AD1981HD

Rev. 0 | Page 15 of 16

JACK PRESENCE DETECTION

HD AUDIO STYLE JACK PRESENCE DETECTION

The AD1981HD uses two jack sense lines for jack presence

detection. Combined with the peripheral enumeration engines,

this enables software to determine if there is a device plugged

into the circuit and what type of device it is. Software can also

reconfigure jacks and amplifiers as necessary, ensuring proper

audio operation and providing jack retasking.

Jack presence is detected using a resistor tree arrangement

outlined in the HD audio specification. Up to four jacks can be

sensed on a single sense line by using different value resistors

must normally have open, isolated switches to use this method

of jack presence detection.

Jack presence is reflected in the HD audio pin widget pin sense

verb. The MSB (Bit 31) indicates the current plugged state of the

connected jack. Jack change interrupts can be enabled using the

unsolicited response verb on each of these nodes. Each jack can

be set to generate a different value to provide event

identification within the software interrupt.

There are two methods to connect the codec to the jack

presence detection pins. In the first method, use a single

2.69 kΩ 1% resistor between the SENSE_A and SENSE_B lines,

but no capacitor. In the second method use a single 2.69 kΩ

1 μF of capacitance on each sense line. Designers should offer

both methods for maximum flexibility.

The specific resistor value for each jack is shown in Table 27.

Use 1% resistors for all jack presence detect circuitry to ensure

accurate detection.

CLASSIC JACK PRESENCE DETECTION

The AD1981HD GPIO pins can be used as classic jack sense

pins in JS_0- and JS_1-style operation (similar to AD1981B

operation). Only two jacks, typically line out and headphone

out, are supported in this configuration. The GPIO pins can be

connected to the left channel wrap-back switch on the jack via a

2.2 kΩ (typical) resistor. The left channel needs a 20 kΩ (typical)

resistor-to-analog ground to complete the circuit. This config-

uration allows autoconfiguration when other devices are plugged

in; for example, when headphones are plugged in, the external

speakers are disabled for private listening.

Table 27. Jack Sense Mapping

SENSE_A

SENSE_B

Resistor

(1% tolerance)

Name

Port

HD Audio Node ID

Name

Port

HD Audio Node ID

5.1 kΩ

Line Out

D

0x05

N/A

N/A

N/A

10.0 kΩ

Line In

C

0x09

N/A

N/A

N/A

20.0 kΩ

Front Microphone

B

0x08

Rear Microphone

F

0x18

39.2 kΩ

Headphone Out

A

0x06

Aux In

E

0x17