General Description
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.
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.
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.
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.
Applications
Features
♦ 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
♦ 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
MAX9720
50mW, DirectDrive, Stereo Headphone
Amplifier with SmartSense and Shutdown
________________________________________________________________ Maxim Integrated Products 1
Ordering Information
19-2859; Rev 0; 4/03
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.
Pin Configuration and Typical Application Circuit appear at
end of data sheet.
