Electronics > RF, Microwave, Ham Radio

Si5351a Voltage not turning my Line Driver ON

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Jeff Weinmann:
Hello,

I've been working on amplifying the clock signal of the Si5351A clock generator.

Observing on an Oscilloscope I see that it constantly puts out 3.3 Volts Peak to Peak square wave with:

+1.67 Volts at the top, and -1.67 Volts at the base.

I've connected it to an Octal Buffer/Line Driver, this one in particular:

https://www.digikey.com/en/products/detail/on-semiconductor/74AC244SC/149106

I just cannot get the line driver to turn on.   Input Voltage on the Datasheet says -.5 to Vcc to +.5V.


The datasheet also states that the ACT244 has TTL-compatible inputs.

So, is 1.67 Volts not a TTL level voltage?   The goal is to power the Line driver at 5 Volts and enable the line driver just by using the clock voltage.


If I cannot get the clock generator to turn this line driver on,  can anyone recommend a Line driver that will?

attached is my schematic on how I'm hooking it up.

thanks to all

MIS42N:
You say you are using an AC part, not ACT. ACT are the TTL compatible ones. The AC on voltage is Vcc dependent, probably 2.5V for a 5V Vcc.

mon2:
https://www.adafruit.com/product/1787

oPossum:

--- Quote from: Jeff Weinmann on June 18, 2021, 12:20:38 am ---The datasheet also states that the ACT244 has TTL-compatible inputs.

So, is 1.67 Volts not a TTL level voltage?   

--- End quote ---

The datasheet will have minimum high levels specified.

Typically...
2.0V for TTL [compatible]
80% of Vcc for CMOS

radiolistener:

--- Quote from: Jeff Weinmann on June 18, 2021, 12:20:38 am ---I've been working on amplifying the clock signal of the Si5351A clock generator.

Observing on an Oscilloscope I see that it constantly puts out 3.3 Volts Peak to Peak square wave with:

+1.67 Volts at the top, and -1.67 Volts at the base.

--- End quote ---

It looks like you forgot to switch from AC coupling to DC coupling on oscilloscope input :)

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