Melexis Introduces Unique Relative Pressure Sensor IC

Melexis, a global microelectronics engineering company, has announced
the MLX90821 relative pressure sensor IC designed for measuring very low
pressures in automotive applications. Using the latest MEMS technology closely
integrated with an analog signal chain and digital signal processing, the
MLX90821 is a system-in-package IC solution for the reliable measurement of
fuel vapor pressure as low as 50 mbar and up to 700 mbar. This makes the
MLX90821 suitable for EVAP systems designed for internal combustion engine or
hybrid vehicles.

Implementing fuel pressure vapor detection using so-called
EVAP (evaporation) systems is increasingly important for automotive
manufacturers, as more regions introduce strict legislation which prohibits the
venting of fuel vapor to the atmosphere. As vapor builds up inside fuel tanks
and crank cases, the EVAP systems are designed to capture, store and
responsibly dispose of the vapor, preventing it from escaping into the air.
Pressure sensors that can operate at very low pressures, like the MLX90821, are
a crucial part of these systems, as they are able to detect even the smallest leaks
that can potentially appear at any point in the EVAP system.

“The MLX90821 is a relative pressure sensor that has the
range, reliability, stability and accuracy to cover EVAP systems for both
internal combustion and hybrid engines,” commented Laurent Otte, Pressure
Sensors Product Line Manager, Melexis. “This gives Tier 1 and module
manufacturers the ability to standardize on a single design for both types of
engine, using a sensor IC that is factory calibrated but can also be customized
for each individual application. Its robust, easy to seal packaging is
certified to operate between -40 ℃ and +150 ℃ and comes
with full PPAP support.”

Fuel vapor pressure measurement is even more complex in
hybrid vehicles, creating demand for more capable sensing solutions. Also, as
EVAP systems in both ICE (internal combustion engine) and hybrid vehicles may
feature several pressure sensor ICs, design flexibility and simplicity are
critical. While being small enough to be used in any size module, the high
level of integration provided through the system-in-package approach makes
designing with the MLX90821 extremely simple, providing what is essentially a
‘plug & play' approach. While both
analog and SENT outputs are provided, the DSP offers the ability to make full use
of the SENT interface's fast channel and slow channel, add diagnostic messaging
and apply custom calibration. The MLX90821 offers many automotive diagnostic
features, including clamping levels, broken track diagnostics and multiple
internal fault diagnostics.

The system-in-package approach uses a MEMS sensor
manufactured through back-side etching. This allows the sensing element to be
exposed to the vapor or other media while providing robust protection against
contaminants present in harsh environments such as fuel vapor systems. The CMOS
part of the system has been developed to deliver design flexibility, while the
entire sensor offers exceptionally high levels of EMC protection and immunity,
making it simple to design into EVAP systems for both ICE and hybrid vehicles.

Each sensor IC is calibrated during the final steps of
manufacture, with the pressure transfer curve and clamping levels stored in the
internal EEPROM. The measurement is provided through the ratiometric analog
output or as a SENT output, which may also contain temperature measurements. An
optional NTC temperature compensation feature makes use of an external NTC,
which may be required when the application also needs to record an accurate
temperature measurement of the media being monitored. Further configuration is
possible using software tools provided and supported by Melexis.