AD1885

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REV. 0

JACK SENSE OPERATION

The AD1885 features two Jack Sense pins (JS0 and JS1) that can be used to automatically mute the LINE_OUT and/or MONO_OUT

audio outputs. When the Jack Sense pins are connected to the output jacks, the AD1885 can sense whether an audio plug has been

inserted into a particular output jack and automatically mute the other unnecessary audio outputs.

The JS1 pin should normally be connected to the HP_OUT jack to automatically mute the MONO_OUT and LINE_OUT audio

signals, while the JS0 pin should normally be connected to the LINE_OUT jack to automatically mute the MONO_OUT signal. It is

also possible to set the D15 bit in the Jack Sense Index Register (72h), which causes JS1 to only mute the LINE_OUT signal. This

option may be desirable in certain audio configurations. Table I summarizes the Jack Sense operation.

Table I. Jack Sense Operation Table

HP_OUT Plug

LINE_OUT Plug

Audio Output States

Audio Output States

(JS1)

(JS0)

(REG 72h, D15 = 0)

(REG 72h, D15 = 1)

OUT

OUT

HP_OUT = ON

HP_OUT = ON

LINE_OUT = ON

LINE_OUT = ON

MONO_OUT = ON

MONO_OUT = ON

OUT

IN

HP_OUT = ON

HP_OUT = ON

LINE_OUT = ON

LINE_OUT = ON

MONO_OUT = MUTE

MONO_OUT = MUTE

IN

OUT

HP_OUT = ON

HP_OUT = ON

LINE_OUT = MUTE

LINE_OUT = MUTE

MONO_OUT = MUTE

MONO_OUT = ON

IN

IN

HP_OUT = ON

HP_OUT = ON

LINE_OUT = MUTE

LINE_OUT = MUTE

MONO_OUT = MUTE

MONO_OUT = MUTE

NOTE: PLUG IN = JACK SENSE HIGH, PLUG OUT = JACK SENSE LOW.

The Jack Sense inputs are active high and their functionality is enabled by default on CODEC power-up. If necessary, the Jack Sense

inputs can be individually disabled by writing to the D8 and D9 bits on the CODEC Jack Sense Index Register (72h).

The Jack Sense pins contain active internal pull-ups. If the Jack Sense inputs are not being used, they should be pulled down to

digital ground using 10 k

Ω resistors. This prevents LINE_OUT and MONO_OUT from becoming muted while the Jack Senses are

enabled.

CONNECTING THE JACK SENSES TO THE OUTPUT JACKS

Headphone Jack

The diagram on Figure 10 shows the preferred method to connect the JS1 Jack Sense line to the HP_OUT jack. This scheme requires

a stereo jack with a normally closed and isolated single switch. The switch holds the Jack Sense line low (grounded) until an audio

plug is inserted, causing the switch to open and the Jack Sense line to go high due to the CODEC internal pull-up. The R2 and R3

resistors keep the electrolytic output caps properly polarized while the HP_OUT jack is not used.

L1 600Z

L2 600Z

C4

470pF

C1

470pF

OPTIONAL EMC

COMPONENTS

ISOLATED

NC SWITCH

+

+

NOTE: LOCATE R1 CLOSE TO CODEC.

JACK SENSE LINE

TO CODEC JS1 (PIN 48)

FROM CODEC HP_OUT_R (PIN 41)

FROM CODEC HP_OUT_L (PIN 39)

HEADPHONE OUT

5

4

3

2

1

Figure 10. Jack Sense Connection to HP_OUT Jack, Using Isolated Switch

Alternatively, when an audio output jack containing an isolated switch is not available, the circuit shown on Figure 11 can be used.

While the audio plug is out, this circuit keeps the Jack Sense line state low, by the pull-down affect of R2 (with no audio present) or

by tracking the lower peaks of the HP_OUT audio signal. Once an audio plug is inserted and the jack switch opens, the Jack Sense

line switches to a high state due to the CODEC internal pull-up, which quickly charges C1 to DVDD.

The R2 and R3 resistors also keep the electrolytic output caps properly polarized while the HP_OUT jack is not used.