SLUSF90A June   2023  – January 2024 TPS562203 , TPS562206

PRODUCTION DATA  

  1.   1
  2. Features
  3. Applications
  4. Description
  5. Pin Configuration and Functions
  6. 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. Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Adaptive On-Time Control and PWM Operation
      2. 6.3.2 Eco-mode Control
      3. 6.3.3 Soft Start and Prebiased Soft Start
      4. 6.3.4 Large Duty Operation
      5. 6.3.5 Current Protection
      6. 6.3.6 Enable Circuit
      7. 6.3.7 Undervoltage Lockout (UVLO) Protection
      8. 6.3.8 Thermal Shutdown
    4. 6.4 Device Functional Modes
      1. 6.4.1 Eco-mode Operation
      2. 6.4.2 FCCM Mode Operation
  8. 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 Custom Design with WEBENCH® Tools
        2. 7.2.2.2 Output Voltage Resistors Selection
        3. 7.2.2.3 Output Filter Selection
        4. 7.2.2.4 Input Capacitor Selection
        5. 7.2.2.5 Bootstrap Capacitor Selection
      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. Device and Documentation Support
    1. 8.1 Device Support
      1. 8.1.1 Development Support
        1. 8.1.1.1 Custom Design with WEBENCH® Tools
    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. Revision History
  11. 10Mechanical, Packaging, and Orderable Information

Package Options

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

Output Filter Selection

The LC filter used as the output filter has a double pole at Equation 4. In this equation, COUT must use effective value after derating, not nominal value.

Equation 4. Frequencydouble pole=12×π×LOUT×COUT

For any control topology that is compensated internally, there is a range of the output filter control topology can support. At low frequency, the overall loop gain is set by the output set-point resistor divider network and the internal gain of the device. The low frequency phase is 180°. At the output filter pole frequency, the gain rolls off at a –40dB per decade rate and the phase drops has a 180 degree drop. The internal ripple generation network introduces a high-frequency zero that reduces the gain roll off from –40dB to –20dB per decade and leads the 90 degree phase boost. The internal ripple injection high-frequency zero is about 41kHz. TI recommends the inductor and capacitor selected for the output filter that the double pole is located about 20kHz, so that the phase boost provided by this high-frequency zero provides adequate phase margin for the stability requirement. For higher than 2V output voltage, TI suggests to add a CFF (Cap of Feed Forward) C4 in schematic to increase the bandwidth and phase margin. The suggested CFF range is 10pF to 100pF. The crossover frequency of the overall system must usually be targeted to be less than one-third of the switching frequency.

Table 7-2 Recommended Component Values
OUTPUT VOLTAGE (V)R1 (kΩ)R2 (kΩ)Min L(uH)TYP L (uH)Max L(uH)Min Cout(uF)Typ Cout(uF)Max Cout(uF)CFF(pF)
0.83.3310.01.21.52.22266110-
1.057.510.01.22.23.32244110-
2.595.030.02.23.34.7224411010
3.3135.030.03.34.76.8224411018
5220.030.03.34.76.8224411018
7320.030.03.34.76.8224411018

Use Equation 5, Equation 6, and Equation 7 to calculate the inductor peak-to-peak ripple current, peak current and RMS current. The inductor saturation current rating must be greater than the calculated peak current and the RMS or heating current rating must be greater than the calculated RMS current.

Equation 5. IIP-P=VOUTVINMax×VINMax-VOUTLOUT×fSW
Equation 6. IIPEAK=IO+IIP-P2
Equation 7. ILO(RMS)=IO2+112×IIP-P2

For this design example, the calculated peak current is 3.68A and the calculated RMS current is 3.03A. The inductor used is a WE 74437349022.

The capacitor value and ESR determines the amount of output voltage ripple. The TPS562203 are intended for use with ceramic or other low ESR capacitors. TI recommends to use 2 × 22µF output cap. Use Equation 8 to determine the required RMS current rating for the output capacitor.

Equation 8. ICO(RMS)=VOUT×VIN-VOUT12×VIN×LOUT×fSW

For this design, two MuRata GRM21BR61A226ME44L 22µF output capacitors are used. The typical ESR is 2mΩ each. The calculated RMS current is 0.286A and each output capacitor is rated for 4A.