LM5148: Error in power up for 24V to 12V 60W DC-DC converter

Hi Bhavik.

Seems like you are hitting current limit here. Can you please fill in the design calculator for this device (https://www.ti.com/tool/LM5148-LM25148DESIGN-CALC) and share with me? 

Thanks,

Best Regards,

Taru

Hi Taru,

Please find attached sheet for your reference.0552.LM5148_LM25148_quickstart_calculator_A4.xlsm  Let me know if anything else required.

Hi Bhavik,

1. What is the load that you are applying here? 

2. If it is a 10A design - I suggest you to keep the OCP level at ~140% of the max rated current i.e. 14A. 

I would also recommend you increase the inductor value. It is on the lower side. Compensation can also be better - the crossover frequency is quite low. (keep crossover frequency from 10-20% of fsw)

Furthermore, If it is a design with 24V to 12V step down at 5A (which is what I see in the quick start calculator) - you can also work with a buck converter (with integrated FETs) like https://www.ti.com/product/LM61495-Q1

Thanks,

Best Regards,

Taru

1) I have connected multiple loads, including plunger and BLDC motor.  So at peak torque condition, current will be 10A.
2) ok.  I will increase OCP level to 14A. also will increase inductance and check if it works.

Apart from that, at many occasion Buck converter is not powering up even if motor is not connected.  So total load on 12V is less than 1A.  Still I am facing issue.  Can you help me to resolve power on issue?  

And can you help me in which error condition, IC is latched?  

HI Bhavik,

Let us go step-by-step - please make the changes we discussed and check what the system response is. 

Bhavik Modi said:

And can you help me in which error condition, IC is latched

All the major protection schemes in the device are non-latching in nature (Thermal Protection, Hiccup Mode Current Limiting, UVLO, etc.). 

Thanks,

Best Regards,

Taru