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

enter image description here

  • \$\begingroup\$ I suspect it's a voltage regulator of some sort? \$\endgroup\$ – josef.van.niekerk Jan 10 '13 at 17:15
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    \$\begingroup\$ I think I saw that used in this circuit \$\endgroup\$ – Phil Frost Jan 10 '13 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\$ – Connor Wolf Jan 11 '13 at 4:18
  • \$\begingroup\$ @Fake Name Hehe! I guess he works for ST Microelectronics. :) \$\endgroup\$ – josef.van.niekerk Jan 11 '13 at 7:26
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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\$ – Connor Wolf Jan 11 '13 at 8:08

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\$ – josef.van.niekerk Jan 11 '13 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.

  • \$\begingroup\$ I don't think it's for regulation; more probably over-voltage or ESD protection of some interconnection. \$\endgroup\$ – Brian Drummond Jan 10 '13 at 17:19
  • \$\begingroup\$ Regardless, it's still 4 diodes in bridge configuration with a Zener in the middle. \$\endgroup\$ – dext0rb Jan 10 '13 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 Jan 10 '13 at 18:29

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