SLVAF76 August   2021 TPS62901 , TPS62902 , TPS62902-Q1 , TPS62903 , TPS62903-Q1

 

  1.   Trademarks
  2. 1Applications With Limited Area
    1. 1.1 Best TPS62903 Configuration to Reduce Size
    2. 1.2 Design Example
  3. 2Applications With High Efficiency and Thermal Requirement
    1. 2.1 Conduction Losses in the MOSFET
    2. 2.2 Conduction Losses in the Inductor
    3. 2.3 Switching Losses in the MOSFET
    4. 2.4 Losses in the Input and Output Capacitors
    5. 2.5 Analysis and Recommendations
  4. 3Conclusion

2.4 Losses in the Input and Output Capacitors

Several losses can be generated in the capacitor including series resistance, leakage, and dielectric loss. In this report, these losses are simplified into a general loss model as equivalent series resistance (ESR). The power loss in the capacitor is calculated by multiplying the ESR by the square of the RMS value of the AC current flowing through the capacitor. Use Equation 5 to estimate the power losses in the input and the output capacitor:

Equation 5. P_Loss_Capacitor=Icap_rms2 × ESR

The RMS current into the input capacitor is typically proportional to the output current and the input and output voltages, it can be estimated using Equation 6:

Equation 6. ICIN_rms=IOUT×(VIN-VOUT)×VOUTVIN

The output capacitor output current can be calculated using RMS value of the inductor current ripple. It can be estimated using Equation 7:

Equation 7. ICOUT_rms=Δ IL23

Selecting a low-ESR multilayer ceramic capacitor (MLCC) is recommended to reduce these losses.