.
3 of 13
DS75LX: Digital Thermometer and Thermostat with Extended Addressing
BLOCK DIAGRAM
PRECISION
REFERENCE
OVERSAMPLING
MODULATOR
DIGITAL
DECIMATOR
V
DD
CONFIGURATION
REGISTER
ADDRESS
AND
I/O CONTROL
SCL
SDA
A
0
A
1
A
2
TEMPERATURE
REGISTER
O.S.
T
OS
AND T
HYST
REGISTERS
THERMOSTAT
COMPARATOR
R
P
GND
Figure 1. Timing Diagram
4 of 13
DS75LX: Digital Thermometer and Thermostat with Extended Addressing
OPERATION—MEASURING TEMPERATURE
The DS75LX measures temperature using a bandgap temperature-sensing architecture. An on-board delta-sigma
analog-to-digital converter (ADC) converts the measured temperature to a digital value that is calibrated in degrees
celsius; for Fahrenheit applications a lookup table or conversion routine must be used. The DS75LX is factory-
calibrated and requires no external components to measure temperature.
At power-up the DS75LX immediately begins measuring and converting its own temperature to a digital value. The
resolution of the digital output data is user-configurable to 9, 10, 11, or 12 bits, corresponding to temperature
increments of 0.5°C, 0.25°C, 0.125°C, and 0.0625°C, respectively, with 9-bit default resolution at power-up. The
resolution is controlled via the R0 and R1 bits in the configuration register as explained in the
Configuration
Register
section of this data sheet. Note that the conversion time doubles for each additional bit of resolution.
After each temperature measurement and analog-to-digital conversion, the DS75LX stores the temperature as a
16-bit two’s complement number in the 2-byte temperature register (see Figure 2). The sign bit (S) indicates if the
temperature is positive or negative: for positive numbers S = 0 and for negative numbers S = 1. The most recently
converted digital measurement can be read from the temperature register at any time. Since temperature
conversions are performed in the background, reading the temperature register does not affect the operation in
progress.
Bits 3 through 0 of the temperature register are hardwired to 0. When the DS75LX is configured for 12-bit
resolution, the 12 MSbs (bits 15 through 4) of the temperature register contain temperature data. For 11-bit
resolution, the 11 MSbs (bits 15 through 5) of the temperature register contain data, and bit 4 reads out as 0.
Likewise, for 10-bit resolution, the 10 MSbs (bits 15 through 6) contain data, and for 9-bit the 9 MSbs (bits 15
through 7) contain data, and all unused LSbs will contain 0s. Table 1 gives examples of 12-bit resolution digital
output data and the corresponding temperatures.
Figure 2. Temperature, T
H
, and T
L
Register Format
MS Byte
bit 15
S
bit 7
2
-1
bit 14
2
6
bit 6
2
-2
bit 13
2
5
bit 5
2
-3
bit 12
2
4
bit 4
2
-4
bit 11
2
3
bit 3
0
bit 10
2
2
bit 2
0
bit 9
2
1
bit 1
0
bit 8
2
0
bit 0
0
LS Byte
Table 1. 12-Bit Resolution Temperature/Data Relationship
TEMPERATURE (°C)
+125
+25.0625
+10.125
+0.5
0
-0.5
-10.125
-25.0625
-55
DIGITAL OUTPUT
(BINARY)
0111 1101 0000 0000
0001 1001 0001 0000
0000 1010 0010 0000
0000 0000 1000 0000
0000 0000 0000 0000
1111 1111 1000 0000
1111 0101 1110 0000
1110 0110 1111 0000
1100 1001 0000 0000
DIGITAL OUTPUT
(HEX)
7D00h
1910h
0A20h
0080h
0000h
FF80h
F5E0h
E6F0h
C900h
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