STM32F401XD datasheet(62/135 Pages) STMICROELECTRONICS

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Electrical characteristics

STM32F401xD STM32F401xE

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6.3.2

VCAP1/VCAP2 external capacitors

Stabilization for the main regulator is achieved by connecting external capacitor CEXT to the

VCAP1 and VCAP2 pin. For packages supporting only 1 VCAP pin, the 2 CEXT capacitors

are replaced by a single capacitor.

CEXT is specified in Table 16.

Figure 20. External capacitor CEXT

1. Legend: ESR is the equivalent series resistance.

1. Applicable only when the code is executed from Flash memory. When the code is executed from RAM, no wait state is

required.

2. Thanks to the ART accelerator and the 128-bit Flash memory, the number of wait states given here does not impact the

execution speed from Flash memory since the ART accelerator allows to achieve a performance equivalent to 0 wait state

program execution.

3. Refer to for frequencies vs. external load.

4. VDD/VDDA minimum value of 1.7 V, with the use of an external power supply supervisor (refer to Section 3.14.2: Internal

reset OFF).

5. Prefetch is not available. Refer to AN3430 application note for details on how to adjust performance and power.

6. The voltage range for the USB full speed embedded PHY can drop down to 2.7 V. However the electrical characteristics of

D- and D+ pins will be degraded between 2.7 and 3 V.

Table 16. VCAP1/VCAP2 operating conditions(1)

1. When bypassing the voltage regulator, the two 2.2 µF VCAP capacitors are not required and should be

replaced by two 100 nF decoupling capacitors.

Symbol

Parameter

Conditions

CEXT

Capacitance of external capacitor with available

VCAP1 and VCAP2 pins

2.2 µF

ESR

ESR of external capacitor with available VCAP1 and

VCAP2 pins

< 2

CEXT

Capacitance of external capacitor with a single VCAP

pin available

4.7 µF

ESR

ESR of external capacitor with a single VCAP pin

available

< 1

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