LMX2572LP: input level of OSCin (Single-ended input buffer) of LMX2572LP

akihiko yokouchi

Part Number: LMX2572LP

I would like to confirm the input level of OSCin (Single-ended input buffer) of LMX2572LP.
In the catalog, the OSCin input voltage is listed as min: 0.3 to max: 3.6V.
Is it safe to assume that this value is Vp-p from Figure 154?
And if the impedance is 50Ω, is it safe to assume that min:-6.48dBm to max:15.11dBm?

Regards,
Akihiko Yokouchi

3 months ago

0 Noel Fung 3 months ago

TI__Guru* 85480 points

Hi Yokouchi-san,

See below the definition of Voscin.

Your dBm values are correct.

Please note, the input impedance is hi-Z, for 50Ω system, we need to add a 50Ω shunt resistor or enable the internal termination, IPBUF_TERM = 1.

0 akihiko yokouchi 3 months ago in reply to Noel Fung

Intellectual 330 points

Hi Noel,

Thanks for the confirmation.

If I set IPBUF_TERM = 1, will it be ok without mounting 51Ω on R25 or R30 of the evaluation board?
By the way, I am thinking of inputting 10MHz to OSCINP (pin 8), is that ok?
Also, should I input the level considering that it will drop by 3dB inside the IC?

Regards,
Akihiko Yokouchi

0 Noel Fung 3 months ago in reply to akihiko yokouchi

TI__Guru* 85480 points

Hi Yokouchi-san,

Correct, if you have IPBUF_TERM = 1, you don't need R25. In single-ended input mode, IPBUF_TYPE = 1, OSCin* pin is ignored, so we can keep R30.

If the 50Ω source is, for example, 1V, we will have 1V at OSCIN pin:

- IPBUF_TERM = 1, R25 is removed

- IPBUF_TERM = 0, R25 is populated

+1 akihiko yokouchi 3 months ago in reply to Noel Fung

Intellectual 330 points

Hi Noel,

Thank you for the confirmation.
Understood.

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LMX2572LP: input level of OSCin (Single-ended input buffer) of LMX2572LP