STM32F102XB datasheet(43/76 Pages) STMICROELECTRONICS

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STM32F102x8, STM32F102xB

Electrical characteristics

Doc ID 15056 Rev 4

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Note:

For CL1 and CL2 it is recommended to use high-quality ceramic capacitors in the 5 pF to

15 pF range selected to match the requirements of the crystal or resonator. 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.

Load capacitance CL has the following formula: CL = CL1 x CL2 / (CL1 + CL2) + Cstray where

Cstray is the pin capacitance and board or trace PCB-related capacitance. Typically, it is

between 2 pF and 7 pF.

Caution:

To avoid exceeding the maximum value of CL1 and CL2 (15 pF) it is strongly recommended

to use a resonator with a load capacitance CL ≤ 7 pF. Never use a resonator with a load

capacitance of 12.5 pF.

Example: if you choose a resonator with a load capacitance of CL = 6 pF, and Cstray = 2 pF,

then CL1 = CL2 = 8 pF.

Figure 19.

Typical application with a 32.768 kHz crystal

5.3.7

Internal clock source characteristics

The parameters given in Table 23 are derived from tests performed under ambient

temperature and VDD supply voltage conditions summarized in Table 8.

High-speed internal (HSI) RC oscillator

ai14978b

OSC32_OU T

OSC32_IN

fLSE

CL1

STM32F102xx

32.768 KH z

resonator

Bias

controlled

gain

CL2

Resonator with

integrated capacitors

Table 23.

HSI oscillator characteristics(1)

VDD = 3.3 V, TA = –40 to 105 °C unless otherwise specified.

Symbol

Parameter

Conditions

Min

Typ

Max

Unit

fHSI

Frequency

MHz

DuCy(HSI) Duty cycle

ACCHSI

Accuracy of the HSI

oscillator

User-trimmed with the RCC_CR

1(3)

Factory-

calibrated(4)

TA = –40 to 105 °C

–2

2.5

TA = –10 to 85 °C

–1.5

2.2

TA = 0 to 70 °C

–1.3

TA = 25 °C

–1.1

1.8

tsu(HSI)

(4)

HSI oscillator

startup time

µs

IDD(HSI)

(4)

HSI oscillator power

consumption

100

µA

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