Pins of UC2844A

Hello Takahiro-san,

Thank you for your interest in the UC2844A PWM controller.

The documentation for the bonding of this part is not readily available, so I spoke with an IC designer about this question.  He said that generally the "NC" pins do not have any internal connections, but to be certain about it, one can use an ohmmeter and measure the resistance from each NC pin to the GND pin (not to PGND pin).

They should read very high resistance (Meg-ohms) in both polarities of the meter probes.

I hope this resolves your concerns.

Regards,
Ulrich

Thank you for your answer!

We think internal circuit of NC pin is different by products.

Because your member said this:https://e2e.ti.com/support/power-management/f/196/p/807284/2994133#2994133

 it may connect with internal circuit for possible unexposed functionality, some manufacturers may designate some pins for their internal use only

(e.g. calibration or testing)

We want to know the information about UC2844ADCR if NC pin is connected to other pin or circuit inside the IC  and

we want to avoid pin connection mistakes in mounting process.

NC pin of UC2844ADCR is not connected to other pin or circuit inside the IC.

Is this understanding correct?

Best regards,

Takahiro Nishizawa

Thank you for your answer!

How is your situation?

We hope earlier answer.

Best regards,

Takahiro Nishizawa

Hello Takahiro san,

In order to be certain that there are no internal bonds from the "NC" pins to a circuit on the IC, it is necessary to consult with the factory to check the wire-bond document.  This document is not readily available, so I have an inquiry sent to the factory about it.

I am not sure when I will receive a reply, but I will check with them each day to get the answer.

Regards,
Ulrich

Thank you for your support!

We are waiting for earlier answer.

Best regards,

Takahiro Nishizawa

Thank you for your support!

How is your situation?

We are waiting for your answer.

Best regards,

Takahiro Nishizawa

Hello Takahiro san,

I received an answer from the factory this morning and I can now tell you with certainty that all pins of the UC2844A that are labeled "NC" have absolutely no connections to any internal circuits.  The NC pins are truly open and floating.  I expect that external connections made by mistake to any NC pin are very unlikely to cause any problem to the controller, since the external circuits near the controller are typically low-voltage and low frequency. 

I will make exceptions to this statement for mistaken connections to external circuits that carry very high voltage or very high frequency content (>> switching frequency).  Although there will be no direct circuit contact, excess voltage stress may cause a breakdown; and in the case of high frequency, pin-to-pin capacitance may possibly couple noise into an adjacent-pin controller function.  These situations should be avoided.

I have received the bond-wire diagram for the UC2844A to verify this statement.  This applies to all devices in the UC1842A, UC1843A, UC1844A, and UC1845A family of controllers (ref datasheet: www.ti.com/.../uc2844a.pdf ).

I am unable to provide you with the actual document because it contains other proprietary information. 
I hope this reply is sufficient for your customer's assurance. 

Regards,
Ulrich

Thank you for your support!

We understand your answer.

Your answer : 

I will make exceptions to this statement for mistaken connections to external circuits that carry very high voltage or very high frequency content (>> switching frequency). 

Do you know the concrete value about very high voltage or very high frequency?

For example, over --V or over --kHz.

Best regards,

Takahiro Nishizawa