mcf5282 Freescale Semiconductor, Inc, mcf5282 Datasheet - Page 601

• Manufacturer Part Number: mcf5282
• Manufacturer: Freescale Semiconductor, Inc

Figure 28-50
stress conditions.
The current into the signal (I
Where:
V
V
V
R
R
The current into (I
bipolar transistor (K
I
Where:
I
A method for minimizing the impact of stress conditions on the QADC is to strategically allocate QADC
inputs so that the lower accuracy inputs are adjacent to the inputs most likely to see stress conditions.
Also, suitable source impedances should be selected to meet design goals and minimize the effect of stress
conditions.
Freescale Semiconductor
In
INJ
Stress
Selected
Stress
EB
BE
= – K
= Parasitic NPN base/emitter voltage
is either I
= Parasitic PNP emitter/base voltage
= Source impedance (10 kΩ resistor in
= Adjustable voltage source
N
= Source impedance on channel selected for conversion
* I
shows an active parasitic bipolar NPN transistor when an input signal is subjected to negative
INJ
INJN
Figure 28-51
In
or I
) the neighboring pin is determined by the K
N
‹‹ 1). The I
INJP
MCF5282 and MCF5216 ColdFire Microcontroller User’s Manual, Rev. 3
Figure 28-50. Input Signal Subjected to Negative Stress
Figure 28-51. Input Signal Subjected to Positive Stress
.
INJN
V
IN
V
IN
shows positive stress conditions can activate a similar PNP transistor.
V
or I
V
STRESS
In
STRESS
+
INJP
can be expressed by this equation:
I INJP
I INJN
+
) under negative or positive stress is determined by these equations:
=
=
R
V Stress V EB
-------------------------------------------------------------- -
R
SELECTED
–
---------------------------------------------- -
R
(
STRESS
10 kΩ
R
V Stress V BE
Figure 28-50
SELECTED
STRESS
10 kΩ
R Stress
R Stress
–
I
injP
I
IN
–
I
I
injn
IN
AN
–
AN
Parasitic
Device
AN
V DDA
AN
Parasitic
)
n+1
n
and
Device
n+1
n
Signal Under
Adjacent
Signal Under
Stress
Signal
Figure 28-51
Adjacent
N
Stress
Signal
(current coupling ratio) of the parasitic
Queued Analog-to-Digital Converter (QADC)
V
DDA
on stressed channel)
Eqn. 28-1
Eqn. 28-2
28-63