WEBENCH® Tools/LM5010: LM5010 giving constant ~7V at output

Hi

I did a simulation based  TI Spice simulation , it can deliver 12V . Can you help test the waveform  ,especially FB and SW. 

Thanks

Hi Daniel,

Thanks for simulation result, its really helpful.

Let me check FB and SW on my Oscilloscope and get back to you.

Regards,

Anurag

HI Anurag:

thanks 

Hi Daniel,

Following is my waveform for VSW as observed on Oscilloscope:

Regards,

Anurag

Hi

is the device working at no load condition or full load condition?

is the CH2 is 100mV/div and where is 0 for CH2?

it looks like you high side is not fully turn on.

Thanks

Hi Daniel,

I tried another assembled PCB.

It is giving me 12V at output, but as soon as I am connecting a 12V/250mA load, its coming down to ~5V-4V.

It is working fine on simulation, but not on actual circuit.

In oscilloscope I am getting somewhat square waves at output, which is not uniformly 12V.

Should I add a ripple rejection circuit as suggested in datasheet or Is it caused by 330uH (higher value)Inductor?

Can you please verify layout of following schematic:

Regards,

Anurag

HI

what is C7 Voltage rating? can you try to increase it or add one more paralleling with C7?

use 100V diode see any help.

pls help take SW waveform and Vo waveform when issue happened.

Thanks

Hi,

C7 is 25V, I have tried adding one more in parallel to make it 20uF.

I will try 100V.

Regards,

Anurag

This is the SW waveform, when VIN is 50V.

Hi

is the time 100ms/div? it is more like Vo start up then drop down waveform instead of SW. there is no any swiching .

Hi Daniel,

Sorry for late reply.

Yes, it is 100ms/div, if its Vo startup then what should I do if its repeating itself.

Regards,

Anurag

HI

what's the load condition?  can you also check SS,VCC and SD waveform. Normally the Vo dropdown should be some off signal on the device.

Thanks

Hi Daniel,

It seems like there is no switching.

I have tried two different circuits for 12V and one also for 10V.

But none of them seem to work.

This is my current schematic, after calculating values using TI Calculator

As you can see R2 is 3k and R1 is 1k, it is same schematic as mentioned in LM5010EVAL

It is designed for 10V.

I have tested this circuit using 48V-52V and following is the output I am getting:

As I am connecting Load, It is getting dropped immediately even at 10mA.

As you can see it is at 0V.

Another thing is that I have tried checking SW pin, to see if switching is happening and following is the SW output;

It seems to be output voltage, as it is at same 12V reference and it drops to 0V on load.

I am attaching new layout as well, although I have tested this schematic on both this one and previous layouts.

I am considering to use LM5164 next, but I am not quite sure whether that will work either. Should I consider any Buck controller, in case?

Regards,

Anurag

Hi

can you try to configure the ripple injection as type 3?

Hi Daniel,

I have tried following schematic after calculating accordingly:

I have introduced C6, C9 and R5.

But, Voltage is still dropping to 9.3V at 200mA, 8.5V at 300mA and further 6V at 500V.

In feedback I am getting ripple peak to peak to of 3V-4.5V.

Regards,

Anurag

Hi Daniel,

Can you please review this Layout?

And can you tell me why there are gaps(vertical line and arc around via) on bottom ground plane of LM5010 EVM on page 6:

Regards,

Anurag