Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronic Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

ESD diodes: do they need any guardring ?

Status
Not open for further replies.

DoYouLinux

Advanced Member level 4
Joined
Sep 26, 2007
Messages
113
Helped
3
Reputation
6
Reaction score
4
Trophy points
1,298
Activity points
2,152
esd guard ring

Hi all,

I am trying to design my own ESD protection pads using two basic diodes. Do I need to place any guardring close to the diodes. My diodes are Nwell diodes.

Thank you very much

DYL
 

Fom

Advanced Member level 2
Joined
Mar 10, 2004
Messages
633
Helped
84
Reputation
168
Reaction score
31
Trophy points
1,308
Location
Taiwan
Activity points
4,451
esd double diode esd substrate connection

You need the guard ring to prevent latch-up problem.
 

DoYouLinux

Advanced Member level 4
Joined
Sep 26, 2007
Messages
113
Helped
3
Reputation
6
Reaction score
4
Trophy points
1,298
Activity points
2,152
need of guard ring

Thanks a lot, Fom and hung wai ming :)

By the way, for the guard ring, should it be the "P-tap" connected to the "Ground" ?
 

mdcui

Advanced Member level 4
Joined
Aug 23, 2005
Messages
109
Helped
28
Reputation
56
Reaction score
5
Trophy points
1,298
Location
california, USA
Activity points
2,078
how+guard+rings+help+in+esd

usually for ESD device, you need guard ring, and some times even double guardring for two reason:
1. guard ring with enough contact and metal connection can help distribute ESD zapping current, sometimes current flows more through the guardring than from the substrate.
2. isolate the noise introduced by the diode under normal operation, since IO signal may easily have negative glitch, and will introduce noise into substrate without guardring the collect the carrier current.

but the distance of double guardring need to be controlled well since it can easily form a collateral npn transistor. and without enough conatct or strong metal power bus on top of metal ring, it will be less effective.
 
  • Like
Reactions: Imello

    Imello

    points: 2
    Helpful Answer Positive Rating

DoYouLinux

Advanced Member level 4
Joined
Sep 26, 2007
Messages
113
Helped
3
Reputation
6
Reaction score
4
Trophy points
1,298
Activity points
2,152
guard ring esd diodes

Thank you very much, mdcui :)

For double guarding, you mean, one is "p-sub" contact connected to ground and the other one is "n-well" contact connected to Vdd, right ? If so, for the latter one, I need to draw N-well all around the diodes and connect the N-well to Vdd. Am I correct ?
 

engrak

Member level 3
Joined
Sep 23, 2006
Messages
64
Helped
4
Reputation
8
Reaction score
4
Trophy points
1,288
Activity points
1,537
back to back diodes in esd

i think u r correct.
 

Status
Not open for further replies.
Toggle Sidebar

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top