HCS12 VDD1,2 Supply pins

cancel
Showing results for 
Show  only  | Search instead for 
Did you mean: 

HCS12 VDD1,2 Supply pins

665 Views
pedroferreira
Contributor I

Good afternoon,

We are making use of a microcontroller from the former HCS12 family, namely MC9S12XDP512CAG.

Due to a manufacturing issue, the pins VDD1,2 are mistakenly connected to a 3.3V source, instead of left open (for internal voltage regulator, since VREGEN is connected to 3.3V).

In the datasheet it says explicitly that these pins should have no load and should not be connected together.
VDDPLL is free (not connected to 3.3V).

The boards work and seem not to have any issue. Detected by now.

We’d like to know what could be the repercussions of this issue.
And in terms of danger/damage, accuracy or life cycle of the processor?

1 Reply

544 Views
RadekS
NXP Employee
NXP Employee

Hi Pedro,

The VDD1,2 pins are output pins from internal 2.5V regulator. These pins must not be left open. The bypass capacitors must be used at these pins for covering power consumption spikes during transistor switching.


The connecting these pins to the 3.3V power supply is an obvious issue. In that case, the internal regulator is not active and internal logics (digital modules, CPU, SRAM,…) are overloaded by high voltage. Since the absolute maximum VDD voltage is 3V, the MCU may work even at 3.3V, but the lifetime may be probably limited. Also, other electrical parameters may differ. In extreme case, the device might be damaged.

From RM:“Absolute maximum ratings are stress ratings only. A functional operation under or outside those maxima is not guaranteed. Stress beyond those limits may affect the reliability or cause permanent damage to the device.

The operating range for VDD pins is 2.35 to 2.75V. Unfortunately, I am afraid that we cannot establish any specific parameters like accuracy or life cycle for such situation. We simply didn’t validated MCU under such conditions. For work beyond absolute maximum ratings, we cannot provide any warranty.

I hope it helps you.

Have a great day,
Radek

-----------------------------------------------------------------------------------------------------------------------
Note: If this post answers your question, please click the Correct Answer button. Thank you!
-----------------------------------------------------------------------------------------------------------------------