LM5175-Q1: Not getting output and VCC

Hi Akhil,

Thank you for using E2E forums, please allow us sometime to get back to you on this.

BR,

Haroon

Hi Akhil,

It seems the load on VCC is do high and the LDO is not able to supply the required current.

As a first step can you slowly increase the voltage on the EN/UVLO pin.

At a voltage of ~ 1V the device will go into standby mode and enable the LDO without starting to switch.

What voltage can you measure then at the VCC pin (with diodes assembled).

Best regards,

 Stefan

Hello Stefan,

We try as you told us, we get 7.32V on VCC Pin of IC with Diodes Assembled at 1V on EN Pin.

Hi Akhil,

so the Boot seems to be OK and it can then be somewhere at the Gate drives.

Please check when the VCC drops what Gate signals are switching.

How many boards have you checked and on how many do you see this fail.

Would be good to check 2-3 boards to ensure that this is not a soldering issue.

Best regards,

 Stefan

Hello Stefan,

I checked It as You told,

The result is High Side Gate is working Perfectly and Shows 5.8V on Gate pin on High side Mosfets . But Low side gate is not Working as it shows 200mV on Gate pin of Mosfets.

Best regards,

Akhil

Hi Akhil,

is this not voltage for both low side gate signals?

It looks like there is a short or damage here. So please check at that point.

Best regards,

 Stefan

Hello Stefan,

Buck Mode is working for now as i gave 18+ Voltage to my PCB and as per FB Pin it gives me 12.74V but when i am increasing Load Current, It cuts off and On as i Upload the video for your reference. Also Boost mode is not working as I mentioned before Low side Gate driver is not working for both Mosfets.

Thank you in advance.

Best Regards,

Akhil

HI Akhil,

if you do not see the low side MOSFET gate signals (BUCK and BOOST side MOSFETs) then something in your PCB is wrong or the LM7175 got damaged.

Esp. Before starting operation the Low side Gate signals should go high to ensure precharging of the BOOT Caps.

Note: the Video does not work in this forum.

Best regards,

 Stefan

Hello Stefan,

Now, I get Voltage as per FB Resistors configuration but while i take 0.4A Current on load at 12.7V. of output voltage, My Mosfets are Heat up and smoked.

Can you please Help us to resolve this problem?

HI Akhil,

can you please fill the design details and the MOSFET parameters into the quickstart calculator:

https://www.ti.com/tool/download/LM5175QUICKSTART-CALC

and share it here.

Can you also share the schematic.

Please let me also know what you had to fix/change to get the output voltage as expected.

Best regards,

 Stefan