VDDA1 Power supply switching in MC9S12XEP100

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VDDA1 Power supply switching in MC9S12XEP100

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mandarsansare
Contributor I

Hello,
We are using MC9S12XEP100 in our project design.


For power conservation we are planning to cut-off VDDA supply in low power modes of circuit.

In datasheet section: A.1.2 Power Supply states that "The VDDA, VSSA pin pairs supply the A/D converter and parts of the internal voltage regulator."

also, in Figure 23-1. VREG_3V3 Block Diagram: the VDDA and VSSA pins are connected to LVD block and regulator block.

So my questions are,
1. Can we turn off VDDA supply and expect from micro that the functionality apart from ADC will work properly?

2. Whether this kind of supply switching is permitted?

3. If we turn off VDDA, and after some time we turn it on can we expect micro to be working in normal operation?

Thank you in advance. :smileyhappy:

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3 Replies

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danielmartynek
NXP TechSupport
NXP TechSupport

Hello,

As you can see in Section A.1.2 Power Supply, S12XE RM rev.1.25

VDDX and VDDA are connected internally, VDDA must be >= VDDX

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BR, Daniel

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mandarsansare
Contributor I

Thank You Daniel for quick reply. 
so the conclusion is we cannot use this kind of power supply switching in circuit, doing this will damage the micro.

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danielmartynek
NXP TechSupport
NXP TechSupport

Yes, beyond absolute maximum ratings device might be damaged (Table A-1, footnote 1).

It would be powered from VDDX anyway via the diodes.

BR, Daniel

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