STM32H723VG datasheet(107/227 Pages) STMICROELECTRONICS

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DS13313 Rev 2

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STM32H723xE/G

Electrical characteristics

208

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 32. 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).

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

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

match the requirements of the crystal or resonator (see Figure 15). 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. The 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.

Note:

For information on selecting the crystal, refer to application note AN2867 “Oscillator design

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

Table 32. 4-50 MHz HSE oscillator characteristics(1)

1. Guaranteed by design.

Symbol

Parameter

Operating

conditions(2)

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

Min

Typ

Max

Unit

Oscillator frequency

MHz

Feedback resistor

200

kΩ

IDD(HSE)

HSE current

consumption

During startup(3)

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

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

Startup

1.5

mA/V

tSU(4)

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.

Start-up time

VDD is stabilized

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