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| STM8L15 Datasheet, PDF (81/122 Pages) STMicroelectronics – 8-bit ultralow power MCU, up to 32 KB Flash, 1 KB Data EEPROM RTC, LCD, timers, USART, I2C, SPI, ADC, DAC, comparators | |||
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STM8L151xx, STM8L152xx
Electrical parameters
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...).
Table 31. LSE oscillator characteristics
Symbol
Parameter
Conditions
Min Typ
Max
Unit
fLSE
Low speed external oscillator
frequency
32.768
kHz
RF Feedback resistor
ÎV = 200 mV
C(1) Recommended load capacitance (2)
1.2
MΩ
8
pF
1.4(3)
µA
IDD(LSE) LSE oscillator power consumption
VDD = 1.8 V
450
VDD = 3 V
600
VDD = 3.6 V
750
gm Oscillator transconductance
tSU(LSE)(4) Startup time
3
VDD is stabilized
1
nA
µA/V
s
1. C=CL1=CL2 is approximately equivalent to 2 x crystal CLOAD.
2. The oscillator selection can be optimized in terms of supply current using a high quality resonator with a small Rm value.
Refer to crystal manufacturer for more details.
3. Guaranteed by design. Not tested in production.
4. tSU(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.
Figure 18. LSE oscillator circuit diagram
Rm
Lm
CO
Cm
Resonator
CL1
OSC_IN
Resonator
fLSE
RF
gm
Consumption
control
OSC_OUT
CL2
STM8
Doc ID 15962 Rev 5
81/122
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