LMK1C1103: Schematic review request

Peter Grinalds

Part Number: LMK1C1103

Hello there TI team,

I am hoping you can provide a schematic review for a my design for a client. I am providing a 36.864MHz oscillating clock into the LMK and then outputting it to two microcontrollers and one ADC (a Texas Instruments TLV320). Is it okay that I tie the 1G high so that it starts as soon as Vdd is stable? Then when I bring the oscillator up the buffer will then pass out the clock signal? Additionally, is it okay that I do my fanout signal impedance balancing by simply calculating the impedance of the trace to the sink IC and then add a resistor in series to bring the overall impedance up to 50ohms?

Thanks so much,

Peter

over 1 year ago

0 Andrea Vallenilla over 1 year ago

TI__Genius 10985 points

Hello Peter,

The power supply filtering your using should be fine but it's a little weak. I would recommend something like this (p. 13 in data sheet):

Peter Grinalds said:
Is it okay that I tie the 1G high so that it starts as soon as Vdd is stable?

Is this why you did not add a pull resistor to the schematic?

Apart from those 2 points everything looks good.

Best,

Andrea

0 Peter Grinalds over 1 year ago in reply to Andrea Vallenilla

Prodigy 160 points

Hi there Andrea,

Thank you so much for the reply and consideration. My question regarding the ferrite bead is this: is there a known problem that the ferrite bead would address or is this more of a preventative measure. And further, is a ferrite bead the better solution over a pi filter? Is there any application note with oscope measurement with the ferrite filter that I might find to educate myself?

Regarding the pull up resistor, yes, I would like it to turn on ASAP and do not want to risk transience causing the pin to drift low due to too weak of a pull up. Would you recommend a pull up?

Thanks so much,

Peter

0 Andrea Vallenilla over 1 year ago in reply to Peter Grinalds

TI__Genius 10985 points

Hello Peter,

The ferrite bead is not needed or the pi filter, I meant adding another high frequency cap would be good.

Peter Grinalds said:
Regarding the pull up resistor, yes, I would like it to turn on ASAP and do not want to risk transience causing the pin to drift low due to too weak of a pull up. Would you recommend a pull up

We do recommend a pull-up to limit any leakage current, however it's not needed.

Best,

Andrea

0 Peter Grinalds over 1 year ago in reply to Andrea Vallenilla

Prodigy 160 points

Okay thank you I will do so. Thanks for the replies and assistance!

0 Andrea Vallenilla over 1 year ago in reply to Peter Grinalds

TI__Genius 10985 points

No problem, glad I could help!

Clock & timing

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LMK1C1103: Schematic review request