WM8580
Production Data
Figure 35 and Figure 36 show typical power up scenarios in a real system. Both AVDD and DVDD
must be established, and VMID must have reached the threshold Vporr before the device is ready
and can be written to. Any writes to the device before Device Ready will be ignored.
Figure 35 shows DVDD powering up before AVDD. Figure 36 shows AVDD powering up before
DVDD. In both cases, the time from applying power to Device Ready is dominated by the charge
time of VMID.
A 4.7µF capacitor (minimum) is recommended for decoupling on VMID. The charge time for VMID
will dominate the time required for the device to become ready after power is applied. The time
required for VMID to reach the threshold is a function of the VMID resistor string and the decoupling
capacitor. To reduce transient audio effects during power on, the stereo DACs on the WM8580 have
their outputs clamped to VMID at power-on. This increases the capacitive loading of the VMID
resistor string, as the DAC output AC coupling capacitors must be charged to VMID, and hence the
required charge time. To ensure minimum device startup time, the VMIDSEL bit is set by default,
thus reducing the impedance of the resistor string. If required, the VMID string can be restored to a
high impedance state to save power once the device is ready.
REGISTER ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
R29
ADC CONTROL 1
1Dh
8
VMIDSEL
1
VMID Impedance Selection
0 = High impedance, power
saving
1 = Low impedance, fast power-
on
DEVICE ID READBACK
Reading from registers R0, R1 and R2 returns the device ID and revision number. R0 returns 80h,
R1 returns 85h, R2 returns the device revision number. Device ID readback is not possible in
continuous readback mode (CONTREAD=1).
HARDWARE CONTROL MODE
The WM8580 can be controlled in Hardware Control Mode or Software Control Mode. The method of
control is determined by the state of the HWMODE pin. If the HWMODE pin is low, Software Control
Mode is selected. If the HWMODE pin is high, Hardware Control Mode is selected.
In Hardware Control Mode the user has limited control over the features of the WM8580. Most of the
features will assume their default settings but some can be modified using external pins.
HWMODE
SWMODE
0
1
0
1
Software Control Hardware Control
2-wire control
3-wire control
Table 69 Hardware/Software Mode Setup
DIGITAL ROUTING CONTROL
See page 22 for a more detailed explanation of the Digital Routing Options within the WM8580. In
Software Control Mode, the values of register bits DAC_SRC, PAIFTX_SRC and TXSRC configure
the signal path routing between interfaces. In hardware mode, similar control can be achieved via
pins DR1, DR2, DR3 and DR4 as detailed in Table 70 and Table 71.
PIN
DR1
DR2
0
1
DAC_SRC=S/PDIF receiver
DAC_SRC=PAIF receiver
PAIFTX_SRC=ADC output
PAIFTX_SRC=S/PDIF
receiver
Table 70 DR1 / DR2 Operation
PD Rev 4.3 August 2007
72
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
