[Coco] What do you use for pull-up and pull-down TTL resistor values? (LS series) (coco related project but possibly OT)

[Ed Snider]

Depending on the device, not using a resistor might draw some current unnecessarily.

It’s a judgment call depending on the particular device, and often not required, but using a pulldown
is better in my opinion (aside from the extra component taking up board space).  I’m talking in general,
not just standard TTL logic.

I’ve used both methods, depends on the situation.

In any case, using a pulldown rather than a direct connection certainly won’t hurt, and will
probably be more power efficient.

- Ed



> On Apr 22, 2019, at 1:55 PM, Salvador Garcia via Coco <coco at maltedmedia.com> wrote:
> 
> Hi Ed,
> 
> When I did my share of pulling up or down inputs, I pulled up or down depending on the TTL (for example, unused AND inputs got pulled up, unused OR or buffer inputs got pulled down); however, I never used a resistor when pulling down to gnd. Is this something that is important, given that you mention that it might not be good practice?
> 
> Thanks! Salvador
> 
> 
> 
>    On Monday, April 22, 2019, 2:33:15 PM EDT, Ed Snider <zippster278 at gmail.com> wrote:  
> 
> <snipped>
> 
> It will always be safe to tie them high or low through a pulp/pulldown (within the chip voltage ratings).
> Usually it can be tied to ground without a resistor, though that probably isn’t best practice.
> 
> I generally use 10K for the value, though the value here isn’t critical.
> 
> - Ed
> 
> <snipped>  
> 
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