The LMG3626 turn-on slew rates are programmed as discussed in the Turn-On Slew-Rate Control section. The design consideration is the trade-off between power supply efficiency and EMI / transient ringing. Slower turn-on slew-rates lessen EMI and ringing problems but can increase switching losses and vice versa.

In normal quasi-resonant flyback-converter operation, the power switch operates at both ZVS and also non-ZVS valley switching depending on operating conditions. The valley switching occurs at zero transformer current. Therefore, there are no switching cross-over losses in quasi-resonant converters. The only switching loss is the switch-node capacitive loss during valley switching. So the turn-on slew rate has no impact on the converter loss. This seems to indicate to use the slowest turn-on slew rate setting. The turn-on slew rate setting, however, can have a secondary impact on converter loss from the switch turn-on delay.

Depending on how the quasi-resonant controller implements valley switching, the switch turn-on delay can cause the power-converter to switch after the valley and increase capacitive switching losses. Since the switch turn-on delay increases as the turn-on slew rate is decreased, using slower turn-on slew rates can increase power supply losses. If the quasi-resonant controller compensates for switch turn-on delay, then there is no loss penalty for using the slowest turn-on slew rate setting. Otherwise, design optimization between switching noise problems and switching losses must be performed.

The turn-on slew rate is programmed by setting R_DRV to the recommended typical programming resistance shown in the Turn-On Slew-Rate Control section.