LMX2594: No Clock Outputs

Travian Sampson

Part Number: LMX2594

Tool/software:

I have been having issues getting an clock output out of LMX2594RHA. I have used the recommended connections (capacitors, resistors, GND, etc) for each pin based on the datasheet. Is there any common issues with getting outputs out of this part?

over 1 year ago

0 Noel Fung over 1 year ago

TI__Guru** 115650 points

Hi Travian,

If it is locked but no output while OUTA_PD or OUTB_PD are not equal to 1, probably you forgot to pull up the output pins with 50Ω resistors.

0 Travian Sampson over 1 year ago in reply to Noel Fung

Prodigy 20 points

Hey,

The outputs do have the resistors as shown in your diagram above

0 Travian Sampson over 1 year ago in reply to Noel Fung

Prodigy 20 points

0 Dean Banerjee over 1 year ago in reply to Travian Sampson

TI__Mastermind 28031 points

Travian,

Here are a few possibilities:

1. Ensure that OUTA_PD = OUTB_PD = 0 so that the output is not powered down

2. How do we know that the device is in lock? have you checked the lock detect pin or read back rb_LD from the registers? You can also check the tuning voltage at the Vtune pin, it should be around 1.2 V. If it's at 0 V or 2.5 V, then you are not locked.

3. Ensure POWERDOWN=RESET = 0

4. Set OUT_MUTE = 0 and OUT_FORCE=1 to ensure that the output buffer does not get muted due to calibration

5. After all the regsters are programmed, then ensure that you program register R0 with FCAL_EN=1 to get the VCO calibration to run.

Regards,
Dean

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LMX2594: No Clock Outputs