Datasheet

Table Of Contents
MC68HC908GP20Rev 2.1 Advance Information
Freescale Semiconductor 391
23.13 ADC Characteristics
Characteristic
(1)
Symbol Min Max Unit Comments
Supply voltage V
DDAD
2.7
(V
DD
min)
5.5
(V
DD
max)
V
V
DDAD
should be tied
to the same potential
as V
DD
via separate
traces.
Input voltages
V
ADIN
V
REFH
0
1.5
V
DDAD
V
DDAD
VV
ADIN
<= V
REFH
Resolution B
AD
88Bits
Absolute accuracy
(V
REFL
= 0 V, V
DDAD
= V
REFH
=
5 V ± 10%)
A
AD
± 1/2 ± 1 LSB Includes quantization
ADC internal clock f
ADIC
0.5 1.048 MHz
t
AIC
= 1/f
ADIC
, tested
only at 1 MHz
Conversion range R
AD
V
REFL
V
REFH
VV
REFL
= V
SS
Power-up time t
ADPU
16 t
AIC
cycles
Conversion time t
ADC
16 17 t
AIC
cycles
Sample time
(2)
t
ADS
5—
t
AIC
cycles
Zero input reading
(3)
Z
ADI
00 01 Hex V
IN
= V
REFL
Full-scale reading
(3)
F
ADI
FE FF Hex V
IN
= V
REFH
Input capacitance C
ADI
(20) 8 pF Not tested
Input leakage
(4)
Port B
——± 1 µA
Notes:
1. V
DD
= 5.0 Vdc ± 10%, V
SS
= 0 Vdc, V
DDAD
= 5.0 Vdc ± 10%, V
SSAD
= 0 Vdc, V
REFH
= 5.0 Vdc ± 10%, V
REFL
= 0
2. Source impedances greater than 10 k adversely affect internal RC charging time during input sampling.
3. Zero-input/full-scale reading requires sufficient decoupling measures for accurate conversions.
4. The external system error caused by input leakage current is approximately equal to the product of R source and input
current.