Project Code: APM-AUTO-SENSOR-2013
ADI Automotive Sensor and Sensor Interface Solution
Application Description
Automobiles must become increasingly greener to meet emerging legislation for improved fuel economy and reduced emissions. These requirements can
only be fulfilled by improving the efficiency of the traditional internal combustion engine, achieved through improvements in combustion, sensing, and
control, leading to the need for higher sensor and signal conditioning accuracy and integration. There are typically more than 100 sensors in a vehicle, and
sensors can typically be categorized into six functions, including pressure, current, capacitance, position, speed, and temperature sensors.
System Requirement and Design Challenge
Vehicle sensors are used across multiple applications in powertrain, chassis/safety and body systems. Improvements in fuel economy, emissions and vehicle
performance need to be improved simultaneously in power train systems. For sensors, this results in significant performance improvements and/or
features that are challenging to achieve in areas such as dynamic range, accuracy, diagnostics, and robustness (EMC, ESD, temperature, etc.).
Pressure Sensor
Many pressure sensors are required in high pressure and harsh environments to measure air or fluid pressures. Some power train examples include
in-cylinder, transmission oil, diesel common rail, GDI fuel, diesel particulate filter (DPF), and exhaust gas recirculation (EGR) pressure. Safety applications
include brake fluid and occupant detection weight or pressure. High pressure and harsh environment applications require that the sensor element
(capacitive or piezo-resistive) is separated from the signal conditioning IC. A piezo-resistive (strain gauge) solution, can, for example, measure pressure
ranges up to 2800 bar.
The strain gauge technology is based on a resistive bridge. Four strain gauges are attached to a diaphragm to form a diaphragm-type pressure transducer.
The output signal is as small as 10 mV. The system errors include mechanical output, thermal output, tolerance, and gauge factor errors. The total errors can
reach up to 100% FSR. Hence, the conditioning circuit must be highly accurate and have low drift. Multiple-variable compensations related to gain, offset,
temperature, and linearity are also required.
Pressure sensors are placed mainly in harsh environments. A typical operating temperature range is −40°C to +125°C and, in some cases, up to 150°C. The
sensors also require high EMC capability and diagnostic functions.
Current Sensor
To improve fuel economy and energy management, the position of the solenoid valves in the fuel injection system and automatic gear boxes must be precisely
controlled. In addition, electric motor current for power “on demand” must be monitored more accurately. High accuracy, a low offset (an offset needs <5 mV and
an offset drift needs <20 μV), a high bandwidth (some cases require up to 500 kHz), a wide common-mode voltage range (up to 65 V), and a wide operating
temperature range (up to 125°C) in a harsh environment comprise the typical design challenges.
Capacitance Sensor
Capacitance sensors have advantages such as their low system cost, different shape feasibilities, and low power consumption. They are typically applied
as proximity detectors in a keyless entry system, rain detectors, humidity sensors, and fuel level/quality sensors. Capacitance sensors are sensitive to
environmental changes and, thus, require a high resolution, accurate, adjustable common-mode capacitance, and EMI immunity.
Position and Speed Sensors
In EPS and BLDC/PMSM motor control applications, position/speed measurement requires a fast response, good accuracy (up to 0.1°), robustness, and low
drift. Diagnostic functions are also needed.
Temperature Sensor
Wide temperature ranges and high accuracies are required in some high temperature automotive applications such as transmission control. A typical temperature
range is −40°C to +150°C and, in some cases, up to 175°C. Further, an accuracy of ±2°C or ±1°C is required.
Solutions from Analog Devices, Inc.
With long term good relationships with worldwide leading automotive suppliers, plus the experience of high performance signal processing, high reliability, and
quality product development, Analog Devices (ADI) is the leader and is able to provide optimized solutions to meet these challenges.
automotive.analog.com
Automotive Sensor and Sensor Interface System Block
POWER TRAIN
LAMBDA SENSOR
TRANSMISSION TEMPERATURE
TEMPERATURE
SENSOR
ENGINE SPEED
SENSOR
BODY
ENGINE OIL PRESSURE
IN-CYLINDER PRESSURE
AIR CONDITION PRESSURE
STRAIN
GAGE
POWER
TRAIN
ECU
PRESSURE SENSE
SIGNAL CONDITION
RAIN DETECTION
CAPACITOR DIGITAL
CONVERTER
HUMIDITY SENSING
CAPACITOR DIGITAL
CONVERTER
PROXIMITY DETECTION
FOR KEYLESS ENTRY
CAPACITOR DIGITAL
CONVERTER
FUEL LEVEL AND QUALITY SENSING
CHASSIS SAFETY
ADI PARTICIPANTS
ECUS
SOLENOID
BODY
ECU
RF
CAPACITOR/IMPEDANCE
DIGITAL CONVERTER
CURRENT SENSE
WHEEL SPEED SENSOR
RESOLVER
RESOLVER DIGITAL
CONVERTER
STEERING ANGLE
RESOLVER
RESOLVER DIGITAL
CONVERTER
BRAKE PRESSURE
STRAIN
GAGE
PRESSURE SENSE
SIGNAL CONDITION
STEERING TORQUE
CURRENT SENSE
SHUNT
RESISTOR
CHASSIS
ECU
RESOLVER DIGITAL
CONVERTER
RESOLVER
Note: The signal chains above are representative of the system block diagram of an automotive sensor interface design. The technical requirements of the blocks vary, but the products
listed in
Pressure Sensor
ADI’s strain gauge signal condition ICs, the AD8556 and AD8557, can be used to measure strain gauge resistive bridges by combining digital correction
techniques. The AD8556 has internal EMI filters. The AD8556 and AD8557 both have low offset, low offset drift, and high CMRR. ADI’s new generation strain gauge
signal condition IC, the ADA4556, can be used to interface with strain gauge resistive bridges using first- or second-order order temperature compensation and
nonlinearity correction. It has a PGA with 6× to 820× gain and 12-bit ADC. Further, it has multiple diagnostic functions such as open/short fault, pressure
error, internal temperature sensor error, voltage regulator error, VIN error, EEPROM error, and watchdog detections. The customer can set the diagnostic clamp
voltage level. The analog output pin can also be used as a zero wire programming interface.
This introduces several system benefits. The ICs can support a temperature range of −40°C to 150°C. The EEPROM qualifies for a 10-year retention at 150°C.
System accuracy after calibration can achieve ±0.1%. The condition supports a wide range of pressure sensor sensitivities with PGA gain. No additional
protection diodes or transorbs are required to meet GM EMI/EMC specifications (60 V level). The 6 kV ESD protection has a good robust performance. The bulk
current injection (BCI) performance on global pins can fulfill the OEM requirements and standard ISO-7637-2 (tested/passed to +150/−170 V).
Current Sensor
ADI’s current sense amplifiers support shunt based precise current sensors on both the high and low sides. ADI provides more than 10 IC’s in two different
architectures, including difference and current sense amplifier types. The difference amplifier type is based on an input resistor divider. The AD8207/AD8208/
AD8209 parts have the EMI filter inside, providing higher EMC performance. The AD8207 has zero drift function (offset drift <1 μV/°C) and maximum
offset is < 0.5 mV. The current sense amplifier type is based on a high voltage process to withstand the high common-mode voltage. They have low input
bias currents and high input impedances and are suitable for meeting the high bandwidth (up to 500 kHz) and CMRR (up to 120 dB) requirements. Both
architecture types have good input common-mode step response capability.
ADI also has a current threshold monitor solution for the total current monitor and overcurrent protection. The AD8214 has a very low 200 ns prop delay.
Capacitance Sensor
ADI has the special sigma-delta (Σ-Δ) architecture capacitance-to-digital converter (CDC), which is based on good ADC architecture. The Σ-Δ modulator uses
charge balancing techniques to help customers obtain the capacitance value more easily and more accurately.
The AD7150 is designed for proximity detection and has a 16-bit CDC and an on-board state machine to deal with environmental changes. It can ignore the
slow change on the sensor capacitance caused by environmental factors such as temperature, humidity, and dirt. The AD7150 only responds to fast changes,
such as approaching hands, and triggers the key’s communication between the vehicle and RF transponder.
2 | ADI Automotive Sensor and Sensor Interface Solution
The AD7745/AD7746 are high resolution, Σ-Δ CDCs. The capacitance to be measured is connected directly to the device inputs. The architecture features an
inherently high resolution (24-bit no missing codes, up to 21-bit effective resolution), high linearity (±0.01%), and high accuracy (±4 fF factory calibrated). It
can be used in position rain detection, humidity, and fuel level sensors.
The AD5933 is a high precision impedance converter that combines an on-board frequency generator with a 12-bit, 1 MSPS ADC. The frequency generator
allows an external complex impedance to be excited with a known frequency. The on-board ADC samples the response signal from the impedance, and an
on-chip DSP engine processes a discrete fourier transform (DFT). The DFT algorithm returns a real (R) and imaginary (I) data word at each output frequency. It
can be used in fuel level and quality sensors. It can also measure the mixing ratio of the gasoline and ethanol in the flex fuel application.
Position and Speed Sensors
ADI has a wide portfolio and long tradition in resolver-to-digital converters (RDC). The AD2S1205 and AD2S1210 are able to track rates at up to 3125 RPS.
Their accuracies can reach ±2.5 arc minutes. The AD2S1205 is a 12-bit RDC, and the AD2S1210’s 10-bit/12-bit/14-bit/16-bit resolution can be set by the
user. The chips have differential inputs and incremental encoder outputs with programmable fault detection thresholds.They can be used in motor shaft angle
and speed measurements in transmissions, EPS, and HEV/EV motors.
Temperature Sensor
The ADI’s TMP36 is accurate to ±2°C of the full-scale linearity and 0.5°C of the full-scale with a temperature range of −40°C to +125°C and an analog
output. The ADI’s ADT7311 and ADT7312 are accurate to ±1°C of the full-scale with a temperature range of −40°C to +150°C and a digital SPI output. The
temperature range of the ADT7312 can increase from −40°C to +175°C with a bare die package.
ADI Products
Part Number
Description
Temperature
Benefits
Pressure Signal Condition
AD8556
4.5 V to 5.5 V, includes OTP to support calibration, 2 kV ESD HBM, 70 to 1280 gain,
10 μV offset, 65 nV/°C, 94 dB CMRR, package: SO-8, LFCSP-16
(please contact ADI for auto grade)
−40°C to +140°C
EMI filters, VDD = 5 V
AD8557
2.7 V to 5.5 V, includes OTP to support calibration, 2 kV ESD HBM, 28 to 1300 gain,
12 μV offset, 65 nV/°C, 96 dB CMRR, package: SO-8, LFCSP-16
(please contact ADI for auto grade)
−40°C to +125°C
Low cost, VDD = 3.3 V or 5 V
ADA4556W
(Sampling)
4.5 V to 5.5 V VCC, includes EEPROM to support temperature and nonlinearity
compensation, 6 kV ESD HBM, 6 to 820 gain, ZWI program interface combined with
analog output, package: LFCSP-16
−40°C to +150°C
Temperature and nonlinearity
compensation
AD8202W
−8 V to +28 V input common-mode range, −8 V to +35 V survival, 20 V/V gain,
unidirectional, 50 kHz bandwidth, 10 μV/°C offset drift, 0.3% gain error, 20 ppm/°C
gain drift, 2 kV ESD HBM, 82 dB CMRR typ, 80 dB worst case, package: SO-8,
MSOP-8, bare die
−40°C to +125°C
Difference amplifier, solenoid control
AD8205W
−2 V to +65 V input common-mode range, −5 V to +68 V survival, 50 V/V gain,
bidirectional, 50 kHz bandwidth, 4.5 mV max offset, 15 μV/°C offset drift, 1.2% gain
error, 30 ppm/°C gain drift, 2.5 kV ESD HBM, 80 dB CMRR typ, 76 dB worst case,
package: SO-8
−40°C to +125°C
Difference amplifier, motor control with
EMI filter
AD8206W
−2 V to +65 V input common-mode range, −25 V to +75 V survival, 20 V/V gain,
bidirectional, 100 kHz bandwidth, 4.5 mV max offset, 15 μV/°C offset drift, 1.2%
gain error, 30 ppm/°C gain drift, 3 kV ESD HBM, 80 dB CMRR typ, 76 dB worst case,
package: SO-8
−40°C to +125°C
Difference amplifier, motor control with
EMI filter
AD8207W
−4 V to +65 V input common-mode range, −25 V to +75 V survival, 20 V/V gain,
bidirectional, 100 kHz bandwidth, 0.4 mV max offset, 1 μV/°C offset drift, 0.3% gain
error, 15 ppm/°C gain drift, 3 kV ESD HBM, 80 dB CMRR typ, 80 dB worst case,
package: SO-8
−40°C to +125°C
Difference amplifier, zero drift with EMI
filter
AD8208W
−2 V to +45 V input common-mode range, −24 V to +80 V survival, 20 V/V gain,
unidirectional, 80 kHz bandwidth, 4 mV max offset, 20 μV/°C offset drift, 0.3% gain
error, 20 ppm/°C gain drift, 4.5 kV ESD HBM, 80 dB CMRR typ, package: SO-8,
MSOP-8
−40°C to +125°C
Difference amplifier, robust, solenoid
control with EMI filter
AD8209W
−2 V to +45 V input common-mode range, −24 V to +80 V survival, 14 V/V gain,
unidirectional, 80 kHz bandwidth, 4 mV max offset, 15 μV/°C offset drift, 0.3% gain
error, 20 ppm/°C gain drift, 8 kV ESD HBM, 80 dB CMRR typ, package: MSOP-8
−40°C to +125°C
Difference amplifier, robust, solenoid
control with EMI filter
AD8216W
0 V to 65 V input common-mode range, −40 V to +80 V survival, 3 V/V gain,
bidirectional, 3 kHz bandwidth, 3 mV max offset, 20 μV/°C offset drift, 0.4% gain
error, 15 ppm/°C gain drift, 4.5 kV ESD HBM, 90 dB CMRR typ, 80 dB worst case,
package: SO-8, MSOP-8
−40°C to +125°C
Difference amplifier, fast output response
with EMI filter
Current Sense
automotive.analog.com 
| 3
ADI Products (Continued)
Part Number
Description
Temperature
Benefits
AD8210W
−2 V to 65 V input common-mode range, −5 V to 68 V survival, 20 V/V gain,
bidirectional, 500 kHz bandwidth, 1.8 mV max offset, 8 μV/°C offset drift, 0.5% gain
error, 20 ppm/°C gain drift, 7.5 kV ESD HBM, 120 dB CMRR typ, 80 dB worst case,
package: SO-8
−40°C to +125°C
Current sense amplifier, motor control,
high bandwidth, high CMRR
AD8211W
−2 V to 65 V input common-mode range, −3 V to 68 V survival, 20 V/V gain,
unidirectional, 500 kHz bandwidth, 2.5 mV max offset, 10 μV/°C offset drift, 0.4%
gain error, 13 ppm/°C gain drift, 4 kV ESD HBM, 120 dB CMRR typ, 80 dB worst case,
package: SO-T23-5
−40°C to +125°C
Current sense amplifier, solenoid control,
SOT-23 package
AD8212W
7 V to 65 V input common-mode range (up to 500 V with external high voltage PNP),
7 V to 68 V survival, adjustable gain, unidirectional, 500 kHz bandwidth, 3 mV max
offset, 10 μV/°C offset drift, 1% gain error, 50 ppm/°C gain drift, 4 kV ESD HBM, 90 dB
CMRR typ, package: MSOP-8
−40°C to +125°C
Current sense amplifier
Current output
500 V with $0.03 external transistor,
including 5 V regulator
AD8213W
−2 V to 65 V input common-mode range, −3 V to 68 V survival, 20 V/V gain,
unidirectional, 500 kHz bandwidth, 2.2 mV max offset, 12 μV/°C offset drift, 0.5% gain
error, 25 ppm/°C gain drift, 4 kV ESD HBM, 90 dB CMRR typ, package: MSOP-10
−40°C to +125°C
Current sense amplifier
Dual channel
AD8215W
−2 V to 65 V input common-mode range, −3 V to 68 V survival, 20 V/V gain,
unidirectional, 450 kHz bandwidth, 2.5 mV max offset, 10 μV/°C offset drift, 0.3%
gain error, 15 ppm/°C gain drift, 4 kV ESD HBM, 120 dB CMRR typ, 80 dB worst case,
package: SO-8
−40°C to +125°C
Current sense amplifier
Solenoid control
SO-8 package
AD8214W
5 V to 65 V input common-mode range, 0 V to 68 V survival, adjustable gain,
unidirectional, 500 kHz bandwidth, 8 mV max offset, 15 μV/°C offset drift, 2.5 kV ESD
HBM , package: MSOP-8
−40°C to +125°C
Current threshold monitor
200 nS prop delay, including 2.4 V regulator
New Gen
(Sampling)
−2 V to 80 V input common-mode range, −4 V to 85 V survival, 50 V/V gain,
bidirectional, 50 kHz bandwidth, 0.4 mV max offset, 0.5 μV/°C offset drift, 0.35%
gain error, 10 ppm/°C gain drift, 2 kV ESD HBM, 100 dB CMRR typ, 86 dB worst case,
package: SO-8, MSOP-8
−40°C to +125°C
Zero drift, with EMI filters
Input common-mode range up to 80 V
Capacitor-to-Digital Converter
AD7150
2-channel, 16-bit CDC, I2C interface, ±4 pF capacitor range, 10 pF CapDAC
range(please contact ADI for auto grade)
−40°C to +85°C
MSOP-10 package
AD7745
1-channel, 24-bit CDC, 2.7 V to 5.25 V supply voltage with internal temperature sensor,
±4 pF capacitor range, 17 pF CapDAC range, ±4 fF, I2C interface
−40°C to +125°C
TSSOP-16 package
AD7746
2-channel, 24-bit CDC, 2.7 V to 5.25 V supply voltage with internal temperature sensor,
±4 pF capacitor range, 17 pF CapDAC range, ±4 fF, I2C interface
(please contact ADI for auto grade)
−40°C to +125°C
TSSOP-16 package
AD5933W
Impedance converter, 12-bit 1 MSPS ADC, programmable output peak-to-peak
excitation voltage to a maximum frequency of 100 kHz, I2C interface, real (R) and
imaginary (I) measurement
−40°C to +125°C
SSOP-16 package
Resolver Digital Converter
AD2S1205
(ADW71205)
12-bit resolution, 1250 RPS max tracking rate, 11 arc minutes accuracy (Y grade), 22
arc minutes accuracy (W grade)
−40°C to +125°C
LQFP-44 package
AD2S1210W
10-bit, 12-bit, 14-bit, 16-bit adjustable resolutioin, 3125 RPS/1250 RPS/156.25 RPS
max tracking rate (CLK = 10.24 MHz), 2.5 arc minutes typ accuracy
−40°C to +125°C
LQFP-48 package
Temperature Sensor
TMP36
(ADW75001)
Temperature error at 1°C ambient temperature, analog output, ±2°C full-scale
accuracy
−40°C to +150°C
SOT-23-5 package
ADT7311W
±1°C full-scale accuracy, SPI interface
−40°C to +150°C
SO-8 package
ADT7312W
±1°C full-scale accuracy, SPI interface
−40°C to +175°C
Bare die package
* W suffix represents automotive grade.
4 | ADI Automotive Sensor and Sensor Interface Solution
Design Resources
Evaluation Boards
• AD8555ARZ-EVAL
• EVAL-AD7746EBZ
• EVAL-AD7746LBZ
• EVAL-SDP-CB1Z
• EVAL-ADA4556
• EVAL-AD7746RBZ
• EVAL-AD5933EBZ
• EVAL-AD2S1210EDZ
• EVAL-AD7150EBZ
• EVAL-AD7746HBZ
• EVAL-AD2S1205SDZ
• EVAL-CED1Z
• EVAL-ADT7X10EBZ
Reference Circuits
• using the AD7150 capacitance-to-digital converter (CDC) for proximity sensing applications (CN0095)—www.analog.com/CN0095
• high voltage, high precision current sensing with output level shifting using the AD8210 current sense amplifier and the AD8274 difference amplifier
(CN0116)—www.analog.com/CN0095
• extending the capacitive input range of the AD7745 and AD7746 (CN0129)—www.analog.com/CN0095
• high current driver for the AD2S1210 resolver-to-digital reference signal output (CN0192)—www.analog.com/CN0095
• high accuracy impedance measurements using 12-bit impedance converters (CN0217)—www.analog.com/CN0095
• 500 V common-mode voltage current monitor (CN0218)—www.analog.com/CN0095
Design Tool
• ADA4556 evaluation software (including the coefficient calculator )
ADI’s TMP36 has ±2°C full-scale linearity accuracy and 0.5°C of full scale with a temperature range of −40°C to +125°C and an analog
output. ADI’s ADT7311 and ADT7312 have ±1°C full-scale accuracy with a temperature range of −40°C to +150°C and a digital SPI output.
The temperature range of the ADT7312 can increase from −40°C to +175°C with a bare die package.
For More Automotive Application and Product Information, Please Visit
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