SN74LVC1GX04: output source impedance at Y port

Max Schleger

Part Number: SN74LVC1GX04

HI,

I want to filter my squarewave at the output Y to a Sine Wave.
To dimensioning my filters right and don't get problems in therms of signal integrity and EMC because of the reflections.
I need to know the Output Surce Impedance of the output Y port. so I can fit the Impedance to my system.

can somebody provide this Infomation to me.
because i cant find it on the data sheet.

Thanks
Max

over 4 years ago

0 Clemens Ladisch over 4 years ago

Guru 243180 points

The worst-case output impedance can be derived from the worst-case V_OL.

The typical V_OL is not specified; to estimate it, see Input and Output Characteristics of Digital Integrated Circuits at 3.3-V Supply Voltage (SZZA010).

0 Emrys Maier over 4 years ago

TI__Guru* 96591 points

Hey Max,

I'd estimate around 10~15 ohms for an LVC device. It's very common to add a series resistance at the output to get a higher impedance for matching to a 50 or 75 ohm line.

0 Max Schleger over 4 years ago in reply to Emrys Maier

Prodigy 50 points

HI Emrys,

thanks for the estimation.

Why is it common to match the impedance by a reststor ?

Which reflects back in to the IC Output and not with a Ballon so a LC network wich would match the impedance with less reflections.

Cheers

Max

0 Clemens Ladisch over 4 years ago in reply to Max Schleger

Guru 243180 points

That resistor is right near the output pin, so there is not enough distance to get much of a reflection. Therefore, it is not necessary to use anything more expensive than a resistor.

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SN74LVC1GX04: output source impedance at Y port