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VLSI System Design – ECES 681. Lecture: Interconnect -1 Prashant Bhadri [email protected] Office: Rhodes Hall - 933C Department of ECECS, College of Engineering, University of Cincinnati. Noise. What is noise?

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VLSI System Design – ECES 681

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Vlsi system design eces 681

VLSI System Design – ECES 681

Lecture: Interconnect -1

Prashant Bhadri

[email protected]

Office: Rhodes Hall - 933C

Department of ECECS, College of Engineering, University of Cincinnati


Noise

Noise

  • What is noise?

    • auditoryexperienceofsoundthatlacksmusicalquality; soundofanykind (especiallyunintelligibleordissonantsound)

    • Electrical noise may be said to be the introduction of any unwanted energy, which tend to interfere with the proper reception and reproduction of transmitted signals.


Vlsi system design eces 681

  • External Sources

    • Atmospheric

    • Industrial

    • Extraterrestrial

    • Solar noise

    • Cosmic noise

  • Internal Noise

    • This is the noise generated by any of the active or passive devices found in the receiver.

    • Can it be a transmitter?

    • How about on chip, in a system design, board design etc.


Chip noise

Chip Noise

  • Circuit noise includes all the disturbances induced by the circuit’s topology.

  • Interconnect noise includes noise coming from capacitive or inductive coupling between interconnects.

  • Power supply noise, which refers to deviations of the supply and ground voltages from their nominal values.

  • Substrate noise in mixed-signal integrated circuits: the charge injected in the substrate by the logic gates during the transitions may interfere severely with the operation of sensitive analog circuits.

Reference: Bartolo’s Thesis, Chapter 1


Vlsi system design eces 681

Reference: Digital System Engineeringhttp://eeclass.stanford.edu/ee273/


Vlsi system design eces 681

Reference: Digital System Engineeringhttp://eeclass.stanford.edu/ee273/


Vlsi system design eces 681

Reference: Digital System Engineeringhttp://eeclass.stanford.edu/ee273/


Vlsi system design eces 681

Reference: Digital System Engineeringhttp://eeclass.stanford.edu/ee273/


Vlsi system design eces 681

Reference: Digital System Engineeringhttp://eeclass.stanford.edu/ee273/


Vlsi system design eces 681

Reference: Digital System Engineeringhttp://eeclass.stanford.edu/ee273/


Vlsi system design eces 681

Reference: Digital System Engineeringhttp://eeclass.stanford.edu/ee273/


Vlsi system design eces 681

Reference: Digital System Engineeringhttp://eeclass.stanford.edu/ee273/


Vlsi system design eces 681

Reference: Digital System Engineeringhttp://eeclass.stanford.edu/ee273/


Vlsi system design eces 681

Reference: Digital System Engineeringhttp://eeclass.stanford.edu/ee273/


Vlsi system design eces 681

Reference: Digital System Engineeringhttp://eeclass.stanford.edu/ee273/


Shot noise

Shot Noise

  • In a transistor the major contributor to noise is called shot noise.

  • The formula for shot noise in a diode is given as:


Thermal noise

Thermal Noise

  • The noise generated by the agitation and interaction of electrons is called thermal noise. The internal kinetic energy of a particle can be expressed through its temperature.

  • The kinetic energy of a body is zero at a temperature of absolute zero.

  • The noise generated by a resistor, for example, is proportional to its absolute temperature as well as the bandwidth over which the noise is to be measured.


Vlsi system design eces 681

  • Any ordinary resistor not connected to a voltage source will have a voltage associated with it.

  • If the load is noiseless and is receiving the maximum noise power generated by our noisy resistor then:


Vlsi system design eces 681

Flicker Noise

  • Flicker noise dominates the noise spectrum at low frequency.

Reference: Noise Sources in Bulk CMOS, paper by Kent H. Lundberg


Vlsi system design eces 681

Reference: Digital System Engineeringhttp://eeclass.stanford.edu/ee273/


Other issues

Other Issues

  • Charge Injection

  • Capacitive Feed-through


Vlsi system design eces 681

Charge Injection

Solution

Problem

  • When the switch is on, the voltage across the sampling capacitor tracks the time-varying input signal within the bandwidth.

  • Some charges are present in the MOS channel, this is a result of forming a conducting channel under the MOS gate.

  • When the switch is turned off, charges either flow to the input source or to the sampling capacitor and create a small voltage which . is a function of several parameters which include input impedance, source impedance, clock falling edge, etc.

Reference: http://kabuki.eecs.berkeley.edu/~gchien/thesis/Masters/appB/appendixB.pdf


Clock feed through

Clock Feed-through

  • When the clock voltage on the gate switches between high and low, this voltage.

  • drop is coupled into the signal via the capacitor divider.

  • The clock feed-through can be corrected to the first order by using a differential signal path.

  • As long as the error is present on both signal inputs and the same magnitude, it can be cancelled by taking the input differentially.

  • This technique, once again, depends on the absolute matching of transistors.

Reference: http://kabuki.eecs.berkeley.edu/~gchien/thesis/Masters/appB/appendixB.pdf


Vlsi system design eces 681

Reference: Digital System Engineeringhttp://eeclass.stanford.edu/ee273/


Vlsi system design eces 681

Reference: Digital System Engineeringhttp://eeclass.stanford.edu/ee273/


How will you remove noise during the chip design phase any ideas

How will you remove noise during the chip design phase?   Any Ideas ??


Noise figure

Noise Figure

  • Used to assess the performance.

  • Additionally compares two devices in order to evaluate their performance + compares the signal and the noise at the same point to ensure that noise is not excess.

  • This term is used to describe how noisy a device is.

  • It is a ratio of the signal to ratio at the input to the signal to noise ratio at the output.


Reading assignment

Reading Assignment

  • Paper Name : Design Methodologies for Noise in Digital Integrated Circuits

  • Author: Kenneth L. Shepard

  • Department of Electrical Engineering

  • Columbia University, New York, NY 10027

  • Website: http://www.cisl.columbia.edu/faculty/shepard/group/dac_noise.pdf


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