SLUU180B January   2022  – February 2022 TPS40070 , TPS40071

 

  1.   Trademarks
  2. 1Introduction
  3. 2Description
  4. 3Schematic
    1. 3.1 Output Filter Components
    2. 3.2 MOSFET Selection
    3. 3.3 Frequency Feedforward Resistor Selection
    4. 3.4 Output Voltage Setpoint
    5. 3.5 Short Circuit Protection Resistor Selection
    6. 3.6 Miscellaneous Parts
    7. 3.7 Control Loop Compensation
  5. 4Test Setup
  6. 5Results
    1. 5.1 Control Loop Characteristics
  7. 6Assembly Drawing and PCB Layout
  8. 7List of Materials
  9. 8Reference
  10. 9Revision History

3.7 Control Loop Compensation

The TPS40071 incorporates voltage mode control with feedforward compensation to minimize gain variations with a variable supply voltage. A type-3 compensation circuit is used to provide two zeroes and three poles as detailed below.

The power circuit LC double pole corner frequency, fC, is found to be 10.6 kHz, and the output capacitor ESR zero occurs in the vicinity of 1.1 MHz. The first pole is located at placed at the origin to improve dc regulation.

The first zero is placed at 758 Hz:

Equation 6. f Z 1 =   1 2   ×   π   × R 7 +   R 8 × C 6

The second zero is selected to be near the LC corner frequency at 10.4 kHz:

Equation 7. f Z 1 =   1 2   ×   π   ×   R 5   ×   C 6

The second and third poles are placed at 192 kHz and 194 kHz to roll off the high frequency gain:

Equation 8. fP2= 12 × π × R5 ×(C4- C5(C4+ C5))
Equation 9. fP3= 12 × π × R8 × C6