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ADA4870 Short Circuit protection using issue

Hi Experts,

 

I saw below in Page19 of ADA4870 spec.

 

ON, INITIAL POWER-UP, AND SHORT-CIRCUIT After initial power-up, the ON pin must be pulled low to ensure that the amplifier is turned on. Subsequently, floating the ON pin enables the short-circuit protection feature while the amplifier remains on. While ON is held low, the short-circuit protection feature is disabled.

 

 

I have a question, if I used multi pcs ADA4870, used only one signal path to control "ON" PINs.

I mean, I tied the all ADA4870 "ON" PINs together.

After power up, ON pin pulled low, all ADA4870 are turned on.

Subseuently, I get All "ON" PINs floating(I just remove the low signal, with HiZ of control signal path), but All ADA4870 "ON"pins are tied still.

If one pcs ADA4870 occurs short circuit, this pcs ADA4870's ON pin will be Voltage rose up, right?

But, the others ADA4870 are not short circuit, the ON pins will affect the short circuit ADA4870 ON pin Voltage, is it right?

I mean, the short circuit ADA4870 ON pin will not rise Voltage up effectively, maybe short protection is failed, is it ture?

I want to know that, how about the ON pin's internal circuit block is it? A simple model is OK for me.

I want to know it clearly, this will help me to config the control signal of ADA4870 correctly.

Any suggested circuit of multi pcs ADA4870 using?

I need to turn on multi pcs ADA4870 at same time, and make sure short protection worked. thanks a lot!

 

 

 

B&R

Tom

 

  • Hi Experts,

    Could you help to support for this case? thanks a lot!

  • Hi,

    My apologies. I'll be contacting our product expert regarding this question and get back to you as soon as possible.

    Regards,

    Phil

  • Hi,

    Please check the comments below:

    If one pcs ADA4870 occurs short circuit, this pcs ADA4870's ON pin will be Voltage rose up, right?

    Yes. The ON bar pin is referred to VEE. I assume the supply voltages are +/-20V. The ON bar floating voltage would be around -17.6 to -18.2V. While the short circuit event occurs, the ON bar voltage will go up a little bit to around -18.29V. Please be aware, those voltages are for +/-20 supplies only and there will be part to part differences.But, the others ADA4870 are not short circuit, the ON pins will affect the short circuit ADA4870 ON pin Voltage, is it right?

    Yes.

    I mean, the short circuit ADA4870 ON pin will not rise Voltage up effectively, maybe short protection is failed, is it ture?

    Yes.

    I want to know that, how about the ON pin's internal circuit block is it? A simple model is OK for me.

    The ON bar impedance is approximately 20k Ohm.

    I want to know it clearly, this will help me to config the control signal of ADA4870 correctly.

    Any suggested circuit of multi pcs ADA4870 using?

    I would suggest control the ON bar pins separately while using multiple ADA4870s.

    Please let me know if you need more help.

     

    Regards,

    Yihang