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Posted: **Tue Jan 27, 2015 11:26 pm**

Dajgoro wrote:

BigDumbDinosaur wrote:

Dajgoro wrote:

Can anyone recommend a schottky diode model that is easily obtainable and affordable in large quantities?
I prefer trough hole for now.

Edit: I need the drives for tristating the bus too, so I can have another device access the bus.

Please see attached for a suggestion.

The attachment 74s1053_schottky_array_16.pdf is no longer available

Nice, but looking on ebay they tend to be a bit expensive.

Is there an electronics distributor in your area that might be able to get it for you at a more reasonable cost?

An alternative would be to use Thevenin termination, which is just a bunch of resistors. The 74ABT245 transceivers you are using can source 32ma and sink 64ma, which gives you some leeway in choosing appropriate resistor values. For a start, I would try 220 ohms from the '245 outputs up to Vcc and 330 ohms from the '245 outputs to ground. That combination would produce a characteristic impedance of around 100 ohms on each signal.

You could use discrete resistors (1/4 watt carbon film recommended) or a resistor array. I use the latter on my SCSI host adapter for bus termination.

4100r_array_bourns.pdf: Resistor Array; (218.85 KiB) Downloaded 71 times

resistor_array_bourns_4300Rseries.pdf: Resistor SIPs; (210.63 KiB) Downloaded 76 times

resistor_array_bourns_4600Rseries.pdf: Resistor SIPs; (235.14 KiB) Downloaded 65 times

transmission_line_terminations.pdf: Some transmission line termination theory.; (314.95 KiB) Downloaded 70 times

Posted: **Wed Jan 28, 2015 8:56 am**

That would be ok if I only had 74ABT245 as siganl sources, other modules might have different characteristics.
I tried sending an email to unicornelectronics to see if they had them, but their mailbox is full.

Posted: **Wed Jan 28, 2015 6:55 pm**

Dajgoro wrote:

That would be ok if I only had 74ABT245 as siganl sources, other modules might have different characteristics.

In that case, Schottky diodes (discrete or array) would probably be your best bet.

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