SLUU182A January   2004  – March 2022 TPS5124

 

  1.   Trademarks
  2. 1Introduction
  3. 2Features
  4. 3Schematic
  5. 4Design Procedure
    1. 4.1 Frequency Setting
    2. 4.2 Inductance Value
    3. 4.3 Output Capacitors
    4. 4.4 Input Capacitors
      1. 4.4.1 Case One: D1, D2 < 0.5
      2. 4.4.2 Case Two: D2 < 0.5 < D1
    5. 4.5 Compensation Design
    6. 4.6 Current Limiting
    7. 4.7 Timer Latch
      1. 4.7.1 Undervoltage Protection
      2. 4.7.2 Short Circuit Protection
      3. 4.7.3 Overvoltage Protection
      4. 4.7.4 Disabling the Protection Function
        1. 4.7.4.1 Disabling the Overcurrent Protection
        2. 4.7.4.2 Disabling the Overvoltage Protection or Undervoltage Protection
  6. 5Test Results
    1. 5.1 Efficiency Curves
    2. 5.2 Typical Operating Waveform
    3. 5.3 Start-Up Waveform
    4. 5.4 Output Ripple Voltage and Load Transient
  7. 6Layout Guidelines
    1. 6.1 Low-Side MOSFET
    2. 6.2 Connections
    3. 6.3 Bypass Capacitor
    4. 6.4 Bootstrap Capacitor
    5. 6.5 Output Voltage
  8. 7PCB Layout
  9. 8List of Materials
  10. 9Revision History

4.2 Inductance Value

The inductance value can be calculated using Equation 1.

Equation 1. L =   V O U T f   m i n ×   I R I P P L E   ×   1 -   V O U T V I N ( m a x )

where

  • IRIPPLE is the ripple current flowing through the inductor.

The ripple current affects the output voltage ripple and core losses. Based on 20% ripple current and 300 kHz, the inductance value is calculated as 2.2 μH. An off-the-shelf 2.2-μH inductor from Vishay is chosen. The part number is IHLP−5050CE−01−2R2M01. The DCR is 7 mΩ and the DCR-related conduction loss is 1.6 W, which is about 3.3% of output power.

The same procedure is followed to choose the inductor for Channel 2. The same inductor is chosen.