Chapter 23 Analog-to-Digital Converter (ADC)
MPC5602P Microcontroller Reference Manual, Rev. 4
586
Freescale Semiconductor
Figure 23-5. Sampling and conversion timings
The sampling phase duration is:
where ndelay is equal to 0.5 if INPSAMP is less than or equal to 06h, otherwise it is 1. INPSAMP must
be greater than or equal to 3 (hardware requirement).
The total evaluation phase duration is:
INPCMP must be greater than or equal to 1 and INPLATCH must be less than INCMP (hardware
requirements).
The total conversion duration is (not including external multiplexing):
The timings refer to the unit T
ck
, where f
ck
= (1/2 x ADC peripheral set clock).
Table 23-2. ADC sampling and conversion timing at 5 V / 3.3 V for ADC0
Clock
(MHz)
T
ck
(
s)
INPSAMPLE
1
Ndelay
2
T
sample
3
T
sample
/T
ck
INPCMP
T
eval
(
s)
INPLATCH
T
conv
(
s)
T
conv
/
T
ck
6
0.167
4
0.5
0.583
3.500
1
1.667
0
2.333 14.000
7
0.143
4
0.5
0.500
3.500
1
1.429
0
2.000 14.000
8
0.125
5
0.5
0.563
4.500
1
1.250
0
1.875 15.000
0.5 cycles
2.5 cycles
Sampling phase
Successive approximation / evaluation phase
10 cycles
Latching phase:
The capacitors field input
switch is opened
Note:
Operating conditions — INPLATCH = 0, INPSAMP = 3, INPCMP = 1 and Fadc clk = 20 MHz
End of conversion
Tsample
INPSAMP ndelay
–
Tck
=
INPSAMP 3
Teval 10 Tbiteval
10
INPCMP Tck
=
=
INPCMP 1
and INPLATCH INPCMP
Tconv Tsample Teval ndelay T
ck
+
+
=