SLOS318L april   2000  – august 2023 THS4130 , THS4131

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Revision History
  6. 5 Device Comparison Table
  7. 6 Pin Configuration and Functions
  8. 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 Typical Characteristics
  9. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
    4. 8.4 Device Functional Modes
      1. 8.4.1 Power-Down Mode
  10. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Output Common-Mode Voltage
        1. 9.1.1.1 Resistor Matching
      2. 9.1.2 Driving a Capacitive Load
      3. 9.1.3 Data Converters
      4. 9.1.4 Single-Supply Applications
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
      3. 9.2.3 Application Curve
    3. 9.3 Power Supply Recommendations
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
        1. 9.4.1.1 PowerPAD™ Integrated Circuit Package Design Considerations
      2. 9.4.2 Layout Example
  11. 10Device and Documentation Support
    1. 10.1 Documentation Support
      1. 10.1.1 Related Documentation
    2. 10.2 Receiving Notification of Documentation Updates
    3. 10.3 Support Resources
    4. 10.4 Trademarks
    5. 10.5 Electrostatic Discharge Caution
    6. 10.6 Glossary
  12. 11Mechanical, Packaging, and Orderable Information

Package Options

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

9.2.2 Detailed Design Procedure

Figure 9-5 shows a multiple-feedback (MFB) low-pass filter. The transfer function for this filter circuit is:

H d f = K - f F S F × f c 2 + 1 Q j f F S F   ×   f c   + 1 × R t 2 R 4   +   R t   1 + j 2 π f R 4 R t C 3 2 R 4   +   R t  
Equation 4. w h e r e   K   =   R 2 R 1 , F S F   ×   f c = 1 2 π 2 × R 2 R 3 C 1 C 2   , a n d   Q   =   2 × R 2 R 3 C 1 C 2 R 3 C 1 +   R 2 C 1   +   K R 3 C 1

K sets the pass-band gain, fc is the cutoff frequency for the filter, FSF is a frequency scaling factor, and Q is the quality factor.

Equation 5. F S F = R e 2 + I m 2   a n d   Q   =   R e 2 + I m 2 2 R e

where Re is the real part and Im is the imaginary part of the complex pole pair. Setting R2 = R, R3 = mR, C1 = C, and C2 = nC results in:

Equation 6. F S F ×   f c =   1 2 π R c 2 × m n   a n d   Q   =   2 × m n 1 + m ( 1 + K )

Start by determining the ratios, m and n, required for the gain and Q of the filter type being designed, then select C and calculate R for the desired fc.