TPIC8101%20Training integrado detectar picado.pdf

Knock Sensor Training TPIC8101 Thomas Cosby

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Knock Sensor Basics

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Knock Sensor - Background • Almost all cars have knock sensors to meet OBDII emissions control requirements. • Engine knock can occur when the charge inside the cylinder detonates causing a pinging sound. This can be a result of: • Improper engine timing • Using the wrong octane gasoline • Worn or defective spark plugs

•

• Cars/Trucks have knock sensors mounted on the engine block • Knock sensors are piezo-electric elements  – The vibrations of the engine are converted into electric signals

• Knocking is controlled using spark timing

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Knock Sensor - Types

Knock sensor construction • Piezo element to detect pressure wave. • Resistor element to for open load detection • Signal returns and cable shield.

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Knock Sensor – Mounting Location ENGINE

SENSOR

Most engines have two knock sensors

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Ignition System Timing

Intake C cle

Combustion Cycle 6/27/2011

Com ression C cle

Exhaust Cycle 6

Knock Sensor - Waveforms

Typical noise content in a running engine.

Typical places where noise occurs in the ignition cycle. 6/27/2011

Typical flat response type knock signal

Typical resonant response type signal. 7

TPIC8101: Knock Sensor Interface

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TPIC8101: Knock Sensor Interface •

Dual-channel Engine Knock Sensor Interface

•

External Clock Frequencies up to 24 MHz  –

4, 5, 6, 8, 10, 12, 16, 20, and 24 MHz

•

SPI interface (for Microprocessor)

•

Programmable Gain

• Engine Knock Detector Signal Processing • Analog Signal Processing With Filter Characteristics - Piezoelectric sensing - Accelerometer sensing

Package: DW (20-pin, 1.27 mm pitch)

•

Pro rammable Band-Pass Filter Center Fre .

•

Programmable Input Frequency Pre-scaler 

•

Operating Temp. Range: - 40ºC to 125ºC

• Broad µC selection via 9 selectable ext. clock frequencies • Selectable input channels improve accuracy • Choice of output signal profile: analog or digital • Can use for general analog signal processing • Advanced SPI mode capability available

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• System-level diagnostics of device capable via Test Mode

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Knock Sensor Applications Schematic VDD/2

100 nF

Vref 

+ -

CH1P CH1N

+ -

Mux

CH1FB

R

R

CH2P CH2N

3.3 nF

SAR 10-bit ADC

3rd Order AAF

+



fs = 200 kHz

-

CH2FB

Knock Sensor 1

R

R

Programmable

Programmable

Programmable

Band-Pass

Gain

Rectifier 

Filter 

3.3 nF

DSP XIN

Knock Sensor 2

R2R

SPI

10-bit DAC

+

fs = 200 kHz

Test Mode

-

DSP Control XOUT

VDD

GND

OUT

 __  CS

SCLK

SDI

SDO

 ____  TEST

470 pF

1 MΩ

INT / HOLD

1 kΩ

 A/D

Note: R > 25 kΩ

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Microcontroller 

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Engine Knock Sensor Key Parameters Basic DC Quiescent Condition Parameters • • •

Output (Buffer) Amplifier Parameters

Quiescent current (I DDQ): 7.5 mA (typ.) Max. Operating current (I DD(OP)): 20 mA Hysteresis Voltage (Serial IF & Pre-scaler): 0.4 V (typ.)

• • • •

High-level output volt. (VOH): VDD-0.15 (typ.) Low-level output volt. (V OL): 175 mV (max.) Ripple voltage: 10 mV (max.) Settling time (t s): 20 µs (max.)

Input Amplifier Parameters • • • • •

Cross-coupling attention: 40 dB (min.) Open-loop gain (Av): 100 dB (typ.) Gain Bandwidth Product: 2.6 MHz (typ.) CMRR range: 60 – 80 dB

Prescaler/Oscillator Parameters: • • •

Min. input peak amplitude: 150 mV Input Capacitance: 7 pF Leakage Current: -1 µA to +1 µA

Anti-Aliasing Filter Parameters • • •

Frequency response (1 kHz to 20 kHz): ±1 dB Attenuation @ 100 kHz: -15 dB to -10 dB -

Recommended Operation Conditions • • • •

Regulated input voltage (VDD): -0.3 V to +5.5 V Output voltage range (buffer): -0.3 V to +5.5 V Input voltage range: 0.05 V to (VDD-0.05) V DC Input Current (I IN): ±1 µA > for CH1P, CH1N, CH2P, and CH2N pins

•

Operating Temperature Range: •

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-40ºC to +125ºC

DC Input Voltage (V DCIN): ½ VDD > for CH1P, CH1N, CH2P, and CH2N pins

•

Continuous Power Dissipation: 100 mW (max.)

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TPIC8101 Knock Sensor Block Diagram

VIN AIN

AP

ABP

τC

AINT

AO

 Auto

VO

tINT (System Transfer Function)

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TPIC8101 Transfer Function T  INT 

V OUT  =

∫

V  IN  sin(π   f    BP t )dt * A IN  * A P  * A BP  * A INT  *

0

V OUT  =

V  IN   f  

* (− cos(π   f    BP t )

π   BP 

V OUT  =

V  IN   f  

1 t C 

* AOUT  +V  RESET  1

TINT 

* A IN  * A P  * A BP  * A INT  * 0

t C 

* (1 − cos(π   f    BP T   INT )) * A IN  * A P  * A BP  * A INT  *

π   BP 

OUT 

=

V  IN   f  

− cos π   BP 

 INT 

 IN 

 P 

 BP 

π   BP 

T  INT  =

1 t C  1 t C 

* AOUT  +V  RESET  OUT 

+

 RESET 

 N 

V OUT  =

 f   V  IN 

* (1 − (−1)) * A IN  * A P  * A BP * A INT  *

π  

V OUT  =

V  IN  π  

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 INT 

* AOUT  +V  RESET 

* 2 * A IN  * A P  * A BP * A INT  *

T  INT  t C 

T  INT  t C 

* AOUT  +V  RESET 

* AOUT  +V  RESET  13

TPIC8101 Transfer Function, continued

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TPIC8101 Input Settings

VIN 2 channels AIN = R2/R1

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TPIC8101 DSP Settings AP

ABP

τC

AINT = 2

ABP = 2 at the center frequency. Assumes that AIN = 1. Set to match sensor outputs τC

AP

AP

Datasheet page 10

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TPIC8101 Integrator Programming

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TPIC8101 Integrator Programming, continued

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TPIC8101 SPI Interface

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TPIC8101 Default SPI Mode

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TPIC8101 Advanced SPI Mode

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TPIC8101 Test Mode

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TPIC8101: Application Example

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Application Requirements Requirements: • VIN = 7.3KHz, 300mVpp (Knock Sensor specification) • Oscillator = 6MHz (Microprocessor clock specification) • Knock window (TINT)= 3ms (system spec) • OUT = 4.5V (Microprocessor interface specification) Need to set: • Input amplifier gain (AIN) • Programmable gain (AP) • Integration time constant (TC)

4.5V = 0.15*AP*2.55*3ms/100µs + 0.125

Set AIN = 1; R1 = R2

 AP = 0.38

⇒

TC is typically TINT/(2*π*VOUT) ⇒ TC = 3ms / (2*π*4.5) = 106µs

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TPIC8101 Application Schematic

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TPIC8101 SPI Settings Parameter Oscillator

Calculated Value 6MHz

Programmed Value 6MHz

Channel

1

1

f C0

7.3KHz

7.27KHz

42

2A

00101010

 AP

0.38

0.381

34

22

10100010

TC

106µs

100µs

10

0A

10001010

TINT

3ms

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Code DEC HEX

SPI 01000010 11100000

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TPIC8101EVM Waveforms

7270KHz, 300mVpp

INT, 4.48V

Output

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