WM8994 datasheet(141/359 Pages) WOLFSON

141 / 359 page

Production Data

WM8994

PD, April 2012, Rev 4.4

141

The headphone output incorporates a common mode, or ground loop, feedback path which provides

rejection of system-related ground noise. The return path is via HPOUT1FB. This pin must be

connected to ground for normal operation of the headphone output. No register configuration is

required.

Note that the HPOUT1FB pin should be connected to GND close to the headphone jack, as illustrated

in Figure 36.

EARPIECE DRIVER OUTPUT CONFIGURATIONS

The earpiece driver outputs HPOUT2P and HPOUT2N are driven by the HPOUT2MIX output mixer,

which can take inputs from the mixer output PGAs MIXOUTLVOL and MIXOUTRVOL, or from the low

power, differential Direct Voice path IN2LP/VRXN and IN2RP/VRXP. Fine volume control is available

on the output mixer paths using MIXOUTLVOL and MIXOUTRVOL. A selectable -6dB attenuation is

available on the HPOUT2MIX output, as described in Table 67 (refer to the “Analogue Output Signal

Path” section).

The earpiece outputs are designed to operate in a BTL configuration, driving 50mW into a typical 16



ear speaker.

For suppression of pop noise there are two separate enables for the earpiece driver; HPOUT2_ENA

enables the output stage and HPOUT2_IN_ENA enables the mixer and input stage.

HPOUT2_IN_ENA should be enabled a minimum of 50

s before HPOUT2_ENA – see “Control Write

Sequencer” section for an example power sequence.

LINE OUTPUT CONFIGURATIONS

The four line outputs LINEOUT1P, LINEOUT1N, LINEOUT2P and LINEOUT2N provide a highly

flexible combination of differential and single-ended configurations, each driven by a dedicated output

mixer. There is a selectable -6dB gain option in each mixer to avoid clipping when mixing more than

one signal into a line output. Additional volume control is available at other locations within each of

the supported signal paths. For more information about the line output mixing options, refer to the

“Analogue Output Signal Path” section.

Typical applications for the line outputs (single-ended or differential) are:



Handset or headset microphone output to external voice CODEC



Stereo line output



Output to external speaker driver(s) to support additional loudspeakers

When single-ended mode is selected for either LINEOUT1 or LINEOUT2, a buffered VMID must be

enabled as a reference for the outputs. This is enabled by setting the LINEOUT_VMID_BUF_ENA bit

as defined in Table 76.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R56 (0038h)

AntiPOP (1)

LINEOUT_VMID_BUF_E

Enables VMID reference for line

outputs in single-ended mode

0 = Disabled

1 = Enabled

Table 76 LINEOUT VMID Buffer for Single-Ended Operation

WM8994 Datasheet(PDF) 141 Page - Wolfson Microelectronics plc

WM8994 Datasheet(HTML) 141 Page - Wolfson Microelectronics plc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL