The following formulas show how to estimate the device power dissipation under continuous-conduction mode (CCM) operations. These formulas must not be used if the device is working in the discontinuous-conduction mode (DCM) or pulse-skipping Eco-mode.

The device power dissipation includes:

1. Conduction loss:
   Pcon = I_OUT² × R_DS(on) × V_OUT / V_IN

   • where

   • I_OUT is the output current (A)
   • R_DS(on) is the on-resistance of the high-side MOSFET (Ω)
   • V_OUT is the output voltage (V)
   • V_IN is the input voltage (V)
2. Switching loss:
   Psw = 0.5 × 10^–9 × V_IN² × I_OUT × ƒ_SW

   • where

   • ƒ_SW is the switching frequency (Hz)
3. Gate charge loss:
   Pgc = 22.8 × 10^-9 × ƒ_SW
4. Quiescent current loss:
   Pq = 0.11 × 10^-3 × V_IN

Therefore:

where

• Ptot is the total device power dissipation (W)

For given T_A:

where

• T_J is the junction temperature (°C)
• T_A is the ambient temperature (°C)
• Rth is the thermal resistance of the package (°C/W)

For given T_JMAX = 150°C:

where

• T_JMAX is maximum junction temperature (°C)
• T_AMAX is maximum ambient temperature (°C)