LMK03318: Questions on output impedance

Prasoon Joshi

Prodigy 240 points

Part Number: LMK03318
Other Parts Discussed in Thread: LMK1C1102, SN74AXC1T45

Tool/software:

Hi,

I have a question on the required series impedance on the output of LMK03318 on the PCB:

I am configuring some banks as LVCMOS 1.8V. This is driving some SN74AUC receivers, SN74AXC1T45 tranceiver, LMK1C1102 buffer, CDCEL925PW and SMAs. I see that the EVM has the SMAs AC coupled. I was thinking of just running a trace from output to input for these LVCMOS connections. Should I put in a impedance in series at the outputs?
I am configuring some banks as AC LVPECL 3.3V. The datasheet recommends AC coupling to receiver. Can I couple the output as DC to the receiver? The receiver's data sheet shows that the receiver can be coupled as either AC or DC

Thanks,

Prasoon

11 months ago

+1 Kadeem Samuel 11 months ago

TI__Mastermind 23280 points

Prasoon,

The LVCMOS output impedance of the LMK03318 is 50-Ohms, and does not strictly require an external series termination resistor. It may help to populate a 0-Ohm in the event that a slight adjustment needs to be made for better impedance matching.

The LVPECL outputs of the LMK03318 can be DC-coupled, but they will have a different common-mode voltage than typical LVPECL. The common-mode voltage is provided below:

Thanks,

Kadeem

0 Prasoon Joshi 11 months ago in reply to Kadeem Samuel

Prodigy 240 points

Thanks Kadeem.

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LMK03318: Questions on output impedance