ADUM3070 Schematic Review

Hello Team;

Could you kindly help on the ADUM3070 Schematic Review; please?

Input: 5V; output : current 0.3A, voltage 5V,

My question:

1. For ISO-5V output; the VDD2 and Vreg should be connected together to the 5V_ISO; correct?

2. other component value are properly selected in the design?

Many thanks;


  • Bellye: My answers to your requests:
    1. Yes, we recommend that you connect VDD2 and Vreg for VISO = 5V.

    2. The schematic review:

    Recommend 0.1uF for C574, 577, do not need C576.

    Recommend the use of transformer with equivalent specs to those listed in the datasheet. TR3,.has a primary inductance pins 1-3 of only 73uH, but the datasheet recommends 60 to 100uH minimum for each winding, which is pins 1-2 or 2-3. For pins 1-3 this would require 4 times the 60 to 100uH minimum for each winding, which is pins 1-2 or 2-3, for a value between pins 1-3 of 240 to 400uH.

    The part number for L8 is not shown, it is recommended for your 0.3A application to use a 47uH inductor with equivalent specs for 0.4 to 0.5A forward current and to not saturate.

    Regards, Brian

  • Hi Bkennedy;

    For the transformer pri inductance value from 240~400uH; is it a hard requirement? Or we can adjust it based on the application scenarios. 

    For this circuit with max 0.3A output current, the peak inductor current is around 0.3 + V/L*Ton = 0.3+0.2= 0.5A. while the selected transformer saturation current is 0.9A and ADUM3070 internal cycle by cycle current limit is 1.3A. Thus; would this transformer be OK for this application?

    Look forward to your advice. Many thanks!

  • Hi Bkennedy;

    May I have your feedback to above questions; please? Many thanks!


  • Bell: The 240uH to 400uH total primary inductance is a hard requirement. The datasheet states this is necessary for smooth operation of the ADum347x pulse by pulse current limit circuit, which can help protect against build up of saturation currents in the transformer. The Wurth Elektroniks 750316029 you chose will not meet these requirements, but their part no 750313790 will meet these requirements.

    Regards, Brian