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CSD23285F5: Low power MOSFET - question of pure electronic

Nico92
Prodigy 90 points
Part Number: CSD23285F5
Other Parts Discussed in Thread: CSD75208W1015, CSD75207W15

Hello everyone,

I need an ultra low power P-channel MOSFET to rectify a low voltage oscillation, so I used this one

CSD23285F5 

But the body diode ruin my cicrcuit because the current flow back to the source trough the body diode... is there any similar MOSFET without body diode? Or wich is more resistant to positive DS voltage? I can allow les tha micro-ampères of current losses. My circuit apply a maximum of 1V on Vds, it is not so much and I hope a solution will exist?

THank you for help

  • 0
    TI__Expert 6755 points
    Nico,

    Thanks for the post.
    As part of the device structure all power MOSFETs come with a body diode and all are similar characteristics, so any single MOSFET would not help you.
    However, we do have some small dual common source devices , the smallest being the CSD75208W1015 , (1x1.5mm) this has diodes back to back which would stop current flowing through a body di0de, you could tie the gates together to turn the devices on and off at the same time. If a lower resistance device needed you could try the CSD75207W15 (1.5x1.5)

    I hpe this helps
  • 0 in reply to Chris Bull
    Prodigy 90 points

    Hello Chris, thanks for your help,

    What do you mean by "this has diodes back to back which would stop current flowing through a body di0de, you could tie the gates together to turn the devices on and off at the same time"?

    I turn on the FET to let the current pass and charge a capacitor during the positive half-wave (500 mV peak) of the electromagnetic transducer voltage, the problem is that during the negative half wave I have a negative voltage on the source pin, a positive one on the drain and the current flows back to the transducer discharging the cap connected to the drain

  • 0 in reply to Nico92
    TI__Expert 6755 points

    Nico,

    Looking at the schematic of the CSD75208W1015 on the front page (image below) you can see that the body diode cathodes are connected to the source. If you have a no connect to the sources and simply tie the gates together to allow current to flow from drain to drain then it is not possible for current to flow through the body diodes as one body diode will block the other in either direction.

  • 0 in reply to Chris Bull
    TI__Expert 6755 points

    for some reason image did not show, in previous post

  • 0 in reply to Chris Bull
    Prodigy 90 points

    mmmmh, but How can I drive the FET (Voltage gate-source negative) without connecting the source of this double FET?

    this is how I use the P-channel MOSFET:

    when the wave of VG2 is positive, i put a negative voltage on Vdrive to charge the cap, but during the negative wave I have losses du to the body diode.If I don't connect the source of the double fet, I will not be able to drive the FET right?

    best regards

    Nico

  • 0 in reply to Nico92
    TI__Expert 6755 points

    Typical Back to Back Load Switch Schematic.pptxNicolas,

    Although you are not connected to the source of the FET it will still have a voltage, basically the voltage on the drain minus the body diode voltage drop, so if you pull the gate to ground this will mean the gate will be negative with respect to source and so conduct.

    I quickly drew the schematic in the attached for your reference on what is commonly used, also TI has an app note here (  ) that gives a little detail also.

  • 0 in reply to Chris Bull
    Prodigy 90 points
    thank you, for your answer, your time and your help

    Best

    Nico