LM75A
Digital temperature sensor and
thermal Watchdog
Product data sheet
Supersedes data of 2001 Jul 16
2004 Oct 05
INTEGRATED CIRCUITS
Philips Semiconductors Product data sheet
LM75ADigital temperature sensor and thermal Watchdog
2
2004 Oct 05
GENERAL DESCRIPTION
The LM75A is a temperature-to-digital converter using an on-chip
band-gap temperature sensor and Sigma-delta A-to-D conversion
technique. The device is also a thermal detector providing an
over-temp detection output. The LM75A contains a number of data
registers: Configuration register (Conf) to store the device settings
such as device operation mode, OS operation mode, OS polarity
and OS fault queue as described in the functional description
section; temperature register (Temp) to store the digital temp
reading, and set-point registers (Tos & Thyst) to store programmable
overtemp shutdown and hysteresis limits, that can be communicated
by a controller via the 2-wire serial I
2
C-bus interface. The device
also includes an open-drain output (OS) which becomes active
when the temperature exceeds the programmed limits. There are
three selectable logic address pins so that eight devices can be
connected on the same bus without address conflict.
The LM75A can be configured for different operation conditions. It
can be set in normal mode to periodically monitor the ambient
temperature, or in shutdown mode to minimize power consumption.
The OS output operates in either of two selectable modes: OS
comparator mode and OS interrupt mode. Its active state can be
selected as either HIGH or LOW. The fault queue that defines the
number of consecutive faults in order to activate the OS output is
programmable as well as the set-point limits.
The temperature register always stores an 11-bit 2’s complement
data giving a temperature resolution of 0.125 °C. This high
temperature resolution is particularly useful in applications of
measuring precisely the thermal drift or runaway.
The device is powered-up in normal operation mode with the OS in
comparator mode, temperature threshold of 80 °C and hysteresis of
75 °C, so that it can be used as a stand-alone thermostat with those
pre-defined temperature set points.
FEATURES
•Pin-for-pin replacement for industry standard LM75 and offers
improved temperature resolution of 0.125 °C and specification of
a single part over power supply range from 2.8 V to 5.5 V.
•Small 8-pin package types: SO8 and TSSOP8
•I
2
C-bus interface with up to 8 devices on the same bus
•Power supply range from 2.8 V to 5.5 V
•Temperatures range from –55 °C to +125 °C
•11-bit ADC that offers a temperature resolution of 0.125 °C
•Temperature accuracy of:
±2 °C from –25 °C to +100 °C
±3 °C from –55 °C to +125 °C
•Programmable temperature threshold and hysteresis set points
•Supply current of 3.5 µA in shut-down mode for power
conservation
•Stand-alone operation as thermostat at power-up.
•ESD protection exceeds 2000 V HBM per JESD22-A114,
200 V MM per JESD22-A115 and 1000 V CDM per JESD22-C101
•Latch-up testing is done to JESDEC Standard JESD78 which
exceeds 100 mA
APPLICATIONS
•System thermal management
•Personal computers
•Electronics equipment
•Industrial controllers.
ORDERING INFORMATION
T
amb
= –55
°
C to +125
°
C
TYPE NUMBER
Topside mark
PACKAGE
TYPE
NUMBER
Topside
mark
NAME DESCRIPTION VERSION
LM75AD LM75A SO8 plastic small outline package; 8 leads; body width 3.9 mm SOT96-1
LM75ADP LM75A TSSOP8 plastic thin shrink small outline package; 8 leads; body width 3 mm SOT505-1
WATCHDOG is a trademark of National Semiconductor Corporation.
Philips Semiconductors Product data sheet
LM75ADigital temperature sensor and thermal Watchdog
2004 Oct 05
3
PINNING
Pin configuration
1
2
3
45
6
7
8SDA
SCL
OS
GND
V
CC
A0
A1
A2
SL01388
Figure 1. SO8 and TSSOP8 pin configurations.
Pin description
PIN SYMBOL DESCRIPTION
1 SDA Digital I/O. I
2
C serial bi-directional data line.
Open Drain.
2 SCL Digital input. I
2
C serial clock input.
3 OS Overtemp Shutdown output. Open Drain.
4 GND Ground. To be connected to the system
ground.
5 A2 Digital input. User-defined address bit2.
6 A1 Digital input. User-defined address bit1.
7 A0 Digital input. User-defined address bit0.
8 V
CC
Power supply.
SIMPLIFIED BLOCK DIAGRAM
OS
A2 A1 A0 SCL
GND
BIAS
REFERENCE
OSC
POWER–ON
RESET
CONFIGURATION
REGISTER
SDA
11–BIT
SIGMA–DELTA
A–TO–D
CONVERTER
POINTER
REGISTER
COUNTER
TIMER
COMPARATOR
/ INTERRUPT
TEMPERATURE
REGISTER
TOS
REGISTER
THYST
REGISTER
LOGIC CONTROL AND INTERFACE
BAND–GAP
TEMP
SENSOR
V
CC
SL01389
LM75A
Figure 2. Simplified block diagram.
Philips Semiconductors Product data sheet
LM75ADigital temperature sensor and thermal Watchdog
2004 Oct 05
4
TYPICAL APPLICATION
8
2
SCL
1
SDA
3LM75A
OS
5
A2
6
A1
7
A0
4
GND
I
2
C-BUS
V
CC
POWER SUPPLY
BUS
PULL-UP
RESISTORS
DIGITAL LOGIC
0.1 µF
10 kΩ
V
CC
DETECTOR OR
INTERRUPT LINE
SL01390
10 kΩ10 kΩ
Figure 3. Typical application.
ABSOLUTE MAXIMUM RATINGS
1
SYMBOL
PARAMETER MIN. MAX. UNIT
V
CC
to GND –0.3 6.0 V
Voltage at input pins –0.3 6.0 V
Current at input pins –5.0 5.0 mA
OS output sink current – 10.0 mA
OS output voltage –0.3 6.0 V
ESD
Human Body Model – 2000 V
Machine Model – 200 V
T
stg
Storage temperature range –65 150 °C
T
j
Junction temperature – 150 °C
NOTE:
1. This is a stress rating only. Functional operation of the device as indicated in the operational section is not applied to this absolute maximum
rating. Stresses above those listed in ‘Absolute Maximum Ratings’ may cause permanent damage to the device and exposure to any of
these rating conditions for extended periods may affect device reliability.
OPERATING RATINGS
SYMBOL PARAMETER MIN. MAX. UNIT
V
CC
Supply voltage 2.8 5.5 V
T
amb
Operating ambient temperature range –55 125 °C
Philips Semiconductors Product data sheet
LM75ADigital temperature sensor and thermal Watchdog
2004 Oct 05
5
DC ELECTRICAL CHARACTERISTICS
V
CC
= 2.8 V to 5.5 V, T
amb
= –55 °C to +125 °C unless otherwise noted.
SYMBOL
PARAMETER CONDITIONS MIN. TYP.
1
MAX. UNIT
T
ACC
Temperature accuracy
T
amb
= –25 °C to +100 °C –2 – +2 °C
T
amb
= –55 °C to +125 °C –3 – +3 °C
T
RES
Temperature resolution 11-bit digital temp data – 0.125 – °C
T
CON
Temperature conversion Normal mode – 100 – ms
I
DD
Supply quiescent current
Normal mode: I
2
C inactive – 100 – µA
Normal mode: I
2
C active – – 1.0 mA
Shut–down mode – 3.5 – µA
V
IH
HIGH-level input voltage Digital pins (SCL, SDA, A2–A0) 0.7 × V
CC
– V
CC
+ 0.3 V
V
IL
LOW-level input voltage Digital pins –0.3 – 0.3 × V
CC
V
V
IHYS
Input voltage hysteresis
SCL and SDA pins – 300 – mV
A2–A0 pins – 150 – mV
I
IH
HIGH–level input current Digital pins; V
IN
= V
CC
–1.0 – 1.0 µA
I
IL
LOW-level input current Digital pins; V
IN
= 0 V –1.0 – 1.0 µA
V
OL
LOW-level output voltage
SDA and OS pins; I
OL
= 3 mA – – 0.4 V
I
OL
= 4 mA – – 0.8 V
I
LO
Output leakage current SDA and OS pins; V
OH
= V
CC
– – 10 µA
OSQ OS fault queue Programmable 1 – 6 Conv
2
Tos Overtemp shutdown Default value – 80 – °C
Thyst Hysteresis Default value – 75 – °C
C
IN
Input capacitance Digital pins – 20 – pF
NOTE:
1. Typical values are at V
CC
= 3.3 V and T
amb
= 25 °C.
2. Conv: device A-to-D conversion.
