STM32L151C6-A datasheet(74/129 Pages) STMICROELECTRONICS

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Electrical characteristics

STM32L151x6/8/B-A STM32L152x6/8/B-A

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DocID024330 Rev 4

For CL1 and CL2, it is recommended to use high-quality external ceramic capacitors in the

5 pF to 25 pF range (typ.), designed for high-frequency applications, and selected to match

the requirements of the crystal or resonator (see Figure 17). CL1 and CL2 are usually the

same size. The crystal manufacturer typically specifies a load capacitance which is the

series combination of CL1 and CL2. PCB and MCU pin capacitance must be included (10 pF

can be used as a rough estimate of the combined pin and board capacitance) when sizing

CL1 and CL2. Refer to the application note AN2867 “Oscillator design guide for ST

microcontrollers” available from the ST website www.st.com.

Recommended load

capacitance versus

equivalent serial resistance

of the crystal (RS)(3)

RS = 30 Ω

-20

IHSE

HSE driving current

VDD= 3.3 V, VIN = VSS

with 30 pF load

IDD(HSE)

HSE oscillator power

consumption

C = 20 pF

fOSC = 16 MHz

2.5 (startup)

0.7 (stabilized)

C = 10 pF

fOSC = 16 MHz

2.5 (startup)

0.46 (stabilized)

Oscillator transconductance

Startup

3.5

tSU(HSE)

(4)

Startup time

VDD is stabilized

1. Resonator characteristics given by the crystal/ceramic resonator manufacturer.

2. Guaranteed by characterization results.

3. The relatively low value of the RF resistor offers a good protection against issues resulting from use in a

humid environment, due to the induced leakage and the bias condition change. However, it is

recommended to take this point into account if the MCU is used in tough humidity conditions.

4. tSU(HSE) is the startup time measured from the moment it is enabled (by software) to a stabilized 8 MHz

oscillation is reached. This value is measured for a standard crystal resonator and it can vary significantly

with the crystal manufacturer.

Table 29. HSE oscillator characteristics(1)(2) (continued)

Symbol

Parameter

Conditions

Min Typ

Max

Unit

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