LMK00804B-Q1: LMK00804B output can it drive 50ohm SMA load

Vinayak Chabbi

Part Number: LMK00804B-Q1
Other Parts Discussed in Thread: LMK00804B, AWR1243

Hello,

I have couple of questions on LMK00804B-Q1.

First thing is, will this drive 50 ohm load? if yes then what is the VOH and VOL levels?

I'm using this in AWR1243, for Clock as per the reference design of cascaded AWR1243. My Question here is, LMK0084B has PU and PD on CLKn pin but for CLK pin it has only PD. I'm directly connecting output of AWR1243 OSC_CLKOUT to CLK pin of AWR1243 and CLKn I have added the voltage divider which gives 0.7V at CLKn pin. 33.2 Ohm in series, and trace impedance is 50Ohm. One of LMK00804B output is used in another Board through SMA. Here due to mismatch of voltage reference in CLK and CLKn pin, will their be any issues with duty cycle? Attaching my Circuit snapshot for your reference.

Regards,

Vinayak

over 4 years ago

0 Lane Boyd over 4 years ago

TI__Genius 16845 points

Hi Vinayak,

Yes, this device can drive 50 ohm loads. I checked on my bench driving the 50ohm internal oscilloscope termination, VOH = 1.73V and VOL = -10mV.

You will want the CLKn voltage divider to apply a bias at the common mode level of the CLK input (AWR1243 OSC_OUT). You are correct in stating that mismatch in the bias voltage on the CLKn pin and common mode level on the CLK pin can cause duty cycle distortion.

Kind regards,
Lane

0 Vinayak Chabbi over 4 years ago in reply to Lane Boyd

Expert 1100 points

Hello Lane,

Thanks for clarification.

what is the supply used in the setup for testing the LMK00804B? 1.8V ?

Regards,

Vinayak

0 Lane Boyd over 4 years ago in reply to Vinayak Chabbi

TI__Genius 16845 points

Hi Vinayak,

The Electrical Characteristics specify the supply conditions. The device was tested at all supply levels.

Kind regards,
Lane

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LMK00804B-Q1: LMK00804B output can it drive 50ohm SMA load