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TPS28226: Unable to get any output signal!

user4135279
Prodigy 50 points
Part Number: TPS28226
Other Parts Discussed in Thread: TPS28225

Hi, I am building a DC to DC converter using a TPS28226 and 2 N-Channel mosfets. I have been unable to get any response at all from the MOSFET driver. I have gone so far with debugging as to isolate the TPS completely, it is now fed from a 40KHz TTL square wave, VDD is connected to 5V DC (as is the enable pin) I am using a 220nF.. 100nf.. 1nF boot strap capacitor, and have tested with and without a SI7288DP dual N-mosfet with 15V supply. Both gate drive pins remain at zero volts regardless. I have tested with ICs from 2 different supplies, they are all non responsive and I am completely at a loss! 

  • 0
    TI__Mastermind 31580 points
    Hi

    I have asked one of our applications engineers to support your application question.

    Regards

    Peter
  • 0
    TI__Intellectual 2910 points

    user4135279,

    Thank you for using the TPS28226 in your design. This device requires a higher VDD than what you have described. Most likely, the outputs are not functioning because the device is in undervoltage lockout (UVLO) state. During power up, both gate drive outputs remain low until voltage VDD reaches UVLO threshold, typically 6.35 V. Once the UVLO threshold is reached, the condition of the gate drive outputs is defined by the input PWM and EN/PG signals. During power down the UVLO threshold is set lower, typically 5.0 V.

    Per the datasheet Recommended Operating Conditions, the VDD range for this gate driver should be between 6.8 and 8.0 V.

    Assuming raising the VDD to meet this UVLO spec is not an option, you can replace this driver with the pin-for-pin replacement TPS28225 device from TI. This is a 3.5V UVLO version of the same driver. The VDD recommended operating range is from 4.5V to 8.0V.

    I hope this post answers your question. If it has, please press the green "Verify Answer" button below.

    - Daniel

  • 0 in reply to Daniel Ruiz
    Prodigy 50 points
    Many thanks Daniel! i was pulling my hair out trying to figure out what I as doing wrong!