RE:Bidirectional ESD SCR - ESD protection

[akshaykumarls]

RE:Bidirectional ESD SCR

Hi,
ESD SCR operates as breakdown device during positive ESD and simple forward biased diode during negative ESD and provide protection . I would like to know why this SCR cannot be used as ESD Protection Device both for positive and negative ESD events at the pad.

If possible reply to following ID.

akshaykumarls@gmail.com


Regards
Akshay

 

[dick_freebird]

RE:Bidirectional ESD SCR

Because an SCR is not a symmetric device (NPNP != PNPN).

A triac is a bidirectional SCR pair that can / must be triggered
in the appropriate direction.

 

[mikersia]

RE:Bidirectional ESD SCR

Can be used, if there is an effective power clamp

 

[akshaykumarls]

Re: RE:Bidirectional ESD SCR

Hi mikersia,
Can you please elaborate on that.

 

[mikersia]

RE:Bidirectional ESD SCR

Please see at Sofics solutions for HV (e.g. WP-2010-Q1-1.pdf). Such unsymmetric ESD clamps are oftenly used for HV design. E.g. TI used such protection for some old 0.35um families (see scla013d app.note e.g.). Ideology of such ESD protection can be defined as "Common Discharge Line",- when each I/O pin have identical ESD clamp (based on SCR, NPN, Zener, ...) to common line (GND typically). Distributed active power clamps can improve protection significantly for long distant pins.