Design Goal Design an Analog-to-Digital Conversion chip to meet demands of high quality voice applications such as: Digital Telephony, Digital Hearing Aids and VOIP. TEAM W3: Digital Voice Processor 525 Jarrett Avery (W3-1) Sean Baker (W3-2) Huiyi Lim (W3-3) Huiyi Lim (W3-3) Sherif Morcos (W3-4) Amar Sharma (W3-5) Date: 2/8/2006 Size Estimates/ Floorplan Design Manager: Abhishek Jajoo

Status  Design Proposal  Project chosen: 16 bit Delta-Sigma ADC  Basic specs defined  Architecture  Matlab Simulated  Behavioral Verilog Simulated  Structural Verilog – Done, but not simulated  Schematic  Analog components created & simulated with digital behavioral Verilog models  Floorplan  Initial floorplan created based on estimates of component areas  Layout  Simulation / Verification

In Case You Forgot… (A Summary of Last Week) Applications of the DVP-525 Applications of the DVP-525 VoIP, Digital Telephony, Encrypted Communications VoIP, Digital Telephony, Encrypted Communications Digital Hearing Aids Digital Hearing Aids How the DVP-525 works: How the DVP-525 works: Uses Delta-Sigma modulation of input signal and decimation to convert an analog signal into 16 bit binary numbers Uses Delta-Sigma modulation of input signal and decimation to convert an analog signal into 16 bit binary numbers

Algorithm Detail Decimation (Sinc Filter, Downsample) Measure Peak Amplitude (Peak Input Indicator) Digital Output Digital Peak Indicator Analog Input Lowpass Filter Analog to Digital Conversion (Delta-Sigma Modulator)

Hardware That Makes it Happen (Modulator) Integrators Comparator

Modulator Schematic

Algorithm Detail Decimation (Sinc Filter, Downsample) Measure Peak Amplitude (Peak Input Indicator) Digital Output Digital Peak Indicator Analog Input Lowpass Filter Analog to Digital Conversion (Delta-Sigma Modulator)

Hardware That Makes it Happen (Decimator)

Sinc Filter Behavioral Verilog

Sinc Filter Structural Verilog

Algorithm Detail Decimation (Sinc Filter, Downsample) Measure Peak Amplitude (Peak Input Indicator) Digital Output Digital Peak Indicator Analog Input Lowpass Filter Analog to Digital Conversion (Delta-Sigma Modulator)

Hardware That Makes it Happen (Peak Input Indicator)

PII Function Behavioral Verilog

PII Function Structural Verilog

Clock Divider New component added to digital portion of design New component added to digital portion of design Takes as input the oversampled clock and outputs the Nyquist clock Takes as input the oversampled clock and outputs the Nyquist clock We are using an oversampling factor of 256 We are using an oversampling factor of 256 So, need to divide oversampled clock by 256 So, need to divide oversampled clock by 256 Implemented with a 7-bit counter and a T (toggle) flip-flop Implemented with a 7-bit counter and a T (toggle) flip-flop Every time counter overflows (reaches 128), flip- flop toggles (Cout connected to flip-flop’s clock) Every time counter overflows (reaches 128), flip- flop toggles (Cout connected to flip-flop’s clock) This produces a clock with 1/256 the input frequency This produces a clock with 1/256 the input frequency

Hardware That Makes it Happen (Clock Divider)

Clock Divider Behavioral Verilog

Clock Divider Structural Verilog

Simulation – MatLab First modeled the modulator in the time domain, and fed it simple sine wave input: First modeled the modulator in the time domain, and fed it simple sine wave input:

Simulation – MatLab (cont’d) Then fed the bitstream created by the modulator into the decimator: Then fed the bitstream created by the modulator into the decimator:

Simulation (cont’d) Now, we have simulated entire design in a mixed-signal environment Now, we have simulated entire design in a mixed-signal environment Analog portion represented by generic components Analog portion represented by generic components Digital portion represented by behavioral Verilog code Digital portion represented by behavioral Verilog code Simulated together in Cadence using AHDL Simulated together in Cadence using AHDL

Simulation – Cadence

Simulation (cont’d) Simulated behavioral models of PII function & clock divider in ModelSim Simulated behavioral models of PII function & clock divider in ModelSim Verified generation of Nyquist clock by clock divider module Verified generation of Nyquist clock by clock divider module Verified updates of maximum & minimum values of sinc filter output by PII function module Verified updates of maximum & minimum values of sinc filter output by PII function module

Simulation – ModelSim

Transistor Count Estimates Analog Analog 3 x Analog Op Amps, 3 x 24 = 72 3 x Analog Op Amps, 3 x 24 = 72 Resistive/Capacitive Elements Resistive/Capacitive Elements Digital Digital 8 x 18-bit registers, 8 x 400 = x 18-bit registers, 8 x 400 = x 12-bit register, 1 x 260 = x 12-bit register, 1 x 260 = x 18-bit adders, 8 x 510 = x 18-bit adders, 8 x 510 = x 24-bit counter, 1 x 870 = x 24-bit counter, 1 x 870 = x 7-bit counter, 1 x 250 = x 7-bit counter, 1 x 250 = x 12-bit equality function, 1 x 120 = x 12-bit equality function, 1 x 120 = x 18 bit muxes, 2 x 110 = x 18 bit muxes, 2 x 110 = 220 Misc logic = 200 Misc logic = 200 Total = 9,300 transistors Total = 9,300 transistors

Initial Floorplan Total Area = 77, 750 sq μm

Power Considerations How much power will our chip consume? How much power will our chip consume? Ultra low-power hearing aids burn about 1 mW Ultra low-power hearing aids burn about 1 mW Do we need special low-power adders? Do we need special low-power adders? Brandt & Wooley ’94 suggested using static CMOS ripple carry adders Brandt & Wooley ’94 suggested using static CMOS ripple carry adders Looked at other papers proposing low-power, high-performance adders Looked at other papers proposing low-power, high-performance adders These designs were more geared toward other applications using clocks over 100 MHz These designs were more geared toward other applications using clocks over 100 MHz Since we’re using a 5 MHz clock & a 20 KHz clock, ripple carry is ideal for us Since we’re using a 5 MHz clock & a 20 KHz clock, ripple carry is ideal for us

Power Considerations (cont’d) Brandt & Wooley listed their chip’s power consumption at 6.5 mW at 3V Brandt & Wooley listed their chip’s power consumption at 6.5 mW at 3V Our design much smaller and runs at much lower speed (20 KHz vs. 176 KHz) Our design much smaller and runs at much lower speed (20 KHz vs. 176 KHz) We’ll be using 1.8V source We’ll be using 1.8V source Estimate chip’s total power at about 5 mW Estimate chip’s total power at about 5 mW Sinc filter – 1 or 2 mW Sinc filter – 1 or 2 mW PII Function & Clock Divider – 1 mW PII Function & Clock Divider – 1 mW Analog Portion – 2 or 3 mW Analog Portion – 2 or 3 mW

Analog Device Sizes Some concern about sizing of analog components Some concern about sizing of analog components Average size of analog transistors = 30 μm x 0.5 μm = 15 sq μm Average size of analog transistors = 30 μm x 0.5 μm = 15 sq μm Average size of analog resistors (500 Ω) = 24 μm x 600 nm = 14.4 sq μm Average size of analog resistors (500 Ω) = 24 μm x 600 nm = 14.4 sq μm Average size of analog capacitors (1 pF) = 30 μm x 30 μm = 900 sq μm Average size of analog capacitors (1 pF) = 30 μm x 30 μm = 900 sq μm May have to look at alternatives May have to look at alternatives

Design Decisions Decided on using static CMOS ripple carry adders Decided on using static CMOS ripple carry adders Decided on modifying PII function to allow user to input time period to wait before clearing max and min registers Decided on modifying PII function to allow user to input time period to wait before clearing max and min registers Using 24-bit counter with 20 KHz clock to compare against wait period Using 24-bit counter with 20 KHz clock to compare against wait period Upper 12 bits of counter compared to wait period Upper 12 bits of counter compared to wait period Gives wait period range of 200 ms to 14 minutes Gives wait period range of 200 ms to 14 minutes Decided on generating our own Nyquist clock (20 KHz) Decided on generating our own Nyquist clock (20 KHz) If clock needs to be cleaner, we can always go back to assuming two clock inputs If clock needs to be cleaner, we can always go back to assuming two clock inputs Decided on analog component values (RC values) Decided on analog component values (RC values)

Problems and Questions Have we bitten off more than we can chew? Have we bitten off more than we can chew? 9,000+ transistors is a lot for 2-3 digital designers 9,000+ transistors is a lot for 2-3 digital designers Much of transistor count taken up by repeated modules like adders, registers Much of transistor count taken up by repeated modules like adders, registers Can always reduce design (PII function, clock divider) Can always reduce design (PII function, clock divider) Analog device sizes Analog device sizes Do we need to change our design? Do we need to change our design?

Results More comfortable with overall design More comfortable with overall design More familiar now with mixed analog/Verilog simulations More familiar now with mixed analog/Verilog simulations Ready to move forward with design Ready to move forward with design Structural Verilog simulations Structural Verilog simulations Overall schematic including both analog & digital portions of design Overall schematic including both analog & digital portions of design Topology, gate sizing, RLC selection for analog parts Topology, gate sizing, RLC selection for analog parts Layout Layout