Datasheet

Electrical parameters STM8L151xx, STM8L152xx
80/131 DocID15962 Rev 13
HSE crystal/ceramic resonator oscillator
The HSE clock can be supplied with a 1 to 16 MHz crystal/ceramic resonator oscillator. All
the information given in this paragraph is based on characterization results with specified
typical external components. In the application, the resonator and the load capacitors have
to be placed as close as possible to the oscillator pins in order to minimize output distortion
and startup stabilization time. Refer to the crystal resonator manufacturer for more details
(frequency, package, accuracy...).
Figure 17. HSE oscillator circuit diagram
HSE oscillator critical g
m
formula
R
m
: Motional resistance (see crystal specification), L
m
: Motional inductance (see crystal specification),
C
m
: Motional capacitance (see crystal specification), Co: Shunt capacitance (see crystal specification),
C
L1
=C
L2
=C: Grounded external capacitance
g
m
>> g
mcrit
Table 31. HSE oscillator characteristics
Symbol Parameter Conditions Min Typ Max Unit
f
HSE
High speed external oscillator
frequency
1- 16 MHz
R
F
Feedback resistor 200 - k
C
(1)
Recommended load capacitance
(2)
20 - pF
I
DD(HSE)
HSE oscillator power consumption
C = 20 pF,
f
OSC
= 16 MHz
--
2.5 (startup)
0.7 (stabilized)
(3)
mA
C = 10 pF,
f
OSC
=16 MHz
--
2.5 (startup)
0.46 (stabilized)
(3)
g
m
Oscillator transconductance 3.5
(3)
--mA/V
t
SU(HSE)
(4)
Startup time V
DD
is stabilized - 1 - ms
1. C= C
L1
= C
L2
is approximately equivalent to 2 x crystal C
LOAD
.
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 guaranteed by Design. Not tested in production.
4. t
SU(HSE)
is the startup time measured from the moment it is enabled (by software) to a stabilized 16 MHz oscillation. This
value is measured for a standard crystal resonator and it can vary significantly with the crystal manufacturer.
OSC_OUT
OSC_IN
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
.47
g
mcrit
2  f
HSE

2
R
m
 2Co C+
2
=