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MAX9723
(Rev.:2005)

Stereo DirectDrive Headphone Amplifier with BassMax, Volume Control, and I2C

Maxim Integrated 

Stereo DirectDrive Headphone Amplifier with

BassMax, Volume Control, and I2C

PIN

THIN QFN

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

EP

BUMP

UCSP

D1

C1

B1

A1

B2

A2

A3

B3

A4

B4

C4

D4

C3

D3

D2

C2

—

Pin Description

NAME

VDD

C1P

PGND

C1N

SCL

PVSS

SDA

SHDN

SGND

INL

INR

SVSS

BBR

OUTR

OUTL

BBL

EP

FUNCTION

Power-Supply Input. Bypass VDD to PGND with a 1µF capacitor.

Charge-Pump Flying Capacitor Positive Terminal

Power Ground. Connect to SGND.

Charge-Pump Flying Capacitor Negative Terminal

Serial Clock Input. Connect a 10kΩ pullup resistor from SCL to VDD.

Charge-Pump Output. Connect to SVSS. Bypass PVSS with a 1µF capacitor

to PGND.

Serial-Data Input. Connect a 10kΩ pullup resistor from SDA to VDD.

Shutdown. Drive SHDN low to disable the MAX9723. Connect SHDN to VDD while bit 7

is high for normal operation (see the Command Register section).

Signal Ground. Connect to PGND.

Left-Channel Input

Right-Channel Input

Headphone Amplifier Negative Power-Supply Input. Connect to PVSS.

Right BassMax Input. Connect an external lowpass filter between OUTR and BBR to

apply bass boost to the right-channel output. Connect BBR to SGND if BassMax is not

used (see the BassMax (Bass Boost) section).

Right Headphone Output

Left Headphone Output

Left BassMax Input. Connect an external lowpass filter between OUTL and BBL to

apply bass boost to the right-channel output. Connect BBL to SGND if BassMax is not

used (see the BassMax (Bass Boost) section).

Exposed Paddle. Connect EP to SVSS or leave unconnected.

Detailed Description

The MAX9723 stereo headphone amplifier features

Maxim’s patented DirectDrive architecture, eliminating

the large output-coupling capacitors required by con-

ventional single-supply headphone amplifiers. The

MAX9723 consists of two 62mW Class AB headphone

amplifiers, hardware/software shutdown control, inverting

charge pump, integrated 32-level volume control,

BassMax circuitry, comprehensive click-and-pop sup-

pression circuitry, and an I2C-compatible interface (see

the Functional Diagram/Typical Operating Circuit). A

negative power supply (PVSS) is created internally by

inverting the positive supply (VDD). Powering the ampli-

fiers from VDD and PVSS increases the dynamic range of

the amplifiers to almost twice that of other single-supply

amplifiers, increasing the total available output power.

The MAX9723 DirectDrive outputs are biased at SGND

(see Figure 1). The benefit of this 0V bias is that the

amplifier outputs do not have a DC component, elimi-

nating the need for large DC-blocking capacitors.

Eliminating the DC-blocking capacitors on the output

saves board space, system cost, and improves low-fre-

quency response.

An I2C-compatible interface allows serial communica-

tion between the MAX9723 and a microcontroller. The

MAX9723 is available with two different I2C addresses

allowing two MAX9723 ICs to share the same bus (see

Table 1). The internal command register controls the

shutdown status of the MAX9723, enables the BassMax

circuitry, sets the maximum gain of the amplifier, and

sets the volume level (see Table 2). The MAX9723’s

BassMax circuitry improves audio reproduction by

boosting the bass response of the amplifier, compen-

sating for any low-frequency attenuation introduced by

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