LP2998MA Ripple Issue

DanielZhang

Hello

We use LP2998MA for DDRII. The output ripple is about 50mV ( Measure with 20MHz BW ). Th eoutput capacitor is polymer capacitor, 220uF.

I have tried several kind of capacitors, such as ceremic and tan-capacitor.

I am not sure if it is oscillation? or just normal ripple?

If I connect a 10ohm resistor from VTT to ground, the ripple will decrease to 5-10mV. I want to know the reason, and if it will cause other issues.

Thanks.

over 12 years ago

0 Denislav Petkov over 12 years ago

TI__Mastermind 19891 points

Hi Daniel,

We will take a look at this and provide some feedback. I am hoping we can give you an update on Monday.

What is the voltage on the VCC pin (pin6) in your schematic?

What is the polymer cap part number?

Regards,

Denislav

0 DanielZhang over 12 years ago in reply to Denislav Petkov

Prodigy 70 points

CAP PL 220UF/6.3V 6.3*5.7 SMD,NICHICON,

P/N: FP-6R3ME221M-SBR
ESR:12m ohm
DS can be found here
http://www.nichicon.co.jp/english/products/pdf/2012fpcap_catalog_sssasb.pdf

Vcc=3.3V

Thanks for your feedback.

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LP2998MA Ripple Issue