AD1986ABSTZ datasheet(53/56 Pages) AD

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AD1986A

Rev. 0 | Page 53 of 56

JACK PRESENCE DETECTION

The AD1986A uses two jack sense lines for presence detection

on up to eight external jacks. These lines, combined with the

device detection circuitry, enable software to determine whether

there is a device plugged into the circuit and what type of device

it is. With this feature, software can reconfigure jacks and

amplifiers as necessary to ensure proper audio operation.

Jack presence is detected using a resistor tree arrangement. Up

to four jacks can be sensed on a single sense line by using a

different value resistance for each jack between the sense line

and ground (AVSS). Each sense line must have a single 2.49 kΩ

1% resistor connected between the sense line and AVDD. The

specific resistor values for each jack are shown in Table 116.

One percent tolerance resistors should be used for all jack

presence circuitry to ensure accurate detection.

AUDIO JACK STYLES (NC/NO)

The jack sense lines on the AD1986A can be programmed for

use with normally-open (NO) or normally closed (NC) switch

types. Current standard stereo audio jacks have wrap-back pins

that are normally closed. New audio jacks use isolated, normally

open switches, which are required for resistive ladder jack

presence detection. Each sense group (A or B) must have the

same style of jack for presence detection to function correctly.

However, the group (A or B) sense type can be programmed

separately to accommodate systems with different styles of jacks

on the front versus rear panel.

The AD1986A defaults to the isolated, normally open switch

types on power-up. The jack sense style for SENSE_A is

controlled by the JSINVA bit (Register 0x7A Bit D11). The jack

sense style for SENSE_B is controlled by the JSINVB bit

(Register 0x7A Bit D15). Writing a 1 to these bits will configure

the corresponding sense circuit for normally closed instead of

normally open switch types.

Wrap-back jacks cannot be used in microphone-capable cir-

cuits. For this reason isolated switches are recommended. The

codec defaults to sensing No style switches and this method is

preferred.

Normally-Open Switches

If a connection is not present, do not install the sense resistor

pertaining to that connection.

If a connection is present, but there is no related switch (such as

an internal connection), install the sense resistor pertaining to

that connection.

Normally Closed Switches

Connections capable of MIC bias require isolated switches to

function correctly. When using normally closed, wrap-back

switches, the jack resistor must be split into two values. One

value connects the sense line to the jack switch and the other

connects the related audio connection to AVSS. The total

resistance (sense line to AVSS) must equal the value specified in

Table 116.

If a connection is not present, install the sense resistors

pertaining to that connection.

If a connection is present, but there is no related switch (such as

an internal connection), do not install the sense resistors

pertaining to that connection.

Table 116. Jack Sense Mapping

JACK_SENSE_A

JACK_SENSE_B

Resister (1% tolerance)

Mnemonic

Jack

Mnemonic

Jack

4.99 k

Ω

JS7

LINE OUT

JS0

10.0 k

Ω

LINE IN

JS4

C/LFE

JS3

20.0 k

Ω

MIC_1/2

JS5

SURROUND

JS2

40.2 k

Ω

HP_OUT

JS1

AUX IN

JS6

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