Probably to decrease parasitic inductance on the power and ground pins.? Wirebonds make great inductors, and as the edge speeds increased, ground and power bounce became a problem.? V = L*di/dt.? I assume the power and ground pins went to the center of the package.? Corner pins are the worst possible choice for inductance.Jim Ford?Sent from my Verizon, Samsung Galaxy smartphone
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-------- Original message --------From: Harvey White <madyn@...> Date: 7/4/20 12:47 PM (GMT-08:00) To:
[email protected] Subject: Re: [TekScopes] S-52 only works with lowered +15 V power supply 74L series of chips should be checked for pin compatibility with anything else.? Not sure why they did that, but that's been a design problem for any number of years when substituting.Also, not all 7400 series chips have power and ground at 14/7 or 16/8.? Surprise....HarveyOn 7/4/2020 2:21 PM, unclebanjoman wrote:> While checking the circuit I just discover that SN74L93 and SN74LS93 are NOT pin-to-pin compatible!> I was using the "classical" 7493 datasheet from Texas Instruments datasheet and wondering how it worked ...> I never imagined that the 74L93 had a different pinout! I found the correct pin-out in a very old National databook.>> Max>> >>
