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
PACKAGE
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.
