electronic engineering Electronics engineering is a sub-discipline of electrical engineering which emerged in the early 20th century and is distinguished by the additional use of active components such as semiconductor devices to amplify and control electric current ...

, ground bounce is a phenomenon associated with

transistor upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink). A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch e ...

switching where the

gate voltage The threshold voltage, commonly abbreviated as Vth or VGS(th), of a field-effect transistor (FET) is the minimum gate-to-source voltage (VGS) that is needed to create a conducting path between the source and drain terminals. It is an important s ...

can appear to be less than the local

ground potential In an electrical system, a ground loop or earth loop occurs when two points of a circuit are intended to have the same ground reference potential but instead have a different potential between them. This is typically caused when enough curren ...

, causing the unstable operation of a

logic gate A logic gate is an idealized or physical device implementing a Boolean function, a logical operation performed on one or more binary inputs that produces a single binary output. Depending on the context, the term may refer to an ideal logic gate, ...

Description

Ground bounce is usually seen on high density

VLSI Very large-scale integration (VLSI) is the process of creating an integrated circuit (IC) by combining millions or billions of MOS transistors onto a single chip. VLSI began in the 1970s when MOS integrated circuit (Metal Oxide Semiconductor) c ...

where insufficient precautions have been taken to supply a logic gate with a sufficiently low impedance connection (or sufficiently high

capacitance Capacitance is the capability of a material object or device to store electric charge. It is measured by the change in charge in response to a difference in electric potential, expressed as the ratio of those quantities. Commonly recognized are ...

) to ground. In this phenomenon, when the base of an NPN transistor is turned on, enough current flows through the emitter- collector circuit that the silicon in the immediate vicinity of the emitter-ground connection is pulled partially high, sometimes by several volts, thus raising the local ground, as perceived at the gate, to a value significantly above true ground. Relative to this local ground, the base voltage can go negative, thus shutting off the transistor. As the excess local charge dissipates, the transistor turns back on, possibly causing a repeat of the phenomenon, sometimes up to a half-dozen bounces. Ground bounce is one of the leading causes of "hung" or

metastable gate In electronics, metastability is the ability of a digital electronic system to persist for an unbounded time in an unstable equilibrium or metastable state. In digital logic circuits, a digital signal is required to be within certain voltage or ...

s in modern digital circuit design. This happens because the ground bounce puts the input of a flip flop effectively at voltage level that is neither a one nor a zero at clock time, or causes untoward effects in the clock itself. A similar

voltage sag Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to m ...

phenomenon may be seen on the collector side, called supply voltage sag (or ''V''_CC sag), where V_CC is pulled unnaturally low. As a whole, ground bounce is a major issue in nanometer range technologies in VLSI. Ground bounce can also occur when the circuit board has poorly designed ground paths. Improper ground or V_CC can lead to local variations in the ground level between various components. This is most commonly seen in circuit boards that have ground and V_CC paths on the surfaces of the board.

Reduction

Ground bounce may be reduced by placing a 10-30 ohm resistor in series to each of the switching outputs to limit the current flow during the gate switch.http://www.altera.com/literature/an/archives/an075.pdf

References

{{Reflist * Jeff Barrow,
Reducing Ground Bounce
', (2007), Analog Devices * Vikas Kumar,
Ground Bounce Primer
', (2005), TechOnLine (now EETimes). *
Ground Bounce in 8-Bit High-Speed Logic
', Pericom Application Note. *
AN-640 Understanding and Minimizing Ground Bounce
', (2003) Fairchild Semiconductor, Application Note 640. *
Minimizing Ground Bounce & VCC Sag
', White Paper, (2001) Altera Corporation. *
Ground Bounce part-1 and part-2 by Douglas Brooks
',Articles, Ultra Cad Design. Electronic engineering Electrical phenomena Transistors

Description

Reduction

See also

References