MC68336/376
ELECTRICAL CHARACTERISTICS
MOTOROLA
USER’S MANUAL
Rev. 15 Oct 2000
A-28
Table A-14 QADC Conversion Characteristics (Operating)
(VDDI and VDDA = 5.0 Vdc ± 5%, VSSI and VSSA = 0 Vdc, TA = TL to TH,
0.5 MHz
≤ fQCLK ≤ 2.1 MHz, 2 clock input sample time)
Num
Parameter
Symbol
Min
Typ
Max
Unit
1
Resolution1
NOTES:
1. At VRH – VRL = 5.12 V, one count = 5 mV.
1 Count
—
5
—
mV
2
Differential nonlinearity2
2. This parameter is periodically sampled rather than 100% tested.
DNL
—
± 0.5
Counts
3
Integral nonlinearity
INL
—
± 2.0
Counts
4
fQCLK = 0.999 MHz
5
PQA
PQB
fQCLK = 2.097 MHz
6
PQA
PQB
3. Absolute error includes 1/2 count (2.5 mV) of inherent quantization error and circuit (differential, integral, and
offset) error. Specification assumes that adequate low-pass filtering is present on analog input pins — capacitive
filter with 0.01
F to 0.1 F capacitor between analog input and analog ground, typical source isolation
impedance of 20 k
.
4. Assumes fsys = 20.97 MHz.
5. Assumes clock prescaler values of:
QACR0: PSH = %01111, PSA = %1, PSL = 100)
CCW: BYP = %0
6. Assumes clock prescaler values of:
QACR0: PSH = %00110, PSA = %1, PSL = 010)
CCW: BYP = %0
AE
—
± 2.5
± 4.0
Counts
5
Source impedance at input7
7. Maximum source impedance is application-dependent. Error resulting from pin leakage depends on junction
leakage into the pin and on leakage due to charge-sharing with internal capacitance.
Error from junction leakage is a function of external source impedance and input leakage current. In the following
expression, expected error in result value due to junction leakage is expressed in voltage (Verrj):
Verrj = RS X IOFF
where IOFF is a function of operating temperature. Refer to Table A-12. Charge-sharing leakage is a function of input source impedance, conversion rate, change in voltage between
successive conversions, and the size of the decoupling capacitor used. Error levels are best determined
empirically. In general, continuous conversion of the same channel may not be compatible with high source
impedance.
RS
—20
—
k