SLUUCJ2 July   2021 UCC14240-Q1


  1.   Trademarks
  2. 1Introduction
    1. 1.1 Pin Configuration and Functions
  3. 2Description
    1. 2.1 EVM Electrical Performance Specifications
  4. 3Schematic
  5. 4EVM Setup and Operation
    1. 4.1 Reference
    2. 4.2 External Connections for Easy Evaluation
    3. 4.3 Powering the EVM
      1. 4.3.1 Power on for Start-up
      2. 4.3.2 Power off for Shutdown
    4. 4.4 EVM Test Points
    5. 4.5 Oscilloscope Probes: Probing the EVM
  6. 5 Performance Data
    1. 5.1 Efficiency Data
    2. 5.2 Regulation Data
    3. 5.3 Start-up Waveforms
    4. 5.4 Inrush Current
    5. 5.5 AC Ripple Voltage
    6. 5.6 EN and /PG Timing
    7. 5.7 Shutdown
    8. 5.8 Steady State
    9. 5.9 Thermal Performance
  7. 6Assembly and Printed Circuit Board (PCB) Layers
  8. 7Bill of Materials (BOM)
  9. 8Revision History

Powering the EVM

CAUTION: Do not attempt to start the EVM by applying the EN shorting jumper while VIN and +5V DC Bias power supplies are enabled. Doing so can result in unpredictable, erratic start up due to excessive signal bounce induced at J3, EN, as seen in Figure 4-2. It is recommended to leave the EN shorting jumper in the J3:2-3 position and control ON/OFF by enabling or turning ON/OFF the +5V DC Bias power supply. If it is desired to use the EN shorting jumper for ON/OFF control, a simple RC filter can be applied to the J3 header, on the bottom of the PCB, as shown in Figure 4-3 which gives the proper start-up signals shown in Figure 4-4. Adding the RC filter inverts the ENA logic as described in Table 4-1 such that removing the jumper turns ON the EVM with controlled ENA and inserting the EN jumper into J3:1-2 (OFF) turns OFF the EVM. Applying the shorting jumper to J3:2-3 (ON) has no effect, even though the RC filter is applied as shown in Figure 4-3


Figure 4-2 ENA Erratic Signal Bounce Causing VDD Collapse (top: ENA, 5V/div, mid: /PG, 5V/div, bot: VDD, 10V/div), time = 10ms/div unless otherwise noted.


Figure 4-3 RC Debounce Filter, J3 PCB Bottom, R=5.11 kΩ, C=100 nF


Figure 4-4 ENA Signal Bounce Removed by Addition of RC filter (top: ENA, 5V/div, mid: /PG, 5V/div, bot: VDD, 10V/div), time = 2ms/div unless otherwise noted.
Table 4-1 ENA Operation
EN ConfigJumper RemovedJumper Install J3:1-2 (OFF)Jumper Install J3:2-3 (ON)Comment
No RC filterOFFOFFONEN chatter
500 µs RC filter R = 5.11 kΩ, C = 100 nFONOFFNo effectNo EN chatter
  • Hot Surface. Contact may cause burns. U1 package surface can reach temperatures of 45°C above ambient. Do not touch!
  • Do not test this EVM unless you are trained in the proper safety, handling and testing of power electronics.