SLVU097B October   2003  – October 2021 TPS54350

 

  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 Switching Frequency
      3. 1.3.3 Input Filter
      4. 1.3.4 UVLO Programming
      5. 1.3.5 Synchronization
      6. 1.3.6 Power Good
      7. 1.3.7 Synchronous Low-Side FET
      8. 1.3.8 Optional Output Filtering
  3. 2Test Setup and Results
    1. 2.1  Input/Output Connections
    2. 2.2  Efficiency
    3. 2.3  Power Dissipation
    4. 2.4  Output Voltage Regulation
    5. 2.5  Load Transients
    6. 2.6  Loop Characteristic
    7. 2.7  Output Voltage Ripple
    8. 2.8  Input Voltage Ripple
    9. 2.9  Gate Drive
    10. 2.10 Powering Up and Down
  4. 3Board Layout
    1. 3.1 Layout
  5. 4Schematic and Bill of Materials
    1. 4.1 Bill of Materials
  6. 5Revision History

1.3.1 Output Voltage Setpoint

Changing the value of R2 can change the output voltage in the range of 0.9 V to 5 V. The value of R2 for a specific output voltage can be calculated by using Equation 1. Table 1-3 list the values for R2 for some common output voltages.

Table 1-3 Output Voltage Programming
OUTPUT VOLTAGE (V) R2 VALUE (Q)
1.2 2.87 k
1.5 1.47 k
1.8 976
2.5 549
3.3 374
5.0 221
Equation 1. R2=1 kΩ × 0.891 VVO-0.891 V

The minimum output voltage is limited by the minimum controllable on time of the device, 125 ns, and is dependent upon the duty cycle and operating frequency. The approximate minimum output voltage can be calculated using Equation 2:

Equation 2. VO(min) = 125 nsec × fs × VI(max)