MCF5212 FREESCALE [Freescale Semiconductor, Inc], MCF5212 Datasheet - Page 38

• Manufacturer Part Number: MCF5212
• Description: Microcontroller Family Hardware Specification
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Preliminary Electrical Characteristics
2.11.1 Equivalent Circuit for ADC Inputs
Figure 10-17 shows the ADC input circuit during sample and hold. S1 and S2 are always open/closed at
the same time that S3 is closed/open. When S1/S2 are closed & S3 is open, one input of the sample and
hold circuit moves to (V
switches are flipped, the charge on C1 and C2 are averaged via S3, with the result that a single-ended
analog input is switched to a differential voltage centered about (V
every cycle of the ADC clock (open one-half ADC clock, closed one-half ADC clock). Note that there are
additional capacitances associated with the analog input pad, routing, etc., but these do not filter into the
S/H output voltage, as S1 provides isolation during the charge-sharing phase. One aspect of this circuit is
that there is an on-going input current, which is a function of the analog input voltage, V
clock frequency.
38
NOTES:
1
2
3
4
5
6
7
SINAD
All measurements are preliminary pending full characterization, and were made at V
ground
INL measured from V
LSB = Least Significant Bit
INL measured from V
Includes power-up of ADC and V
ADC clock cycles
The current that can be injected or sourced from an unselected ADC signal input without impacting the performance of the
ADC
ENOB
Name
SFDR
THD
1.
2.
3.
4.
Analog Input
Parasitic capacitance due to package, pin-to-pin and pin-to-package base coupling; 1.8pF
Parasitic capacitance due to the chip bond pad, ESD protection devices and signal routing; 2.04pF
Equivalent resistance for the channel select mux; 100 ohms
Sampling capacitor at the sample and hold circuit. Capacitor C1 is normally disconnected from the input and is only
connected to it at sampling time; 1.4pF
Total Harmonic Distortion
Spurious Free Dynamic Range
Signal-to-Noise plus Distortion
Effective Number OF Bits
1
IN
IN
= V
= 0.1V
MCF5213 Microcontroller Family Hardware Specification, Rev. 1.2
REFL
REFH
REFH
Characteristic
2
to V
-V
REF
REFL
to V
IN
Table 32. ADC Parameters
= V
IN
)/2, while the other charges to the analog input voltage. When the
REFH
= 0.9V
125Ω ESD Resistor
REFH
(V
REFH
Preliminary
3
- V
REFL )
/ 2
8pF noise damping capacitor
1
S1
(continued)
TBD
TBD
TBD
Min
9.1
S2
REFH
4
-V
S3
67 to 70.3
61 to 63.9
DD
Typical
REFL
10.6
-75
= 3.3V, V
C2
C1
)/2. The switches switch on
S/H
REFH
Freescale Semiconductor
Max
C1 = C2 = 1pF
= 3.3V, and V
REF
and the ADC
Unit
Bits
dB
dB
dB
REFL
=