SLAT163 July   2024 AFE43902-Q1 , AFE439A2 , AFE53902-Q1 , AFE539A4 , AFE539F1-Q1 , AFE639D2 , DAC43204 , DAC43401 , DAC43401-Q1 , DAC43701 , DAC43701-Q1 , DAC43901-Q1 , DAC43902-Q1 , DAC53001 , DAC53002 , DAC53004 , DAC53004W , DAC53202 , DAC53204 , DAC53204-Q1 , DAC53204W , DAC53401 , DAC53401-Q1 , DAC53701-Q1 , DAC539E4W , DAC539G2-Q1 , DAC63001 , DAC63002 , DAC63004 , DAC63004W , DAC63202 , DAC63202W , DAC63204 , DAC63204-Q1 , DAC63204W

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1What is a Smart DAC?
  5. 2What is a Smart Analog Front End (AFE)?
  6. 3Smart DAC selection guide
  7. 4Smart AFE Selection Guide
  8. 5Applications
    1. 5.1 Lightning
      1. 5.1.1 Light Emitting Diode (LED) Biasing and Linear Fade-In Fade-Out
      2. 5.1.2 LED Biasing With LED Driver
      3. 5.1.3 Analog Thermal Foldback
        1. 5.1.3.1 Single Slope Thermal Foldback
        2. 5.1.3.2 Multi-Slope Thermal Foldback
      4. 5.1.4 Logarithmic Fade-In/Fade-Out
      5. 5.1.5 LED Sequencing
    2. 5.2 Control
      1. 5.2.1 Voltage Margining and Scaling With Voltage Output Smart DAC
      2. 5.2.2 Thermoelectric Cooling (TEC) Control
        1. 5.2.2.1 TEC Control Using DC/DC Driver
        2. 5.2.2.2 TEC control using h-Bridge driver
      3. 5.2.3 Analog Power Control (APC) of a Laser
      4. 5.2.4 Constant Power Control
    3. 5.3 Microcontroller Independent Fault Management and Communication
      1. 5.3.1 Programmable Comparator Using Smart DAC
      2. 5.3.2 GPI-to-PWM
      3. 5.3.3 If-Then-Else Logic
    4. 5.4 Driver
      1. 5.4.1 Lens Positioning Control for Camera Module Auto-Focus and Image Stabilization
      2. 5.4.2 Laser Drive
    5. 5.5 Miscellaneous Smart DAC Applications
      1. 5.5.1 Software-less Medical Alarm Generation
      2. 5.5.2 555 Timer

5.2.3 Analog Power Control (APC) of a Laser

Analog power control of a laser is a simple circuit designed to control power through a laser module (combination of a laser diode and a photodiode). Smart DAC provides a closed loop control of such system.

The output of the DAC controls the gate voltage across MOSFET which along with the drain resistor controls the amount of current flow through the laser. The intensity of the laser is monitored by the photodiode, output of which is sensed by the feedback pin of the smart DAC to close the loop. Smart DAC also integrates a programmable comparator which can be used for over-current protection.

This configuration is resilient to temperature variations of the laser diode along with resister/component mismatch and FET aging. This configuration also maintains the consistency of the laser across multiple platforms. Integrated non-volatile memory is used to store all of the biasing parameters and insures software-free operation.

Table 5-10 Design Implementation
Hardware Block Diagram Figure 5-10 Hardware Block Diagram
Design Benefits Suggested device
  • Closed loop control of a laser bias point
  • Auto-calibration of a biasing point across multiple systems
  • Configurable GPI to turn on/off the DAC or bring the DAC to safety level in case of a fault
  • NVM to store all configuration for software-free operation
End Equipment Design help