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Driver Design for Noise Reduction without Polysilicon Resistors

IP.com Disclosure Number: IPCOM000103743D
Original Publication Date: 1993-Jan-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 1 page(s) / 50K

Publishing Venue

IBM

Related People

Fentanes Jr, J: AUTHOR [+2]

Abstract

The utilization of CMOS processes has greatly reduced the resistance of polysilicon wires. Thus, polysilicon resistors are unworkable for building delay lines for simultaneous switching noise control in Very Large Scale Integration Off Chip Drivers. The circuit depicted in the accompanying figure achieves an excellent di/dt control without utilizing polysilicon wire resistors as timing components. Conventional Off Chip Driver noise control is generally accomplished by splitting the output stage of the driver into sections which are switched in a staggered fashion by a delay line, typically an RC chain. This staged turn-on produces less noise. However, this conventional approach depends upon polysilicon wires to implement the resistors in the RC chain.

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Driver Design for Noise Reduction without Polysilicon Resistors

      The utilization of CMOS processes has greatly reduced the
resistance of polysilicon wires.  Thus, polysilicon resistors are
unworkable for building delay lines for simultaneous switching noise
control in Very Large Scale Integration Off Chip Drivers.  The
circuit depicted in the accompanying figure achieves an excellent
di/dt control without utilizing polysilicon wire resistors as timing
components.  Conventional Off Chip Driver noise control is generally
accomplished by splitting the output stage of the driver into
sections which are switched in a staggered fashion by a delay line,
typically an RC chain.  This staged turn-on produces less noise.
However, this conventional approach depends upon polysilicon wires to
implement the resistors in the RC chain.

      In the circuit depicted in the accompanying figure, the delay
line is constructed of a chain of pass gates and inverters.  A given
stage must charge the gate capacitance of its segment of the output
transistor, turning that transistor on.  This charge condition is
detected by an inverter which turns on the pass gates which will
permit charging the next stage.  Control of di/dt is so effective
with this approach that current grows linearly in time (i.e., di/dt
is constant) over the driver turn-on time.

      Disclosed anonymously.