• State
  • Locked Locked
  • Replies 5 replies
  • Subscribers 64 subscribers
  • Views 683 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.

BQ25505: VSTOR rises above VBAT_OV after re-enable

user3925379
Prodigy 100 points
Part Number: BQ25505

Hi,

I've been running some simulations using OrCad and the BQ25505 and I've ran into a problem. With the IC on and VBAT_OV=4,2V the simulation runs fine, but after I disable the IC for a while using the EN pin, once I enable it again, VSTOR goes up to 4,67V driving VBAT to that same voltage. Is this expected? Shouldn't V_STOR cap at VBAT_OV? Attached are the simulation results and schematic. Thanks in advance.

Best Regards,

Rafael Névoa

  • 0
    TI__Intellectual 1640 points
    Hello,

    Can you drive the EN pin with VBAT_SEC voltage and check to see if this issue persists?
    Also, Yes, the VSTOR should be clamped at VBAT_OV.
    Can you explain the VBAT_OV Spikes you see in your plot? I did the calculation from your schematic, and the VBAT_OV should be around 4.15V
  • 0 in reply to Upal Patel
    Prodigy 100 points

    Hi Upal,

    Thank you for your answer. I'm using the VPULSE source on the EN pin to validate the enabling/disabling of the IC. Below is the output when the EN pin is driven by VBAT_SEC. The simulation crashes after 25ms.

    Those VBAT_OV spikes seem to be part of the normal behaviour of the BMU. Below are the simulation results of the Texas Instruments provided transient model for the BQ25505 using a solar input. As you can see those spikes also show up there.

    Also, if the BMU is always on (EN pin always low) everything seems to work fine as you can see by the screenshot below.

    Best Regards,

    Rafael Névoa

  • 0 in reply to user3925379
    Prodigy 100 points

    There was a problem with two of the screenshots, here's a repost.

    ---------------------------------------------------------------------------------------------------------------------------

    In reply to Upal Patel:

    Hi Upal,

    Thank you for your answer. I'm using the VPULSE source on the EN pin to validate the enabling/disabling of the IC. Below is the output when the EN pin is driven by VBAT_SEC. The simulation crashes after 25ms.

    Those VBAT_OV spikes seem to be part of the normal behaviour of the BMU. Below are the simulation results of the Texas Instruments provided transient model for the BQ25505 using a solar input. As you can see those spikes also show up there.

    Also, if the BMU is always on (EN pin always low) everything seems to work fine as you can see by the screenshot below.

    Best Regards,

    Rafael Névoa

  • 0 in reply to user3925379
    TI__Intellectual 1640 points
    Hello Rafael,
    Thank you for the plots, when I asked you to drive EN pin with VBAT, I meant can you source your VPULSE with the VBAT voltage, which I'm guessing is 4.2V ? rather than 5V pulse.
    Let the simulation run for a bit, and then drive the EN pin with 4.2V pulse, and can you please check to see if VSTOR still rises to 4.76V?
    Thank you very much.
  • 0 in reply to Upal Patel
    Prodigy 100 points

    Hi Upal,

    Here are the results of the simulations. I added a small resistor of 54 Ohm in series with the VIN source.

    -Driving the EN pin with 4.2V

    -Driving the EN pin with 4V

    -Driving the EN pin with 5V

    Basically the problem still occurs, which probably means it is not related to the voltage i'm using to drive the EN pin. Do you think that this is a problem related to the model or simulation only? Or will it happen on the PCB? 

    Best Regards,

    Rafael Névoa