Datasheet

(2)
The oscillator selection can be optimized in terms of supply current using a high quality resonator with
small R
m
value. Refer to crystal manufacturer for more details
(3)
Data based on characterization results, not tested in production.
(4)
t
SU(HSE)
is the start-up time measured from the moment it is enabled (by software) to a stabilized 16
MHz oscillation is reached. This value is measured for a standard crystal resonator and it can vary
significantly with the crystal manufacturer.
Figure 20: HSE oscillator circuit diagram
OSCOUT
OSCIN
f
HSE
to core
C
L1
C
L2
R
F
STM8
Resonator
Consumption
control
g
m
R
m
C
m
L
m
C
O
Resonator
HSE oscillator critical g
m
equation
g
mcrit
= (2 × Π × f
HSE
)
2
× R
m
(2Co + C)
2
R
m
: Notional resistance (see crystal specification)
L
m
: Notional inductance (see crystal specification)
C
m
: Notional capacitance (see crystal specification)
Co: Shunt capacitance (see crystal specification)
C
L1
= C
L2
= C: Grounded external capacitance
g
m
>> g
mcrit
Internal clock sources and timing characteristics10.3.4
Subject to general operating conditions for V
DD
and T
A
.
High speed internal RC oscillator (HSI)
Table 34: HSI oscillator characteristics
UnitMaxTypMinConditionsParameterSymbol
MHz16Frequencyf
HSI
75/124DocID14771 Rev 12
Electrical characteristicsSTM8S105xx