STM32H7B3II datasheet(108/238 Pages) STMICROELECTRONICS

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Figure 31. Low-speed external clock source AC timing diagram

OSC32 _IN

External

STM32

clock source

VLSEH

tf(LSE)

tW(LSE)

90 %

10 %

T LSE

tr(LSE)

tW(LSE)

fLSE_ext

VLSEL

High-speed external clock generated from a crystal/ceramic resonator

The high-speed external (HSE) clock can be supplied with a 4 to 50 MHz crystal/ceramic resonator oscillator.

All the information given in this paragraph are based on characterization results obtained with typical external

components specified in Table 49. 4-50 MHz HSE oscillator characteristics. 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 on the

resonator characteristics (frequency, package, accuracy).

Table 49. 4-50 MHz HSE oscillator characteristics

Symbol

Parameter

Operating conditions(1)

Min(2)

Typ(2)

Max(2)

Unit

Oscillator frequency

MHz

Feedback resistor

200

kΩ

IDD(HSE)

HSE current consumption

During startup(3)

VDD=3 V, Rm=30 Ω

CL=10 pF at 4 MHz

0.35

VDD=3 V, Rm=30 Ω

CL=10 pF at 8 MHz

0.40

VDD=3 V, Rm=30 Ω

CL=10 pF at 16 MHz

0.45

VDD=3 V, Rm=30 Ω

CL=10 pF at 32 MHz

0.65

VDD=3 V, Rm=30 Ω

CL=10 pF at 48 MHz

0.95

Gmcritmax

Maximum critical crystal gm

Startup

1.5

mA/V

tSU(4)

Start-up time

VDD is stabilized

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

2. Guaranteed by design.

3. This consumption level occurs during the first 2/3 of the tSU(HSE) startup time.

STM32H7B3xI

Operating conditions

DS13139 - Rev 8

page 108/238

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