DESCRIPTION
As discussed in application note, AN728, the Si9113 power supply controller is an ideal choice for ISDN terminal equipment, where high efficiency at a low power level is one of most important criteria. Therefore, Vishay Siliconix has developed versions of a dual output flyback application demonstration boards, the Si9113D1 and the Si9113D2, which use different regulation schemes. These readily available demo boards are configured to deliver approximately 800 mW at 3.3-V, and40-V. These outputs and can be easily modified for other output voltages at approximately same power level. The flyback converters are designed to operate from a wide input voltage range of 28 V to 99 V and are polarity protected by a diode bridge. The Si9113D1 and Si9113D2, both operate at 20-kHz switching frequency to achieve the best possible efficiency. The transformer is selected to be slightly larger in this application so that the same area product would be good enough for an even lower window utilization factor (w.u.f.) transformer in order to meet the stringent requirements of clearance and creepage distances.

FEATURES
ISDN-NT Input Voltage Range 28 V to 99 V
Non-Polar Input
3.3-V/120-mA, 40-V/12-mA Outputs With Up To 80% Efficiency
Up to 68% Efficiency at 80-mW Load
40 V Isolated By 3 kV From Input And 3.3-V Output – Si9113D1
3.3 V, 40 V Isolated By 1.5 kV From Input/Each Other – Si9113D2
Current Mode Control, 0.6-V Fast Over-Current Protection
Max 50% Duty Cycle Operation
1.3-MHz Error Amp
Soft-Start
<10-µA Supply Current for +VIN <18 V
Programmed Start/Stop
Internal Start-Up Circuit
Power_Good Output