LM4132 output ripple

Albert Ng

Other Parts Discussed in Thread: LM4132

I am using it to power a FPGA PLL input voltage of 1.8V at 11mA.

This FPGA input voltage has a requirement of no larger than 10mV pp ripple up to 80MHz. I am wondering if the LM4132 can meet this requirement. I have a feeling it will, but I can only see the output noise voltage only spec to 10Hz, which is much lower frequency range than I need. Thanks.

over 12 years ago

0 Michael Hartshorne over 12 years ago

TI__Genius 10680 points

Hi Albert,

The total noise from 0.1 HZ to 80 MHz would be tough to calculate, however the noise density after 100 Hz falls below 10 uV/rt(Hz) so it can be neglected outside of this range for a rough calculation. Assuming the noise density is 15 uVrms/rt(Hz) in the 0.1 Hz to 100 Hz band, then the total noise is 15uVrms*rt(100)*crestfactor = roughly 500 uVp-p. It should be fine.

A cap. directly on the output of the device will help reduce noise as well.

Regards,

Mike

0 Albert Ng over 12 years ago in reply to Michael Hartshorne

TI__Prodigy 200 points

Thank you so much for the answer and explanation. It helps. Thanks!

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LM4132 output ripple