FUNCTIONAL OVERVIEW Design a synchronous 4-bit up and down counter Operates at 25MHz on the positive edge of the clock Designed to drive a 10pF capacitive load Latches a valu e at any point by toggling the enable
COUNTER DESIGN FLOW COUNTER T_FLIP_FLOP D FLIP_FLOP XOR SCHMITT TRIGGERSUPER BUFFER COMBINATIONAL LOGIC
SCHEMATIC
COUNTER TESTBENCH
LAYOUT
SIGNAL FLOW
Schmitt Trigger Design Designed For: VTH(LH) of 3V VTH(HL) of 2V VTH(LH ) VTH(HL)
Schmitt Layout
Schmitt Trigger Validation
Super Buffer Design (Assumed 4 stages) Design First Stage Inverter With Symmetric delays Calculate Ratio Wp/Wn For Each Successive Stage: (Where N is the Nth Stage) α^N(Wp/Wn)
Test Bench Output
French Fried Design I(max) for AL (Metal 1) = 1 x 10^5 A/cm^2 Our Buffer: 5.27 x 10^5 A/cm^2
Super Buffer Layout
T-Flip Flop Schematic Preset Clear Clock Enable
T-Flip Flop Layout
T-FF Transient Response
H-Tree Clocking Scheme
Conclusion 4 Bit Counter with up and down count capability Preset, Clear, Enable Inputs Operates at 25Mhz Clock Frequency with a delay of 6ns from Super Buffer. Input Noise Immunity 2.5V +/- 20% Output power of 60mW Driving 10pF Load Total Area of 406um x 925um = 3.76e-3cm^2