Datasheet

4.1.1.1 Input impedance and ADC accuracy
R
F
C
F
R
S
R
L
R
SW1
C
P2
V
DD_IO
Sampling
Source Filter Current Limiter
EXTERNAL CIRCUIT INTERNAL CIRCUIT SCHEME
R
S
Source Impedance
R
F
Filter Resistance
C
F
Filter Capacitance
R
L
Current Limiter Resistance
R
SW1
Channel Selection Switch Impedance
R
AD
Sampling Switch Impedance
C
P
Pin Capacitance (two contributions, C
P1
and C
P2
)
C
S
Sampling Capacitance
C
P1
R
AD
Channel
Selection
V
A
C
S
Figure 5. Input equivalent circuit
Table 16. ADC conversion characteristics (for 12-bit)
Symbol Parameter Conditions
1
Min Typ Max Unit
f
CK
ADC Clock frequency (depends on
ADC configuration) (The duty cycle
depends on AD_CK
2
frequency)
— 15.2 80 80 MHz
f
s
Sampling frequency 80 MHz — — 1.00 MHz
t
sample
Sample time
3
80 MHz@ 100 ohm source
impedance
275 800 — ns
t
conv
Conversion time
4
80 MHz 650 — — ns
t
total_conv
Total Conversion time t
sample
+
t
conv
(for standard and extended
channels)
80 MHz 1.5
5
— — µs
Total Conversion time t
sampl
e +
t
conv
(for precision channels)
1 — —
C
S
6
ADC input sampling capacitance — — 3 5 pF
C
P1
6
ADC input pin capacitance 1 — — — 5 pF
C
P2
6
ADC input pin capacitance 2 — — — 0.8 pF
R
SW1
6
Internal resistance of analog
source
V
REF
range = 4.5 to 5.5 V — — 0.3 kΩ
V
REF
range = 3.15 to 3.6 V — — 875 Ω
R
AD
6
Internal resistance of analog
source
— — — 825 Ω
INL Integral non-linearity — –2 — 2 LSB
DNL Differential non-linearity — –1 — 1 LSB
Table continues on the next page...
Analog
MPC5748G Microcontroller Datasheet Data Sheet, Rev. 2, 05/2014.
Freescale Semiconductor, Inc.
Preliminary
23