Intel PXA27X manual Intel PXA27x Processor Voltage Domains Sheet 1, Voltage Description

Intel® PXA27x Processor Family Power Requirements

Table 2. Intel® PXA27x Processor Voltage Domains (Sheet 1 of 2)

Voltage	Description
VCC_BATT	BATTERY VOLTAGE:
	Voltage-limited power from the main battery, or directly from a backup battery, at
	nominal 3.0 V (±25%). VCC_BATT must be supplied to start the power manager. When
	the main battery is installed, VCC_BATT powers the real-time clock and power
	management circuitry during initial power-on, sleep, deep sleep and sleep wake-up, so
	it remains powered from the backup battery when the main power source has been
	discharged or removed. See Section 2.2, “Batteries” on page 14 for information about
	directly connecting VCC_BATT to the backup battery or main battery.
	NOTE: The power management integrated circuit (PMIC) output drivers for logic
	signals nRESET, nVDD_FAULT, nBATT_FAULT, PWR_SDA, GPIO0 and
	GPIO1 must be powered from the VCC_BATT supply. This also applies to all
	other digital outputs such as the JTAG signals driving PXA27x processor
	inputs on the VCC_REG domain. Any devices that have a digital input driven
	by a PXA27x processor digital output powered from the VCC_REG domain
	must tolerate output high drive levels between 2.25 V and 3.75 V.
	NOTE: VCC_BATT must be driven by a regulator whose output is matched to the
	VCC_IO regulator so that VCC_IO and VCC_BATT remain within 200 mV of
	each other when the VCC_IO regulator is enabled.
VCC_CORE	CORE VOLTAGE:
	Dynamically variable core voltage of 0.85 V to 1.55 V. VCC_CORE also powers internal
	peripheral logic blocks such as the memory controller, LCD controller, digital audio, and
	serial ports. It does not power the internal SRAM. In a full featured system, this supply
	is software controllable as described in Section 6.1, “VCC_CORE Regulator and
	Dynamic Voltage Management” on page 29. In a simple system, this supply might be a
	fixed voltage chosen to meet the minimum voltage requirement for the highest
	frequency at which the PXA27x processor operates. In systems that use standby mode,
	there must also be a provision to set VCC_CORE to 1.10 V (±10%) prior to entry into
	standby mode. VCC_CORE must be enabled when PWR_EN is asserted and disabled
	when PWR_EN is de-asserted.
VCC_PLL	PHASE-LOCK LOOP VOLTAGE:
	1.3 V (±10%) for internal PLL circuits, fixed. VCC_PLL must not be connected to
	VCC_CORE, even though they both may be at the same voltage: 1.3 V. A separate
	low-noise voltage source is recommended to keep the PLL supply clean. This supply
	must be enabled when PWR_EN is asserted and disabled when PWR_EN is
	de-asserted.
VCC_SRAM	Power for the internal SRAM during operation in run or turbo modes. This supply is
	fixed at 1.1 V (±10%). If the core supply (VCC_CORE) is also fixed at 1.1V (no dynamic
	voltage changes are used and the maximum core clock frequency is not supported),
	these two supplies are connected together and powered by a common regulator. In
	sleep and deep-sleep modes, VCC_SRAM is powered down and the internal SRAM
	banks, under program control, are powered from an internal regulator connected to
	VCC_BATT. Doing so retains their contents although no accesses are allowed.
	VCC_SRAM must be enabled when PWR_EN is asserted and disabled when
	PWR_EN is de-asserted.

Application Note 9