MAX98090BEWJ+T Maxim Integrated, MAX98090BEWJ+T Datasheet - Page 146

• Manufacturer Part Number: MAX98090BEWJ+T
• Description: Interface - CODECs 5V 130mW Stereo Headphone Amp
• Manufacturer: Maxim Integrated

MAX98090
Jack Detection Interrupt Generation
Whenever a jack is inserted or removed and the state of
either LSNS or JKSNS changes, a jack detection event is
indicated with the jack configuration change flag (JDET,
Table 78). If the jack detection event is not masked
(IJDET, Table 79), it also generates an interrupt on IRQ.
The jack detection event bit (JDET) is clear on read. An
I
assertion on IRQ (if present). Unless a read occurs after
each jack detection event, both the JDET bit and the IRQ
interrupt will remain asserted and no new events or inter-
rupts can be detected.
A change in state from LSNS = 1 to LSNS = 0 indicates
that a jack has been inserted, while a change in state from
LSNS = 0 to LSNS = 1 indicates that a jack has been
removed. When an insertion occurs, if JKSNS does not
change and remains at JKSNS = 1, a headset insertion
is indicated, while a change in state from JKSNS = 1 to
JKSNS = 0 indicates headphones have been inserted. The
state transitions, and the interrupt events generated, are
ideally used for state machine control in any jack detection
software drivers.
Operation with an Internal Pullup Resistance
The device has both a strong and weak internal pullup
option. The internal pullup resistors are only active if
the device is in shutdown (SHDN = 0,Table 6) or when
MICBIAS is disabled (MBEN = 0, Table 7), and they
allow jack detection and identification to function in those
states. This functionality is ideal for cases where the
device is put into a sleep or shutdown state, but needs to
trigger a device or system level interrupt signal for wake
on insertion operation.
When JDWK is low (default, Table 70), the strong inter-
nal pullup is used (approximately 2.4kΩ referenced to
SPKLVDD). This configuration is capable of detecting and
identifying both headphone and headset insertion. When
JDWK is high, the weak internal pullup (approximately
5µA to SPKLVDD) is used. The weak internal pullup mini-
mizes the supply current after jack insertion and is ideal
for wake on insertion cases where the system might not
immediately power up. The weak internal pullup cannot
bias a microphone load, and therefore, cannot identify
headset insertion or accessory button presses.
Figure 44 details how jack detection works with the
internal pullup resistance. In case 1, jack detection is
disabled and both MICBIAS and JACKSNS are high
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2
C read clears both the JDET bit status and the interrupt
impedance. In this state, LSNS and JKSNS retain the last
valid jack detection result. In case 2, no jack is inserted
and the internal pullup resistance to SPKLVDD conducts
JACKSNS up above both the load and jack sense com-
parator thresholds. In this case, with an open circuit jack,
both the strong and weak internal pullups produce the
correct jack detection result and the only power consump-
tion is that required to bias the internal comparators. In
case 3, a headphone jack is inserted shorting JACKSNS
to ground, well below both the load and jack sense
comparator thresholds. In this state, both the strong and
weak internal pullups produce the correct jack detection
result but the strong internal pullup consumes significantly
more current than the weak internal pullup. In case 4, a
headset jack is inserted. In this state, the strong and weak
internal pullups produce different jack detection results.
The strong internal pullup biases the headset MIC (and
JACKSNS) to a level between the load sense and jack
sense comparator thresholds that produces the correct
jack detection result. The weak internal pullup, however,
is not strong enough to bias a headset MIC and as a
result it falsely reports that a headphones jack is present.
Operation with an External Pullup Resistance
The internal pullup resistance is sufficient for wake on
interrupt or basic jack detection and identification, but
an external pullup resistance to MICBIAS is required to
properly bias and current limit a headset microphone
(Figure 42). When jack detect is enabled and the device is
active (SHDN = 1, Table 6) with MICBIAS enabled (MBEN
= 1, Table 7), JACKSNS is placed into a high-impedance
state and the internal pullup resistor is disabled. In this
state, the external pullup resistor then determines the bias
voltage level at JACKSNS.
Figure 45 details the operation of jack detection with an
external pullup resistance. In Case 1, jack detection is
disabled. As a result, the internal jack detect compara-
tors are disabled and LSNS/JKSNS retain their last valid
jack detection result. In case 2, no jack is inserted and
the external pullup resistance to MICBIAS conducts
JACKSNS up above both the load and jack sense
comparator thresholds. In case 3, a headphone jack is
inserted shorting JACKSNS to ground, well below both
the load and jack sense comparator thresholds. In case 4,
a headset jack is inserted and the external pullup biases
the headset MIC (and JACKSNS) to a level between the
load sense and jack sense comparator thresholds.
Ultra-Low Power Stereo Audio Codec
Maxim Integrated │ 146