pull-up/pull-down/short-protection resistor design

From: Johnson Liuis (gpsabove_at_yahoo.com)
Date: 03/01/05 

Date: Tue, 1 Mar 2005 14:52:47 -0700

Please do not laugh at these newbie questions.
I am looking into some sample circuit design and wants to learn how to use
resistors for the following purposes:

1) pull-up/pull-down resistor for unused pins. It seems that 10K was used
for some cases while 4.7K or 150K was used for other cases. Any big
difference when use different resistors for this purpose? Which one can
better sustain the noise?

2) short-protection/current-limiter for pins that support both Input and
Output. For the data bus, the pins were grounded with 150K resistor (for
example, D0 to D0 first, then to ground with a resistor); for some control
pins, 22R resistors were used to connect them (for example, RXRDY to RXRDY
with a resistor). So what is the benefit to connect the data bus to ground
with a big resistor, to speed the transaction time or sustain noise? What
is the benefit to connect the pins with a resistor without grounding them?

Thanks in advance.

Johnson

Relevant Pages

  • Re: pull-up/pull-down/short-protection resistor design
    ... >> is the benefit to connect the pins with a resistor without ... > and basically create a short from Vcc to ground. ... > the circuit, or the power dissipation, any good. ...
    (comp.arch.embedded)
  • Re: Pull up resistors on Spartan 3 mode pins
    ... Trivial aspects of the design are not properly documented - that's been admitted - but the corrections have not been brought to our attention. ... And the Spartan3 devices have an explicitly low pullup impedance that should be virtually immune to any crosstalk that's applied to an unconnected pin. ... I'd expect the antenna of connecting a 10 kohm resistor to the internal 3 kohm pullup would introduce more noise than leaving the pin unconnected. ... Will the mode pins which appear to always have external pullups independent of the HWSWAP_EN pin behave fine when no external resistors are connected? ...
    (comp.arch.fpga)
  • Re: Replacing Tektronix 465 range bulb
    ... it with LED and a resistor if I can get to it. ... I definitely would consider LEDs and resistor ... pins become intermittent at the ceramic substrate solder junction. ... Amazing that you could solder them at all,the plating/tinning on those ...
    (sci.electronics.repair)
  • Re: Battery bias directly to grid
    ... There are four grid pins (thanks, Chris, that is indeed what ... > resistors in parallel to four pins than one resistor (somehow attached ... Anything which can oscillate, does oscillate, unless something to stop it ...
    (rec.audio.tubes)
  • Re: Replacing Tektronix 465 range bulb
    ... and a resistor if I can get to it. ... I definitely would consider LEDs and resistor in ... At first I thought that it was the socket but it turned out that the pins ... water soluble flux because rosin flux just would not work wit those pins. ...
    (sci.electronics.repair)