SM74611: SM74611 3.3V Operating Observation

alikaan

Part Number: SM74611
Other Parts Discussed in Thread: LM5050-1

Hi there,

We used the SM74611 diode for our voltage regulation application for single board computer. It needs 3.3V and 2 ampers for operation. Single board computer couldn't start because of the voltage switching. I added the scope image for voltage in.

In the datasheet lowest voltage is 1V, so I think it should work fine with 3.3V.

Thanks!

over 6 years ago

0 Karikalan Selvaraj over 6 years ago

TI__Genius 16305 points

Hi Alikaan,

Output voltage of SM74611 will have switching behaviour and it is due to the zero Iq design where charge pump turns on/off.

Could you consider using and L and C after the SM74611 to avoid seeing the switching?

Regards,
Kari.

0 alikaan over 6 years ago in reply to Karikalan Selvaraj

Expert 2315 points

Hi Kari,

Thanks for your reply. I already have 10uH inductor and 100uF tantalum capacitor at the output stage. I removed them but diode is still switching.

Thanks.

0 alikaan over 6 years ago in reply to Karikalan Selvaraj

Expert 2315 points

Hi Kari,

Is there any update for this problem?

Thanks.

0 Karikalan Selvaraj over 6 years ago in reply to alikaan

TI__Genius 16305 points

Hi Alikaan,

Can you share the schematic portion of SM74611, so that we can support better?

Regards,
Kari.

0 alikaan over 6 years ago in reply to Karikalan Selvaraj

Expert 2315 points

Hi Kari, schematic is attached.

0 alikaan over 6 years ago in reply to alikaan

Expert 2315 points

Is there any opinion about this error?

0 alikaan over 6 years ago in reply to Karikalan Selvaraj

Expert 2315 points

Hi Kari,

I attached the schematic, do you have any opinion about this problem?

0 Karikalan Selvaraj over 6 years ago in reply to alikaan

TI__Genius 16305 points

Hi Alikaan,

I am trying to simulate the schematic and see if the output pulsed behaviour can be minimised.
Basically we need reduce the capacitance after SM74611 and increase the capacitance after inductor IND1 and IND2.

Is it possible for you to simulate this and check?

Regards
Kari.

0 Karikalan Selvaraj over 6 years ago in reply to Karikalan Selvaraj

TI__Genius 16305 points

Hi

Other option is to use LM5050-1 for 5V.
For 3.3V, you can use LM5050-1 with it supply biased from another supply about 5V.

Regards,
Kari.

0 alikaan over 6 years ago in reply to Karikalan Selvaraj

Expert 2315 points

Hi Kari,

For biasing with 5V, where should use it for LM5050 ? I'm asking for pin configuration.

0 Karikalan Selvaraj over 6 years ago in reply to alikaan

TI__Genius 16305 points

Hi

Supply an external bias to Vs pin of LM5050-1 and this voltage must be atleast 5V.
This way LM5050 can support 3.3 V rails.

Regards,
Kari.

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SM74611: SM74611 3.3V Operating Observation