Digital Ldo Power Selection; Iovdd Connection - Silicon Laboratories EFR32xG14 Wireless Gecko Reference Manual

10.3.7 Digital LDO Power Selection

The digital LDO may be powered from one of two supply pins, depending on the configuration of the REGPWRSEL bit in the
EMU_PWRCTRL register. At startup, the digital is powered from the AVDD pin. When powered from AVDD, the LDO current is limited
to 20 mA. Out of startup, firmware should configure and enable the DCDC (if desired) and then set REGPWRSEL=1 before increasing
the core clock frequency.
REGPWRSEL Digital LDO Power Source
0 (default) AVDD pin
1 DVDD pin

10.3.8 IOVDD Connection

The IOVDD supply(s) must be less than or equal to AVDD. IOVDD will typically be connected to either the DC-DC Output (V
the main supply.
Because V will be unpowered (i.e., floating) at startup, if IOVDD is powered from the DC-DC converter then any circuit attached to
DCDC
IOVDD will not be powered until the DC-DC is configured (or the bypass switch is enabled).
Note: This constraint can have serious and unintended side-effects. For example, if IOVDD=V
1. It isn't directly possible to program an unprogrammed device on a PCB through the serial wire interface. Programming the device
requires IOVDD to be present (i.e., for SWCLK, SWDIO, etc), and IOVDD won't be present until after the part is programmed (i.e.,
the DC-DC is enabled in firmware to power up V
supply for V during programming.
DCDC
2. Some unprogrammed devices are preloaded with a bootloader. The bootloader is expecting to read a logic high on the SWCLK pin
to determine if the bootloader should execute. With no valid IOVDD voltage present, the code may incorrectly decide to execute
the bootloader, which will cause the system to wait in the bootloader until a reset occurs.
Additionally, upon entry into EM4 Shutoff, the DC-DC converter configuration is reset to its default (Unconfigured) configuration. If
IOVDD = V , then any circuits attached to IOVDD will remain unpowered until the system is reset to exit EM4 Shutoff, and the DC-
DCDC
DC is configured (or the bypass switch is enabled).
Any application with powering external loads from the DC-DC converter must take into consideration the maximum allowable DC-DC
load current. Refer to the data sheet for DC-DC load current specification.
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Table 10.5. Digital LDO Power Configuration
Comments
Maximum LDO current in this configuration is 20 mA. Firmware
should configure REGPWRSEL to 1 after startup.
This configuration supports all core frequencies, and should be used
after startup.
). It is possible to work around this issue, however, by providing an external
DCDC
Reference Manual
EMU - Energy Management Unit
:
DCDC
Rev. 1.1 | 229
) or
DCDC