LM5022: How to change or increase the hysteresis of LM5022 UVLO ?

Hello Kygo,

Thanks for promoting or products.

The LM5022 UVLO shutdown threshold = 1.25V

As per the example in the datasheet, where RUV1 = 2.61K and RUV2 = 10K:

Minimum input voltage (rising), necessary to exceed the threshold on the UVLO pin = 6.04V

When the UVLO threshold is exceeded (upwards), the current source is activated to instantly raise the voltage at the UVLO pin:
The 20µA current creates an additional voltage drop of 20µA * 2.61K = 0.0522V on the low side resistor, so the level, that the UVLO pin sees, jumps up to 1.3022V
20µA * 2.61K = 0.0522V hysteresis at the UVLO pin.

The input now needs to drop down to 5.79V to bring the UVLO pin down to below 1.25V
When the UVLO pin voltage falls below 1.25V the 20µA current source is turned off, causing the voltage at the UVLO pin to fall down to 1.198V

The input voltage needs to rise up to 6.04V again to turn the LM5022 back on

Hysteresis on the supply voltage = 0.25V
When you increase the values of the divider resistors you will get a higher hysteresis.

Best regards,
Harry

Hi Harry 

Thank you for the feedback!

More question,

The OCP function of LM5022 has no hiccup mode.
Instead, the figure on the right outputs the drop voltage mode.

Because the customer's input range is a bit large (9-75VDCin)... If customer want to design the OCP current protection point (Ilim) in the above picture to be as consistent as possible within the input range!!!!
Can those components in the picture below be adjusted? THX

Hello Kygo,

All components can be adjusted.

In am not sure, if I understood what exactly the question is.

Can you please explain in more detail?

Thanks,

Harry

Can I ask two questions?!Thanks!!

<1>Minimum input voltage (rising), necessary to exceed the threshold on the UVLO pin = 6.04V

    =>How to get the value of 6.04V?

<2>The input now needs to drop down to 5.79V to bring the UVLO pin down to below 1.25V

    =>How to get the value of 5.79V?

Hello Kygo,

Just use Ohm's law for resistor dividers:
VIN * RUV2 / (RUV1 + RUV2) = UVLO threshold
Rising: 6.02V * 2.61K / (2.61K + 10K) = 1.25V
Falling: 5.79V * 2.61K / (2.61K + 10K) = 1.198V ; 1.198V + 0.0522V [offset due to the 20µA current through RUV1] = 1.25V

Regards,
Harry

Hi Harry

Thank you

The figure of LM5022 OCP function 

I want to improve as below:

Can those components in the picture below be adjusted?

Hello Kygo,

Where do you find the information for the blue curve?
Please explain.

The LM5022 can not regulate on average current (e.g. generating a fixed output current for charging a battery).
The inner peak current mode control loop is meant to stabilize the output voltage, not the (average) output current.
The Overcurrent protection should never be triggered, only tf a component breaks.
The level of the OCP threshold cannot be modified independently

Regards,
Harry

Hi Harry

Thank you

<1>The OCP function of LM5022 occures output voltage drop?!

<2>The Overcurrent protection should never be triggered, only tf a component breaks.

       Can you please explain in more detail ?!

HELLO Harry

Thanks for your support

one more question

The current sense resistor has to be calculated properly, so that this process can work as described above.

=>"current sense resistor" refers to RSNS ?!

Correct