LMX1205: LMX1205 SYSREFREQ Pin VCM Biasing Requirement

Hori Shota

Expert 1930 points

Part Number: LMX1205
Other Parts Discussed in Thread: LMX1204

Hi team,

For the LMX1205, is a VCM biasing circuit required on the SYSREFREQ pin?

For comparison, the LMX1204 datasheet recommends a SYSREFREQ input circuit that biases the signal to VCM (see the figure below from the LMX1204 datasheet).

Does the LMX1205 require a similar VCM biasing circuit, or can the SYSREFREQ pin be connected directly without VCM biasing?

Best Regards,
Shota

LMX1205: LMX1205 SYSREFREQ_VCM Register Setting, SYSREFREQ Bias Requirement, and CLKIN Bias Network Necessity - Clock & timing forum - Clock & timing - TI E2E support forums

1 month ago

0 Hori Shota 28 days ago

Expert 1930 points

Hi team,

We are still waiting for your response.

Is this device no longer supported? If so, could you please let us know its support status and whether there is a recommended replacement device?

Best Regards,
Shota

0 Noel Fung 24 days ago in reply to Hori Shota

TI__Guru** 122540 points

Hi There,

SYSREFREQ input pins can be configured to with or without internal bias voltage.

Internal bias voltage is necessary when SYSREFREQ is AC-coupled, SYSREFREQ_VCM = 0x0, 0x1 or 0x2.

If DC-coupled is desired, we should setup SYSREFREQ as no internal bias, SYSREFREQ_VCM = 0x3.