MAX14627ETAT 데이터 시트보기 (PDF) - Maxim Integrated
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MAX14627ETAT Datasheet PDF : 16 Pages
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MAX14627/MAX14628
Low-Power Headset Detectors with
SEND/END Button Support
Detailed Description
The MAX14627/MAX14628 manage headsets by inte-
grating 3.5mm jack insertion detection, microphone bias
generation, and SEND/END button press detection. Both
devices feature a low-power microphone mode to reduce
the high bias current required for microphone operation
while it is not in use. These devices require only a single
three-state input (MODE) to select between call mode
and two different low-power modes. See the Internal
LDO Regulator and SEND/END Button Press Detection
sections for details about the differences between these
two devices.
Internal LDO Regulator
The devices integrate a low-noise, low-dropout regulator
(LDO) for biasing the microphone connected to MIC. The
LDO output voltage is set at 2.2V for the MAX14627 and
2.8V for the MAX14628. The LDO is enabled and enters
low-noise mode (LNM) when the MODE input is logic-
high and a jack is detected (DETIN is low). Pull the MODE
input low or leave it open to put the LDO in low-power
shutdown mode (SDM).
Connect a 1FF capacitor from CAP to ground as close as
possible to the pin.
Microphone Operation
and Bias Voltage Generation
An externally preamplified microphone is connected to
MIC. Connect MIC to RES through an external 2.2kI
resistor to bias the microphone.
The devices generate a bias voltage (VBIAS) at RES.
VBIAS is connected to the internal LDO when the LDO is
on or connected to VCC when the LDO is off.
Microphone Low-Power Mode (MPLP)
A microphone draws a large amount of current due to the
2.2kI required bias resistor when it is connected. This
current is dissipated even when the microphone is not
in use for audio input. This allows the SEND/END button
detection to operate. The devices feature internal circuitry
to reduce this current while simultaneously detecting
SEND/END button press events.
When a jack is inserted (DETIN is low and DET is assert-
ed low) and if MODE is pulled low, these devices enter
the microphone low-power mode (MPLP). In this mode,
MIC is periodically connected to VBIAS (= VCC) through
the 2.2kI resistor to RES only for a short duration (120Fs
pulse over an 8ms period) to check for the SEND/END
button press event (switch to GND in both MAX14627/
MAX14628 and switch open in the MAX14628 only).
The devices exit MPLP when the MODE input transitions
to logic-high or to high-Z state.
Note that VBIAS is disconnected from RES when no jack is
inserted and microphone low-power mode is not entered.
Jack Insertion Detection
The devices monitor the DETIN input to detect jack inser-
tion/removal events. Debounce circuitry ensures that
transient voltages do not force the device to enter or exit
microphone low-power mode due to false jack insertion/
removal detection. DETIN input is capable of handling
±15kV HBM ESD event.
The devices are designed for sockets with a normally
open pin. Without the 3.5mm jack inserted at DETIN, the
input is pulled high by a large internal pullup resistor
(1MI). When the jack is plugged in, DETIN is pulled to
ground through the detection pin of the jack. DET is then
asserted (after 300ms debounce time) and MIC is biased
according to the logic state of the MODE input as follows:
• If MODE is low, the external 2.2kI resistor connects
MIC to VCC in pulsing mode (MPLP) waiting for a
SEND/END button press event.
• If MODE is high, the external 2.2kI resistor connects
MIC to LDO output continuously.
• If MODE is high-Z, MIC is internally pulled down.
The devices feature an internal series 100kI resistor
at DETIN and do not require a series resistor between
DETIN and the jack even when a direct drive audio out-
put is connected to DETIN through the detection pin of
the jack. DETIN withstands input voltages down to -2V.
Ensure that the total capacitance on DETIN is less than
100pF.
SEND/END Button Press Detection
The devices monitor the MIC input to detect SEND/END
button press events. The SEND/END button press with
the 4P microphone headset is detected and pulls the
SWD output low if the voltage at MIC falls below the
MIC switch to GND detection threshold (0.22 O VBIAS) for
longer than 30ms.
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