STM32H7B3AI datasheet(86/238 Pages) STMICROELECTRONICS

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6.3.2

VCAP external capacitor

Stabilization for the embedded LDO regulator is achieved by connecting an external capacitor CEXT to the VCAPx

pin. CEXT is specified in Table 25. VCAP operating conditions. Two external capacitors must be connected to

VCAP pins (refer to Getting started with STM32H7A3/7B3 and STM32H7B0 hardware development (AN5307).

Figure 23. External capacitor CEXT

ESR

R Leak

Legend: ESR is the equivalent series resistance.

Table 25. VCAP operating conditions

When the internal LDO voltage regulator is switched OFF, the two 2.2 µF VCAP capacitors are not required. However all VCAPx

package pins must be connected together and it is recommended to add a ceramic filtering capacitor of 100 nF as close as

possible to each VCAPx pin.

Symbol

Parameter

Conditions

CEXT

External capacitor for LDO enabled

2.2 µF(1)(2)

ESR

ESR of external capacitor

< 100 mΩ

1. This value corresponds to CEXT typical value. A variation of ±20% is tolerated.

2. If the VCAP3 pin is available (depending on the package), it must be connected to the other VCAP pins. No additional

capacitor is required.

6.3.3

SMPS step-down converter

The devices embed a high power efficiency SMPS step-down converter requiring external components. Refer

to Getting started with STM32H7A3/7B3 and STM32H7B0 hardware development (AN5307) for the required

components and tradeoffs.

Table 26. Characteristics of SMPS step-down converter external components

Symbol Parameter

Conditions

CIN

Capacitance of external capacitor on VDDSMPS

4.7 µF

ESR of external capacitor

100 mΩ

Cfilt

Capacitance of external capacitor on VLXSMPS pin

220 pF

COUT

Capacitance of external capacitor on VFBSMPS pin

10 µF

ESR of external capacitor

20 mΩ

Inductance of external Inductor on VLXSMPS pin

2.2 µH

Serial DC resistor

150 mΩ

ISAT

DC current at which the inductance drops 30% from its value without current.

1.7 A

IRMS

Average current for a 40 °C rise: rated current for which the temperature of the inductor is raised 40°C

by DC current

1.4 A

STM32H7B3xI

Operating conditions

DS13139 - Rev 8

page 86/238

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