I'm trying to understand what the following symbol is for. It's found in this schematic.

unknown schematic symbol

  • \$\begingroup\$ I suspect it's a voltage regulator of some sort? \$\endgroup\$ Commented Jan 10, 2013 at 17:15
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    \$\begingroup\$ I think I saw that used in this circuit \$\endgroup\$
    – Phil Frost
    Commented Jan 10, 2013 at 17:25
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    \$\begingroup\$ What it means is the person who drew that schematic is terrible at drawing readable schematic symbols. \$\endgroup\$ Commented Jan 11, 2013 at 4:18
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    \$\begingroup\$ @josef.van.niekerk - I think you mean Olimex (They're the people who drew that schematic, and yes, their schematics are pretty much universally horrible). \$\endgroup\$ Commented Jan 11, 2013 at 8:08
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    \$\begingroup\$ I'd say this is a component or collection/cluster of components/symbols, not a symbol in and of itself. /librarian \$\endgroup\$
    – DJG
    Commented Jul 20, 2021 at 20:27

3 Answers 3


This device is a transient voltage suppressor for USB D+ and D- signals. It protects the device from static voltages that may develop when inserting or removing USB devices to connectors.

The four diodes (on side) act as clamping diodes that conduct to suppress ESD.

This or similar device can be found in this Semtech catalog

  • \$\begingroup\$ Awesome, that's really clever, I didn't think of ESD at all. \$\endgroup\$ Commented Jan 11, 2013 at 6:51

Looks like electrostatic discharge (ESD) protection on a USB port. Any port that a user can touch should have protection against finger zaps frying the chip connected to it.

Have a look at the datasheet for TI TPD2E001 to get an idea what the specs might be.



it is 5 symbols enclosed in one device. 4 normal diodes in a bridge configuration with a zener diode in the middle for simple regulation.

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    \$\begingroup\$ I don't think it's for regulation; more probably over-voltage or ESD protection of some interconnection. \$\endgroup\$
    – user16324
    Commented Jan 10, 2013 at 17:19
  • \$\begingroup\$ Regardless, it's still 4 diodes in bridge configuration with a Zener in the middle. \$\endgroup\$
    – dext0rb
    Commented Jan 10, 2013 at 17:24
  • \$\begingroup\$ I was going to say, "balanced modulator". I'm glad you guys saved me the embarrassment. I'm going with the USB answers. The "pass-through" design supports that notion. \$\endgroup\$
    – gbarry
    Commented Jan 10, 2013 at 18:29

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