MMC2114 MOTOROLA [Motorola, Inc], MMC2114 Datasheet - Page 523

• Manufacturer Part Number: MMC2114
• Description: M CORE Microcontrollers
• Manufacturer: MOTOROLA [Motorola, Inc]

19.11.7.2 Error Resulting from Leakage
MMC2114 • MMC2113 • MMC2112 — Rev. 1.0
MOTOROLA
The external circuit described in
Measurements of an AC component of the external signal must take the
characteristics of this filter into account.
A series resistor limits the current to a pin therefore, input leakage acting
through a large source impedance can degrade A/D accuracy. The
maximum input leakage current is specified in
Electrical Specifications
higher operating temperatures. In the temperature range from 125°C to
50°C, the leakage current is halved for every 8°C to 12°C reduction in
temperature.
Assuming V
corresponds to 5 mV of input voltage. A typical input leakage of 200 nA
acting through 10 k of external series resistance results in an error of
0.4 count (2.0 mV). If the source impedance is 100 k
leakage of 100 nA is present, an error of 2 counts (10 mV) is introduced.
In addition to internal junction leakage, external leakage (for example, if
external clamping diodes are used) and charge sharing effects with
internal capacitors also contribute to the total leakage current.
Table 19-15
accuracy for different values of source impedance. The error is listed in
terms of 10-bit counts.
Freescale Semiconductor, Inc.
For More Information On This Product,
Queued Analog-to-Digital Converter (QADC)
Filter Capacitor (C
Table 19-14. External Circuit Settling Time to 1/2 LSB
0.001 F
0.01 F
100 pF
0.1 F
RH
1 F
Go to: www.freescale.com
illustrates the effect of different levels of total leakage on
–V
RL
= 5.12 V, 1 count (with 10-bit resolution)
F
)
(Operating). Input leakage is greater at
760 s
760 ns
100
7.6 s
76 s
76 ns
Table 19-14
Queued Analog-to-Digital Converter (QADC)
Source Resistance (R
760 s
7.6 ms
760 ns
7.6 s
76 s
1 k
Pin Connection Considerations
is a low-pass filter.
Table 23-7. QADC
760 s
7.6 ms
10 k
76 ms
7.6 s
76 s
Advance Information
and a typical
F
+ R
SRC
100 k
760 ms
7.6 ms
760 s
)
76 ms
76 s
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