SLVU777A September   2012  – November 2021 TPS54020

 

  1.   Trademarks
  2. 1Introduction
    1. 1.1 Background
    2. 1.2 Performance Specification Summary
    3. 1.3 Modifications
      1. 1.3.1 Output Voltage Setpoint
      2. 1.3.2 Slow-Start Time
      3. 1.3.3 Adjustable UVLO
      4. 1.3.4 Input Voltage Rails
  3. 2Test Setup and Results
    1. 2.1  Input / Output Connections
    2. 2.2  Efficiency
    3. 2.3  Output Voltage Load Regulation
    4. 2.4  Output Voltage Line Regulation
    5. 2.5  Load Transient
    6. 2.6  Control Loop Response
    7. 2.7  Output Voltage Ripple
    8. 2.8  Input Voltage Ripple
    9. 2.9  Start Up
    10. 2.10 Pre-Bias Start Up
    11. 2.11 Hiccup Mode Current Limit
  4. 3Board Layout
    1. 3.1 Layout
  5. 4Schematic and Bill of Materials
    1. 4.1 Schematic
    2. 4.2 Bill of Materials
  6. 5Revision History

1.3.1 Output Voltage Setpoint

The output voltage is set by the resistor divider network of R7 and R10. The lower divider resistor R10 should not be modified and should remain at 2.55 kΩ. To change the output voltage of the EVM, it is necessary to change the value of resistor R7. Changing the value of R7 changes the output voltage between 0.6 V and 5 V. The value of R7 for a specific output voltage is calculated using Equation 1.

Equation 1. GUID-A31950C2-AEEC-4465-8DBE-52F1EB04CB62-low.gif

Table 1-3 lists the R7 values for some common output voltages. Note that VIN must then be within a range so that the minimum on time is greater than 150 ns. The values given in Table 1-3 show both the ideal required values and the closest E96 standard values.

Table 1-3 Output Voltage Examples with R10 of 2.55 kΩ
DESIRED VOUTIDEAL R7CLOSEST E96 MATCHRESULTING VOUT
1.85.100 kΩ5.11 kΩ1.802
2.58.075 kΩ8.06 kΩ2.496
3.311.475 kΩ11.5 kΩ3.306
5.018.700 kΩ18.7 kΩ5.000