Xtrinsic Pressure Sensors - Capabilities and Applications

Seyed Paransun, Vice President and General Manager, Sensor and Actuator Solutions Division at Freescale Semiconductor, Inc., talks to AZoSensors about Xtrinsic Pressure Sensors.

Can you explain how Freescale’s MPXHZ9000 pressure sensors work?

The MPXHZ9000 is an Xtrinsic barometric pressure sensor.  The device is used to measure the atmospheric air pressure. Atmospheric air pressure is a necessary data input for fuel injection systems to achieve optimal engine performance and low emissions.

The MXPHZ9000 Xtrinsic pressure sensor is a system-in-package (SiP). The super small outline package (SSOP) contains two die. One MEMS pressure sensor and one digital signal processing IC. The MEMS pressure sensor is based on a piezo-resistive (PRT) Wheatstone bridge implemented on a thin deformable diaphragm realised with a deep reactive ion etching (DRIE) process.

What are the advantages to this line of pressure sensors?

The MPXHZ9000 Xtrinsic pressure sensors are essentially a replacement for an aging line of products. As technology becomes obsolete after several years of service and production, it is necessary to develop new generations of devices based on the latest most efficient technologies in terms of wafer processing, trimming, and testing of the devices.  This is also an economic imperative.

As such, the MPXH9000 Xtrinsic pressure sensors are our newest line of automotive barometric sensors using a DRIE process to etch a diaphragm and a digital signal processing ASIC allowing the digital trimming of the device, improved testing, and additional diagnostic function. The previous generation was using a wet KOH etching and an analog signal processing chain. The trimming of the device was done with a laser. Such techniques are no longer used for high volume production.

For our customers, the main advantage is the guarantee of large volume supply at competitive prices from a proven automotive sensor supplier. The MPXHZ9000 Xtrinsic pressure sensors will be used on millions of automotive applications around the world for the next 10 to 15 years.

What type of automotive engines does this type of pressure sensor best suit?

The typical application for such a pressure sensor is atmospheric pressure measurement for diesel engine management. Unlike a gasoline engine, diesel engines are always running with an excess of air. However, at high altitude, the air density is lower for efficiently running the engine. This information is communicated by the sensor to the diesel ECU, which automatically reduces the amount of diesel injected in the cylinder.  This is to prevent the emission of heavy black carbon fumes.

The other typical application is the measurement of gasoline engine intake manifold air pressure. This information together with the air temperature is used to calculate the proper air/fuel ratio going into the cylinder.  Such sensors are used on all fuel injected cars (close to 100% nowadays) and can be also found on fuel injected motorcycles or other small engines.

These types of sensors are also used on liquefied petroleum gas (LPG) engines.

Can you describe the main application areas for this sensor technology?

The main application area for this sensor technology is atmospheric pressure measurement for diesel and gasoline engines. However, the same sensor technology is also used for altimeter sensors in GPS, and to measure the pressure change in a vehicle door during a side impact (crash sensor).

How will these sensors help with pollution control?

The sensor provides the atmospheric pressure information to the engine control ECU. This information is used to calculate the right amount of fuel that needs to be injected in the cylinder. Atmospheric pressure is changing with weather conditions and with altitude. Without the atmospheric pressure information, the engines would run poorly at high altitudes and generate too much black carbon fumes and toxic emissions.

How do these pressure sensors compare to similar sensor technology on the market?

The vast majority of barometric pressure sensors on the market are produced using a MEMS process. The principle is to create a diaphragm that responds to applied pressure. There are different techniques used to measure the change of the diaphragm.  Freescale is using a piezo resistive Wheatstone bridge, a proven accurate and reliable technique.

What are the distinct features to this family of pressure sensors and how does this benefit their application?

One of the features of this new family of pressure sensors is to be pin-to-pin compatible in terms of form and function with the previous generation. This eliminates any board redesign for our customers – the new sensor can be used as a direct drop-in replacement.

The device has some other unique distinctive features. The clipping levels (low and high pressure) can be factory-programmed to suit specific customer needs in terms of diagnostic. For the same diagnostic reason, the device includes an open ground diagnostic feature.

In terms of robustness, the sensing element is protected by specific silicone gel, making the device resistant to high humidity and common automotive media for extended product life. In terms of packaging, the device is available with our without a porting option.  The porting option enables tube attachment for remote sensing applications.

Are there still functional elements to this line of pressure sensors that need to be modified to help improve the efficiency of this novel technology?

We are continuously looking at improvement in terms of accuracy, reliability, and production costs. The MPXHZ9000 Xtrinsic pressure sensor is currently state-of-the-art technology and no immediate improvement is planned or needed.

How is this technology evolving?

The challenge in MEMS technology is to make smaller, more accurate, and cheaper devices to expand the application of MEMS products to broader markets.  As such, we see continuous improvement in MEMS design and process technology, as well as higher integration towards a system solution.  

About Seyed Paransun

Seyed Paransun is the Vice President and General Manager, Sensor and Actuator Solutions Division, Freescale Semiconductor, Inc. Since May 2011, Seyed Paransun is the Vice President and General Manager of the Sensor and Actuator Solutions Division for Freescale Semiconductor, Inc. He came to Freescale with more than 25-year experience within the semiconductor and electronics industries. Throughout those years, he gained deep knowledge of critical market drivers and key players in each segment.  

Prior to Freescale, Seyed was the Senior Vice President and General Manager of the Test Business Unit at Amkor Technology.  In this leadership role, he oversaw three technology development centers in the U.S. and Asia.  He was also responsible for technical marketing, sales, supplier management, development, and the aggregate P&L of seven facilities globally. Among his notable accomplishments at Amkor was the development and implementation of a cost-reduction strategy, which resulted in a substantial revenue and profit growth for the company.  

Seyed’s successful career includes a 16-year tenure with National Semiconductor, where he held several leadership positions. Seyed holds a Master of Business Administration degree from San Jose University, as well as a Master of Science degree in Electrical Engineering and a Bachelor of Science degree in Electrical Engineering from the University of Utah. His work has been featured in Electronics Letters and Test & Measurement World Magazine.