General Description
The MAX9729 stereo DirectDrive™ headphone amplifi-
er features bass boost, volume control, an input mux,
and an I
2
C/SMBus™-compatible serial interface. This
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 DirectDrive architecture, elimi-
nating the need for large DC-blocking capacitors. 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 suppression
circuitry reduces audible transients during power and
shutdown cycles.
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
using the I
2
C/SMBus-compatible serial interface. A low-
power, 5µA shutdown mode is controlled through an
external logic input or the serial interface.
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).
Features
♦ DirectDrive Headphone Amplifier Eliminates
Bulky DC-Blocking Capacitors
♦ 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
♦ Industry-Leading Click-and-Pop Suppression
♦ I
2
C-Compatible 2-Wire Interface
♦ Short-Circuit Protection
♦ 1.8V to 3.6V Single-Supply Operation
♦ Available in Space-Saving, Thermally Efficient
28-Pin TQFN-EP (5mm x 5mm x 0.8mm)
MAX9729
Stereo Headphone Amplifier with BassMax,
Volume Control, and Input Mux
________________________________________________________________
Maxim Integrated Products
1
19-0857; Rev 0; 7/07
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.
EVALUATION KIT
AVAILABLE
Ordering Information
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.
