SNVU821 November   2023 TPS92642-Q1

 

  1.   1
  2.   TPS92642EVM-203 5-A Synchronous Buck IR LED Driver Evaluation Module
  3.   Trademarks
  4. 1Introduction
  5. 2Warnings and Cautions
  6. 3Description
    1. 3.1 Typical Applications
    2. 3.2 Features
    3. 3.3 Connector and Test Point Description
    4. 3.4 Electrical Performance Specifications
  7. 4Test Setup
    1. 4.1 Input Supplies and LED Load Connections
    2. 4.2 Pulse Duty Cycle Limit (PLMT) Control
    3. 4.3 Analog Dimming Using IADJ
    4. 4.4 PWM Dimming Using nExt_PWM Test Points
    5. 4.5 Switching Frequency Set Point Using RON
  8. 5Performance Data and Typical Characteristic Curves
    1. 5.1 Efficiency
    2. 5.2 Analog Dimming
    3. 5.3 PWM Dimming
    4. 5.4 PWM Dimming Waveforms
  9. 6Schematic
  10. 7PCB Layout
  11. 8Bill of Materials

4.3 Analog Dimming Using IADJ

Analog dimming is controlled by IADJ (TP4) test point or by using the resistor divider attached to VCC. The voltage on the IADJ pin sets the regulated LED current using Equation 6.

Equation 6. GUID-18B738F2-9A3C-41F8-952B-1B6FD65A2DC6-low.svg
GUID-20230911-SS0I-LCVV-G2DZ-M5QTXJNTH758-low.svgFigure 4-6 IADJ Using External Supply

There is a placeholder for the resistor divider. RFB2 (R7) and RFB1 (R12) has to be calculated for the desired ILED. See Figure 4-7 for the circuit diagram and Equation 7 is the equation for setting the LED current.

Equation 7. GUID-2253C5AE-8B6D-4433-9FAA-9A8958080A8F-low.svg
GUID-69E59653-16E6-4919-8215-9B6EB46179F9-low.svgFigure 4-7 Setting IADJ Using On-Board Resistor Divider

The default value for RCS R1 is 33 mΩ, R7 is 22.8 kΩ, and R5 is 100 kΩ. See Equation 8. The result is a default pulsed current of 2.0 A.

Equation 8. GUID-20230912-SS0I-2K77-KCTZ-6MPMDDFLRWXP-low.svg