19-4478; Rev 0; 10/09
Active Noise-Cancelling Solution
for Stereo Headsets
MX895A
General Description
Features
o 2.7V to 4.5V Operation
o Low Headphone Amplifier Noise
The MAX9895A is a complete audio subsystem for
active noise-cancelling (ANC) stereo headsets. The
device features three stages for each right and left
channel. A microphone preamplifier, an analog sound
processing block, and a headphone amplifier combine
to create a simple and very flexible active noise-cancel-
ing system.
o Low-Noise Microphone Preamplifiers with 2.2V
Bias
o Stereo 33mW into 16Ω Capacitorless Headphone
Amplifiers
o Microphone Output Path Available for Speech
The MAX9895A features a feed-forward architecture,
where outside microphones sense the ambient noise
and on-board analog sound processing generates the
compensation signal needed for noise reduction. This
further supports the mechanical isolation of the headset
by attenuating sound that leaks through the mechanics
of the headphone.
Transmission
o Adjustable Microphone Gain by I2C Interface or
External Resistors
o Low External Component Count
Ordering Information
The microphone preamplifiers feature programmable
gain, allowing alignment of the microphone and driver
tolerances and left-right channel matching. The head-
phone amplifiers are output capacitorless and can
deliver 33mW into a 16Ω transducer.
The MAX9895A has three modes of operation: ANC on,
PTL, and ANC off. The ANC-on mode demonstrates the
noise-canceling performance of the device. PTL (push-
to-listen) mode sends the microphone signals directly
to the headphones to temporarily listen to the surround-
ings. ANC off disables noise-canceling, but allows use
of the headphone amplifiers during music playback.
PIN-
GAIN
(V/V)
PART
TEMP RANGE
PACKAGE
MAX9895AEWX+ -40°C to +85°C
MAX9895AETL+ -40°C to +85°C
36 WLP
1
1
40 TQFN-EP*
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
Simplified Block Diagram
The MAX9895A is available in a space-saving WLP or
TQFN package and is specified over the -40°C to
+85°C extended temperature range.
MAX9895A
HEADPHONE
LEFT
ANALOG
SIGNAL PROCESSING
Applications
Noise-Cancelling Headphones/Headsets
Headsets for Mobile Communication
Mobile Phones
MICROPHONE
INPUT LEFT
MIC
PREAMP
HEADPHONE
AMP
LINE
IN LEFT
HEADPHONE
RIGHT
Portable Gaming Devices
ANALOG
SIGNAL PROCESSING
E-Books
MICROPHONE
INPUT RIGHT
MIC
PREAMP
HEADPHONE
AMP
LINE
IN RIGHT
Pin Configurations appear at end of data sheet.
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.