MAX98090AETL+ Maxim Integrated, MAX98090AETL+ Datasheet - Page 148

• Manufacturer Part Number: MAX98090AETL+
• Description: Interface - CODECs 5V 130mW Stereo Headphone Amp
• Manufacturer: Maxim Integrated

Specifications of MAX98090AETL+

• Rohs: yes

MAX98090
Figure 46. Jack Detection with Internal Analog Microphones
Accessory Button Detection
After jack insertion, the device can detect button presses
on any accessories that include a microphone and a
switch that shorts the microphone ring to ground. Button
presses can be detected either when MICBIAS is enabled
or if it is disabled and the strong internal pullup is used
(JDWK = 0). A button press changes the state of JKSNS
from 1 to 0 until the button is released, and this change
in state generates an event on the jack detection change
flag (JDET). This event is used to trigger the appropriate
action associated with the key press.
Jack Detection with Internal Analog
Microphones
If the application requires fixed internal analog
microphone(s), and must also detect, identify, and oper-
ate with a headset microphone, the general jack dete-
caion application circuit (Figure 43) does not operate
as expected. The complication introduced by an internal
analog microphone is detailed in Figure 46.
When no jack is inserted (case 1) the internal pullup resis-
tance attempts to pull JACKSNS above the load sense
www.maximintegrated.com
SINGLE-ENDED
MICROPHONE
ANALOG
MBEN = 0 OR
JDETEN = 1
JKSNS = 1
JDWK = X
SHDN = 0
LSNS = 0
OPEN
JACK
1
FALSE JACK DETECTION WITH
INTERNAL ANALOG MICROPHONE
BIAS CURRENT PATH
2.2kΩ
2.2kΩ
HI-Z
1µF
1µF
1µF
1µF
V
ANALOG
MIC INPUT 2
V
MICBIAS
V
ANALOG
MIC INPUT 1
V
JACKSNS
HPL
HPR
HPSNS
IN+
IN-
IN+
IN-
COMPARATORS
JACK DETECT
SPKLVDD
ENABLED
PULLUP
SINGLE-ENDED
MICROPHONE
comparator threshold. However, the external pullup to
MICBIAS creates an unintended current path through the
internal analog microphone pullup. As a result, the voltage at
JACKSNS is biased to a level between the jack sense and
load sense comparator thresholds, resulting in a false head-
set jack detection. When a headset jack is inserted, there is
a parallel load on JACKSNS between the inserted headset
jack and the internal analog microphone. This could poten-
tially result in a headset being reported as headphones.
A Schottky diode with a very low forward drop (case 2)
can be inserted in series with the external pullup resis-
tance. When MICBIAS is disabled, the Schottky diode
is reverse biased and the current path is blocked. When
MICBIAS is enabled, the diode is forward biased and the
external pullup to mic bias functions as detailed in Figure
45. The diode does introduce a series voltage drop, and
the MICBIAS voltage and/or the series resistance value
might need to be adjusted to compensate and ensure that
the headset MIC is properly biased. Alternatively, a switch
can be used in series either above or below the internal
analog microphone to break the bias current path when
MICBIAS is disabled.
Ultra-Low Power Stereo Audio Codec
ANALOG
MBEN = 0 OR
JDETEN = 1
JKSNS = 1
JDWK = X
SHDN = 0
LSNS = 0
OPEN
JACK
2 SCHOTTKY DIODE BLOCKS BIAS CURRENT
PATH TO INTERNAL ANALOG MICROPHONE
CURRENT PATH BLOCKED
2.2kΩ
2.2kΩ
HI-Z
1µF
1µF
1µF
1µF
Maxim Integrated │ 148
V
ANALOG
MIC INPUT 2
V
MICBIAS
V
ANALOG
MIC INPUT 1
V
JACKSNS
HPL
HPR
HPSNS
IN+
IN-
IN+
IN-
COMPARATORS
JACK DETECT
SPKLVDD
ENABLED
PULLUP