Leakage Power Minimization in Ultrawideband UWB Communications Circuits
Leakage Power Minimization in Ultra-wideband (UWB) Communications Circuits Edgar Wangolo
Presentation Plan n n n UWB: concept and applications Leakage power in sub-micron CMOS Leakage minimization techniques Application to PLL’s Prescaler Project time table References
UWB - Concept n n FCC: bandwidth is more than 25% of a center frequency or more than 1. 5 GHz Typically implemented in a carrierless fashion n n Directly modulate an “impulse” with a very sharp rise and fall time => a waveform that occupies several GHz Historically started with radar applications for military use
UWB Vs. Narrowband Communications Narrowband Communication Ultrawideband Communication Time-domain behavior Impulse Modulation 1 Frequency-domain behavior 1 0 time 3 frequency 10 GHz (FCC Min=500 Mhz) 0 1 Frequency Modulation 2. 4 GHz
Operation Principles (“Spectrum Underlay“) Narrowband (e. g GSM: +35 d. Bm/MHz) Transmit Power Spectral Density WCDMA (typ. +15 d. Bm/MHz) [d. Bm/MHz] UWB (e. g – 41 d. Bm/MHz) 1 Frequency/GHz 10 Bandwidth (GSM : WCDMA : UWB) ~ 1 : 10000
UWB Spectrum FCC ruling permits UWB spectrum overlay Bluetooth, 802. 11 b Cordless Phones Microwave Ovens PCS Emitted Signal Power GPS n 802. 11 a “Part 15 Limit” -41 d. Bm/Mhz UWB Spectrum 1. 6 1. 9 2. 4 3. 1 5 Frequency (Ghz) 10. 6
UWB Vs. Narrowband UWB Transceiver ADC CLK DIGITAL GAIN TX ANAL OG: LNA A/D MIXER Q A/D F SYNTH D/A PA I MIXER D/A DIGITAL: Narrowband Transceiver
UWB: Advantages High Bandwidth, high data rate n Low power spectral densities n Simple, low cost n Immunity to interference Challenges: n Low/Medium Range n Signal to noise ratio is still an issue n
UWB: Applications n n n Accurate positioning (through wall radar, tracking) High quality wireless video Satellite communications Air traffic control Medical imaging Etc.
PLL Block Diagram 30 – 40% of total power input PFD up down Charge Pump Loop Filter %N VCO output 40% of total power Today’s monolithic PLL’s use Phase Frequency Detectors (PFD), charge pumps, and an optional frequency divider in the feedback path.
Fin N-digit Fractional-N Prescaler Fout 2/3 2/3 P 0 P 1 P 2 Pn N=2 n+2 n-1 Pn-1+2 n-2 Pn-2+…+2 P 1+P 0
Circuit Power n n n Dynamic Power: determined by circuit performance requirement. Short_Circuit Power: Both PU and PD circuit partially conduct. Small percentage. (<10%) Leakage Power: Increasingly important, and many issues dependent, such as device geometry, temperature, doping, processing and data pattern dependent, etc. It is very complicated and worthy to study more to improve it.
Leakage Power Sources Sub-threshold Gate oxide PN
Leakage control: MTCMOS
Smart Switch Series (Triple-S)
RCSFF: Reduced-Clock Swing Flip-Flop
Timetable n n n Literatures: Circuit Design: Simulations: Presentation: Report: March 10 March 16 March 28 April 6 April 20
References n n n Hiroshi Kawagushi and Takayasu Sakurai, “A Reduced Clock-Swing Flip-Flop (RCSFF) for 63% Power reduction”, IEEE Journal of Solid State Circuits, Vol. 33, N 05, May 1998 Tschanz et. Al, “Dynamic Sleep Transistor and body bias for active leakage power control of microprocessor”, IJSSC, Nov 2003 J. T. Kao and A. Chandrakasan, “ Dual Threshold Voltage Techniques for Low-Power Digital Circuits”, IEEE Journal of Solid -State Circuits, July 2000
- Slides: 18