LM5020: LM5022 for design question

Hi Micky,

Thanks for considering the use of LM5020 in your design.

Here are my answers to your questions:

1.When I turned on, Vin supplied power to the LM5020. When Vcc is established, the Vin power supply is cut off internally, and Vcc supplies power to the LM5020. Is this right?

If you have an auxiliary winding that raises voltage on VCC pin above regulation target, then the internal regulator will turn off. Make sure there is a diode in series from external VCC winding to VCC pin. Additionally, if VIN is lower than VCC pin external voltage, please place external diode in series from input voltage source to VIN pin. This will prevent current from flowing back into the input. 

2.(Premise Vin stays on all the time), continue question 1. When I disconnect Vcc, will the internal power supply to LM5020 by Vin be changed? Will the LM5020 work normally at this time? Or do I need to reconnect Vin for the LM5020 to work normally?

In the event of a fault where auxiliary VCC supply is inactive, the LDO will be activated. Make sure external current draw on VCC line is limited such that power dissipated in internal regulator is less than maximum power dissipation of controller.

3.I want to set up a protection circuit. In addition to grounding UVLO, which IC Pin can achieve this effect?

LM5020 has cycle-by-cycle current limit protection using the CS pin and internal thermal shutdown protection. 

4.Will LM5020 always detect the presence of Vin, or is it only useful before Vcc is established?

LM5020 is always detecting the VIN. 

5.If my protection is automatically restored, I only need to pull the UVLO to the ground, wait for the recovery time, and then pull the UVLO high, will the LM5020 operate normally? There is no need to reconnect Vin.

Unless your circuit needs protection other than current limit and thermal shutdown, the IC will be controlled by these two protection features until the condition is removed. There is no need to ground UVLO/reconnect VIN. If this does not answer your question, please let me know.   

Please let me know if you have any other questions. 

Richard

Hi Micky,

1. If I have auxiliary winding, Vin will only be supplied to the IC at the first moment of power-on. After waiting for Vcc to be established by the auxiliary winding, the IC internally cuts off the switch supplied from Vin to the IC, and the auxiliary winding is supplied to the IC through Vcc. Does this mean? Thank you.

You are correct in your understanding.

2. Is the LDO you are talking about the internal LDO of the IC or the external LDO connected by Vin? I can’t see the internal LDO from the block diagram. It means that the winding power supply of the auxiliary group of Vcc is abnormal, as long as Vin is still powered normally, the IC can still work normally, or the IC will automatically shut down.

The LDO I'm talking about is the internal LDO of the IC (7.7V series regulator) 

3. As far as I know, the protection of CS is to limit the current. Exceeding the CS voltage will not cause Latch or Auto-recovery protection. How do I design the Input OCP of this IC? Thank you.

If you have concerns of over current condition on input, you can increase soft-start capacitance. This will ensure smooth startup. If that is not enough, you can use TI efuse controllers.

Thanks,

Richard

Hi Micky,

Sorry for the delay. If VCC voltage falls below 6V, controller should turn off.

Thanks,

Richard