• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 32 subscribers
  • Views 705 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.

TPL7407L Hot Plugging

NoamG
Prodigy 20 points

Hi,

I have a problem which might be relevant here.

We have a design which uses TPL7407 to drive a signal tower with LEDs and a buzzer.

All use 24V. All use max 65mA. The buzzer has inrush current of ~250mA.

Problem is, the cable to the signal tower is occasionally connected and disconnected while fully powered.

And then, the TPL7407 is burning, with fire and smoke etc. The buzzer circuit is damaged, and the TPL7407 has a visible damage near pin 9 (COM).

It is far from how I like it to be handled, but I need to protect against it. Education can only go so far. :-(

I hear that DS2003 had no such problem, so I guess the internal LDO is the prime suspect.

I've added 0.1u and 10u caps on the COM pin, and ESD protection (NUP4304) on the buzzer signal.

Series resistor on the signal line (as a current limit) affects the buzzer, so I hope to avoid it.

How do you recommend further protecting this signal?

Zener on the COM pin?

Thanks,

 Noam

  • 0
    TI__Guru**** 164796 points
    Noam,

    Unlike the ULN2003 or DS2003, the TPL7407 has a VCC pin labeled COM. A bypass capacitor on COM is highly recommended.

    Does the cable provide power to COM pin or does it just go the LEDS and buzzer (loads)?
    Can you share the buzzer part number?

    LEDS can be hot plugged because they are not inductive. I'm not sure about the buzzer.
    I believe caps on COM and a diode across buzzer will be enough protection.

    When TPL7407 was damaged, do you know if the LEDS or buzzer was active?