ST10F276Z5 STMicroelectronics, ST10F276Z5 Datasheet - Page 192

• Manufacturer Part Number: ST10F276Z5
• Description: 16-BIT MICROCONTROLLER WITH MAC UNIT, UP TO 832 KBYTES FLASH MEMORY AND UP TO 68 KBYTES RAM
• Manufacturer: STMicroelectronics

Specifications of ST10F276Z5

• Single Voltage Supply: 5V ±10% (embedded regulator for 1.8 V core supply)

Electrical characteristics
192/239
Input leakage and external circuit
The series resistor utilized to limit the current to a pin (see R
with a large source impedance, can lead to a degradation of A/D converter accuracy when
input leakage is present.
Data about maximum input leakage current at each pin is provided in the datasheet (Electri-
cal Characteristics section). Input leakage is greatest at high operating temperatures and in
general decreases by one half for each 10° C decrease in temperature.
Considering that, for a 10-bit A/D converter one count is about 5mV (assuming V
5 V), an input leakage of 100nA acting though an R
an error of exactly one count (5mV); if the resistance were 100kΩ, the error would become
two counts.
Eventual additional leakage due to external clamping diodes must also be taken into
account in computing the total leakage affecting the A/D converter measurements. Another
contribution to the total leakage is represented by the charge sharing effects with the sam-
pling capacitance: C
the conversion rate of a single channel (maximum when fixed channel continuous conver-
sion mode is selected), it can be seen as a resistive path to ground. For instance, assuming
a conversion rate of 250 kHz, with C
1 / f
the error induced by the voltage partitioning between this resistance (sampled voltage on
C
respect the following relation:
The formula above places constraints on external network design, in particular on resistive
path.
A second aspect involving the capacitance network must be considered. Assuming the three
capacitances C
equivalent circuit shown in
close), a charge sharing phenomena is installed.
Figure 48. Charge sharing timing diagram during sampling phase
S
) and the sum of R
C
C
S
, where f
V
V
V
V
CS
A
A2
A1
F
, C
C
1
represents the conversion rate at the considered channel). To minimize
P1
S
S
and C
Voltage Transient on C
being substantially a switched capacitance, with a frequency equal to
+ R
V A
F
Figure
P2
+ R
2
⋅
R S
----------------------------------------------------------------------------- -
are initially charged at the source voltage V
L
+
+ R
47), when the sampling phase is started (A/D switch
R F
S
SW
equal to 4 pF, a resistance of 1MΩ is obtained (R
+
S
R L
+ R
R EQ
+
AD
R SW
T
S
, the external circuit must be designed to
∆V < 0.5 LSB
+
t
L
R AD
= 50kΩ of external resistance leads to
<
τ
τ
1
2
1
-- - LSB
2
L
< (R
= R
in
L
SW
Figure
(C
S
+ R
+ C
AD
P1
47), in combination
) C
+ C
S
A
<< T
P2
(refer to the
)
ST10F276Z5
S
AREF
=
EQ
=