19-2859; Rev 0; 4/03
50mW, DirectDrive, Stereo Headphone
Amplifier with SmartSense and Shutdown
General Description
Features
The MAX9720 stereo headphone amplifier combines
Maxim’s DirectDrive architecture and SmartSense™, an
automatic mono/stereo detection feature. Conventional
headphone amplifiers require a bulky DC-blocking
capacitor between the headphone and the amplifier.
DirectDrive produces a ground-referenced output from
a single supply, eliminating the need for large DC-
blocking capacitors, saving cost, board space, and
component height.
♦ DirectDrive Eliminates Bulky DC-Blocking
Capacitors
♦ SmartSense Automatic Short Detection
♦ Low 5mA Quiescent Current
♦ Fixed Gain Eliminates External Feedback Network
MAX9720A: -1V/V
MAX9720B: -1.41V/V
♦ 50mW per Channel Output Power
♦ Ultra-Low 0.003% THD+N
SmartSense automatically detects the presence of a
short at either the left or right amplifier output. Under a
fault condition, the shorted output is automatically dis-
abled and the stereo input signal is automatically mixed
and routed to the remaining active channel. This feature
is useful in cell phone and PDA applications where a
variety of headphone jacks with unknown loads can be
inserted into the headphone jack socket. SmartSense
prevents both damage to the amplifier and eliminates
battery drain into a shorted load.
♦ High PSRR (92dB at 217Hz)
♦ Integrated Click-and-Pop Suppression
♦ 1.8V to 3.6V Single-Supply Operation
♦ Thermal Overload Protection
♦ Available in Space-Saving Packages
16-Bump UCSP (2mm x 2mm x 0.6mm)
16-Pin TSSOP
The MAX9720 delivers up to 50mW per channel into a
16Ω load and has an ultra-low 0.003% THD+N. A high
(92dB at 217kHz) power-supply rejection ratio (PSRR)
allows the device to operate from noisy digital supplies
without additional power conditioning. The gain of the
MAX9720 is set internally, further reducing component
count. Two gain options are available (-1V/V, MAX9720A
and -1.41V/V, MAX9720B). The headphone outputs
include a comprehensive click-and-pop circuitry that
eliminates audible glitches on startup and shutdown. A
shutdown mode provides a fast 250µs turn-on time.
Ordering Information
PIN/BUMP-
PACKAGE
GAIN
(V/V)
PART
TEMP RANGE
MAX9720AEBE-T -40oC to +85oC
MAX9720BEBE-T -40oC to +85oC
16 UCSP-16
16 UCSP-16
16 TSSOP
-1
-1.41
-1
MAX9720AEUE
MAX9720BEUE
-40oC to +85oC
-40oC to +85oC
16 TSSOP
-1.41
The MAX9720 operates from a single 1.8V to 3.6V
supply and consumes only 5mA of supply current. The
MAX9720 also features thermal overload protection,
and is specified over the extended -40°C to +85°C tem-
perature range. The MAX9720 is available in a tiny
(2mm x 2mm x 0.6mm) 16-bump chip-scale package
(UCSP™) and a 16-pin TSSOP package.
Simplified Block Diagram
3.6V TO 1.8V
SUPPLY
Applications
MAX9720
R
IN
PDAs
Smart Phones
R
OUT
Cellular Phones
MP3 Players
Notebook PCs
Tablet PCs
HPS
Portable Audio Equipment
MODE1
MODE2
ALERT
+
SmartSense
L
OUT
SmartSense and UCSP are trademarks of Maxim Integrated
Products, Inc.
L
IN
Pin Configuration and Typical Application Circuit appear at
end of data sheet.
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.