LMH3401: LM3401 has causes dips on positive power rail

Vladimir Aparin

Part Number: LMH3401
Other Parts Discussed in Thread: LM3401,

When I'm using LM3401 as illustrated on image below I got dips on positive voltage rail.
We already checked power domain and it's looking good. It's a copy from previous project.
There are no dips without installed amplifiers.
Issue happens on both channels in separately.

What can you recommend to fix it?

over 8 years ago

0 Samir Cherian over 8 years ago

TI__Genius 12631 points

Vladimir,
Are you using power supply bypass capacitors close to the device pins? What values of capacitance and how far are the caps from the pins? A layout picture would be helpful.

How much current can your source supply?

Also, I think your common-mode setting may be too high. If you look at the datasheet on page 6, the minimum and maximum recommended common-mode voltage is 2V from the supply. you are currently around 1.7V from the supply. The typical value is 1.6V so the amplifier should work, however it may be marginal. You could try changing the common-mode to say 1.75V and see if the problem goes away.

-Samir

0 Rohit Bhat over 8 years ago in reply to Samir Cherian

TI__Genius 15975 points

Hi Vladimir/Sergey,

Would it be possible to provide power to only one channel of the LMH3401 keeping 1.25V CM, and see if the dips in the positive power rail diminish? You could remove the L21 and L22, and power up only channel A LMH3401. Also, do the dips resemble to ripples on the positive power supply or the DC voltage is just shifted down to a lower voltage? Would it be possible to add 4.7uF capacitor between the 3.75V and -1.25V supply not referenced to ground?

Best Regards,

Rohit

0 Vladimir Aparin over 8 years ago

Expert 2610 points

Thanks to all.

Now problem are founded and fixed.
There was a problem in power supply.

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LMH3401: LM3401 has causes dips on positive power rail