• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 63 subscribers
  • Views 643 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.

Original question:

BQ25504EVM-674: Changing UV and OV of BQ25504EVM

BQ25504EVM-674: Provide power for a microcontroller with BAT-OK

BEZAK
Intellectual 465 points

Part Number: BQ25504EVM-674

Hi,

I am using a thermoelectric generator to provide energy to run data recording on a microcontroller. I am using bq25504EVM as a power management board. I want to set it up in a way that microcontroller turn on only if BAT-OK is high. I change the voltage of BAT-OK to 3.3V so I can connect it to a microcontroller. The problem is the microcontroller is ok during sleep (4micro amp, 3.3V) but during the time that it is active the voltage of BAT-OK is changed to 1.2V instead of 3.3V. What is the current limitation on BAT-OK? I am drawing 50mA at 3.3V when the microcontroller is active.

Thanks,

Bee

  • 0
    TI__Intellectual 1640 points
    Hello,

    The BQ25504 has an input cycle by cycle current limit of 280mA. You can expect over 100-150mA of output current minus efficiency and variation.
    Can you please let me know where do you have your microcontroller connected?
    Also, can you provide me with a scope capture of VBAT, VSTOR, and VBAT_OK? Thank you very much.
  • 0 in reply to Upal Patel
    Intellectual 465 points

    Thanks for your reply, I have a fully charged capacitor connected to VBAT. Fig 2 shows the VBAT and VBAT-OK are charged and high value. Then when I connect the microcontroller to the VBAT-OK the voltage drops like Fig1. Other configurations are shown in Fig 3.

    I know the microcontroller draws 50mA at 3.3V. 

    If I connect the microcontroller to Vstor everything is fine and it works but then I like to use VBAT-OK to keep the microcontroller off when there is no enough energy,

    Thanks,

    Bee

  • 0 in reply to BEZAK
    TI__Intellectual 1640 points
    Hello,
    The VBAT_OK signal is used to indicate turning on and off system load on the VSTOR pin. I don't think you can connect the load to VBAT_OK pin, you can program turn on and off the system load connected on VSTOR pin by programming the VBAT_OK_HYST and VBAT_OK values.