SLVAFP0 December   2023 LMR51610

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Specifications
    1. 2.1 Input Voltage Range
    2. 2.2 Output Current Range
  6. 3External Component Selection
    1. 3.1 Duty Cycle Calculation
    2. 3.2 Output Voltage Calculation
    3. 3.3 Inductor Selection
    4. 3.4 Input and Output Capacitor
    5. 3.5 Enable Level Shift
    6. 3.6 Output Clamp Diode
  7. 4Evaluation Results
    1. 4.1 Typical Performance
    2. 4.2 Loop Response Bench Verification
  8. 5Conclusion
  9. 6References
  10. 7LMR50410 Design Example
    1. 7.1 LMR50410 Output Current Range
    2. 7.2 LMR50410 Efficiency

3.3 Inductor Selection

Focused on light loading application the designed inductor current ripple is 20% to 40% the inductor average current ,and the total loading with 100mA as example, show SCH in the following.

Notice the current limit is 1.6A for LMR51610. And the max Iout can support for IBB use Equation 7. KIND is a coefficient that represents the amount of inductor ripple current relative to the maximum output current of the device, usually K=0.2 – 0.4. IOUT_IC = 1A for LMR51610. Dnorm = 0.38 at VIN_norm = 24V, K=0.4, fsw = 400khz, result L=56uH.

Equation 7. GUID-F46627F0-37AE-41F4-AD77-95DC87504F22-low.gif

The LMR51610 is protected from over-current conditions by cycle-by-cycle current limit. To prevent inductor saturation in case of short circuit conditions, the inductor saturation current needs to be greater than the device maximum peak current limit.