L-827e.A3 phyCORE-i.MX 6UL/ULL Hardware Manual
© PHYTEC Messtecknik GmbH
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6.4 Switching Supply Voltages for External Logic
The phyCORE’s logic circuitry is directly supplied from the module's main input voltage VDD_3V3 (3.3 V). If the
external components on a customer baseboard are supplied with the same 3.3 V source as the module, there is no
need for special power-up or power-down sequences. Otherwise, it is mandatory for the i.MX 6UL/ULL that external
devices are supplied later than the module itself. Please use signal X_PMIC_STBY_REQ or X_RESET_OUT which is
brought out at pin 102 on the phyCORE connector X1 to switch supply voltages on a carrier board. Use of
X_PMIC_STBY_REQ or X_RESET_OUT ensures that external components are only supplied when the supply voltages
of the i.MX 6UL/ULL are stable.
That way, voltages at the IO pins of the phyCORE-i.MX 6UL/ULL which are sourced from the supply voltage of
peripheral devices attached to the SOM are avoided. These voltages can cause a current flow into the controller
especially if peripheral devices attached to the interfaces of the i.MX 6UL/ULL are supposed to be powered while the
phyCORE
‑
i.MX 6UL/ULL is in suspend mode or turned off. The bus switches' output enable to the SOM can be
controlled by signals X_PMIC_STBY_REQ or X_RESET_OUT to prevent these voltages from occurring.
Use of level shifters supplied with voltages switched by the signals X_PMIC_STBY_REQ, or X_RESET_OUT allows
converting the signals according to the needs of the custom target hardware. Alternatively, signals can be
connected to an open drain circuitry with a pull-up resistor attached to VDD_3V3.
6.5 Backup Power (VDD_SNVS)
To back up the i.MX 6UL/ULL's low power domain (SNVS_LP) and its RTC, a secondary voltage source of 2.4 V to 3.6
V can be attached to the phyCORE
‑
i.MX 6UL/ULL at pin 94 of X1. VDD_SNVS is supplied by VDD_3V3 over diode D1 to
if no backup supply is available. If a backup supply is connected to pin 94 of X1 diode D1 ensures that only
VDD_SNVS_IN is supplied when the primary system power (VDD_3V3) is removed.
Note
If a non-rechargeable source is used a diode should be placed in the VDD_SNVS path on the carrier board!