SLOSEB7B September   2024  – December 2024 LOG300

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics Low Noise Amplifier (LNA) 
    6. 5.6 Electrical Characteristics Log Detector
    7. 5.7 Electrical Characteristics LNA + Log Detector (AFE)
    8. 5.8 Typical Characteristics: VCC = 5V
    9. 5.9 Typical Characteristics: VCC = 3.3V
  7. 6 Parameter Measurement Information
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Offset Correction Loop (OCL)
      2. 7.3.2 Single and Differential Input
      3. 7.3.3 Input Frequency Detect
    4. 7.4 Device Functional Modes
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Ultrasonic Distance Measurement
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Application Curves
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Third-Party Products Disclaimer
    2. 9.2 Receiving Notification of Documentation Updates
    3. 9.3 Support Resources
    4. 9.4 Trademarks
    5. 9.5 Electrostatic Discharge Caution
    6. 9.6 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • RGT|16
  • D|16
Thermal pad, mechanical data (Package|Pins)
Orderable Information

7.3.2 Single and Differential Input

The Log Detector block of the LOG300 supports both single-ended and differential input signals. Irrespective of the type of input signal, the impedances from the Log_Inp and Log_Inm pins to AGND have to be matched.

The requirement for impedance matching arises from the fact that any supply noise or externally coupled noise passes through these impedances and generates an input voltage. If the impedances are mismatched at the two inputs a differential voltage is seen by the Log Detector block thereby increasing the minimum output voltage at the Log_Out pin. This results in degradation of the dynamic range.

Impedance matching for differential input case can be easily achieved by replicating source impedance on both pins.

However for single-ended inputs, impedance matching can be quite complex. If board space is not limited TI recommends to copy the input structure at the Log_Inp pin as, is on to the Log_Inm input. Please take note of the default internal output impedance of the LNA of 1kΩ when copying the structure to the Log_Inm pin.

If the above recommendation is not possible, match the impedances between the two pins at the frequency with the highest probability of noise coupling. For example if the VCC supply is being derived by a DC/DC converter switching at a frequency of 500kHz, using option 1 gives the best impedance matching between Log_Inp and Log_Inm. If the VCC ripple is at 100kHz then both option 1 and option 2 result in the same rejection response.

LOG300 Impedance Structure at Log_Inp and Log_Inm
AFE design with BPF of 1MHz
Figure 7-1 Impedance Structure at Log_Inp and Log_Inm
LOG300 Impedance vs Frequency at Log_Inp and Log_Inm Figure 7-2 Impedance vs Frequency at Log_Inp and Log_Inm