Appendix A MCU Electrical Specifications
S12ZVHY/S12ZVHL Family Reference Manual Rev. 1.05
Freescale Semiconductor
777
A.1.2.4
TEST
This pin is used for production testing only. The TEST pin must be tied to ground in all applications.
A.1.3
Current Injection
Power supply must maintain regulation within operating VDDX or V
DD
range during instantaneous and
operating maximum current conditions.
shows a 5 V GPIO pad driver and the on chip voltage
regulator with VDDX output. It shows also the power and ground pins VSUP, VDDX, VSSX and VSSA.
Px represents any 5 V GPIO pin. Assume Px is configured as an input. The pad driver transistors P1 and
N1 are switched off (high impedance). If the voltage V
in
on Px is greater than V
DDX
a positive injection
current I
in
will flow through diode D1 into VDDX node. If this injection current I
in
is greater than I
Load
,
the internal power supply VDDX may go out of regulation. Ensure the external V
DDX
load will shunt
current greater than maximum injection current. This is the greatest risk when the MCU is not consuming
power; e.g., if no system clock is present, or if the clock rate is very low which would reduce overall power
consumption.
Figure A-1. Current Injection on GPIO Port if V
in
> V
DDX
V
BG
Pad Driver
VDDX
VSSX
VSSA
VSUP
V
in
> V
DDX
I
in
I
in
Voltage Regulator
D1
P1
N1
C
Load
I
SUP
I
Load
I
DDX
P2
Px
+
_
