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TPS51225: Output OVP and UVP

Brian Gosselin
Expert 4575 points
Part Number: TPS51225

Hello,

Pg. 15 of the TPS51225 datasheet talks about the behavior of the TPS51225 during an OV and UV condition.  My questions are regarding the following statements:

"When the VFBx reaches 0V, the driver output is latched as DRVH off, DRVL on."

"The undervoltage protection (UVP) latch is set when the VFBx voltage remains lower than UVP trip threshold for 250us or longer.  In this fault condition, the controller latches DRVH low and DRVL low and discharges the outputs."

For both OV and UV, the datasheet uses the term, "latch".  So when an OV or UV condition occurs and the devices latches, do you need to power cycle the part to get it to release the latch?  The datasheet does not mention what happens when you are no longer in an OV or UV condition.

Also, a couple other questions:

What is NOC and ZC comparators for as seen on page 9?  What does NOC and ZC stand for?  Can we provide any insight into the resistor divider values for OC, NOC, and ZC?

Thanks in advance for your support.

Best Regards,
Brian Gosselin

  • 0
    TI__Mastermind 18510 points

    Hi Gosselin,

    Yes, your understanding is right, because UV/OV protection for this part is latch off, so when the protection happen, what can do to release the latch to restart is toggling Enable or power on/off Vin.

    ZC is used for detecting inductor current to determine when to get into DCM, when the inductor current get to zero, low-side will be turned off, current will be continued by body-diode of low-side mos.

    As for NOC(Negative OC), means when happen inductor current goes back reversely to Low-side mosfet in some cases, such as Low-side discharge enable....

    when the reverse current goes higher to big enough, NOC will be triggered, usually it is smaller than or same with OC. 51225 is same as oc.

    Yuchang