ADAU1361BCPZ-R7 datasheet(34/78 Pages) AD

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Data Sheet

ADAU1361

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common mode (AVDD/2), which is used as the virtual headphone

reference.

Figure 44. Capless Headphone Configuration Diagram

Table 19. Capless Headphone Register Settings

Bit Name

Setting

R36

DACEN[1:0]

11 = both DACs on

R22

MX3EN

1 = enable Mixer 3

MX3LM

1 = unmute left DAC input

R24

MX4EN

1 = enable Mixer 4

MX4RM

1 = unmute right DAC input

R28

MX7EN

1 = enable Mixer 7

MX7[1:0]

00 = common-mode output

R33

MONOM

1 = unmute mono output

MOMODE

1 = headphone output

R29

LHPVOL[5:0]

Desired volume for LHP output

LHPM

1 = unmute left headphone output

R30

HPMODE

1 = headphone output

RHPVOL[5:0]

Desired volume for RHP output

RHPM

1 = unmute right headphone output

Headphone Output Power-Up/Power-Down

Sequencing

To prevent pops when turning on the headphone outputs, the user

must wait at least 4 ms to unmute these outputs after enabling

the headphone output with the HPMODE bit. This is because of

an internal capacitor that must charge before these outputs can be

used. Figure 45 and Figure 46 illustrate the headphone power-up/

power-down sequencing.

For capless headphones, configure the MONOOUT pin before

unmuting the headphone outputs.

Figure 45. Headphone Output Power-Up Timing

Figure 46. Headphone Output Power-Down Timing

Ground-Centered Headphone Configuration

The headphone outputs can also be configured as ground-centered

outputs by placing coupling capacitors on the LHP and RHP pins.

Ground-centered headphones should use the AGND pin as the

ground reference.

When the headphone outputs are configured in this manner, the

capacitors create a high-pass filter on the outputs. The corner

frequency of this filter, at which point its attenuation is 3 dB, is

calculated by the following formula:

f3dB = 1/(2π × R × C)

where:

C is the capacitor value.

R is the impedance of the headphones.

For a typical headphone impedance of 16 Ω and a 47 μF capacitor,

the corner frequency is 211 Hz.

Jack Detection

When the JACKDET/MICIN pin is set to the jack detect func-tion,

a flag on this pin can be used to mute the line outputs when

headphones are plugged into the jack. This pin can be configured

in Register R2 (digital microphone/jack detection control register,

Address 0x4008). The JDFUNC[1:0] bits set the functionality of the

JACKDET/MICIN pin.

Additional settings for jack detection include debounce time

(JDDB[1:0] bits) and detection polarity (JDPOL bit). Because the

jack detection and digital microphone share a pin, both functions

cannot be used simultaneously.

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