WM8711_10 Datasheet, PDF (22/47 Pages) Wolfson Microelectronics plc – Internet Audio DAC with Integrated Headphone Amplifier

Production Data
WM8711 / WM8711L
The recommended external components required to complete the application are shown in Figure 11.
HPOUT
C1
R1
AGND
AGND
Figure 11 Headphone Output Application Drawing
Recommended values are C1 = 220uF (10V electrolytic), R1 = 47k
C1 forms a DC blocking capacitor to isolate the dc of the HPOUT from the headphones. R1 form a
pull down resistor to discharge C1 to prevent the voltage at the connection to the headphones from
rising to a level that may damage the headphones.
DEVICE OPERATION
DEVICE RESETTING
The WM8711/L contains a power on reset circuit that resets the internal state of the device to a
known condition. The power on reset is applied as DCVDD powers on and released only after the
voltage level of DCVDD crosses a minimum turn off threshold. If DCVDD later falls below a minimum
turn on threshold voltage then the power on reset is re-applied. The threshold voltages and
associated hysteresis are shown in the Electrical Characteristics table.
The user also has the ability to reset the device to a known state under software control as shown in
the table below.
REGISTER
ADDRESS
0001111
Reset Register
BIT
LABEL
8:0 RESET
Table 6 Software Control of Reset
DEFAULT
DESCRIPTION
not reset
Reset Register
Writing 00000000 to register resets
device
When using the software reset. In 3-wire mode the reset is applied on the rising edge of CSB and
released on the next rising edge of SCLK. In 2-wire mode the reset is applied for the duration of the
ACK signal (approximately 1 SCLK period, refer to Figure 21).
w
PD Rev 4.4 April 2007
22