lmk04828 pulser mode

Sailin

Other Parts Discussed in Thread: LMK04828

Hello,i am using the pulser mode of lmk04828,and it seems that it has been worked out;But the rectangular pulse of the output is not so steep!The user guide of lmk04828 demostrate the output as following(3.2.2 Pulsed SYSREF):

but the result i got is:

I don't think it's something about the configuration,and the circuit of the output is here:

I do need a steep rising edge of the pulse,so where do you think of the problem might be?Thank you!

over 10 years ago

0 Gabe Ayala over 10 years ago

TI__Genius 10320 points

Hi there,

Try replacing C50 and C51 with 0 ohm and DC coupling. It is recommended to run pulsor SYSREF with DC coupling to avoid common mode voltage ramping due to the AC coupling caps.

Gabe

0 Timothy T over 10 years ago

TI__Mastermind 28550 points

Can you confirm that you have the SYNC_DISSYSREF = 1 and SYNC_DIS# = 1 for the used output clock? These fields are located in register 0x144.

73,

Timothy

0 Sailin over 10 years ago in reply to Timothy T

Prodigy 60 points

Hello Timothy,thanks for your answer,i am sure that i have configured the 0x144 to FF after toggling SYNC_POL pin;The configuration sequence is as following:
0x144 --00;

0x143 --91;

0x143 --B1;

0x143 --91;

0x144 --FF;

0x143 --11;

0x13E --03;

0x139 --02;
0x143 --12;

0x143 --12;

0x143 --32;

0x143 --12

0 Sailin over 10 years ago in reply to Gabe Ayala

Prodigy 60 points

Hello Gabe,thanks for your suggestion!But when i replace C50 and C51 with 0 ohm resisitor,the result is here:

I am not sure this is what you mean,or you think that i should remove the balun as well?

0 Timothy T over 10 years ago in reply to Sailin

TI__Mastermind 28550 points

The TC1-1-13MA+ balun is a 1:1 ohms ratio balun. So it is possible there is a bad impedance match. Consider trying to test with a single ended LVPECL output bypassing the balun.

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lmk04828 pulser mode