• State
  • Locked Locked
  • Replies 10 replies
  • Subscribers 64 subscribers
  • Views 479 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM5175-Q1: Not getting output and VCC

Akhil Kalariya
Prodigy 40 points
Part Number: LM5175-Q1
Other Parts Discussed in Thread: LM5175

Hi,

We've designed a PCB with LM5175 for typical application requirement as suggested in datasheet parameters.

When we give 12V supply we're getting 3.7V at VCC Pin of IC.

We've tried by removing Diodes D6 and D7 Which connects VCC to BOOT1 and BOOT2 respectively, then we get 7.3V at VCC pin.

So, when we place diodes again sill there is issue with VCC pin voltage.

Please find attached schematic file for reference.

LM5175_CKT.pdf

  • 0
    TI__Genius 10385 points

    Hi Akhil,

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

    BR,

    Haroon

  • 0 in reply to Haroon Wardak
    TI__Guru 58521 points

    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

  • 0 in reply to Stefan Schauer
    Prodigy 40 points

    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.

  • 0 in reply to Akhil Kalariya
    TI__Guru 58521 points

    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

  • 0 in reply to Stefan Schauer
    Prodigy 40 points

    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

  • 0 in reply to Akhil Kalariya
    TI__Guru 58521 points

    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

  • 0 in reply to Stefan Schauer
    Prodigy 40 points

    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

  • 0 in reply to Akhil Kalariya
    TI__Guru 58521 points

    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

  • 0 in reply to Stefan Schauer
    Prodigy 40 points

    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?

  • 0 in reply to Akhil Kalariya
    TI__Guru 58521 points

    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