SLIS110C April   2003  – March 2015 TPIC8101

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Description (continued)
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Timing Requirements
    7. 7.7 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Functional Terminal Description
        1. 8.3.1.1  Supply Voltage (VDD)
        2. 8.3.1.2  Ground (GND)
        3. 8.3.1.3  Reference Supply (Vref)
        4. 8.3.1.4  Buffered Integrator Output (OUT)
        5. 8.3.1.5  Integration/Hold Mode Selection (INT/HOLD)
        6. 8.3.1.6  Chip Select for SPI (CS)
        7. 8.3.1.7  Oscillator Input (XIN)
        8. 8.3.1.8  Oscillator Output (XOUT)
        9. 8.3.1.9  Data Output (SDO)
        10. 8.3.1.10 Data Input (SDI)
        11. 8.3.1.11 Serial Clock (SCLK)
        12. 8.3.1.12 Test (TEST)
        13. 8.3.1.13 Feedback Output for Amplifiers (CH1FB and CH2FB)
        14. 8.3.1.14 Input Amplifiers (CH1P, CH1N, CH2P, and CH2N)
      2. 8.3.2 Timing Information
    4. 8.4 Device Functional Modes
      1. 8.4.1 System Transfer Equation
      2. 8.4.2 Programming in Normal Mode (TEST = 1)
      3. 8.4.3 Default SPI Mode
      4. 8.4.4 Advanced SPI Mode
      5. 8.4.5 Digital Data Output from the TPIC8101
    5. 8.5 Programming
      1. 8.5.1 Programming Examples
      2. 8.5.2 Programming in TEST Mode (TEST = 0)
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
      3. 9.2.3 Application Curve
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Trademarks
    2. 12.2 Electrostatic Discharge Caution
    3. 12.3 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

9 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

9.1 Application Information

The TPIC8101 can interface with one or two flat type or resonant knock sense elements. Flat type (non-resonant) sensors have a wider frequency bandwidth than resonant type sensors. A microprocessor must also interface with the TPIC8101 as shown in Figure 5. The microprocessor may sample the output data either through SPI or by sampling the analog OUT signal.

9.2 Typical Application

TPIC8101 sch_application_slis110.gifFigure 5. Application Schematic

9.2.1 Design Requirements

After the knock sense element and the microprocessor are chosen, the designer can choose the TPIC8101 settings. The settings that must be programmed through SPI are: ƒbp, ƒosc, AP, τC, and channel. If the analog output is used, then the INT/HOLD signal must be supplied by the microprocessor.

The input amplifier gain (AIN) is typically set to 1 by setting R1 = R2. R1 and R2 should be chosen to be greater than 25 kΩ.

Table 5. System Design Constraints

PARAMETER CONSTRAINT VALUE FOR DESIGN EXAMPLE
VIN Amplitude of input signal from knock sensor; determined by knock sensor specification 300 mVpp
ƒbp Bandpass center frequency; determined by knock sensor specification 7.3 kHz
ƒosc Oscillator frequency; determined by microprocessor 6 MHz
tINT Integration window; determined by system specification. This is half the period of the INT/HOLD signal (when using a 50% duty cycle) which is generated by the microprocessor. 3 ms
VOUT Maximum voltage on the OUT pin for the maximum VIN 4.5 V

9.2.2 Detailed Design Procedure

Design parameters to set:

AIN: Input amplifier gain, typically set to 1

AP: Programmable gain

τC: Integration time constant

Design equations:

Equation 3. TPIC8101 Eq03_LIS510.gif
Equation 4. TPIC8101 Eq04_LIS510.gif

Use Equation 2 to solve for AP:

Equation 5. TPIC8101 Eq05_LIS510.gif

For this design example, use the parameters specified in Table 5. This example is for a resonant knock sensor.

Using Equation 4:

Equation 6. TPIC8101 Eq06_LIS510.gif

Using Equation 5:

Equation 7. TPIC8101 Eq07_LIS510.gif

AP = 0.38

Table 6 lists the parameters to program.

Table 6. Parameters to Program

Parameter Calculated Value Programmed Value Code SPI
DEC HEX
Oscillator 6 MHz 6 MHz 1000010
Channel 1 1 11100000
ƒC0 7.3 kHz 7.27 kHz 42 2A 101010
AP 0.38 0.381 34 22 10100010
τC 106 µs 100 µs 10 0A 10001010

Figure 6 shows the input and output signals for this design example.

For a resonant knock sensor (as in the design example), the center frequency of the bandpass filter is set to the resonant frequency of the knock sensor. For a flat-type knock sensor, the bandpass filter design equation can be used to determine where the center frequency should be set.

The transfer function of the biquadratic bandpass IIR filter is:

Equation 8. TPIC8101 Eq08_LIS510.gif
Equation 9. TPIC8101 Eq09_LIS510.gif

9.2.3 Application Curve

TPIC8101 app_curve_1_LIS110.gifFigure 6. TPIC8101 Waveform