Power Supply, Reset and Boot mode

Pin Signal Description type I/O
49,50 3V3_IN 3.3V Module power supply input power I
51 NRST_PWREN Reset and Peripheral Power Enable 1V8/3V3 OD I/O
52 BOOTMODE Boot Mode Select 3V3 I

Power Supply

QS modules operates on a single 3.3V power supply. All other voltages are handled onboard so there is no need to care about such things on the baseboard. Nevertheless, pay attention to the absolute maximum ratings of directly connected processor pins during power-up and as long as no power is provided.

Operating conditions

Parameter Description Min Typ Max
3V3_IN Power Supply Voltage 3.1V 3.3V 3.6V

NRST_PWREN - Reset and Peripheral Power Enable

This dual function pin is used as reset input and peripheral power supply enable output. Depending on the QS module the function is slightly different.

The example below uses a load switch. 3V3QS is a main power supply connected to 3V3_IN of the QS module and 3V3 is used for the peripherals on the baseboard.

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QSMP

3.3V NRST_PWREN is directly connected to STM32MP1 NRST and NRST_CORE and enables the DDR memory power supply VDD_DDR. 10nF capacitors on NRST and NRST_CORE protects the device against parasitic resets.

The STM32MP1 has permanent internal pull-up resistors to 3.3V. Refer also to page 174, chap. 6.3.18 NRST and NRST_CORE pin characteristics:

QS8M

1.8V NRST_PWREN is directly connected to i.MX8M POR_B (1.8V level) and PMIC RESETO. RN6T567 RESETO is an open drain host reset output. RESETO is pulled low during power-on and power-off sequences and is released after the power-on sequence has finished and all supplies are valid.

A 10K pull-up to 1.8V is used onboard.

BOOTMODE

System Boot Mode Select - The operational system boot mode of the module upon system reset is determined by the settings of this pin. This can be either boot from Flash or boot from USB. The default state is boot from Flash. Leave unconnected if no used.

The polarity depends on the QS module:

BOOTMODE DEFAULT BOOT FROM FLASH BOOT FROM USB
QSMP pull-up 1 0
QS8M pull-down 0 1

QSCOM Standard Contact Group Index

Pins Funktion Pins Funktion Pins Funktion Pins Funktion
1-4 SPI 19-35 Ethernet 49-52 Power Supply, Reset and Boot mode 79-88 MIPI/LVDS Display Interface
5-10 I2C 36-39 SD Interface 53-76 18-bit RGB Display Interface 89-96 UART
11-14 CAN 43-48 USB 77-78 Backlight and Display Control 97-100 SPI