Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsLinear ICsLinear IC - Audio amplifier Headphones (2-channel, stereo) Class AB TQFN 12 (3x3)

General Description

The MAX9724C/MAX9724D stereo headphone ampli-

fiers are designed for portable equipment where board

space is at a premium. These devices use a unique,

DirectDrive

architecture to produce a ground-refer-

enced output from a single supply, eliminating the need

for large DC-blocking capacitors, saving cost, board

space, and component height. The MAX9724 sup-

presses RF radiation received by input and supply

traces acting as antennas and prevents the amplifier

from demodulating the coupled noise. The MAX9724C

offers an externally adjustable gain while the

MAX9724D has an internally preset gain of -1.5V/V. The

MAX9724C/MAX9724D deliver up to 60mW per channel

into a 32Ω load and have low 0.02% THD+N. An 80dB

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

these devices to operate from noisy digital supplies

without an additional linear regulator. Comprehensive

click-and-pop circuitry suppresses audible clicks and

pops on startup and shutdown.

The MAX9724C/MAX9724D operate from a single 2.5V

to 5.5V supply, consume only 3.5mA of supply current,

feature short-circuit and thermal-overload protection,

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

temperature range. The devices are available in tiny

12-bump UCSP™ (1.5mm x 2mm) and 12-pin thin QFN

(3mm x 3mm x 0.8mm) packages.

Applications

Features

♦ Improved RF Noise Rejection (Up to 67dB Over

Typical Amplifiers)

♦ No Bulky DC-Blocking Capacitors Required

♦ Low-Power Shutdown Mode, < 0.1µA

♦ Adjustable Gain (MAX9724C) or Fixed -1.5V/V

Gain (MAX9724D)

♦ Low 0.02% THD+N

♦ High PSRR (80dB at 1kHz) Eliminates LDO

♦ Integrated Click-and-Pop Suppression

♦ 2.5V to 5.5V Single-Supply Operation

♦ Low Quiescent Current (3.5mA)

♦ Available in Space-Saving Packages

12-Bump UCSP (1.5mm x 2mm)

12-Pin Thin QFN (3mm x 3mm x 0.8mm)

MAX9724C/MAX9724D

Low RF Susceptibility DirectDrive Stereo Head-

phone Amplifier with 1.8V Compatible Shutdown

________________________________________________________________

Maxim Integrated Products

Ordering Information

19-4130; Rev 0; 5/08

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.

PART

GAIN (V/V)

PIN-PACKAGE

TOP

MARK

MAX9724CEBC+T

Adj. 12 UCSP +AGE

MAX9724CETC+

Adj.

12 TQFN-EP*

+ABJ

MAX9724DEBC+T

-1.5 12 UCSP +AEH

MAX9724DETC+

-1.5

12 TQFN-EP*

+ABK

Note: All devices specified over the -40°C to +85°C operating

range.

Denotes a lead-free package.

T = Tape and reel.

EP = Exposed pad.

Cellular Phones

MP3 Players

Notebook PCs

Handheld Gaming Consoles

LEFT

AUDIO

INPUT

RIGHT

AUDIO

INPUT

SHDN

MAX9724C

LEFT

AUDIO

INPUT

RIGHT

AUDIO

INPUT

MAX9724D

SHDN

DirectDrive OUTPUTS

ELIMINATE DC-BLOCKING

CAPACITORS

DirectDrive OUTPUTS

ELIMINATE DC-BLOCKING

CAPACITORS

FIXED GAIN ELIMINATES

EXTERNAL RESISTOR

NETWORK

Block Diagrams

Pin Configurations appear at end of data sheet.

DVD Players

Smart Phones

PDAs

DirectDrive is a registered trademark of

Maxim Integrated Products, Inc.

UCSP is a trademark of Maxim Integrated Products, Inc.

Summary of content (19 pages)

PAGE 1
9-4130; Rev 0; 5/08 Low RF Susceptibility DirectDrive Stereo Headphone Amplifier with 1.8V Compatible Shutdown The MAX9724C/MAX9724D stereo headphone amplifiers are designed for portable equipment where board space is at a premium. These devices use a unique, 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.
PAGE 2
MAX9724C/MAX9724D Low RF Susceptibility DirectDrive Stereo Headphone Amplifier with 1.8V Compatible Shutdown ABSOLUTE MAXIMUM RATINGS VDD to GND ..............................................................-0.3V to +6V Continuous Input Current into PVSS .................................260mA PVSS to SVSS ........................................................-0.3V to +0.3V Continuous Input Current (any other pin) .........................±20mA PGND to SGND ................................................
PAGE 3
Low RF Susceptibility DirectDrive Stereo Headphone Amplifier with 1.8V Compatible Shutdown (VDD = 5V, PGND = SGND, SHDN = 5V, C1 = C2 = 1µF, RL = ∞, resistive load reference to ground; for MAX9724C gain = -1.5V/V (RIN = 20kΩ, RF = 30kΩ); for MAX9724D gain = -1.5V/V (internally set), TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C, unless otherwise noted.
PAGE 4
Typical Operating Characteristics (VDD = 5V, PGND = SGND = 0V, SHDN = VDD, C1 = C2 = 1µF, RL = ∞, gain = -1.5V/V (RIN = 20kΩ, RF = 30kΩ for the MAX9724C), THD+N measurement bandwidth = 22Hz to 22kHz, both outputs driven in phase, TA = +25°C, unless otherwise noted.) TOTAL HARMONIC DISTORTION PLUS NOISE vs. OUTPUT POWER (TQFN) TOTAL HARMONIC DISTORTION PLUS NOISE vs.
PAGE 5
Low RF Susceptibility DirectDrive Stereo Headphone Amplifier with 1.8V Compatible Shutdown POUT = 5mW VDD = 3V RL = 32Ω 1 VDD = 3V RL = 32Ω 0.1 THD+N (%) THD+N (%) POUT = 10mW THD+N (%) 0.1 0.1 POUT = 8mW POUT = 8mW 0.01 0.01 0.01 MAX9724 toc12 1 MAX9724 toc11 VDD = 3V RL = 16Ω MAX9724 toc10 1 TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY (UCSP) TOTAL HARMONIC DISTORTION PLUS NOISE vs. FREQUENCY (TQFN) TOTAL HARMONIC DISTORTION PLUS NOISE vs.
PAGE 6
Typical Operating Characteristics (continued) (VDD = 5V, PGND = SGND = 0V, SHDN = VDD, C1 = C2 = 1µF, RL = ∞, gain = -1.5V/V (RIN = 20kΩ, RF = 30kΩ for the MAX9724C), THD+N measurement bandwidth = 22Hz to 22kHz, both outputs driven in phase, TA = +25°C, unless otherwise noted.) 50 40 1% THD+N 10% THD+N 60 50 40 30 20 20 10 10 0 1% THD+N 3.0 3.5 4.0 4.5 5.0 5.5 1% THD+N 10 0 2.5 3.0 3.5 4.0 4.5 5.0 10 5.5 100 1000 OUTPUT POWER vs. LOAD RESISTANCE (UCSP) OUTPUT POWER vs.
PAGE 7
Low RF Susceptibility DirectDrive Stereo Headphone Amplifier with 1.8V Compatible Shutdown OUTPUT POWER vs. LOAD RESISTANCE AND CHARGE-PUMP CAPACITOR SIZE (TQFN) CROSSTALK vs. FREQUENCY -40 -60 RIGHT TO LEFT -80 50 C1 = C2 = 0.47μF 40 VDD = 5V fIN = 1kHz THD+N = 1% 30 20 -120 10 100 10k 1k 0 100k 50 OUTPUT POWER vs. LOAD RESISTANCE AND CHARGE-PUMP CAPACITOR SIZE (UCSP) C1 = C2 = 2.2μF OUTPUT SPECTRUM vs.
PAGE 8
Typical Operating Characteristics (continued) (VDD = 5V, PGND = SGND = 0V, SHDN = VDD, C1 = C2 = 1µF, RL = ∞, gain = -1.5V/V (RIN = 20kΩ, RF = 30kΩ for the MAX9724C), THD+N measurement bandwidth = 22Hz to 22kHz, both outputs driven in phase, TA = +25°C, unless otherwise noted.) ENTERING SHUTDOWN VSHDN 5V/div MAX9724 toc34 EXITING SHUTDOWN MAX9724 toc33 MAX9724C/MAX9724D Low RF Susceptibility DirectDrive Stereo Headphone Amplifier with 1.
PAGE 9
Low RF Susceptibility DirectDrive Stereo Headphone Amplifier with 1.8V Compatible Shutdown MAX9724C/MAX9724D Detailed Description The MAX9724C/MAX9724D stereo headphone amplifiers feature Maxim’s DirectDrive architecture, eliminating the large output-coupling capacitors required by conventional single-supply headphone amplifiers.
PAGE 10
the MAX9724 addresses the problem of the RF susceptibility by rejecting RF noise and preventing it from coupling into the audio band. The RF susceptibility of an amplifier can be measured by placing the amplifier in an isolated chamber and subjecting it to an electric field of known strength. If the electric field is modulated with an audio band signal, a percentage of the modulated signal is demodulated and amplified by the device in the chamber.
PAGE 11
Low RF Susceptibility DirectDrive Stereo Headphone Amplifier with 1.8V Compatible Shutdown The MAX9724C/MAX9724D have two power dissipation sources; a charge pump and the two output amplifiers. If power dissipation for a given application exceeds the maximum allowed for a particular package, reduce VDD, increase load impedance, decrease the ambient temperature, or add heatsinking to the device.
PAGE 12
MAX9724C/MAX9724D Low RF Susceptibility DirectDrive Stereo Headphone Amplifier with 1.8V Compatible Shutdown pump’s load regulation and output resistance. A C1 value that is too small degrades the device’s ability to provide sufficient current drive, which leads to a loss of output voltage. Increasing the value of C1 improves load regulation and reduces the charge-pump output resistance to an extent. See the Output Power vs.
PAGE 13
Low RF Susceptibility DirectDrive Stereo Headphone Amplifier with 1.8V Compatible Shutdown RMS OUTPUT VOLTAGE vs. SUPPLY VOLTAGE RMS OUTPUT VOLTAGE (V) 3.5 fIN = 1kHz RL = 10kΩ THD+N = 1% 3.0 LIMITED BY ABS. MAXIMUM RATINGS 2.5 2.0 1.5 2.5 3.0 3.5 4.0 4.5 5.0 sinusoidal signal equates to approximately 5.7VP-P, which means that the audio system designer cannot simply run the lineout stage from a (typically common) 5V supply—the resulting output swing would be inadequate.
PAGE 14
To suppress this noise, and to provide a 2VRMS standard audio output level from a single 5V supply, the MAX9724C can be configured as a line driver and active lowpass filter. Figure 5 shows the MAX9724C connected as 2-pole Rauch/multiple feedback filter with a passband gain of 6dB and a -3dB (below passband) cutoff frequency of approximately 27kHz (see Figure 6 for the Gain vs. Frequency plot). Layout and Grounding Proper layout and grounding are essential for optimum performance.
PAGE 15
Low RF Susceptibility DirectDrive Stereo Headphone Amplifier with 1.8V Compatible Shutdown VDD 0.1μF 15kΩ 1μF 15kΩ INR VDD PVDD BIAS OUTR+ OUTR- 1μF MAX9710 GND PGND MUTE 0.1μF 15kΩ OUTL- SHDN OUTL+ INL VDD 15kΩ μCONTROLLER 100kΩ 100kΩ 0.1μF STEREO DAC OUTL SHDN O.47μF MAX9724D OUTR INL SGND O.
PAGE 16
Low RF Susceptibility DirectDrive Stereo Headphone Amplifier with 1.8V Compatible Shutdown MAX9724C/MAX9724D Functional Diagram/Typical Operating Circuits 2.7V TO 5.5V ON C3 1μF OFF CIN R IN* 0.
PAGE 17
Low RF Susceptibility DirectDrive Stereo Headphone Amplifier with 1.8V Compatible Shutdown 2.7V TO 5.5V ON C3 1μF OFF LEFT AUDIO INPUT CIN 0.47μF 12 (B1) 5 (A2) 6 (B3) VDD SHDN INL RIN* 20kΩ RF* 30kΩ VDD 11 OUTL (A4) HEADPHONE JACK 1 (C1) C1P VSS UVLO/ SHUTDOWN CONTROL CLICK-AND-POP SUPPRESSION CHARGE PUMP C1 1μF SGND VDD 3 (C3) C1N MAX9724D OUTR RIN 20kΩ 10 (A3) SVSS RF 30kΩ PVSS SVSS PGND 4 (C4) C2 1μF 9 (B4) 2 (C2) SGND 7 (A1) CIN RIGHT 0.
PAGE 18
Low RF Susceptibility DirectDrive Stereo Headphone Amplifier with 1.
PAGE 19
Low RF Susceptibility DirectDrive Stereo Headphone Amplifier with 1.8V Compatible Shutdown PACKAGE TYPE PACKAGE CODE DOCUMENT NO. 12 UCSP B12-1 21-0104 12 TQFN-EP T1233-1 21-0136 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.