Question for ref. design of ADuM3471

Dear Sir/Madam,

Our customer asked as following question.

Why does your table-18 of datasheet ADuM3471 show a coil JA4631-Bl (1:2 turns ratio) for Fig-38?

We will make VDD1=5V and Viso=15V.

If so, we should choice a coil JA4650-Bl(1:3 turns ratio), correct?

Please give me your good comment.

Thanks Kaos

  • 0
    •  Analog Employees 
    on Oct 22, 2014 6:33 AM

    Kaos:

    Figure 38 typical application circuit is single supply used typically for 5V to 5V with a turns ratio of 1:2.  Equation (1) in the datasheet page 26 shows that a turns ratio of 1:2 is needed in the example given with Vd = 0.5V, PWM controller duty cycle = 0.3 out of a max of 0.4, and Vdd1(min) = 4.5V..

    For 5V to 15V figure 39 is recommended with the doubler circuit. Equation (2) the datasheet shows that a turns ratio of 1:3 is needed for Vd = 0.5V, duty cycle = 0.30 and Vdd1(min) = 4.5V.

    Regards, Brian