LM76005-Q1 : Switch On/Off operation using Enable signal

Hi Jun

EN pin can be driven directly through MCU. Is there specific reason you want drive through MOSFET?

Thank you

Regards

Onkar Bhakare

There is no special reason. Is it okay to control the converter's Enable signal with only the MCU's GPIO 3.3V signal? Additionally, is there any reason why the IC was damaged when the Enable signal was controlled using the switch I asked about at the very beginning?

thank you.

Hi Jun

jun cha said:

s it okay to control the converter's Enable signal with only the MCU's GPIO 3.3V signal?

Yeah, this is okay

jun cha said:

is there any reason why the IC was damaged when the Enable signal was controlled using the switch I asked about at the very beginning?

As you are operating close to device absolute maximum, it is likely that device would damage due to the spike generated during switching event. 

jun cha said:

Additionally, I want to control the On/Off of the converter by controlling the Mosfet through the MCU as shown below. Is this method also stable? (Using 5V_EN signal)

This configuration won't work, high side NMOS would need more than Vin+Vth to turn on properly. You can either ruse PMOS there or use configuration similar to following.

Hope this helps

Thank you

Regards

Onkar Bhakare

Thank you for your reply.

I have a question because I encountered a problem while testing the PCB I manufactured.

The converter was tested by always connecting Vin and Enable without controlling the Enable signal via a switch or MOSFET.

The first few tests did not cause any problems, but after a few tests, the converter broke when turning on the system, as shown in the photo below.

I looked at your response and you said that since the device is operating close to its absolute value (65V), there is a possibility that the device could be damaged due to the spikes generated during the switching event.

I added a larger capacitor to Vin, thinking it would reduce this phenomenon. (100V / 47uF * 3)

I added capacitors to another PCB and tested it and the same symptoms occurred again.

Will the voltage range I use (44V to 58V) be difficult to apply this product to?

Is there any other way to minimize spikes besides adding capacitors?

I am trying to modify it as follows because you said that switching control through N mosfet will not work properly.

Thank you

Regards

Hi Jun

jun cha said:

I added a larger capacitor to Vin, thinking it would reduce this phenomenon. (100V / 47uF * 3)

Capacitor must be added at EN pin, you can add cap value 100nF. Additionally, you can add resistor of few kOhm in series with switch.  

jun cha said:

Will the voltage range I use (44V to 58V) be difficult to apply this product to?

Yes jun, 65V won't be sufficient as per new standards, typically for 48V in automotive, part with 72 V abs max is selected.

jun cha said:

I am trying to modify it as follows because you said that switching control through N mosfet will not work properly.

Yes Jun, this will work

Thank you

Regards

Onkar Bhakare

hello Onkar. Thank you for your reply.

As you advised, I added resistors in series, but the voltage did not drop much, so I tried to lower the voltage by using resistor distribution as shown in the circuit diagram below. Additionally, I added a 100nF capacitor.

The PCB is intended for use by stepping down the voltage of a non-automotive 48V battery (44V to 58V) to 5V, 12V, or 24V.

Would it be possible to reduce the current problem by limiting the maximum voltage of the Enable signal in the manner above?

Thank you

Regards

Hi Jun