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On the laptop's PCB I see two Schottky barrier diodes connected with reverse polarity between the Vin line and gnd. What is the purpose of this?

At first I suspected that it might be a TVS or a Zener diode, but when I looked at the datasheet, I saw that it was a Schottky barrier diode, product number (EA60QC04,) designator (PD13)

Does this serve as a simple reverse polarity protection? If it was connected in series, there would be a voltage drop and this is an undesirable situation. Was it connected in parallel for this reason it? Were using dual diodes used to dissipate heat in case of reverse polarity?

enter image description here

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  • \$\begingroup\$ Hard to make a guess without seeing the full schematic. Could be a reverse polarity protection provided that there's a fuse of some kind on VIN+ line, or could be clamper for VIN+ line (if that's the case, looks a bit meaningless without the clampers for another positive rail), or could be a freewheeling diode of a buck converter (PR82 looks like a current sense and the rail coming from its left-hand terminal could be a feedback path) provided that VIN+ is coming from a switch (could be on-chip or external). Post the full schematic. \$\endgroup\$ Commented Nov 9, 2023 at 10:16
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    \$\begingroup\$ @RohatKılıç This is a good answer. It seems doubtful to me that other possibilities would apply. \$\endgroup\$ Commented Nov 9, 2023 at 10:29

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Those aren't diodes for general protection as much as they are for keeping PL9 and the VIN+ connector out of trouble when VIN+ gets disconnected, by providing a short-time alternative current path.

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  • \$\begingroup\$ "alternative current path" can you explain this? I couldn't imagine what kind of alternative path there was. \$\endgroup\$
    – Electronx
    Commented Nov 9, 2023 at 10:03
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    \$\begingroup\$ Alternative to current flowing from a connected VIN+. Inductors do not react gracefully to abrupt current changes. The diodes will then source a small amount of charge from the ground that will end up on the capacitors. \$\endgroup\$
    – user107063
    Commented Nov 9, 2023 at 11:15
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These are flyback diodes that shunt inductive kick-back. A good idea whenever there is inductive filtering on the load and/or the parasitic inductances combined with high load cause concern.

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