WM8321 datasheet(65/253 Pages) WOLFSON

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Production Data

WM8321

PD, February 2012, Rev 4.0

DC-DC Converters 1 and 2 support two different switching frequencies, as described in Section 15.6.

Note that the supported output voltage range for these converters is restricted in the 4MHz mode; for

output voltages greater than 1.4V, the 2MHz mode must be used.

The DC-DC Converters are dynamically programmable - the output voltage may be adjusted in

software at any time. These converters are step-down converters; their output voltage can therefore

be lower than the input voltage, but cannot be higher.

Note that the output voltage of DC-DC Converters 1 and 2 may also be controlled using the Dynamic

Voltage Scaling features described in Section 15.6. Software control (using register writes) and

hardware control (using the Hardware DVS Control inputs supported via GPIO) is supported.

Note that the output voltage of the DC-DC Converters may also be controlled by the Hardware

Control inputs. The Hardware Control inputs are alternate functions supported via GPIO. See

Section 15.8 for details of Hardware Control.

When changing the output voltage of DC-DC Converters 1 and 2, the GPIO output “DC-DCm DVS

Done” can be used to confirm the DVS Control has completed; see Section 15.6 for details.

15.5.2 LDO REGULATORS 1-10

The output voltage of the LDO Regulators 1-10 in the ON power state is selected using the

LDOn_ON_VSEL register fields. The output voltage of the LDO Regulators in the SLEEP power state

is selected using the LDOn_SLP_VSEL register fields.

The LDO Regulators are dynamically programmable - the output voltage may be adjusted in software

at any time.

Note that the output voltage of the LDO Regulators may also be controlled by the Hardware Control

inputs. The Hardware Control inputs are alternate functions supported via GPIO. See Section 15.8 for

details of Hardware Control.

15.5.3 LDO REGULATOR 11

The output voltage of LDO11 can be set in two ways - it can be commanded directly, or it can be

commanded to follow the DC-DC Converter 1 output voltage.

When LDO11_VSEL_SRC = 0, then the output voltage of LDO11 is set by LDO11_ON_VSEL (in the

ON state) or by LDO11_SLP_VSEL (in the SLEEP state) in the same way as the other LDOs.

When LDO11_VSEL_SRC = 1, the output voltage of LDO11 follows the output voltage of DC-DC

Converter 1. This enables both domains to be changed at the same time, eg. the processor core and

processor ‘alive’ domains. In this case, the LDO11 output voltage follows DC1_ON_VSEL or

DC1_SLP_VSEL in the ON state or SLEEP state respectively.

Note that, when LDO11_VSEL_SRC = 1, the LDO11 regulator adopts the nearest achievable output

voltage, which may not be identical to the DC-DC1 voltage, due to the more limited range and

resolution of LDO11 - the output voltage of LDO11 is in the range 0.8V to 1.55V in 50mV steps; the

output voltage of DC-DC1 is in the range 0.6V to 1.8V in 12.5mV steps. If DC-DC1 is disabled, then

the LDO11 voltage tracking feature is not supported, and the LDO11 output voltage will be 0.8V.

15.6 DC-DC SYNCHRONOUS BUCK CONVERTER CONTROL

Soft-Start control is provided for each of the DC-DC synchronous buck converters, using the

DCm_SOFT_START register fields. When a DC-DC Converter is switched on, the soft-start circuit will

apply current limiting in order to control the in-rush current. For DC-DC1 and DC-DC2, the current

limit is increased through up to 8 stages to the full load condition. The DCm_SOFT_START registers

select the duration of these stages. (Note that, under light loads, the full start-up may be achieved in

fewer than 8 stages.) A similar function is provided for DC-DC3 and DC-DC4, but only 3 intermediate

stages are implemented for these converters.

When DC-DC3 or DC-DC4 is operating in Hysteretic Mode, the maximum DC output current can be

set using the DC3_STNBY_LIM and DC4_STNBY_LIM registers. See Section 15.4.1 for details of the

DC-DC3 and DC-DC4 operating modes.

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