LM75BD Circuit Board Chips Digital temperature sensor and thermal
watchdog
1. General description
The LM75B is a temperature-to-digital converter using an on-chip
band gap temperature
sensor and Sigma-Delta A-to-D conversion technique with an
overtemperature detection
output.
The LM75B 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; temperature register (Temp) to store the
digital temp reading, and
set-point registers (Tos and Thyst) to store programmable
overtemperature shutdown and
hysteresis limits, that can be communicated by a controller via the
2-wire serial I2C-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 LM75B 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 or 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.
When the LM75B is accessed the conversion in process is not
interrupted
(i.e., the I2C-bus section is totally independent of the Sigma-Delta converter
section) and
accessing the LM75B continuously without waiting at least one
conversion time between
communications willnot prevent the device from updating the Temp
register with a new
conversion result.
The new conversion result will be available immediately after the
Temp register is updated.
The LM75B powers up in the 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.
2. Features
■ Pin-for-pin replacement for industry standard LM75 and LM75A 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
■ I2C-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
■ Frequency range 20 Hz to 400 kHz with bus fault time-out to
prevent hanging up the
bus
■ 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 1.0 µA in shutdown mode for power conservation
■ Stand-alone operation as thermostat at power-up
■ ESD protection exceeds 4500 V HBM per JESD22-A114, 450 V MM per
JESD22-A115 and 2000 V CDM per JESD22-C101
■ Latch-up testing is done to JEDEC Standard JESD78 which exceeds
100 mA
■ Small 8-pin package types: SO8, TSSOP8 and 3 mm × 2 mm XSON8U
3. Applications
■ System thermal management
■ Personal computers
■ Electronics equipment
■ Industrial controllers
