Band-Gap Sensor Creates Temperature-to-Digital IC
Using an on-chip band-gap temperature
sensor and a sigma-delta analogue-to-digital
conversion technique, NXP
Semiconductors’ LM75B provides
temperature-to-digital conversion with
over-temperature detection.
The LM75B contains a number of data registers
that store the device settings, a temperature
register to store the digital temperature reading,
and set-point registers to store programmable
over-temperature shutdown and hysteresis limits.
These registers can be set by a controller using a
two-wire serial I2C-bus interface. The
device also includes an open-drain
output, which activates when the
temperature exceeds programmed
limits.
The LM75B can be configured for
different operating conditions. It can
be set in normalmode to periodically
monitor the ambient temperature, or
operate in shutdownmode to
minimise power consumption. There
are three selectable logic-address
pins so that eight devices can be
connected on the same bus without
address conflict.
The temperature register stores 11-bit 2’s
complement data, giving a temperature resolution
of 0.125°C. This temperature resolution is
particularly useful for the precise measurement of
thermal drift.
When the LM75B is accessed the conversion
process is not interrupted and accessing the
LM75B continuously without waiting at least one
conversion period will not prevent the device from
updating the temperature register.
The output operates in either of two selectable
modes: comparator mode or interruptmode.
While in comparator mode, the LM75B powers-up
for standard operation, with a temperature
threshold of 80°C and hysteresis of 75°C. This
provides stand-alone operation as a thermostat
using pre-defined set points.
Previous Page
Previous Page