Production Data
WM8321
27 VOLTAGE AND CURRENT REFERENCES
27.1 VOLTAGE REFERENCE (VREF)
The main voltage reference generated by the WM8321 is bonded to the VREFC pin. The accuracy of
this reference is optimised by factory-set trim registers.
The voltage reference (VREF) requires an external decoupling capacitor; a 100nF X5R capacitor is
recommended, as noted in Section 30.2. Omitting this capacitor will result in increased noise on the
voltage reference; this will particularly affect the analogue LDOs.
The voltage reference circuit includes a low-power mode, which enables power consumption to be
minimised where appropriate. The low-power reference mode may lead to increased noise on the
voltage reference; this mode should only be selected when minimum power consumption is more
important than voltage stability. Note that the Low Power Reference mode is not supported when the
Auxiliary ADC function is enabled.
The Low Power Reference mode is enabled when REF_LP register is set. The Low Power Reference
mode should only be enabled when the Auxiliary ADC is disabled. Enabling the Low Power Reference
mode will lead to a malfunction of the Auxiliary ADC function.
ADDRESS
BIT
LABEL
REF_LP
DEFAULT
DESCRIPTION
Low Power Voltage Reference Control
0 = Normal
R16387
(4003h)
12
0
1 = Low Power Reference Mode select
Note that Low Power Reference Mode is
only supported when the Auxiliary ADC is
disabled.
Table 83 Low Power Voltage Reference Control
27.2 CURRENT REFERENCE (IREF)
The Power Management circuits of the WM8321 use an integrated current reference.
This current reference (IREF) requires the connection of an external resistor to the IREFR pin; a
100k (1%) resistor is recommended, as noted in Section 30.2. The WM8321 will malfunction if this
resistor is omitted.
PD, February 2012, Rev 4.0
137
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
