SLVUCW0 June   2024 TPSM86837

 

  1.   1
  2.   Description
  3.   Features
  4.   Applications
  5.   5
  6. 1Evaluation Module Overview
    1. 1.1 Introduction
    2. 1.2 Kit Contents
    3. 1.3 Specification
    4. 1.4 Device Information
  7. 2Hardware
    1. 2.1 Start-Up Procedure
    2. 2.2 Input and Output Connections
    3. 2.3 Modifications
      1. 2.3.1 Output Voltage Setpoint
      2. 2.3.2 Mode Selection
      3. 2.3.3 Adjustable UVLO
  8. 3Implementation Results
    1. 3.1 Test Setup and Results
      1. 3.1.1 Output Voltage Ripple
      2. 3.1.2 Start-Up
      3. 3.1.3 Shutdown
  9. 4Hardware Design Files
    1. 4.1 Schematic
    2. 4.2 PCB Layouts
    3. 4.3 Bill of Materials
  10. 5Additional Information
    1. 5.1 Trademarks
  11. 6Reference

2.3.1 Output Voltage Setpoint

To change the output voltage of the EVMs, change the value of resistor R7 (RFB_TOP) and resistor R8 (RFB_BOT). Changing the value of R7 and R8 can change the output voltage above 0.6V. The value of R7 and R8 for a specific output voltage can be calculated using Equation 1.

Equation 1. VOUT=0.6×(1+R7R8)

Table 3-2 lists the R7 and R8 values for some common output voltages.

Table 2-2 Recommended Component Values
Switching Frequency (Hz)OUTPUT VOLTAGE(1)
(V)		R7(2)
(kΩ)		R8
(kΩ)		COUT(3)
(µF)		C8 (pF)(4)
TYP
800k1.057.510.068
1.82010.06847
3.345.310.06247
573.210.03547
1.2M1.057.510.068
1.82010.06847
3.345.310.06247
573.210.035150
(1) Please use the recommended COUT of the higher and closest output rail for unlisted output rails.
(2) R7 = 0Ω for VOUT = 0.6V.
(3) COUT is the sum of effective output capacitance. The effective capacitance is defined as the actual capacitance under DC bias and temperature, not the rated or nameplate values. All high value ceramic capacitors have a large voltage coefficient in addition to normal tolerances and temperature effects. A careful study of bias and temperature variation of any capacitor bank must be made to verify that the minimum value of effective capacitance is provided. Refer to the information of DC bias and temperature characteristics from manufacturers of ceramic capacitors.
(4) R10 and C8 can be used to improve the load transient response or improve the loop-phase margin. The application report, Optimizing Transient Response of Internally Compensated DCDC Converters with Feed-forward Capacitor, is helpful when experimenting with a feed-forward capacitor.