SLUUCH6B september   2022  – september 2023 TPS543B22

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
    1. 1.1 Background
    2. 1.2 Before You Begin
    3. 1.3 Performance Characteristics Summary
  5. 2Configurations and Modifications
    1. 2.1 Output Voltage
    2. 2.2 Switching Frequency (FSEL Pin)
    3. 2.3 Current Limit, Soft-Start Time, and Internal Compensation (MODE Pin)
    4. 2.4 Adjustable UVLO
  6. 3Test Setup and Results
    1. 3.1  Input/Output Connections
    2. 3.2  Efficiency
    3. 3.3  Output Voltage Regulation
    4. 3.4  Load Transient and Loop Response
    5. 3.5  Output Voltage Ripple
    6. 3.6  Input Voltage Ripple
    7. 3.7  Synchronizing to a Clock
    8. 3.8  Start-up and Shutdown with EN
    9. 3.9  Start-up and Shutdown with VIN
    10. 3.10 Start-up Into Pre-Bias
    11. 3.11 Hiccup Current Limit
    12. 3.12 Thermal Performance
  7. 4Board Layout
    1. 4.1 Layout
  8. 5Schematic and Bill of Materials
    1. 5.1 Schematic
    2. 5.2 Bill of Materials
  9. 6Revision History

2.1 Output Voltage

In the U1 design, the output voltage is set by the resistor divider network of R63 (RFBT) and R60 (RFBB). R60 is fixed at 10.0 kΩ to set the FB divider current at approximately 50 µA. To change the output voltage of the EVM, the value of resistor R63 must change. Changing the value of R63 can change the output voltage above the 0.5-V reference voltage (VREF). The value of R63 for a specific output voltage can be calculated using Equation 1. After changing R63, the feedfoward capacitor (C45) can also need to be changed.

Equation 1. R F B T = R F B B × V O U T V R E F       -       1

In the U2 design, there are a few ways to set the output voltage. First, jumper J6 can be used to select between the options shown in Table 2-1. If the desired output voltage is not available, a resistor must be changed. For output voltages less than 1.0 V, TI recommends leaving J3 open and increasing R20. R20 becomes RFBB and the required value for can be calculated with Equation 2, where RFBT is R7 which is 10 kΩ. For output voltages greater than 1.0 V, the jumper output voltage options can be changed by changing one of the resistors R16-R19. The RFBJ resistor value to get a desired equivalent RFBB resistance can be calculated with Equation 3. To use J6 for output voltages 3.3 V or larger, R13 must be reduced from 825 Ω to 0 Ω.

Equation 2. R F B B = R F B T × V R E F V O U T   -   V R E F
Equation 3. R F B J = R F B B   ×   ( R 13   +   R 20 )     -     R 13   ×   R 20 R 20   -   R F B B
Table 2-1 VOUT Selection
JUMPER SETTINGEQUIVALENT BOTTOM FB RESISTOR (RFBB)NOMINAL OUTPUT VOLTAGE
OpenR20 = 10.0 kΩ1.00 V
1 to 2 pin shorted(1)(R16 + R13)||R20 = 7.15 kΩ1.20 V
3 to 4 pin shorted(R17 + R13)||R20 = 4.98 kΩ1.50 V
5 to 6 pin shorted(R18 + R13)||R20 = 3.87 kΩ1.80 V
7 to 8 pin shorted(R19 + R13)||R20 = 1.8 kΩ3.3 V
(1) Default Setting