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MAX9723AETE

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

Maxim Integrated 

MAX9723

Stereo DirectDrive Headphone Amplifier

with BassMax, Volume Control, and I2C

COMMAND BYTE IS STORED ON

RECEIPT OF STOP CONDITION

ACKNOWLEDGE FROM MAX9723

B7 B6 B5 B4 B3 B2 B1 B0

S SLAVE ADDRESS

0 ACK COMMAND BYTE

ACK P

R/W

ACKNOWLEDGE

FROM MAX9723

Figure 6. Write Data Format Example

The MAX9723A and MAX9723B have a maximum

gain setting of -5dB or 0dB, while the MAX9723C and

MAX9723D have a maximum gain setting of +1dB or

+6dB. B5 in the command register programs the maxi-

mum gain (see Tables 5 and 6).

Adjust the MAX9723’s amplifier gain with the volume

control bits [4:0]. The gain is adjustable to one of 32 steps

ranging from full mute to the maximum gain programmed

by B5. Tables 7–10 list all the possible gain settings for

the MAX9723. Figures 7–10 show the volume control

transfer functions for the MAX9723.

Power-On Reset

The contents of the MAX9723’s command register at

power-on are shown in Table 11.

Applications Information

Power Dissipation and Heat Sinking

Linear power amplifiers can dissipate a significant amount

of power under normal operating conditions. The maxi-

mum power dissipation for each package is given in the

Absolute Maximum Ratings section under Continuous

Power Dissipation or can be calculated by the following

equation:

PD (M A X )

=

TJ(M AX )

θJA

−

TA

where TJ(MAX) is +150°C, TA is the ambient temperature,

and θJA is the reciprocal of the derating factor in °C/W as

specified in the Absolute Maximum Ratings section. For

example, θJA for the thin QFN package is +59°C/W.

The MAX9723 has two power dissipation sources, the

charge pump and the two output amplifiers. If the power

dissipation exceeds the rated package dissipation, reduce

VDD, increase load impedance, decrease the ambient

Table 5. MAX9723A and MAX9723B

Maximum Gain Control

MAXIMUM GAIN (dB)

B5

-5

0

0

1

Table 6. MAX9723C and MAX9723D

Maximum Gain Control

MAXIMUM GAIN (dB)

B5

+1

0

+6

1

temperature, or add heatsinking. Large output, supply,

and ground traces decrease θJA, allowing more heat to be

transferred from the package to surrounding air.

Output Dynamic Range

Dynamic range is the difference between the noise

floor of the system and the output level at 1% THD+N.

It is essential that a system’s dynamic range be known

before setting the maximum output gain. Output clipping

will occur if the output signal is greater than the dynamic

range of the system. The DirectDrive architecture of the

MAX9723 has increased dynamic range compared to

other single-supply amplifiers.

Use the THD+N vs. Output Power in the Typical Operating

Characteristics to identify the system’s dynamic range.

Find the output power that causes 1% THD+N for a given

load. This point will indicate what output power causes the

output to begin to clip. Use the following equation to deter-

mine the peak output voltage that causes 1% THD+N for

a given load.

= V O U T _ (P −P ) 2 2(PO U T _1 % ×R L )

where POUT_1% is the output power that causes 1%

THD+N, RL is the load resistance, and VOUT_(P-P) is

the peak output voltage. After VOUT_(P-P) is identified,

determine the peak input voltage that can be amplified

without clipping:

V IN _ (P −P )

=

V O U T _ (P −P )





AV

20





10

where VIN_(P-P) is the largest peak voltage that can be

amplified without clipping, and AV is the voltage gain

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