LM5007: current limit function of LM5007

Oliver Ou

Part Number: LM5007

Hi,

We tested the current limit function of LM5007 and found it's strange comparing with other chips:

When the current limit function was trigged(around 0.7A), the switch frequency would increase according to the equation(5) in datasheet;

but the OCP point is not limited to around 0.7A, the output current can goes up to 1.7A till the output voltage drop to 0;

then the OCP point would fold back to around 0.7A again.

Can you give some comments for this phenomena? and Why we design this kind current limit feature?

Thanks,

Oliver Ou

Around 500mA output, switch frequency=160KHz;

Around 740mA output, switch frequency=324KHz;

The output current still can increase, around 1.7A maximum,

After the output drop to 0A, the current limit fold back to around 0.7A.

over 5 years ago

0 Katelyn Wiggenhorn over 5 years ago

TI__Genius 11040 points

Hello,

I will reach out to the product expert with your question.

Best Regards,
Katelyn

0 Timothy Hegarty over 5 years ago

TI__Guru 57552 points

Hi Oliver

Please forward the schematic and layout for review.

Regards,
Tim

0 Oliver Ou over 5 years ago in reply to Timothy Hegarty

TI__Intellectual 2845 points

Hi Tim,
I have send them to you with mail.

Thanks,
Olive Ou

0 Timothy Hegarty over 5 years ago in reply to Oliver Ou

TI__Guru 57552 points

Hi Oliver,

As we are discussing this by email, I will close out this thread.

Regards,
Tim

0 Timothy Hegarty over 5 years ago in reply to Oliver Ou

TI__Guru 57552 points

Note that the important point here is to select a higher RCL resistor such that a drop in switching frequency occurs when current limit is engaged. See Figure 3 in the LM5007 datasheet.

Regards,
Tim

Power management

Power management forum

LM5007: current limit function of LM5007