General Description

The MAX9721 fixed-gain, stereo headphone amplifier

is ideal for portable equipment where board space is at a

premium. The MAX9721 uses a unique, patented

DirectDrive architecture to produce a ground-referenced

output from a single supply, eliminating the need for large

DC-blocking capacitors, saving cost, board space, and

component height. Fixed gains of -2V/V (MAX9721A),

-1.5V/V (MAX9721B), and -1V/V (MAX9721C) further

reduce external component count.

The MAX9721 delivers up to 20mW per channel into a

32Ω load and achieves 0.006% THD+N. An 80dB at

1kHz power-supply rejection ratio (PSRR) allows the

MAX9721 to operate from noisy digital supplies without

an additional linear regulator. The MAX9721 includes

±8kV ESD protection on the headphone output.

Comprehensive click-and-pop circuitry suppresses

audible clicks and pops at startup and shutdown. A

low-power shutdown mode reduces supply current to

1.0µA (typ).

The MAX9721 operates from a single 0.9V to 1.8V sup-

ply allowing the device to be powered directly from a

single AA or AAA battery. The MAX9721 consumes only

2.2mA of supply current, provides short-circuit protection,

and is specified over the extended -40°C to +85°C tem-

perature range. The MAX9721 is available in a tiny

(1.54mm x 2.02mm x 0.6mm), 12-bump chip-scale

package (UCSP™) and a 12-pin thin QFN package

(4mm x 4mm x 0.8mm).

Applications

Features

♦ Single Cell, 0.9V to 1.8V Single-Supply Operation

♦ Fixed Gain Eliminates External Feedback Network

MAX9721A: -2V/V

MAX9721B: -1.5V/V

MAX9721C: -1V/V

♦ Ground-Referenced Outputs Eliminate DC Bias

♦ No Degradation of Low-Frequency Response Due

to Output Capacitors

♦ 20mW per Channel into 32Ω

♦ Low 0.006% THD+N

♦ High PSRR (80dB at 1kHz)

♦ Integrated Click-and-Pop Suppression

♦ Low Quiescent Current (2.2mA)

♦ Low-Power Shutdown Control

♦ Short-Circuit Protection

♦ ±8kV ESD-Protected Amplifier Outputs

♦ Available in Space-Saving Packages

12-Bump UCSP (1.54mm x 2.02mm x 0.6mm)

12-Pin Thin QFN (4mm x 4mm x 0.8mm)

1V, Fixed-Gain, DirectDrive, Stereo Headphone

Amplifier with Shutdown

________________________________________________________________ Maxim Integrated Products

1

19-3167; Rev 0; 1/04

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.

Ordering Information

PART

TEMP RANGE

PIN-

PACKAGE

TOP

MARK

GAIN

(V/V)

MAX9721AEBC-T* -40

°C to +85°C 12 UCSP-12

ABP

-2

MAX9721AETC

-40

°C to +85°C 12 TQFN-EP** AADZ

-2

MAX9721BEBC-T* -40

°C to +85°C 12 UCSP-12

ABQ

-1.5

MAX9721BETC

-40

°C to +85°C 12 TQFN-EP** AAEA

-1.5

MAX9721CEBC-T*

-40

°C to +85°C 12 UCSP-12

ABR

-1

MAX9721CETC

-40

°C to +85°C 12 TQFN-EP** AAEB

-1

UCSP is a trademark of Maxim Integrated Products, Inc.

Pin Configurations appear at end of data sheet.

*Future product—contact factory for availability.

**EP = Exposed paddle.

MP3 Players

Cellular Phones

PDAs

Smart Phones

Portable Audio Equipment

DirectDrive OUTPUTS

ELIMINATE DC-BLOCKING

CAPACITORS.

C1N

C1P

OUTL

SINGLE

1.5V CELL

AA OR AAA

BATTERY

OUTR

SGND

PGND

MAX9721

INVERTING

CHARGE PUMP

INR

INL

Block Diagram