SLVSHN0A September   2024  – October 2025 TPS548B23

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1  D-CAP4 Control
      2. 6.3.2  Internal VCC LDO and Using External Bias On the VCC Pin
        1. 6.3.2.1 Powering the Device From a Single Bus
        2. 6.3.2.2 Powering the Device From a Split-Rail Configuration
      3. 6.3.3  Multifunction Configuration (CFG1-5) Pins
        1. 6.3.3.1 Multifunction Configuration (CFG1-2) Pins (Internal Feedback)
        2. 6.3.3.2 Multifunction Configuration (CFG1-2) Pins (External Feedback)
        3. 6.3.3.3 Multifunction Configuration (CFG3-5) Pins
      4. 6.3.4  Enable
      5. 6.3.5  Soft Start
      6. 6.3.6  Power Good
      7. 6.3.7  Overvoltage and Undervoltage Protection
      8. 6.3.8  Output Voltage Setting (External Feedback Configuration)
      9. 6.3.9  Remote Sense
      10. 6.3.10 Low-side MOSFET Zero-Crossing
      11. 6.3.11 Current Sense and Positive Overcurrent Protection
      12. 6.3.12 Low-side MOSFET Negative Current Limit
      13. 6.3.13 Output Voltage Discharge
      14. 6.3.14 UVLO Protection
      15. 6.3.15 Thermal Shutdown
    4. 6.4 Device Functional Modes
      1. 6.4.1 Auto-Skip (PFM) Eco-mode Light Load Operation
      2. 6.4.2 Forced Continuous-Conduction Mode
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
        1. 7.2.2.1 Output Voltage Setting Point
        2. 7.2.2.2 Choose the Switching Frequency
        3. 7.2.2.3 Choose the Inductor
        4. 7.2.2.4 Choose the Output Capacitor
        5. 7.2.2.5 Choose the Input Capacitors (CIN)
        6. 7.2.2.6 VCC Bypass Capacitor
        7. 7.2.2.7 BOOT Capacitor
        8. 7.2.2.8 PG Pullup Resistor
      3. 7.2.3 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Documentation Support
      1. 8.1.1 Related Documentation
    2. 8.2 Receiving Notification of Documentation Updates
    3. 8.3 Support Resources
    4. 8.4 Trademarks
    5. 8.5 Electrostatic Discharge Caution
    6. 8.6 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

7.2.2.4 Choose the Output Capacitor

There are three considerations for selecting the value of the output capacitor:

  1. Stability
  2. Steady state output voltage ripple
  3. Regulator transient response to a change load current
First, calculate the minimum output capacitance based on these three requirements. Equation 17 calculates the minimum capacitance to keep the LC double pole below the fP(MAX) in Table 6-1 to meet stability requirements. This requirement helps to keep the LC double pole close to the internal zero. Equation 18 calculates the minimum capacitance to meet the steady state output voltage ripple requirement of 16mV. These calculations are for CCM operation and does not include the portion of the output voltage ripple caused by the ESR or ESL of the output capacitors.

Equation 17. C O U T _ S T A B L I T Y > 1 2 π × f P ( T A B L E ) × 1 + V O U T V I N ( T Y P ) 2 2 × 1 L O U T = 1 2 π × 19.9 k H z × 1 + 3.3 V 12 V 2 2 × 1 0.55 μ H = 101 μ F
Equation 18. C O U T _ R I P P L E > I R I P P L E 8 × V R I P P L E × f S W = 5.95 A 8 × 16 m V × 800 k H z = 58.1 μ F

Equation 20 and Equation 21 calculate the minimum capacitance to meet the transient response requirement of 99mV with a 10A step. These equations calculate the necessary output capacitance to hold the output voltage steady while the inductor current ramps up or ramps down after a load step.

Equation 19. C O U T _ U N D E R S H O O T > L × I S T E P 2 × V O U T V I N m i n × f S W + t O F F _ M I N m a x 2 × V T R A N S × V O U T × V I N m i n - V O U T V I N m i n × f S W - t O F F _ M I N m a x
Equation 20. C O U T _ U N D E R S H O O T > 0.55 μ H × 10 A 2 × 3.3 V 8 V × 800 k H z + 150 n s 2 × 99 m V × 3.3 V × 8 V - 3.3 V 8 V × 800 k H z - 150 n s = 95.9 μ F
Equation 21. C O U T _ O V E R S H O O T > L × I S T E P 2 2 × V T R A N S × V O U T = 0.55 μ H × 10 A 2 2 × 99 m V × 3.3 V = 84.2 μ F

The output capacitance needed to meet the overshoot requirement is the highest value, so this sets the required minimum output capacitance for this example. Stability requirements can also limit the maximum output capacitance. Equation 22 calculates the recommended maximum output capacitance. This calculation keeps the LC double pole above 1/100th the fSW.

Equation 22. C O U T _ S T A B I L I T Y < 50 π × f S W 2 × 1 L = 50 π × 800 k H z 2 × 1 0.55 μ H = 720 μ F

Using more output capacitance is possible, but the stability must be checked through a bode plot or transient response measurement. The selected output capacitance is 6 × 47μF, 10V ceramic capacitors. When using ceramic capacitors, the capacitance must be derated due to DC and AC bias effects. The selected capacitors derate to 48% the nominal value giving an effective total capacitance of 135μF. This effective capacitance meets the minimum and maximum requirements.

This application uses all ceramic capacitors so the effects of ESR on the ripple and transient were ignored. If using non ceramic capacitors, as a starting point, the ESR must be below the values calculated in Equation 23 to meet the ripple requirement and Equation 24 to meet the transient requirement. For more accurate calculations or if using mixed output capacitors, the impedance of the output capacitors must be used to determine if the ripple and transient requirements can be met.

Equation 23. R E S R _ R I P P L E < V R I P P L E I R I P P L E = 26 m V 5.95 A = 4.4 m Ω
Equation 24. R E S R _ T R A N S < V T R A N S I S T E P = 99 m V 10 A = 9.9 m Ω