Resistance to Frequency Converter Amol Mupid Andrew Ricketts.

19
Resistance to Frequency Converter Amol Mupid Andrew Ricketts

Transcript of Resistance to Frequency Converter Amol Mupid Andrew Ricketts.

Page 1: Resistance to Frequency Converter Amol Mupid Andrew Ricketts.

Resistance to Frequency Converter

Amol Mupid

Andrew Ricketts

Page 2: Resistance to Frequency Converter Amol Mupid Andrew Ricketts.

Outline Original design

Component parts Roadblock

Modified design Buffer optimization

Design specification Conclusion

Page 3: Resistance to Frequency Converter Amol Mupid Andrew Ricketts.

400

Chemiresistive Sensors

αACsR1=

Rs

Rs : resistance of nanowire

C : concentration of the gas

A,α : constants that change with type of gas and temperature

350

Page 4: Resistance to Frequency Converter Amol Mupid Andrew Ricketts.

Original design

D

CLK

Q

Qbar

+

-

-

+

Rs

Vout

R4

R1

R2

R3 C

R5

Page 5: Resistance to Frequency Converter Amol Mupid Andrew Ricketts.

Original design components Diode

Spice simulation …but layout issues insurmountable

Page 6: Resistance to Frequency Converter Amol Mupid Andrew Ricketts.

Original design components Zener Diode

More simulations possible …but layout even more challenging

Page 7: Resistance to Frequency Converter Amol Mupid Andrew Ricketts.

Modified design Key point is that what is desired is a

way to control oscillations based on input voltage Voltage Controlled Oscillator (VCO)

Buffer added to output to ensure rapid rise and fall of output square wave

Page 8: Resistance to Frequency Converter Amol Mupid Andrew Ricketts.

VCO design LC tank oscillators

Good phase noise with low power but tuning range is relatively low Output frequency may fall out of range due to

process variations Spiral inductors occupy a lot of area, high cost and

low yield issues. Ring oscillators

Easy integration, high yield, low cost. Less chip area In-phase outputs

Page 9: Resistance to Frequency Converter Amol Mupid Andrew Ricketts.

Single delay cell

Page 10: Resistance to Frequency Converter Amol Mupid Andrew Ricketts.

Schematic of rectified VCO

Page 11: Resistance to Frequency Converter Amol Mupid Andrew Ricketts.

Buffer optimization Initial single stage buffer

Moved output close to binary Had difficulty clamping small swings about

origin Double stage buffer

Delay increase inconsequential Greatly improved clamping range

Page 12: Resistance to Frequency Converter Amol Mupid Andrew Ricketts.

Layout of complete design

Page 13: Resistance to Frequency Converter Amol Mupid Andrew Ricketts.
Page 14: Resistance to Frequency Converter Amol Mupid Andrew Ricketts.

Transistor sizing

Core area 48.75 X162.6 = 7,926(um^2)

Transistor Width (um) Length (um)

Mb1 11.0 0.6

Mp1,Mp2 5.16 0.6

Mp3,Mp4 5.16 0.6

Mn1,Mn2 3.0 0.6

MpInv 18.0 0.6

MnInv 6.0 0.6

Page 15: Resistance to Frequency Converter Amol Mupid Andrew Ricketts.

Voltage dependant output periodicity

0

0.5

1

1.5

2

2.5

3

period(NS)

frequency(GHz)

3.3V3.5V4V4.5V5V

Page 16: Resistance to Frequency Converter Amol Mupid Andrew Ricketts.

Power dissipation ( mW)

0

5

10

15

20

25

30

max power avg power rms power

3.3v3.5V4V4.5V5V

Page 17: Resistance to Frequency Converter Amol Mupid Andrew Ricketts.

Resistance We want the Vcontrol be to

be in between operable range

=> Rs*VDD/ (Rs+ R) has to be in between 3.3V and 5V

Rs

R

Vcontrol

Page 18: Resistance to Frequency Converter Amol Mupid Andrew Ricketts.

Conclusion The change in the sensor resistance

can be detected in “ns” range and converted to square wave pulses

This completely eliminates the need of ADC, huge potential resource savings.

Successfully overcame practical design issues and produced desired results.

Page 19: Resistance to Frequency Converter Amol Mupid Andrew Ricketts.

Thank You

Questions??