Datasheet

DocID15962 Rev 13 81/131
STM8L151xx, STM8L152xx Electrical parameters
112
LSE crystal/ceramic resonator oscillator
The LSE clock can be supplied with a 32.768 kHz 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 18. LSE oscillator circuit diagram
Table 32. LSE oscillator characteristics
Symbol Parameter Conditions Min Typ Max Unit
f
LSE
Low speed external oscillator
frequency
- 32.768 - kHz
R
F
Feedback resistor V = 200 mV - 1.2 - M
C
(1)
Recommended load capacitance
(2)
-8 - pF
I
DD(LSE)
LSE oscillator power consumption
-1.4
(3)
µA
V
DD
= 1.8 V - 450 -
nAV
DD
= 3 V - 600 -
V
DD
= 3.6 V - 750 -
g
m
Oscillator transconductance 3
(3)
-µA/V
t
SU(LSE)
(4)
Startup time V
DD
is stabilized - 1 - s
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 a small R
m
value.
Refer to crystal manufacturer for more details.
3. Data guaranteed by Design. Not tested in production.
4. t
SU(LSE)
is the startup time measured from the moment it is enabled (by software) to a stabilized 32.768 kHz oscillation.
This value is measured for a standard crystal resonator and it can vary significantly with the crystal manufacturer.
OSC_OUT
OSC_IN
f
LSE
C
L1
C
L2
R
F
STM8
Resonator
Consumption
control
g
m
R
m
C
m
L
m
C
O
Resonator
MS32624V1