MAX97236EVKIT+ Maxim Integrated Products, MAX97236EVKIT+ Datasheet - Page 13

• Manufacturer Part Number: MAX97236EVKIT+
• Description: Audio Modules & Development Tools MAX97236 Eval Kit
• Manufacturer: Maxim Integrated Products

Specifications of MAX97236EVKIT+

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

The IC features a low-noise microphone bias generator
and amplifier. The bias voltage resistors are selectable
through I
Ensure that V
phone bias voltage.
The microphone bias line is also used by passive single
button and passive multibutton headsets.
A microphone preamplifier provides an additional gain
of 12dB or 24dB (programmable) with low input-referred
noise and high power-supply rejection.
the configuration of the microphone bias, amplifier, and
microphone. Internal AC-coupling capacitors connect
both the microphone output and also the MBIAS line to a
differential amplifier, giving improved PSRR.
Table 1. Jack Detection and Configuration Load Limits
Figure 4. Microphone Preamplifier Simplified Schematic
Cable Shield Capacitance
Headphone Load Resistance
Headphone Load Inductance
Audio Line Load Resistance
Microphone Load Resistance
2
C register 0x09.
MBIAS
MICVDD
MAX97236
PARAMETER
is greater than the desired micro-
Microphone Preamplifier
Audio Amplifier with Jack Detection
Microphone Bias
Figure 4
SYMBOL
C
R
R
CABLE
R
L
LINE
MIC
HP
HP
shows
The IC features a detection scheme that senses when a
3.5mm plug is inserted into the system jack. After sensing
insertion, a configuration detection algorithm takes over
and reads the makeup of the installed plug. Information
regarding the makeup of the plug is reported back through
the I
autoconfigure mode. This mode allows the IC to automati-
cally enable the correct functional blocks depending upon
the class of cable that has been inserted.
The jack insertion detection uses an inaudible AC wave-
form output on the jack pins to sense when a load is
plugged in. This electrical test is used to verify and work
in conjunction with a mechanical switch (JACKSW). The
mechanical switch, while not used as the main sensing
mechanism, can be used to save system power. When
a jack is plugged into a device, the switch at JACKSW
is closed. When no jack is plugged in, the switch at
JACKSW is open. When the jack switch at JACKSW is
working, the electrical polling of the jack can be done
less often. A test is done every time a jack is sensed to
check if the switch at JACKSW is working correctly. If
the IC deems that the switch at JACKSW is broken, the
system is flagged. At that point, the system can decide
whether to ignore JACKSW results and poll more quickly.
The jack detection and configuration is bounded by
certain load resistance and capacitance limitations. The
correct detection and configuration cannot be guaran-
teed outside those limitations. The limitations are shown
in
Table 1
the IC’s jack configuration algorithm and which class of
cable is found. The status bits of the I
0x02, 0x03) report the load found during testing. The
functional blocks are set automatically if AUTO = 10 or
01 (register 0x01E bits 0 and 1), according to what class
of cable is detected.
MIN
150
Table
0.5
12
30
6
2
C status registers. The device can also be placed in
1.
shows each load case that is detectable with
TYP
Jack Configuration Detection
Configuration Algorithm
Jack Detection and
MAX
1600
500
650
Jack Insertion Testing
50
15
2
C register (0x01,
UNITS
pF
FH
kI
kI
I
13