SLVUCI4B february   2023  – may 2023 TPS7H5001-SP

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2System Design Theory
    1. 2.1  Switching Frequency
    2. 2.2  Leading Edge Blanking
    3. 2.3  Dead Time
    4. 2.4  Enable and UVLO
    5. 2.5  Output Voltage Programing
    6. 2.6  Soft Start
    7. 2.7  Sensing Circuit
    8. 2.8  FAULT Mode
    9. 2.9  HICCUP Mode
    10. 2.10 Slope Compensation
    11. 2.11 Output Capacitance
    12. 2.12 Compensation
  6. 3Test Results
  7. 4Bill of Materials
  8. 5Schematics
  9. 6PCB Layouts
  10. 7References
  11. 8Revision History

2.1 Switching Frequency

Choosing a switching frequency has a tradeoff between efficiency and bandwidth. Higher switching frequencies have larger bandwidth, but a lower efficiency than lower switching frequencies. First, the maximum switching frequency for the requirements had to be calculated. For the calculation, the minimum on time for the device was determined by adding 75 ns for controller on time and 100 ns of LEB.

Equation 1. f s w _ m a x = 1   T s w _ m a x   =   D u t y   C y c l e   t m i n ⁡ _ o n _ t i m e =   0.0833 175   n s =   476   k H z

To make sure the max switching frequency was not approached, the switching frequency was set to 400 kHz. Using equations provided by the data sheet for the TPS7H5001-SP, the RT resistor was chosen to be 260 k. The equation for the switching frequency used is Equation 2.

Equation 2. R T =   112,000 f s w   ( k H z ) - 19.7 = 112,000 399   k H z - 19.7 = 261   k Ω