LM4766TF: obsolescence of isolated package

Martin Seeger

Other Parts Discussed in Thread: LM4766, LM1876

Dear Team,

Recently we noticed that the LM4766TF is discontinued with the comment “Replaced By LM4766T”, see below:

However we see the difference of isolated package vs. non-isolated package in this change and this would be an important factor in the mechanical design.
>> What would be the adequate “isolated-package” replacement for the LM4766TF in order to avoid a mechanical change?

Furthermore, when I was checking another device from this family, I saw that this version is still available with the isolated package?

I am a bit confused now. Could you please comment on that?

Thanks and best regards
Martin

over 7 years ago

0 Ivan Salazar over 7 years ago

TI__Guru* 95335 points

Hi Martin,

Where have you seen the isolated package of LM4766 still available? In the second figure you've attached I only see LM4766T (Non-Isolated Package).
I will look for another possible replacement for LM4766.

Best regards,
-Ivan Salazar
Texas Instruments

0 Martin Seeger over 7 years ago in reply to Ivan Salazar

TI__Expert 5381 points

Hello Ivan,

thanks a lot for your answer.

Sorry if my post was not clear:

Indeed the LM4766 is not available anymore in the isolated package.

When I checked the LM families for a replacement I saw that the LM1876 still has the isolated package version available, assuming that the ending TF is equal to 'isolated package'

Device	Ending	Status
LM4766	T	ACTIVE
	TF	LIFEBUY
LM1876	T	LIFEBUY
	TF	ACTIVE

So I was wondering if all isolated packages are obsolete?

Thanks and best regards
Martin

0 Ivan Salazar over 7 years ago in reply to Martin Seeger

TI__Guru* 95335 points

Hi Martin,

Sorry, I understand now.
There are several LMxxxx devices that are being obsoleted in isolated and non-isolated packages. This is not related specifically to the package.
Regarding the LM4766 replacement I think there is not an exact replacement part with same package/footprint. We could recommend another device but this may be a different package/footprint. Perhaps it could be easier to use a mica washer to isolate the device from the heat sink.

Best regards,
-Ivan Salazar
Texas Instruments

0 Martin Seeger over 7 years ago in reply to Ivan Salazar

TI__Expert 5381 points

Hi Ivan, please allow me to reactivate this thread again.

Regarding the LM4766T : The customer has 2 devices in the design and they are both connected to the same heat sink.
If we we go for the non-isolated package of the LM4766T, they'd be connected via the heat sink - would that be okay? How is the metal tab internally connected - Is it GND?

Thanks and best regards
Martin

0 Ivan Salazar over 7 years ago in reply to Martin Seeger

TI__Guru* 95335 points

Hi Martin,

I'm currently trying to get information about the internal connection of the pad.
Is the heat sink connected to a potential level? (like GND) or is it only connected to the pads of the LM4766 IC's?

Best regards,
-Ivan Salazar
Texas Instruments

0 Martin Seeger over 7 years ago in reply to Ivan Salazar

TI__Expert 5381 points

Hello Ivan,

thanks for your answer.
I am not sure how it is connected right now, but the customer is investigating the best / easiest modification as a mica washer is mechanically not an option.

So the question would be, is it floating, connected to GND or to something else?
In case of floating: What is the withstand-voltage between the heat sink and another pin/connection/potential?

Thanks and best regards
Martin

0 Ivan Salazar over 7 years ago in reply to Martin Seeger

TI__Guru* 95335 points

Martin,

I'm currently trying to get information about the internal connection of the pad.
I asked if the heat sink is only connected to the IC's or connected somewhere else, like GND, because if it is connected only to the IC's then it could be fine if the pad is internally connected to, lets say, GND or VEE, as long as both IC's are in the same system and share its power supply. However we'll need to wait and see what info I can get so we can be sure about this connection.

Best regards,
-Ivan Salazar
Texas Instruments

0 Ivan Salazar over 7 years ago in reply to Martin Seeger

TI__Guru* 95335 points

Hi Martin,

Do you have LM4766T IC at hand? If you do, could you please test for conductivity from pad to pin4 and pins 5/10?
I'll try to do the same test but currently I don't have the IC at hand.

Best regards,
-Ivan Salazar
Texas Instruments

0 Martin Seeger over 7 years ago in reply to Ivan Salazar

TI__Expert 5381 points

Hello Ivan,

thank you for your answer.

No, I do not have samples in the office. Let me order some and test them.

Best Regards
Martin

0 Martin Seeger over 7 years ago in reply to Martin Seeger

TI__Expert 5381 points

Hello Ivan,

I received the samples:
The pad to connected to pin 4, so VEE.

That could be an issue...

Best Regards
Martin

0 Ivan Salazar over 7 years ago in reply to Martin Seeger

TI__Guru* 95335 points

Martin,

The heat sink is connected to GND? or is it connected only between the pads of the LM4766 ICs?

Best regards,
-Ivan Salazar
Texas Instruments

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LM4766TF: obsolescence of isolated package