dc-dc converter and FOD3120

Discussion in 'The Projects Forum' started by jm-a, Nov 6, 2010.

  1. jm-a

    Thread Starter Active Member

    Oct 20, 2010

    I plan to use a dc-dc converter to power an optocoupler FOD3120 , and i have a few questions about it:

    1° Can i use MEA1D1509SC or MEA1D1512SC for the FOD 3120

    Vcc -Vee maxi : 10 --> 30 V

    so +9 -- 9 =18
    or 12--12 =24

    I think i'm right, but when i read for MEA1D1509SC or MEA1D1512SC output current +- 56 mA or +- 42 mA, i don't understand....

    Anyone can help me with a schematic or other?

    2° FOD3120 and MEA1Dxxxx , a good choice?

    Thanks a lot .

  2. SgtWookie


    Jul 17, 2007
    Actually, the FOD3120 is an optoisolator gate driver for IGBT's. It's maximum input Vcc-Vee is 30v, and it also has an undervolt lockout feature; the minimum Vcc-Vee to ensure that the undervolt lockout will disengage (thus enabling the FOD3120) is 15v. The maximum lockout voltage is specified at 13.5v, and there is a 1.5v hysteresis, so adding those two specifications is how I arrived at 15v.

    I suggest that you use the MEA1D1509C, as you will wind up with +/-9v = 18v across Vcc and Vee, which will avoid lockout, and has more output current capacity than the MEA1D1512C.

    You should consider using an 0.1uF (100nF) poly metal film or ceramic cap across the FOD3120's Vcc/Vee pins, as close as possible to the IC, and a somewhat larger cap (perhaps 1uF-50uF depending on the device you're driving and the frequency) within an inch or so of the FOD3120.

    To ensure that the FOD3120 is able to exit lockout, 15v <= (Vcc-Vee) <= 30v. Above 30v, the FOD3120 will be damaged.
    They are 1W devices.
    P=EI, or Power in Watts = Voltage * Current
    Transposing the equation, I=P/E, or Current = Power / Voltage
    1W / 18v = 0.0556 Amperes = 55.6mA
    1W / 24V = 0.0417 Amperes = 41.7mA

    Actually, it's so simple that I am not certain why you need a schematic? You seem to have figured it out by yourself, except I would add a couple of capacitors across the FOD3120's Vcc/Vee terminals.


    Looks good to me, without any further specifications known. I don't have any idea what you'll be driving with it, except it will probably be an IBGT or MOSFET.
    Last edited: Nov 6, 2010
    jm-a likes this.
  3. jm-a

    Thread Starter Active Member

    Oct 20, 2010
    Hi all,

    Thanks a lot for your fast and clear reply , SgtWookie.

    In fact it's only a part of a project to drive a brusless dc motor.