1 High Speed Fully Integrated On-Chip DC/DC Power Converter By Prabal Upadhyaya Sponsor: National Aeronautics and Space Administration (NASA) Advisor Dr. Herbert Hess Microelectronics Research and Communications Institute (MRCI) University of Idaho February 8, 2007

2 Outline Overview Design of the High Speed DC/DC Power Converter Simulation Results Layout Measured Results Planned Future Work Conclusion

3 Overview Last 15 years has seen a significant reduction in size of portable electronics devices

4 Overview Portable system is a collection of various sub- systems Sub-systems may demand multiple input voltages and variable currents

5 Overview On-chip fully integrated DC/DC power converters that provides point of use power conversion can be a possible solution

6 Overview All switch-mode power converters use inductor In the past, most DC/DC power converter were operated at low frequency and with discrete off chip inductor Quality factor (Q) of an inductor is the function of frequency higher Q can be achieved at high frequency f Q

7 Overview Benefits with high frequency switching  Integrated solution for the power converter  Reduced passive size  Higher Q inductor available

8 Overview Challenges with high frequency design  Parasitic capacitance  Power dissipation  Noise  Attenuation

9 Design of the High Speed DC/DC Power Converter

10 Sub-Components Sub-components used in the power converter are A Buck Converter Two Comparators A Voltage Control Oscillator (VCO) A Charge Pump

11 Block Diagram 1.5V <1.5V 01 V t 3.3V 0V

12 Buck Converter

13 Comparator Amplification stage Decision making Stage Buffer stage

14 Ring VCO

15 Charge Pump – Cadence View

16 Simulation Results Cadence Spectre

17 Simulation Results Output Voltage waveform has two kinds of output ripples High frequency ripple due to switching at 1 GHz Low frequency ripple due to control loop at 26 MHz Output Voltage = 1.5 V

18 Simulation Results High frequency ripple is 19 mV Low frequency ripple is 65mV Output waveform

19 Simulation Results Vout with variable load Vout changes with a change in the loading condition, but it takes less than 48 ns for the control loop to restore the output to the required voltage level

20 Simulation Results Comparator produces logic 1 and 0 depending upon the output of the buck converter Comparator Out

21 Simulation Results Logic 1 or 0 from the comparator controls the operation of charge pump. Logic 1 charges the capacitor Logic 0 discharges the capacitor Charge Pump Out

22 Simulation Results VCO Out VCO produces a near triangular wave of 1.02 GHz

23 Simulation Results PWM Duty-cycle of the PULSE driving the buck converter switch is altered based upon the near DC charge pump output voltage Basic operation is to shift the DC level of the VCO signal to change the Duty- cycle of the PULSE

24 Simulation Results Iout Buck converter can supply upto 20mA of peak current.

25 Simulation Results Vo=1.1 V Vo=1.5 V Vo=1.4 V Vo=1.3 V Vo=1.8 V Power converter has output range of 1.0 V to 1.8 V, but limited to loading conditions Peak current of 20mA can be drawn only in the range of 1.0 V to 1.8 V Output voltage range is limited by duty-cycle and comparator

26 Simulation Results PULSE with variable duty cycles Control loop created different duty cycles to adjust converter output Vo=1.1 V Vo=1.5 V Vo=1.3 V Vo=1.8 V

27 Power Converter Layout

28 Layout NMOS Closeloop – Cadence View CAPACITOR BANK INDUCTOR CONTROL CIRCUIT Size 1180u x 900u Picture of a Fabricated Chip - NMOS

29 Layout PMOS Closeloop– Cadence View Size 1180u x 900u Picture of a Fabricated Chip - PMOS

30 Measured Results – Preliminary Output voltageMax Current drawn 1.0 V20 mA 1.2 V20 mA 1.5V20 mA 1.8 V20 mA 2.0 V19 mA 2.2 V17 mA

31 Planned Future Work Increase the switching frequency to achieve  higher Q for inductor  smaller passives Increase efficiency Eliminate low frequency ripple Use the concept over to manufacture power converters in the industrial basis

32 Planned Future Work – Control Ripple

33 Conclusion Fully integrated DC/DC converter realized in silicon The converter takes 3.3V supply and can successfully realize voltage from 1.0 V to 1.8 V while supplying up to 20 mA of current Diameter of the power converter is 1180u x 900u

34 Thank You! Acknowledgements I would like to express my deep gratitude to Mr. Parag Upadhyaya, Washington State University Dr. Deukhyoun Heo, Washington State University And MRCI team For technical discussion and support Acknowledgements I would like to express my deep gratitude to Mr. Parag Upadhyaya, Washington State University Dr. Deukhyoun Heo, Washington State University And MRCI team For technical discussion and support University of Idaho February 8, 2007 High Speed Fully Integrated On-Chip DC/DC Power Converter