SLVU479A October   2011  – August 2021 TPS54821

 

  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 Track In
      4. 1.3.4 Adjustable UVLO
      5. 1.3.5 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 Transients
    6. 2.6  Loop Characteristics
    7. 2.7  Output Voltage Ripple
    8. 2.8  Input Voltage Ripple
    9. 2.9  Powering 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 R8. R7 is fixed at 10 kΩ. To change the output voltage of the EVM, it is necessary to change the value of resistor R8. Changing the value of R8 can change the output voltage above 0.6 V. The value of R8 for a specific output voltage can be calculated using Equation 1.

Equation 1. GUID-EACBF03E-600A-4C47-86CC-36F6E581FE9D-low.gif

Table 1-3 lists the R8 values for some common output voltages. Note that VIN must be in a range so that the on-time is greater than the minimum controllable on-time (94-ns typical, 145-ns maximum), and the maximum duty cycle is less than 95%. The values given in Table 1-3 are standard values, not the exact value calculated using Equation 1.

Table 1-3 Output Voltages Available
OUTPUT VOLTAGE
(V)		R8 VALUE
(kΩ)
1.84.99
2.53.16
3.32.21
51.37