ESD Uni- directional diodes for USB 2.0 data lines

[khalideda]

Hi,

I want to protect the USB data lines of the USB tranciever with ESD diodes. What values of reverse stand off voltages and breakdown voltage should I seek? Can you please recommend one that is SOT-23 and dual uni- directional?

Thanks

 

[KlausST]

Hi,

there are dedicted USB data line protection devices.

You need to take care about USB speed. Especially for USB3.0 speed you need very low capacitance diodes.

I used VBUS054B (very small) and IP4220CZ6 (TSOP-6 / SOT23-6) for USB2.0 devices.

Klaus

 

[khalideda]

Hi,

there are dedicted USB data line protection devices.

You need to take care about USB speed. Especially for USB3.0 speed you need very low capacitance diodes.

I used VBUS054B (very small) and IP4220CZ6 (TSOP-6 / SOT23-6) for USB2.0 devices.

Klaus

Thanks for the reply. I'm looking for SOT-23 footprint. Can you please recommend one? Also can you tell me what voltages (reverse stand off and breakdown) should I be looking for ?

 

[KlausST]

Hi,

did you check both given devices?

Also can you tell me what voltages (reverse stand off and breakdown) should I be looking for ?

You didn´t tell what USB speed.
Usually you need those ESD diodes to protect a USB controller IC. We don´t know what this device is. Read it´s datasheet about protection of the IO (voltages, currents capacitance, speed...).

Klaus

 

[khalideda]

Hi,

did you check both given devices?


You didn´t tell what USB speed.
Usually you need those ESD diodes to protect a USB controller IC. We don´t know what this device is. Read it´s datasheet about protection of the IO (voltages, currents capacitance, speed...).

Klaus

USB 2.0 high-speed 12 Mbps. The IC is 3.3V I/O
I checked the devices you mentioned. I need SOT-23 footprint ICs

 

[KlausST]

Hi,

The IC is 3.3V I/O

This doesn't help much. Or do you want to protect the 3V3 IO lines?

I rather think you want to protect the USB D+ and D- lines. These are 5V signal levels. But the signal levels don't say much how you should protect them. You should find this information in the datasheet.

*****
You keep some informations as a secret..

You need diodes, in SOT23, not much more specifications. Then try BAT54S. But I don't know if they fit to your desired protection level.
Anode to GND, cathode to V_USB (Vcc), center to signal line.
So they give the ESD current to VCC or GND. You need the VCC path to be low impedance for the expected ESD pulse.
Since the ESD pulse charges the VCC capacitor you additionally may need to protect VCC against overvoltage.

Klaus

 

[khalideda]

Hi,


This doesn't help much. Or do you want to protect the 3V3 IO lines?

I rather think you want to protect the USB D+ and D- lines. These are 5V signal levels. But the signal levels don't say much how you should protect them. You should find this information in the datasheet.

*****
You keep some informations as a secret..

You need diodes, in SOT23, not much more specifications. Then try BAT54S. But I don't know if they fit to your desired protection level.
Anode to GND, cathode to V_USB (Vcc), center to signal line.
So they give the ESD current to VCC or GND. You need the VCC path to be low impedance for the expected ESD pulse.
Since the ESD pulse charges the VCC capacitor you additionally may need to protect VCC against overvoltage.

Klaus

I'm sorry for not being clear enough. I'm using the MK20DX256VLH7 as my MCU. It has USB transceiver. Yes I want to protect D+/D- lines of the USB. I found this **broken link removed** on Digi-key. On the datasheet, it's written that it's designed for USB 2.0 application

 

[KlausST]

Hi,

well done...a datasheet.

* usually you first should know about what ESD pulse you expect (you need to withstand) and what your microcontroller can handle.

* now we go backwards:
You see there are different ESD pulse definitions: HBM, machine model, EFT, lightning, ....
from the charts you see the remaining voltages. way below 0V and above 5V.

It is necessary to check the microcontroller datasheet about what it is able to withstand.
For example.
A 12A lightning pulse (8/20us) results in a (typ) 9.5V clamp voltage. (with an about optimal PCB layout).
Can your microcontroller handle this? There is no way around ... you need to read the datasheet and find out.

If you find out that the microcontroller can handle this pulse then everything is OK.
But if it can not handle it you need to add more protection circuit.
* Either in front of the DT1452 to decrease the pulse current to the DT1452
* or between DT1452 and microcontroller to limit the current to the microcontroller..

**
In short:
What ESD pulse do you need to withstand?
What ESD pulse is the microcontroller able to handle?

Klaus

 

[marce]

Why are you so stuck on the devices footprint, picking the best and correct device first should be the criteria, not worrying about the footprint.