AD1986 Analog Devices, AD1986 Datasheet - Page 48

• Manufacturer Part Number: AD1986
• Manufacturer: Analog Devices

AD1986
JACK PRESENCE DETECTION
The AD1986 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 insure 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 (AV
resistor connected between the sense line and AV
specific resistor values for each jack are shown in Table 73. One
percent tolerance resistors should be used for all jack presence
circuitry to insure accurate detection.
AUDIO JACK STYLES (NC/NO)
The jack sense lines on the AD1986 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 AD1986 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.
Table 73. Jack Sense Mapping
Resister (1% tolerance)
4.99k
10.0k
20.0k
40.2k
SS
). Each sense line must have a single 2.49k 1%
Mnemonic
LINE IN
MIC_1/2
HP_OUT
0x
7A D11). The jack
JACK_SENSE_A
DD
. The
Jack
C
B
D
A
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JS
JS7
JS4
JS5
JS1
sense style for SENSE_B is controlled by the JSINVB bit
(Register
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 AV
resistance (sense line to AV
Table 73.
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.
0x
Mnemonic
LINE OUT
C/LFE
SURROUND
AUX IN
7A D15). Writing a 1 to these bits will configure the
Preliminary Technical Data
SS
) must equal the value specified in
JACK_SENSE_B
Jack
H
G
F
E
SS
. The total
JS
JS0
JS3
JS2
JS6