Hi
In my LM5118 configuration, VCC is driven externally, so the internal regulator is not sourcing any current. While I'm guessing the internal LDO regulator would've been the largest source of power dissipation, it still appears that the LM5118 is dissipating power in other ways, especially while in buck-boost mode. What are some other sources of power dissipation in the IC (especially ones that can be estimated/analyzed)?
Thanks
John,
The major source of power dissipation will be in the gate drivers. When you're in buck-boost mode there are two gate drivers in operation which is why there is higher power dissipation in that mode. Also if operating at higher switching frequencies the gate driver losses will be high.
This can be estimated by:
Pdriver = Qg*Vgs*Fsw*Rg
Qg = Total Gate Charge of the FET
Vgs = Gate Drive Voltage (In this case VCC)
Fsw = Switching frequency
Rg = Gate driver resistance (approx 1 Ohm)
This will give you a good estimate of the power dissipation.
The below link has much more detail on calculating Gate driver and MOSFET losses.
-Garrett
