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MC9S12VR-Family - Data Sheet - Freescale Semiconductor

MC9S12VR-Family - Data Sheet - Freescale Semiconductor

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A.1.3 Current Injection<br />

<strong>MC9S12VR</strong> <strong>Family</strong> Reference Manual, Rev. 2.8<br />

MCU Electrical Specifications<br />

Power supply must maintain regulation within operating V DDX or V DD range during instantaneous and<br />

operating maximum current conditions. Figure A-1. shows a 5V GPIO pad driver and the on chip voltage<br />

regulator with VDDX output. It shows also the power & gound pins VSUP, VDDX, VSSX and VSSA. Px<br />

represents any 5V GPIO pin. Assume Px is configured as an input. The pad driver transistors P1 and N1<br />

are switched off (high impedance). If the voltage V in on Px is greated than V DDX a positive injection<br />

current I in will flow through diode D1 into VDDX node. If this injection current I in is greater than I Load ,<br />

the internal power supply VDDX may go out of regulation. Ensure external V DDX load will shunt current<br />

greater than maximum injection current. This will be the greatest risk when the MCU is not consuming<br />

power; e.g., if no system clock is present, or if clock rate is very low which would reduce overall power<br />

consumption.<br />

Voltage Regulator<br />

V BG<br />

+<br />

_<br />

Figure A-1. Current Injection on GPIO Port if Vin > VDDX VSUP<br />

A.1.4 Absolute Maximum Ratings<br />

P2<br />

I SUP<br />

I DDX<br />

C Load<br />

I Load<br />

Pad Driver<br />

VDDX<br />

V in > V DDX<br />

VSSX<br />

VSSA<br />

Absolute maximum ratings are stress ratings only. A functional operation under or outside those maxima<br />

is not guaranteed. Stress beyond those limits may affect the reliability or cause permanent damage of the<br />

device.<br />

This device contains circuitry protecting against damage due to high static voltage or electrical fields;<br />

however, it is advised that normal precautions be taken to avoid application of any voltages higher than<br />

<strong>Freescale</strong> <strong>Semiconductor</strong> 509<br />

P1<br />

N1<br />

Iin D1<br />

I in<br />

Px

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