.. _qs-pow:

Power Supply, Reset and Boot mode
=================================

.. figure:: ../images/qs-pinout-pow.png
   :width: 50%
   :figwidth: 50%
   :align: right
   :alt:
   

+---------+------------+-----------------------------------+------------+---------+
| **Pin** | **Signal** | **Description**                   | **type**   | **I/O** |
+---------+------------+-----------------------------------+------------+---------+
| 49,50   | VIN        | 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 operate with a single 3.3V power supply, while QSX modules can also be 
powered from higher voltages up to 5V nominal. 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.

QS Operating conditions
-----------------------

+---------------+----------------------+---------+---------+---------+
| **Parameter** | **Description**      | **Min** | **Typ** | **Max** |
+---------------+----------------------+---------+---------+---------+
| VIN           | Power Supply Voltage |  3.1V   | 3.3V    | 3.6V    |
+---------------+----------------------+---------+---------+---------+

QSX Operating conditions
------------------------

+---------------+----------------------+---------+-----------+---------+
| **Parameter** | **Description**      | **Min** | **Typ**   | **Max** |
+---------------+----------------------+---------+-----------+---------+
| VIN           | Power Supply Voltage |  3.1V   | 3.3 to 5V | 5.5V    |
+---------------+----------------------+---------+-----------+---------+

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.

.. figure:: ../images/EN_PER.png

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:

 https://www.st.com/resource/en/datasheet/stm32mp157c.pdf
 
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.

QSX
^^^

1.8V NRST_PWREN is directly connected to PCA9450 PMIC_RST_B (1.8V level). 

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           |
+--------------+---------------+---------------------+---------------------+
|   QSXM,QSXP  |   pull-down   |          0          |         1           |
+--------------+---------------+---------------------+---------------------+
 
.. include:: index.rst