19-0857; Rev 0; 7/07
Stereo Headphone Amplifier with BassMax,
Volume Control, and Input Mux
MAX729
General Description
Features
♦ DirectDrive Headphone Amplifier Eliminates
The MAX9729 stereo DirectDrive™ headphone amplifi-
er features bass boost, volume control, an input mux,
Bulky DC-Blocking Capacitors
2
and an I C/SMBus™-compatible serial interface. This
♦ 3:1 Input Multiplexer with Digital-Fade Circuitry
♦ Software-Enabled Bass Boost
♦ 32-Step Integrated Volume Control
♦ Beep Input with Programmable Output Level
♦ Low Quiescent Current
makes the MAX9729 ideal for portable audio applica-
tions where space is at a premium and performance is
essential. The MAX9729 operates from a single 1.8V to
†
3.6V, and uses Maxim’s patented DirectDrive architec-
ture, eliminating the need for large DC-blocking capaci-
tors. The headphone amplifiers deliver 52mW into a
32Ω load, feature low 0.03% THD+N, and high 90dB
PSRR. Maxim’s industry-leading click-and-pop sup-
pression circuitry reduces audible transients during
power and shutdown cycles.
♦ Industry-Leading Click-and-Pop Suppression
2
♦ I C-Compatible 2-Wire Interface
♦ Short-Circuit Protection
♦ 1.8V to 3.6V Single-Supply Operation
♦ Available in Space-Saving, Thermally Efficient
The BassMax feature boosts the bass response of the
amplifier, improving audio reproduction for low-end
headphones. The integrated volume control features 32
discrete volume levels along with a ramping function to
ensure smooth transitions during shutdown cycles and
input selection. The MAX9729’s eight programmable
maximum gain settings allow for a wide range of input
signal levels. A 3:1 multiplexer/mixer allows the selection
and summation of multiple stereo input signal sources.
The MAX9729 also includes a dedicated BEEP input
with independent attenuation control. BassMax, volume
control, gain settings, and input selection are controlled
28-Pin TQFN-EP (5mm x 5mm x 0.8mm)
Applications
Automotive Rear Seat
Entertainment (RSE)
Portable CD/DVD/MD
Players
Cell Phones
Flat-Panel TVs
MP3/PMP Players
Ordering Information
PIN-
PACKAGE
SLAVE
PKG
PART
ADDRESS*
CODE
2
using the I C/SMBus-compatible serial interface. A low-
power, 5µA shutdown mode is controlled through an
external logic input or the serial interface.
MAX9729ETI+
28 TQFN-EP**
101000_
T2855-5
Note: This device is specified over the -40°C to +85°C operating
temperature range.
+Denotes lead-free package.
*Last digit of slave address is pin programmable.
**EP = Exposed pad.
The MAX9729 consumes only 4.8mA of supply current,
provides short-circuit and thermal-overload protection,
and is specified over the -40°C to +85°C extended tem-
perature range. The MAX9729 is available in a space-
saving 28-pin thin QFN package (5mm x 5mm x 0.8mm).
SMBus is a trademark of Intel Corp.
U.S. Patent # 7,061,327
†
Pin Configuration appears at end of data sheet.
Simplified Block Diagram
1.8V TO 3.6V
BML
BassMax
SCL
2
I C INTERFACE
SDA
MAX9729
INL1
INL2
OUTL
OUTR
MIXER
INL3
Σ
Σ
MUX
VOLUME
CONTROL
INR1
INR2
INR3
PGA
PGA
FADER
CONTROL
BEEP
BMR
BassMax
________________________________________________________________ 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.