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I have only rudimentary knowledge of circuit design and need some advice.

I have a printed circuit board used in a device for automotive applications. I would like to include the means to prevent reverse current flow through a resistor on the board. Here is a section of the schematic ...

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The advice I am seeking is what should the value of the diode be. In my case in an automotive application, when the engine is running the voltage could be 14 volts DC or so and the anticipated current could be as high as 1.0 ampere. I have seen articles stating there are different types of diodes for similar applications (junction diode, Schottky diode, etc.). I do not know which kind of diode would be preferred in this application nor do I know how to correctly specify the value for the diode. Any help is appreciated.

Steve

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  • \$\begingroup\$ If that is really a 470 ohm resistor, even at 14 volts the maximum current would be only about 30 mA, which would result in less than 1/2 watt. There is not enough information to determine specifications, but a common 1N5818 Schottky diode should be fine. It can handle 1 amp, with 30V reverse blocking, and 0.33V forward drop at 100 mA. As a Schottky, it has a typical reverse leakage of 10 mA at 100C. \$\endgroup\$
    – PStechPaul
    Jul 21, 2022 at 16:34
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    \$\begingroup\$ This looks like an application for a "Standard Power diode" If the direct current has stored energy and is switched from the load, there can be high voltage generated by the inductance. So more details might help choose the Peak Inverse Voltage rating to be low 30V (Schottky) or high > 1kV (Std Silicon). If not then choose desired package type, max voltage drop @ If and (x) in-stock \$\endgroup\$
    – Tony Stewart EE75
    Jul 21, 2022 at 16:36

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typically, I would use Schottky diodes for such application. The main reason for this type of diode is the low forward-voltage drop (meaning you want to conserve voltage for the rest of the circuit and low forward-voltage means high efficiency of the diode). Since it doesn't sound like you're dealing with any high-speed switching, select the diode based on the following characteristics:

  1. Lowest forward-voltage drop
  2. Sufficient reverse voltage to allow adequate protection against back current flow (you want to clear over the highest, reverse-polarity voltage that may be present at this diode (probably over 25v for this application).
  3. Sufficient current capability for this application. You want to clear the 1A threshold with a bit of margin.

Check out this search criteria I created on Digikey.

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    \$\begingroup\$ Any of these should work for you application. Digikey Search Results \$\endgroup\$
    – Awm0121
    Jul 21, 2022 at 16:15
  • \$\begingroup\$ Thank you for the help. \$\endgroup\$
    – Raising Arizona
    Jul 22, 2022 at 5:11

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