ST STM32H723 User Manual

3.1.1 HSE and LSE bypass (external user clock)
In this mode, an external clock source must be provided to OSC_IN/OSC32_IN pins. For LSE bypass, the
external source has to be "low swing".The signal (square, sinus or triangle) with ~50% duty cycle drives the
OSC_IN/OSC32_IN pin.
3.1.2 External crystal/ceramic resonator (HSE crystal)
The external oscillator has the advantage of producing a very accurate main clock.
Using a 25 MHz oscillator is a good choice for accurate USB OTG high-speed peripheral, I2S and SAI.
The resonator and the load capacitors have to be connected as close as possible to the oscillator pins in order to
minimize the output distortion and start-up stabilization time. The load capacitance values must be adjusted
according to the selected oscillator.
For CL1 and CL2, use high-quality ceramic capacitors in the 5 pF to 25 pF range (typical), designed for high-
frequency applications and selected to meet the requirements of the crystal or resonator. CL1 and CL2 are
usually the same value. The crystal manufacturer typically specifies a load capacitance that is the series
combination of CL1 and CL2. The PCB and MCU pin capacitances must be included when sizing CL1 and CL2
(10 pF can be used as a rough estimate for the combined pin and board capacitance).
The HSERDY flag in the RCC clock control register (RCC_CR) indicates if the high-speed external oscillator is
stable or not. At start-up, the clock is not provided until this bit is set by hardware. An interrupt can be generated if
enabled in the RCC clock interrupt register (RCC_CIR).
If it is not used as clock source, the HSE oscillator can be switched off using the HSEON bit in the RCC clock
control register (RCC_CR).
AN5419
Introduction
AN5419 - Rev 2
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ST STM32H723 Specifications

General

Brand	ST
Model	STM32H723
Category	Microcontrollers
Language	English

Summary

General Information

Power Supply Configuration and Management

Introduction to Power Supplies

Overview of the power supply requirements and features for the microcontrollers.

External Power Supplies and Components

Details on external components and pin connections for power supply inputs.

Power Domains and Voltage Regulators

Explains core, analog, USB, battery, LDO, and SMPS power domains and regulator configurations.

Reset and Power Supply Supervisor Features

Reset and Supervisor Functionality

Covers POR, PDR, BOR, PVD, AVD, system reset, and bypass mode functionalities.

Clock Generation and Management

Introduction to Clock Sources

Overview of available internal and external clock sources and PLLs.

Clock Sources and Security Systems

Details HSE/LSE bypass, crystal oscillators, CSS, and CRS for clock management.

Alternate Function Pin Mapping

Analog Inputs for ADCs

Mapping of analog inputs to ADC1, ADC2, and ADC3, including specialized pads.

ADC Pin Pad Configurations

Describes different pin pad configurations (Pxy_C, Pxy) for ADC performance.

Microcontroller Boot Configuration

Boot Mode Selection and Pin Connection

Explains boot mode selection via option bytes and the BOOT pin.

System Bootloader Mode

Details the embedded bootloader and its communication peripherals.

Debugging Interfaces and Ports

Introduction to Debugging

Overview of host-to-target interface components for debugging.

SWJ Debug Port Configuration

Covers SWJ-DP, TPIU trace port, external triggers, and pin assignments.

Design and Layout Recommendations

PCB Design Best Practices

Guidelines for PCB layout, component positioning, ground, and power supply.

Signal Integrity and Feature Management

Advice on signal handling, unused I/Os, and features for EMC performance.

PCB Routing Guidelines for High-Speed Signals

PCB Stack-up and Signal Layout Basics

Covers PCB stack-up, crystal oscillator, and power supply decoupling.

High-Speed Signal Layout for Interfaces

Details layout guidelines for SDMMC, FMC, Octo-SPI, DFSDM, and ETM interfaces.

Typical Use Case Examples

Document Conclusion