Power and Area Summary
The complete layout of all portions of the design has yet to be
assembled. The following table gives a breakdown of which components
are contributing the most power (under typical operating conditions)
and the area of each block.
Circuit | Power | Area |
Transmit DLL | 15.3mW | 24834um2 |
Receive DLL | 16.2mW | 21304um2 |
Serializer | 3mW | 1600um2 |
Phase Interpolator | 5.6mW | 57000um2 |
Samplers | 240uA x 20 => 23.7mW | 9000um2 |
Tx/Rx | 20mW | 4500um2 |
Encoder | - | 64400um2 |
Decoder | - | 64400um2 |
Bit Lock | 3mW | 32000um2 |
Byte Lock | - | 32400um2 |
Transmit Control | - | 70000um2 |
Retiming Registers | - | 66000um2 |
Total | 86.8mW | 0.45mm2 |
Total Power Consumption for Typical Operation
It can be seen that the analog circuitry in this design dominates the
power consumption due to the static current inherent in the
designs. One method that could be used to reduce the power is to
set a specific speed requirement for the link, say 1 Gbit/s. If more
bandwidth is required from a link, more links can be run in parallel
and synchronized at a higher level, as stated earlier. We could then
reduce the number of analog elements by a factor of 2 and run them
at twice the rate, since we don't have to worry about making the link run
faster than intended.
We could build a 1 Gbit/s link
with only 5 delay elements in the delay lines, and thus half the
samplers and half the latches, and run it at twice the rate. Fewer
delay elements also means less inherent jitter from the DLLs. This
would impose a smaller timing window for all of the digital logic,
however. Instead of a 10 ns cycle time, only 5 ns would now be
available. We need to further
examine the delays of the current digital logic blocks to see if this
is possible.