SNVSCG7 November   2024 LM5190

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  Input Voltage Range (VIN)
      2. 6.3.2  High-Voltage Bias Supply Regulator (VCC, BIAS)
      3. 6.3.3  Precision Enable (EN)
      4. 6.3.4  Power-Good Monitor (PGOOD)
      5. 6.3.5  Switching Frequency (RT)
      6. 6.3.6  Low Dropout Mode
      7. 6.3.7  Dual Random Spread Spectrum (DRSS)
      8. 6.3.8  Soft Start
      9. 6.3.9  Output Voltage Setpoint (FB)
      10. 6.3.10 Minimum Controllable On Time
      11. 6.3.11 Inductor Current Sense (ISNS+, VOUT)
      12. 6.3.12 Voltage Loop Error Amplifier
      13. 6.3.13 Current Monitor, Programmable Current Limit, and Current Loop Error Amplifier (IMON/ILIM, ISET)
      14. 6.3.14 Dual Loop Architecture
      15. 6.3.15 PWM Comparator
      16. 6.3.16 Slope Compensation
      17. 6.3.17 Hiccup Mode Current Limiting
      18. 6.3.18 High-Side and Low-Side Gate Drivers (HO, LO)
    4. 6.4 Device Functional Modes
      1. 6.4.1 Sleep Mode
      2. 6.4.2 Forced PWM Mode and Synchronization (FPWM/SYNC)
      3. 6.4.3 Thermal Shutdown
  8. 7 Application and Implementation
    1. 7.1 Application Information
      1. 7.1.1 Power Train Components
        1. 7.1.1.1 Buck Inductor
        2. 7.1.1.2 Output Capacitors
        3. 7.1.1.3 Input Capacitors
        4. 7.1.1.4 Power MOSFETs
        5. 7.1.1.5 EMI Filter
      2. 7.1.2 Error Amplifier and Compensation
    2. 7.2 Typical Applications
      1. 7.2.1 High Efficiency 400kHz CC-CV Regulator
        1. 7.2.1.1 Design Requirements
        2. 7.2.1.2 Detailed Design Procedure
          1. 7.2.1.2.1 Buck Inductor
          2. 7.2.1.2.2 Current-Sense Resistance
          3. 7.2.1.2.3 Output Capacitors
          4. 7.2.1.2.4 Input Capacitors
          5. 7.2.1.2.5 Frequency Set Resistor
          6. 7.2.1.2.6 Feedback Resistors
        3. 7.2.1.3 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
        1. 7.4.1.1 Power Stage Layout
        2. 7.4.1.2 Gate-Drive Layout
        3. 7.4.1.3 PWM Controller Layout
        4. 7.4.1.4 Thermal Design and Layout
        5. 7.4.1.5 Ground Plane Design
      2. 7.4.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Device Support
      1. 8.1.1 Development Support
    2. 8.2 Documentation Support
      1. 8.2.1 Related Documentation
        1. 8.2.1.1 PCB Layout Resources
        2. 8.2.1.2 Thermal Design Resources
    3. 8.3 Receiving Notification of Documentation Updates
    4. 8.4 Support Resources
    5. 8.5 Trademarks
    6. 8.6 Electrostatic Discharge Caution
    7. 8.7 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

7.1.1.3 Input Capacitors

Input capacitors are necessary to limit the input ripple voltage to the buck power stage due to switching-frequency AC currents. TI recommends using X7S or X7R dielectric ceramic capacitors to provide low impedance and high RMS current rating over a wide temperature range. To minimize the parasitic inductance in the switching loop, position the input capacitors as close as possible to the drain of the high-side MOSFET and the source of the low-side MOSFET. The input capacitor RMS current for a single-channel buck regulator is given by Equation 17.

Equation 17. I C I N , r m s = D × I L O A D 2 × 1 - D + ∆ I L O U T 2 12

The highest input capacitor RMS current occurs at D = 0.5, at which point, the RMS current rating of the input capacitors must be greater than half the output current.

Ideally, the DC component of input current is provided by the input voltage source and the AC component by the input filter capacitors. Neglecting inductor ripple current, the input capacitors source current of amplitude (ILOAD − ISUPPLY) during the D interval and sinks ISUPPLY 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, the peak-to-peak ripple voltage amplitude is given by Equation 18.

Equation 18. ∆ V S U P P L Y = I L O A D × D × 1 - D f S W × C I N + I L O A D × R E S R

The input capacitance required for a particular load current, based on an input voltage ripple specification of ΔVSUPPLY, is given by Equation 19.

Equation 19. C I N ≥ D × 1 - D × I L O A D f S W × ∆ V S U P P L Y - I L O A D × R E S R

Low-ESR ceramic capacitors can be placed in parallel with higher valued bulk capacitance to provide optimized input filtering for the regulator and damping to mitigate the effects of input parasitic inductance resonating with high-Q ceramics. Select the input bulk capacitor based on the ripple current rating and operating temperature range.