• State
  • Locked Locked
  • Replies 7 replies
  • Subscribers 62 subscribers
  • Views 152 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

TPS25947: Operation during overcurrent protection

Fukasawa Taro
Prodigy 60 points
Part Number: TPS25947
Other Parts Discussed in Thread: BQ24079T

Hello.
I am testing the overcurrent protection operation of the TPS25947.
A BQ24079T is connected downstream of the TPS25947 to charge a 1-cell lithium-ion battery.
The downstream of the TPS25947 and the lithium ion battery are configured with a diode OR connection to supply power to the system.
The overcurrent protection is designed with a setting of 2.5A.
When an electronic load (CR mode) is connected downstream of the diode OR and a load is applied, intermittent operation was observed as shown in the attachment.
With the lithium-ion battery unconnected, there is no such operation, and the device turns off when the overcurrent threshold is exceeded.
Do you know the cause of this problem?

Thank you in advance.

  • 0
    TI__Guru 50445 points

    Hi Fukasawa,

    Thanks for reaching out. I will get back by tomorrow by tomorrow EOD on this.

    Regards

    Kunal Goel

  • 0 in reply to Kunal Goel
    TI__Guru 50445 points

    Hi Fukusawa,

    1. Where are you probing current in above waveform and how are you probing?

    2 What is the value of load resistance in above waveform?

    3. What is the behavior of battery voltage and voltage across load?

    4. How much is current limit of input 5V supply? Is it a bench supply?

    5. Can you share waveform with battery removed?

    Regards

    Kunal Goel

  • 0 in reply to Kunal Goel
    Prodigy 60 points

    Hi Kunal,

    The current and voltage waveforms of V_CHRG are measured at R608 in the schematic.
    The load was gradually increased in the CR mode of the electronic load device until the overcurrent protection was activated.
    The 5V power supply was set by bench supply with a current limit of about 3.15A.

    Is it correct to understand that normal operation is "when the overcurrent threshold is exceeded, the output is kept OFF"?

    Regards
    Fukasawa

  • 0 in reply to Fukasawa Taro
    TI__Guru 50445 points

    Hi Fukusawa,

    Yes part should turn of after timer duration of 276ms. Looks like in the waveform you shared above part is turning off after 276ms but it starting again.

    Regards

    Kunal Goel

  • 0 in reply to Kunal Goel
    Prodigy 60 points

    Hi Kunal,

    Are there any conditions under which the overcurrent protection function is deactivated?
    For example, is there a possibility that the following actions will be repeated?
    Immediately after the overcurrent protection is activated, the charger stops, and within a certain period of time the load current falls below a threshold value, the overcurrent protection is deactivated and the supply begins again.

    Regards
    Fukasawa

  • 0 in reply to Fukasawa Taro
    TI__Guru 50445 points

    Hi Fukusawa,

    I will get back by EOD on this.

    Regards

    Kunal Goel

  • 0 in reply to Kunal Goel
    TI__Guru 50445 points

    Hi Fukusawa,

    From the waveform it looks overcurrent protection is not deactivated.  Device overcurrent protection can not disable. if within timer duration current goes back to below ILIM then device will not circuit break and ITIMER will also stop.

    Can you probe ITIMER ,EN,OVLO,ILIM pin(please use a 100ohm resistor between probe and ILIM pin)? That will help to understand device behavior. Also please probe current at R609.

    Regards

    Kunal Goel