Designer’s Guide Community

‹ Previous topic | Next topic ›

Pages: 1

Good layout of bootstrapped switch? (Read 2530 times)

spectrallypure

Community Member

Offline

Posts: 50

Good layout of bootstrapped switch?
Jul 08^th, 2015, 7:35am

Hi! I have designed a classic bootstrapped switch for use in a 1GSa/s ADC, and now I need to layout it. According to my simulations, the effect of the parasitics is CRITICAL for the performance of the switch, so the layout must be done with lots of care.

Since I haven't laid out a bootstrapped switch before, I have no idea what could be a good starting point. Could someone please share any bootstrapped switch layouts, or point me to any references where I can see any examples of how to layout this cell?

Thanks in advance for any help!

Cheers,

Jorge.

P.S. I'm talking about the classic Abo-type boostrapped switch; c.f. attached schematic.

Bootstrapped_switch_Abo.jpg

IP Logged

rfmagic

Community Member

Offline

Posts: 64

Re: Good layout of bootstrapped switch?
Reply #1 - Jul 23^rd, 2015, 12:00pm

Hi,

The main challenge in bootstrap switches layout is to keep the signal path as short as possible in order to avoid too much parasitic effects.
As the bootstrapping circuitry increases the layout size considerably, what you really care about is that the signal path from source to drain in the switch will be very short without too many interactions with the bootstrapping.
The circuit you are presenting is very nice conceptually but you should consider improving it by sharing as much elements as possible i.e. sharing capacitors between other similar cells with the same phases etc..

IP Logged

Pages: 1

‹ Previous topic | Next topic ›