• State TI Thinks Resolved
  • Locked Locked
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 232 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.

LMG1205: Operate in High Static Output state

Art Mecina
Genius 16655 points
Part Number: LMG1205

Hello Guys,

Good day.

Our customer wants to confirm if this device operates in a static high output state where the high side voltage is switched to the output and left there for several minutes?

He is providing a high and low voltage to a load using this device but want to verify operation by testing it in the high state and then the low state. He would like to set the device high and measure the high power supply voltage on its output using a volt meter or oscilloscope and then set the output low and measure it.
Can he do this? set it high and measure a static high output voltage?

In addition, he sees a minimum pulse width in the datasheet but not a maximum *** width so it would seem that static operation is possible; however, there is a bootstrap capacitor to elevate the floating high side supply during a pulse and that would seem to potentially place a limit on the time the device could remain high before the floating voltage decays.

Thanks in advance!

Art

  • 0
    TI__Expert 4070 points

    Hi Art,

    Thanks for reaching out!

    The short answer is, no; for the reason you stated, the floating voltage would decay.  When the high-side gate is pinned on, the V_gs of the high-side FET will decrease as C_boot discharges lower and lower (referenced to the switching node).  Also note, as V_gs decreases, r_ds(on) will increase.  This will probably not work as the switching node (V_HS) will likely be above GND and V_DD of the driver when the high-side is on, therefore not giving the high-side driver sufficient V-gs to turn/stay on for a long time.

    The customer should be able to see what voltage the load will be pulled up to when switching (when using an oscilloscope) and pulled down to.  They could also decrease the switching frequency and increase duty cycle to give the load more time to become "static", but this can only be pushed so far until you run into the same problem.

    Yes, there is no limit on how long you can tell the driver to keep an output high.

    I hope this helped!  If I answered your question, please press the green button or feel free to follow up with additional questions!

    Thanks,

    Aaron Grgurich