SLVUBX0A July   2021  – January 2022 TPSM8A28 , TPSM8A29

 

  1.   Trademarks
  2. 1Introduction
  3. 2Description
  4. 3Getting Started With the TPSM8A29EVM
    1. 3.1 J1 - Input Voltage Supply Connector
    2. 3.2 J4 and J7 - Positive and Negative Output Connectors
    3. 3.3 J2 - Enable Header
    4. 3.4 J5 - Switching Frequency and Operating Mode
    5. 3.5 J6 - Output Voltage Selection Header
  5. 4Test Point Description
    1. 4.1 TP12 - SS/REF_IN
    2. 4.2 TP14 - VCC
  6. 5Test Setup and Results
    1. 5.1 Startup Procedure
    2. 5.2 Efficiency
    3. 5.3 Load Regulation
    4. 5.4 Line Regulation
    5. 5.5 Output Voltage Ripple
    6. 5.6 Startup and Shutdown
    7. 5.7 Load Transient
    8. 5.8 Bode Plot
  7. 6TPSM8A29EVM Schematic
  8. 7TPSM8A29EVM PCB Layers
  9. 8TPSM8A29EVM Bill of Materials
  10. 9Revision History

4.1 TP12 - SS/REF_IN

TP12 is connected to the SS/REF_IN pin of the TPSM8A29. Connecting a capacitor to this pin increases the soft-start time of the converter, as described by Equation 5, where CSS is the calculated external soft-start capacitor, in nF, tSS is the desired soft-start time, in ms, 36 has units of μA, and VINTREF is the internal 0.6 V reference voltage. If no soft-start capacitor is used, the minimum internal soft-start time of 1.5 ms typical is used. By default, a soft-start capacitor is not populated on the EVM, though a footprint for one exists on the bottom of the PCB (C12). The maximum recommended soft-start capacitor is 1 μF.

Equation 5. C S S ( n F ) =   t S S ( m s )   × 36   ( μ A )   V I N T R E F ( V )

The SS/REF_IN pin can also be used to connect an external bias supply to adjust the control loop voltage reference. The FB pin tracks the voltage on the SS/VREF_IN pin. This can be useful in applications where the output voltage needs to by adjusted dynamically in-circuit. The maximum recommended external supply voltage to the SS/REF_IN pin is 1.5 V.