Because of the holidays, TI E2E™ design support forum responses will be delayed from Dec. 25 through Jan. 2. Thank you for your patience.

  • State TI Thinks Resolved
  • Replies 5 replies
  • Answers 2 answers
  • Subscribers 31 subscribers
  • Views 59 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

TPA3250D2EVM: Reset scheme question

Supira Medical
Prodigy 210 points
Part Number: TPA3250D2EVM
Other Parts Discussed in Thread: TPS3802

Tool/software:

Hi,

The EVM uses the 15 volt bus derived from PVdd as a means to determine when PVdd has dropped below a specific value, thereby shutting down the TPS3250. In my application, the 15 volt supply will be coming from a separate power supply and therefore a drop in PVdd will not be detected.

Can I connect PVdd to the TPS3802 reset controller with a suitable resistive divider instead? I can add a zener clamp to ensure the input never exceeds 3.3 volts.

Thanks!

  • 0
    TI__Genius 15100 points

    hi

    you seems are confirming how to let tps3802 work with a voltage which comes from the divider of pvdd.

    do you mean when the pvdd fall down to certain value, the tps3802 might not work properly which can reset the amp?

    it seems fine with your design, it would be better to confirm with tps3802 team whether it has any abnormal behavior when power supply drop.

    tks

    jesse

  • 0 in reply to Jesse Ji
    Prodigy 210 points

    Hi Jesse,

    Let me rephrase my question this way:

    On the EVM, with the resistive divider and 15 volt feed, the trip voltage for a reset condition  is 13.6 volts. If one knew what the PVDD was in a given design, the same 13.6 volts could be generated off PVDD and suitable resistors. I wondered why TI chose to use the 15 volt supply but it occurs to me that it may be because the EVM is rated for a PVDD from 18 to 38 volts. With a variable PVDD, you couldn't guarantee the 13.6 volt trip point otherwise.

    I do have a follow-up question - what is the purpose of adding in PVDD through R61 and C83 to the reset controller?

    Thanks.

  • 0 in reply to Supira Medical
    TI__Expert 5645 points

    Hi Supira,

    The TPS3802 monitors two supplies on this EVM, the PVDD level and the 15V supply. The 15V is fixed for all applications so it has the resistor divider. Since this supply drives the circuitry for all of the lower supply voltages on the EVM, this rail is monitored to ensure the rest of the circuitry is powered. The PVDD is also monitored since it is the high power supply used for the amp itself. When the two supplies (PVDD and +15V) are stable, the capacitors are seen as open circuits meaning the node voltage is from the resistor divider on the 15V supply. If the PVDD supply has a quick transient, the voltage would change slightly as the capacitors need to charge/discharge which could be monitored by the TPS3802. Basically, the capacitors act like an isolator to prevent the two supplies from interacting while allowing for transients of PVDD to still be monitored.

    Regards,

    Ramsey

  • 0 in reply to Ramsey Foote
    Prodigy 210 points

    Hi Ramsey,

    Thanks for the detailed response, which clarifies things. In your opinion, would I be okay going about it the way I've described? Is there any risk to the device if the 12 volt supply remains on while reset is asserted owing to a drop in PVDD?

  • 0 in reply to Supira Medical
    TI__Expert 5645 points

    Hi Supira,

    If you are just wanting to monitor just the PVDD supply and are designing your project such that PVDD is to be a fixed value, you can use a resistor divider here.

    Regards,

    Ramsey