Signal Shielding for the Noise

[amlokesh]

HI,


I have a clock signal , which is creating noise bumps on the adjacent data signal nets . single clock signal is creating noise bumps on around 15 nets . so instead of shielding the victim nets (all those 15 ) can i shield the clock (Agressor net). Can you please help me understand how this signal shielding works .

 

[arthorios]

Hi amlokesh,

You can shield your clock signal by creating an on-chip coaxial "cable" (lots of material around). For example, for a >3-metal process, your clock signal can run through a Metal2 line while being surrounded by M1 and M3 both connected to the ground: M1(GND)-M2(clk)-M3(GND). This way, the clock signal can only couple to the shield (gnd) and not the surrounding nets. For this example, don't forget to surround the clock signal with VIAS from M1 to M3.

Regards

 

[sutapanaki]

When you do this type of shielding, consider also the extra capacitive load to gnd that your clock buffers will have to drive.