WM8350GEB/V Wolfson Microelectronics, WM8350GEB/V Datasheet - Page 115

• Manufacturer Part Number: WM8350GEB/V
• Description: Audio CODECs Audio CODEC plus pwr management
• Manufacturer: Wolfson Microelectronics

Specifications of WM8350GEB/V

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Production Data
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14.4.2
In Development mode, the GPIO1 pin is configured as a DO_CONF output (see Section 20), which is
asserted high to indicate that the WM8350 is about to start up. This may be used to trigger the
‘genie’ to configure the WM8350 via the secondary control interface.
Figure 65 Configuration Timing in Development Mode
On completion of the register configuration, the power-up sequence is initiated by writing a logic 1 to
the CONFIG_DONE bit. If the CONFIG_DONE bit is not set before the maximum set-up time has
elapsed (see Figure 65), then the WM8350 will revert to the OFF state.
An alternative implementation is to start up the WM8350 by setting CONFIG_DONE to ‘1’ without
first programming the converter/LDO settings. By this method, the rising edge of the /RST signal may
be used to trigger the WM8350 configuration process after the device has entered the ACTIVE state.
In this case, the DC-DC converters and LDOs turn on immediately when they are enabled (time slots
are no longer relevant because the WM8350 is already in the ACTIVE state). To reduce in-rush
current, any configuration sequence triggered by /RST should therefore include supply staggering in
software (i.e. time delays between powering up individual supply domains).
Note that, whether using DO_CONF or /RST to trigger configuration, the on-chip watchdog imposes
a time-out for configuration; if the WM8350 watchdog is not serviced, it restarts the system. This can
be prevented, if necessary, by disabling the watchdog.
By default, the DO_CONF output will be set low when the WM8350 enters the OFF state and set
high on every transition from OFF to ACTIVE, re-triggering the external ‘genie’. Also, by default, the
internal control registers will be reset when the WM8350 enters the OFF state. This behaviour can be
changed using the RECONFIG_AT_ON register bit. If RECONFIG_AT_ON is set to 0, then the
control registers will not be reset when going into the OFF state, and the DO_CONF output will
remain set high after the first powering up of the chip, regardless of subsequent state transitions.
De-selection of RECONFIG_AT_ON should be used with caution, as this can potentially lead to
system failures in some applications. If RECONFIG_AT_ON is set to 0, and an OFF event occurs,
then it is possible that control registers will not be set to the intended start-up values when the
WM8350 subsequently returns to the ON state. The impact of this will depend upon the hardware
and software of the particular target application, and is not necessarily a risk in every instance.
Please contact Wolfson Applications support if further guidance is required on this topic.
Note that RECONFIG_AT_ON should never be set to 0 in Custom Modes 01, 10 or 11. Setting this
bit to 0 may result in erroneous behaviour and deviation from the custom configuration settings.
Under default settings, the control registers are always reset in the OFF state.
The register fields DO_CONF and RECONFIG_AT_ON are defined in Table 62.
STARTING UP IN DEVELOPMENT MODE
PD, March 2010, Rev 4.2
WM8350
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