JAJU648A November   2018  – April 2022 TLV3601 , TLV3601-Q1 , TLV3603 , TLV3603-Q1

 

  1.   概要
  2.   Resources
  3.   特長
  4.   アプリケーション
  5.   5
  6. 1System Description
    1. 1.1 Key System Specifications
  7. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 Amplifier and Comparator
      2. 2.2.2 Digital Processing and Control
      3. 2.2.3 Optical Components
        1. 2.2.3.1 Laser Driver and Laser Diode
        2. 2.2.3.2 Photodiode
      4. 2.2.4 Power Supply
    3. 2.3 Highlighted Products
      1. 2.3.1 OPA858 Operational Amplifier
      2. 2.3.2 TLV3501 and TLV3601/3 High-Speed Comparators
      3. 2.3.3 TDC7201 Time-to-Digital Converter
    4. 2.4 System Design Theory
      1. 2.4.1 Transimpedance Amplifier
        1. 2.4.1.1 Bandwidth
        2. 2.4.1.2 Stability Considerations
        3. 2.4.1.3 Noise Performance
      2. 2.4.2 Time-of-Flight Measurement
      3. 2.4.3 Simulations
        1. 2.4.3.1 Bandwidth Simulation
        2. 2.4.3.2 Noise Simulation
        3. 2.4.3.3 OPA858 Loop-Gain and Phase Margin Simulation
  8. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Required Hardware and Software
      1. 3.1.1 Hardware
      2. 3.1.2 Software
    2. 3.2 Testing and Results
      1. 3.2.1 Test Setup
        1. 3.2.1.1 Getting Started: System Setup
          1. 3.2.1.1.1 Laser-Driver Setup
          2. 3.2.1.1.2 Receiver and Optical Setup
      2. 3.2.2 Test Results
        1. 3.2.2.1 Verification and Measured Performance
          1. 3.2.2.1.1 Pulse Response Measurements
            1. 3.2.2.1.1.1 Pulse Response Settling
            2. 3.2.2.1.1.2 Pulse Response vs Output Pulse Width
            3. 3.2.2.1.1.3 Rise and Fall Time
            4. 3.2.2.1.1.4 Overdriven Response
          2. 3.2.2.1.2 Time-of-Flight Test
          3. 3.2.2.1.3 Time-of-Flight Measurement Error Sources
  9. 4Design Files
    1. 4.1 Schematics
    2. 4.2 Bill of Materials
    3. 4.3 PCB Layout Recommendations
      1. 4.3.1 Layout Prints
    4. 4.4 Altium Project
    5. 4.5 Gerber Files
  10. 5Related Documentation
    1. 5.1 Trademarks
  11. 6About the Author
  12. 7Revision History

2.2.3.1 Laser Driver and Laser Diode

The laser driver used in the design is an iC-HB, 155-MHz, triple-laser switch from iC-Haus™. See the Triple 155MHz Laser Switch data sheet for the recommended laser driver for this design. The recommended laser diode is a 1550-nm distributed feedback laser (DFB) LDM5S515-015 from OEQuest™. In a pulsed high-speed application, toggling a laser on and off causes suboptimal performance. Rather than turning the laser off, configure the laser to just less than its turnon threshold when the laser is inactive to ensure a smoother and quicker turnon. This configuration minimizes the effects of parasitic capacitances that require charging and discharging during transient operation.

Figure 2-2 shows a simplified schematic of the laser setup. See Figure 4-2 for the complete printed circuit board (PCB) schematic. Consider each channel of the laser-diode driver to be a voltage-controlled current source (VCCS) with an enable and disable switch. The three parallel channels are as follows:

  • The bias channel sets the laser at its threshold condition
  • Channel 1 drives the signal current that toggles the laser on or off
  • Channel 2 is unused in this application
GUID-0B86387A-04D9-404C-9C2C-C62E0AB9FEA3-low.gifFigure 2-2 Laser Diode Block Diagram

Using the onboard resistor divider and potentiometer subcircuit connected between the 5-V supply and ground sets the bias voltage to control the VCCS. Set the bias supply to 1.15 V and the signal supply on channel 1 to 1.65 V. The jumper statically controls the bias channel state and the trigger generated by the MPS430 controls the signal channel. The adjustable linear regulator (U3) is configured to drive an output voltage of 3.3 V on the 3p3V line. This voltage drives the primary side of the SN74LVC1T45 logic-level translator to shift the 0-V to 3.3-V logic level from the trigger signal of the MSP430 to a 0-V to 5-V digital signal required to drive the iC-HB device. For more information, see Figure 2-1.