JAJSFS7B July 2018 – February 2019 LM5180-Q1
ADVANCE INFORMATION for pre-production products; subject to change without notice.
The 24-V output is DC stacked on top of the 5-V output as they share a common return connection. This enables lower secondary-to-secondary leakage inductance for better cross regulation and also reduced rectifier diode reverse voltage stress. Choose a primary-secondary turns ratio for the effective 19-V secondary based on an approximate 60% max duty cycle at minimum input voltage using Equation 37.
Set the turns ratio of the transformer secondary windings using Equation 38. The transformer turns ratio for both outputs is thus specified as 1 : 1.5 : 0.4.
As before, select a magnetizing inductance of 30 µH based on the minimum off-time constraint and specify a saturation current of 2 A to handle the peak primary current.