Allegro Debuts Sensor Interface IC for Resistive Bridge Pressure Sensors

The A17700 is designed to deliver precise pressure information with low delay time over PWM, SENT or analog outputs. To survive in the tough automotive environment, the device is qualified to AEC-Q100 Grade 0, and adaptable compensation algorithms assure accuracy even in the presence of temperature and sensing bridge variation.

 

The A17700. Image courtesy of Allegro.

 

Allegro estimates that the highly integrated interface sensor will require as many as 30% fewer external components than will competing devices. The smaller component count will enable a smaller footprint for the sensing solution, and thereby engendering a more cost-efficient system design. 

 

Flexible Compensation

Highly accurate pressure sensor readings are obtained by first amplifying and offsetting the sensing media’s input signal to the A17700’s input. Then, flexible polynomial compensation of pressure and temperatures is applied. 

Allegro offers software support in the form of a graphical user interface and programmer libraries to designers. This enables easy use of this flexible algorithm and faster time to project completion for engineers.

As described by Haeyoung Choi, Product Manager for Sensor Interface ICs at Allegro, “The A17700 allows system designers to easily select the optimal algorithm and I/O options that best fit their system requirements, balancing accuracy and end-of-line test times, thereby optimizing the system cost” 

 

Fast Responses

The A17700 offers an input to output chip delay of only 100μs, and there is no output resolution loss. This feature allows for quicker output sampling, which in turn allows undesired membrane oscillations to be filtered by the system. The IC can also implement Fast SENT, which enables messaging at a rate six times faster than possible with regular SENT.

 

Circuit Description

On receiving the sensor in its Wheatstone bridge configuration, the A17700 amplifies and then converts the analog input to digital, and applies a low-pass filter.  Digital signal processing functions assure an accurate and linear output. 

The A17700 interfacing with a transducer. Image courtesy of Allegro.

 

A Manchester programming interface for configurations is also available. It includes onboard EEPROM technology capable of supporting up to 100 read/write cycles for programming of calibration parameters. The EEPROM memory can also to offer traceability throughout the IC’s lifetime 

 

Diagnostics

The IC features a system of integrated diagnostics that will benefit designers facing safety compliance requirements. Internal circuitry changes or temporary faults caused by environmental conditions can be flagged. These conditions include detection of:

 

Broken wires

• Under-voltage and over-voltage conditions
• Under-temperature and over-temperature detection 

The reporting or these statuses can be disabled by designers depending on their needs. 

 

Versions

• The A17700LESBTR-AO offers analog output
• The A17700LESBTR-DO features SENT/PWM output

 

Applications

The A17700 will find application in EVs and hybrids as well as in purely gas-powered vehicles. It can be configured to work with resistive bridge pressure sensors in applications such as:

• Gasoline direct injection (GDI)
• Dynamic brake systems (DBS)
• Automatic transmission oil management. 
• Brake boosters
• HVAC

 

Physical Considerations

• The unit operates over a -40 to 150℃ temperature range
• The device is available in a 4 by 4 mm QFN package with wettable flanks for easier testing 

 

Regulatory and Safety Concerns

• EMC performance rated at 4kV human body model (HBM)