gital Integrated Circuits 2nd Inverter EE4271 EE4271 VLSI Design VLSI Design The Inverter The Inverter Dr. Shiyan Hu Office: EERC 518 [email protected]Adapted and modified from Digital Integrated Circuits: A Design Perspective by Jan M. Rabaey, Anantha Chandrakasan, and Borivoje Nikolic.
EE4271 VLSI Design. Dr. Shiyan Hu Office: EERC 518 [email protected]. The Inverter. Adapted and modified from Digital Integrated Circuits: A Design Perspective by Jan M. Rabaey, Anantha Chandrakasan, and Borivoje Nikolic. Pass-Transistors. Need a circuit element which acts as a switch - PowerPoint PPT Presentation
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Pass-TransistorsPass-Transistors Need a circuit element which acts as a switch When the control signal CLK is high, Vout=Vin When the control signal CLK is low, Vout is open circuited We can use NMOS or PMOS to implement it. For PMOS device, the
Transmission GateTransmission Gate An NMOS transmits a 0 value without degradation while transmits a
Vdd value with degradation A PMOS transmits a Vdd value without degradation while transmits a 0
value with degradation Use both in parallel, then can transmit both 0 and Vdd well. CLK=0, both transistors cut-off CLK=Vdd, both transistors are on. When Vin=Vdd, NMOS cut-off when
Vout=Vdd-Vtn, but PMOS will drag Vout to Vdd. When Vin=0, PMOS cut-off when Vout=|Vtp|, but NMOS will drag Vout to 0.
Dynamic power is due to charging/discharging load capacitor CL
In charging, CL is loaded with a charge CL Vdd which requires the energy of QVdd= CL Vdd2, and all the energy will be dissipated when discharging is done. Total power = CL Vdd2
If this is performed with frequency f, clearly, total power = CL Vdd2 f
If the waveform is not periodic, denote by P the probability of switching for the signal
The dynamic power is the most important power source It is quadratically dependant on Vdd It is proportional to the number of switching. We can slow down the
clock not on the timing critical path to save power. It is not dependent of the transistor itself but the load of the transistor.
Technology ScalingTechnology Scaling Devices scale to smaller dimensions with advancing technology. A scaling factor S describes the ratio of dimension between the
old technology and the new technology. In practice, S=1.2-1.5.