LM2621: Volatge ripple

Pradeep Kumar68

Part Number: LM2621

Hello ,

I am using LM2621 in a RF Transmitter. I generating 8.5V from 5.5V. During testing we have observed that, there is a 11Khz noise getting generated from LM2621. Which is getting modulated with RF. So I am seeing 11Khz Sours at my RF output. I tried change my output filter and switching frequency, but nothing seems to be helping. So can you please help me in eliminating this noise from LM2621 output? Below I have attached my schematic for your reference.

over 5 years ago

0 Zack Liu over 5 years ago

TI__Mastermind 34201 points

Hi Pradeep,
Can you help show me the voltage ripple waveform. Please set the time resolution of oscilloscope to be 50us/div in order to see whether there is a 11kHz noise.
By the way, can you tell me the load current. Is it a dc load current or pulse load current?

0 Pradeep Kumar68 over 5 years ago in reply to Zack Liu

Intellectual 420 points

Hello,

Please find the image below.

We are drawing DC load current of 80mA from LM2621.

0 Zack Liu over 5 years ago in reply to Pradeep Kumar68

TI__Mastermind 34201 points

Hi Pradeep,

Have you ever tried removing L21 and ferrite bead and see the vout ripple? Please also have a look at SW pin waveform without L21 and ferrite bead.

0 Zack Liu over 5 years ago in reply to Zack Liu

TI__Mastermind 34201 points

Hi Pradeep,

I haven't heard back from you. I'm assuming you were able to resolve your issue. If not, just post a reply below.

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LM2621: Volatge ripple