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-

the Functional Diagram/Typical Operating Circuit). A

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.

tion between the MAX9723 and a microcontroller. The

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

Stereo DirectDrive Headphone Amplifier with

_______________________________________________________________________________________

9

Pin Description

PIN

BUMP

THIN QFN

UCSP

NAME

FUNCTION

1D1

2C1

C1P

Charge-Pump Flying Capacitor Positive Terminal

3B1

PGND

Power Ground. Connect to SGND.

4A1

C1N

Charge-Pump Flying Capacitor Negative Terminal

5B2

SCL

Serial Clock Input. Connect a 10k

6A2

to PGND.

7A3

SDA

Serial-Data Input. Connect a 10k

8B3

SHDN

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

9A4

SGND

Signal Ground. Connect to PGND.

10

B4

INL

Left-Channel Input

11

C4

INR

Right-Channel Input

12

D4

13

C3

BBR

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).

14

D3

OUTR

Right Headphone Output

15

D2

OUTL

Left Headphone Output

16

C2

BBL

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).

EP

—

EP