SLVSH66A February   2023  – November 2023 TPSM63608

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Revision History
  6. 5 Device Comparison Table
  7. 6 Pin Configuration and Functions
  8. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 System Characteristics
    7. 7.7 Typical Characteristics
  9. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Input Voltage Range (VIN1, VIN2)
      2. 8.3.2  Adjustable Output Voltage (FB)
      3. 8.3.3  Input Capacitors
      4. 8.3.4  Output Capacitors
      5. 8.3.5  Switching Frequency (RT)
      6. 8.3.6  Precision Enable and Input Voltage UVLO (EN)
      7. 8.3.7  Frequency Synchronization (SYNC/MODE)
      8. 8.3.8  Spread Spectrum
      9. 8.3.9  Power-Good Monitor (PG)
      10. 8.3.10 Adjustable Switch-Node Slew Rate (RBOOT, CBOOT)
      11. 8.3.11 Bias Supply Regulator (VCC, VLDOIN)
      12. 8.3.12 Overcurrent Protection (OCP)
      13. 8.3.13 Thermal Shutdown
    4. 8.4 Device Functional Modes
      1. 8.4.1 Shutdown Mode
      2. 8.4.2 Standby Mode
      3. 8.4.3 Active Mode
  10. 9 Applications and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Applications
      1. 9.2.1 Design 1 – High-Efficiency 6-A (8-A peak) Synchronous Buck Regulator for Industrial Applications
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
          1. 9.2.1.2.1 Custom Design With WEBENCH® Tools
          2. 9.2.1.2.2 Output Voltage Setpoint
          3. 9.2.1.2.3 Switching Frequency Selection
          4. 9.2.1.2.4 Input Capacitor Selection
          5. 9.2.1.2.5 Output Capacitor Selection
          6. 9.2.1.2.6 Other Connections
        3. 9.2.1.3 Application Curves
      2. 9.2.2 Design 2 – Inverting Buck-Boost Regulator with Negative Output Voltage
        1. 9.2.2.1 Design Requirements
        2. 9.2.2.2 Detailed Design Procedure
          1. 9.2.2.2.1 Output Voltage Setpoint
          2. 9.2.2.2.2 IBB Maximum Output Current
          3. 9.2.2.2.3 Switching Frequency Selection
          4. 9.2.2.2.4 Input Capacitor Selection
          5. 9.2.2.2.5 Output Capacitor Selection
          6. 9.2.2.2.6 Other Considerations
        3. 9.2.2.3 Application Curves
    3. 9.3 Power Supply Recommendations
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
        1. 9.4.1.1 Thermal Design and Layout
      2. 9.4.2 Layout Example
  11. 10Device and Documentation Support
    1. 10.1 Device Support
      1. 10.1.1 Third-Party Products Disclaimer
      2. 10.1.2 Development Support
        1. 10.1.2.1 Custom Design With WEBENCH® Tools
    2. 10.2 Documentation Support
      1. 10.2.1 Related Documentation
    3. 10.3 Receiving Notification of Documentation Updates
    4. 10.4 Support Resources
    5. 10.5 Trademarks
    6. 10.6 Electrostatic Discharge Caution
    7. 10.7 Glossary
  12. 11Mechanical, Packaging, and Orderable Information

Package Options

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

8.3.3 Input Capacitors

Input capacitors are necessary to limit the input ripple voltage to the module due to switching-frequency AC currents. TI recommends using ceramic capacitors to provide low impedance and high RMS current rating over a wide temperature range. Equation 2 gives the input capacitor RMS current. The highest input capacitor RMS current occurs at D = 0.5, at which point the RMS current rating of the capacitors must be greater than half the output current.

Equation 2. ICIN,rms=D×IOUT2×1-D+∆iL212

where

  • D = VOUT / VIN is the module duty cycle.

Ideally, the DC and AC components of input current to the buck stage are provided by the input voltage source and the input capacitors, respectively. Neglecting inductor ripple current, the input capacitors source current of amplitude (IOUT – IIN) during the D interval and sink IIN during the 1 – D interval. Thus, the input capacitors conduct a square-wave current of peak-to-peak amplitude equal to the output current. The resultant capacitive component of AC ripple voltage is a triangular waveform. Together with the ESR-related ripple component, Equation 3 gives the peak-to-peak ripple voltage amplitude:

Equation 3. ∆VIN=IOUT×D×1-DFSW×CIN+IOUT×RESR

Equation 4 gives the input capacitance required for a particular load current:

Equation 4. CIN≥IOUT×D×1-DFSW×∆VIN-IOUT×RESR

where

  • ΔVIN is the input voltage ripple specification.

The TPSM63608 requires a minimum of two 10-µF ceramic input capacitors, preferably with X7R or X7S dielectric and in 1206 or 1210 footprint. Additional capacitance can be required for applications to meet conducted EMI specifications, such as CISPR 11 or CISPR 32.

Table 8-2 includes a preferred list of capacitors by vendor. To minimize the parasitic inductance in the switching loops, position the ceramic input capacitors in a symmetrical layout close to the VIN1 and VIN2 pins and connect the capacitor return terminals to the PGND pins using a copper ground plane under the module.

Table 8-2 Recommended Ceramic Input Capacitors
VENDOR(1)DIELECTRICPART NUMBERCASE SIZECAPACITANCE (µF)(2)RATED VOLTAGE (V)
TDKX7RC3216X7R1H106K160AC12061050
MurataX7SGCM32EC71H106KA03K12101050
AVXX7R12105C106MAT2A12101050
MurataX7RGRM32ER71H106KA12L12101050
(1) Consult capacitor suppliers regarding availability, material composition, RoHS and lead-free status, and manufacturing process requirements for any capacitors identified in this table. See the Third-Party Products Disclaimer.
(2) Nameplate capacitance values (the effective values are lower based on the applied DC voltage and temperature).

As discussed in Power Supply Recommendations, an electrolytic bulk capacitance (68 µF to 100 µF) provides low-frequency filtering and parallel damping to mitigate the effects of input parasitic inductance resonating with the low-ESR, high-Q ceramic input capacitors.