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Quad buffer / line driver tri state circuit test rig

Experimentalist

May 18, 2016
3
Joined
May 18, 2016
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3
Hi

Since nobody seems to have any suggestions regarding my other post Baffled - Please help - Quad buffer / line driver tri state circuit issue I am looking for guidance as to how I may be able to build a reliable test rig to test the 74HC125N channel by channel so that I can check my hardware.

My chips are Phillips branded and have the following markings:

74HC125N
BA427 01
UnG0624D

Currently I plan to power the chip at 3.3V between ground and VCC, tie the 3 unused "output enable inputs" to ground and use a 10K pull up on the "output enable input" for the channel under test. This will be the only component so I guess there is little point but I was going to put a 100nF decoupling capacitor as close as possible to VCC for good measure.

What should I use for the data input and how can I reliably check the data output? I do now have an oscilloscope but virtually no experience using it as yet.

I have attached the chip data sheet for reference.

Any guidance gladly received.
 

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  • Phillips 74HC125N - Quad Buffer-Line Driver-TriState.pdf
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AnalogKid

Jun 10, 2015
2,671
Joined
Jun 10, 2015
Messages
2,671
The link in post #2 is to an intentionally incorrect circuit, not sure what it is supposed to teach the OP.

OP - you don't say what you are testing for. Input transition levels, input currents, output voltage levels, output impedance, output currents, bandwidth, logical functions, etc. Also, are you trying for in-circuit testing, or are these stand-alone devices?

ak
 

Experimentalist

May 18, 2016
3
Joined
May 18, 2016
Messages
3
The link in post #2 is to an intentionally incorrect circuit, not sure what it is supposed to teach the OP.

OP - you don't say what you are testing for. Input transition levels, input currents, output voltage levels, output impedance, output currents, bandwidth, logical functions, etc. Also, are you trying for in-circuit testing, or are these stand-alone devices?

ak

I am just trying to prove the devices function correctly. The whole issue is explained in my first post, also linked above. I am using the device to overcome a well known fault in another device where it does not tri state its MISO pin on the SPI bus. I think the SPI clock speed is 22MHz.

I am trying to test it stand alone so as to understand the issue I explain in the other thread.
 
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