• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 63 subscribers
  • Views 308 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:

TPS1H100-Q1: The instantaneous current exceeds the set value when starting

TPS1H100-Q1: How to theoretically calculate whether 1.5A transient current will result in a current limit?

ni ni
Prodigy 60 points
Part Number: TPS1H100-Q1
Other Parts Discussed in Thread: TPS22950-Q1

Tool/software:

Hi:

I asked a question earlier about exceeding the current limit.

Link as follows:

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1333599/tps1h100-q1-the-instantaneous-current-exceeds-the-set-value-when-starting/5077959#5077959

Now I've got the product and I've tested it.

Res(3.9K 1%) is placed on CL pin,So the current calculation limit is 644.9mA.And we test 24pcs samples,current limit is 660~700mA.

After connecting the 4 cameras to TPS1H100-Q1, we captured the starting current and voltage picture.

The maximum instantaneous current is about 800mA, more than 700mA, but there is no trigger current protection.

I have two questions:

1.Why is the output voltage not turned off when the current exceeds the limit?

2.Will the output voltage be shutdown if the peak current reaches 1.5A? Can this be calculated theoretically?

Thanks!

  • 0
    TI__Mastermind 34915 points

    Ni Ni,

    Could you comment on how you are introducing the load to the system? Are you using an eLoad in constant current mode?

    Best Regards,
    Tim

  • 0 in reply to Timothy Logan
    Prodigy 60 points

    Hi

    1.Could you comment on how you are introducing the load to the system?

    Answer:We're using TPS1H100-Q1 to power four cameras at once.

    2.Are you using an eLoad in constant current mode?

    Answer:Yes,We've tried an eLoad in constant current mode.But eLoad cannot simulate the current waveform when the camera is started.Why is there such a spike in current?Because there are LDOs inside the camera, and the LDO does not have a soft start function, the LDO will charge the capacitor when it starts, resulting in current spikes.

    Thanks!

  • 0 in reply to ni ni
    TI__Mastermind 34915 points

    NiNi,

    For a 3.9kOhm resistor on the ILIM pin, you have 20% accuracy which equates to 501mA minimum and 766mA maximum current limits.

    An eLoad in constant current mode would cause this problem- make sure that if the eLoad is being used to use it in constant resistance (CR) mode:

    https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1021866/faq-why-does-my-e-load-cause-my-high-side-switch-to-shut-down

    The best scenario would be to use an actual load or a real resistance/capacitance. When the output channels are turned on, the VIN is already at steady supply, correct? I see a little steep increase in the input voltage right at the beginning of the waveform which would happen if VS is tied to IN.

    One broader question- but is this to power cameras offboard? Generally the high-side switch is there to power 12V nominal automotive systems with off-board loads and which have cabling inductances. If there are no significant inductances on the output- the TPS22950-Q1 might be a better fit as it is made for 5V systems.

    Best Regards,
    Tim