EM357-RTR datasheet(36/241 Pages) SILABS

36 / 241 page

Rev 1.3

6.1. Power Domains

The EM35x contains three power domains:



An “always-on domain” containing all logic and analog cells required to manage the EM35x’s power

modes, including the GPIO controller and sleep timer. This domain must remain powered.



A “core domain” containing the CPU, Nested Vectored Interrupt Controller (NVIC), and peripherals. To save

power, this domain can be powered down using a mode called deep sleep.



A “memory domain” containing the RAM and flash memories. This domain is managed by the power

management controller. When in deep sleep, the RAM portion of this domain is powered from the always-

on domain supply to retain the RAM contents while the regulators are disabled. During deep sleep the flash

portion is completely powered down.

6.1.1. Internally Regulated Power

The preferred and recommended power configuration is to use the internal regulated power supplies to provide

power to the core and memory domains. The internal regulators (VREG_1V25 and VREG_1V8) generate nominal

1.25 and 1.8 V supplies. The 1.25 V supply is internally routed to the core domain and to an external pin. The 1.8 V

supply is routed to an external pin where it can be externally routed back into the chip to supply the memory

domain. The internal regulators are described in "16. Integrated Voltage Regulator" on page 207.

When using the internal regulators, the always-on domain must be powered between 2.1 and 3.6 V at all four

VDD_PADS pins.

When using the internal regulators, the VREG_1V8 regulator output pin (VREG_OUT) must be connected to the

VDD_MEM, VDD_PADSA, VDD_VCO, VDD_RF, VDD_IF, VDD_PRE, and VDD_SYNTH pins.

When using the internal regulators, the VREG_1V25 regulator output and supply requires a connection between

both VDD_CORE pins.

6.1.2. Externally Regulated Power

Optionally, the on-chip regulators may be left unused, and the core and memory domains may instead be powered

from external supplies. For simplicity, the voltage for the core domain can be raised to nominal 1.8 V, requiring only

one external regulator, or the core domain can be powered from the on-chip regulators while the other domains are

powered externally. Note that if the core domain is powered at a higher voltage (1.8 V instead of 1.25 V) then

power consumption increases. A regulator enable signal, REG_EN, is provided for control of external regulators.

This is an open-drain signal that requires an external pull-up resistor. If REG_EN is not required to control external

regulators it can be disabled (see "7.3. Forced Functions" on page 52).

Using an external regulator requires the always-on domain to be powered between 2.1 and 3.6 V at all four

VDD_PADS pins.

When using an external regulator, the VREG_1V8 regulator output pin (VREG_OUT) must be left unconnected.

When using an external regulator, this external nominal 1.8 V supply has to be connected to both VDD_CORE pins

and to the VDD_MEM, VDD_PADSA, VDD_VCO, VDD_RF, VDD_IF, VDD_PRE and VDD_SYNTH pins.

EM357-RTR 数据表(PDF) 36 Page - Silicon Laboratories

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