Solutions for Reducing the Impact of Power Straps on the Die Size

Three possibilities for reducing the impact of power straps on the die size are proposed here. They are then applied to the four previous examples to compare the core areas.

1. Use double bonding and two core supply pads per power supply. This halves the bond wire and power pad resistances.
2. Use wider metal-5 and above power straps. Making them double the size of the metal-1 to metal-4 straps is good. The assumption is that these extra strap widths routed over the top of the standard cells on metal-5 and metal-6 do not affect the routing congestion.
3. Look hard at the spec, and set the Vdd minimum supply voltage at nominal-3% instead of 5%. 3% tolerance is offered by modern voltage regulators.

Now we'll rework the previous examples to derive new values for the metal power strap percentages and hence the increase in the size of the core.

The four examples being reworked are

1. 5LM, all ka_an, k_wn and k_cn equal except k_a5=200%, k_w5=160%, no blocks, 1W power
2. 6LM, various k_an and k_cn, k_wn=80% of k_an, no blocks, 2W power
3. 5LM, all ka_an, k_wn and k_cn equal except k_a5=200%, k_w5=160%, 30% block area, 1W power
4. 6LM, various k_an and k_cn, k_wn=80% of k_an, 30% RAM, 20% analog, 2W power