Bootstrapped Full-Swing CMOS Driver for Low Supply Voltage

Operation

Speaker： Hsin-Chi Laim946602005@mail.ncue.edu.tw

Advisor ︰ Zhi-Ming Lin

National Changhua University of EducationNational Changhua University of EducationGraduate Institute of Integrated Circuit DesignGraduate Institute of Integrated Circuit Design

From

Garcia, J.C., Montiel-Nelson, J.A. and Nooshabadi, S., “Bootstrapped full-swing CMOS driver for low supply voltage operation,“ Design, Automation and Test in Europe (DATE), vol. 1, 6-10 March 2006.

Outline

Introduction Driver Circuit Structure Circuit Operation Results Conclusions

Introduction

Driving large capacitance loads limits the performance of CMOS circuits at low supply voltages.

The bootstrap techniques have been shown to give high performance at low supply voltages.

Use of standard high speed BiCMOS drivers is not viable in low voltage portable electronic systems.

A combined direct and indirect bootstrapped inverter driver (bfi-driver) in triple well CMOS technology is proposed.

Counterpart circuit

Compare with a counterpart direct bootstrap circuit [1]. Where NMOS transistors M8 and M9 are the replacement

for the original NPN bipolar transistors.

Driver Circuit Structure

Two bootstrap capacitors Cb1 and Cb2, and only one inverter X0.

M0 and M3 are charge the bootstrap capacitors Cb1 and Cb2.

M1 and M4 are the bootstrap transistors. M2 forms the pull-down network, while M5 forms the

pull-up network.

Circuit Operation

When Vin is Hi, the node 1 is set to Lo via the inverter X0, and M0 is turned on.

Cb1 is charged to Vdd. M1, M4 and M5 are all turned off.

M3 transistor is turned on causing Cb2 to charge.

At the same time, M2 is driven by Vin and bif-driver is pulled down, the output Vout is set to low.

When Vin goes Lo, the node 1 is set to Hi, M0, M2, and M3 are turned off.

M5 is turned on to pull-up the output. M4 turns on allowing the gate of M1 to be str

ongly driven low due to the bootstrapping effect of Cb2.

The opposite bootstrapping effect of Cb1 directly couples to the output node Vout.

• Cb, Cb1 and Cb2 are realized using NMOStransistors MCb, MCb1 and MCb2,

Results

Driver in [1] Proposed driver

CMOS process 0.13 μm

Area(μm2) 44.17 35.86

Cload 100fF

Supply Voltage 1 V

Delay 316.6 pS 19 pS 94%

Power 1.64 mW 1.28 mW 22%

As seen the Figure of Merit for proposed driver is 23.6-37.5 times smaller.

Conclusions

A high speed and low power consumption direct-indirect bootstrapped full-swing CMOS inverter driver (bfi-driver) was presented.

0.13μm triple well CMOS technology At 1V , bfi-driver is 94% faster and consumes

22% less power compared to a counterpart direct bootstrap circuit.

Thanks for your attention !!