STM32U073R8T3TR datasheet(71/146 Pages) STMICROELECTRONICS

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Figure 17. AC timing diagram for low-speed external clock source

VLSEH

70%

30%

VLSEL

tw(LSEH)

tw(LSEL)

VLSE_ext

tLSE = 1/fLSE_ext

VLSE_ext_PP

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

The high-speed external (HSE) clock can be supplied with a 4 to 48 MHz crystal/ceramic resonator oscillator. All

the information given in this paragraph are based on design simulation results obtained with typical external

components specified in Table 50. 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 50. HSE oscillator characteristics

Specified by design, not tested in production.

Symbol

Parameter

Conditions(1)

Min

Typ

Max

Unit

fOSC_IN

Oscillator frequency

MHz

Feedback resistor

200

kΩ

IDD(HSE)

HSE current consumption

During startup(2)

5.5

VDD = 3 V,

Rm = 30 Ω,

CL = 10 pF @ 8 MHz

0.58

VDD = 3 V,

Rm = 45 Ω,

CL = 10 pF @ 8 MHz

0.59

VDD = 3 V,

Rm = 30 Ω,

C = 5 pF @ 48 MHz

0.89

VDD = 3 V,

Rm = 30 Ω,

CL = 10 pF @ 48 MHz

1.14

VDD = 3 V,

Rm = 30 Ω,

CL = 20 pF @ 48 MHz

1.94

Maximum critical crystal transconductance

Startup

1.5

mA/V

tSU(HSE)(3)

Startup time

VDD is stabilized

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

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

3. 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

STM32U073x8/B/C

Electrical characteristics

DS14548 - Rev 2

page 71/146

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