Design Considerations

Input Source Impedance

The impedance of the input source connecting to the DC/DC power modules will interact with the modules and affect the stability. A low ac-impedance input source is recommended. If the source inductance is more than a few µH, we advise adding a 10 to 100 µF electrolytic capacitor (ESR < 0.7 Ω at 100 kHz) mounted close to the input of the module to improve the stability.

Layout and EMC Considerations

Delta’s DC/DC power modules are designed to operate in a wide variety of systems and applications. For design assistance with EMC compliance and related PWB layout issues, please contact Delta’s technical support team. An external input filter module is available for easier EMC compliance design. Below is the example of using Delta latest FL75L07 7A surface mountable input filter tested with V48SR15004 to meet class B compliance.

Schematic and Components

Filter = Delta EMI Filter, FL75L07; L1 = 1uH differential inductor;

CX = 100uF/100V low impedance electrolytic capacitance; CY1 = 0.22uF low impedance SMT ceramic capacitance.

EMC Test Result

Test result is in compliance with EN55022 class B as shown below.

Average mode, @ Vin = 48V, Iout=4.4A

Suggested Layout

DS_V48SR15004_06122007