MAX9723DEVKIT+ Datasheet MAX9723DEVKIT+ | P4-P6

Gain Range and Gain Settings

The MAX9723 offers two options for the maximum vol-

ume setting (A

V_VOL

)

The MAX9723A/MAX9723B have

selectable maximum gains of -5dB or 0dB, while the

MAX9723C and MAX9723D have selectable maximum

gains of +1dB or +6dB.

The Gain Range checkbox (Figure 3) allows the user to

select between the two maximum gain ranges. See Table

2 for the corresponding gain range of each IC version.

The MAX9723 also includes a 32-level volume control

that adjusts the overall gain (A

V_VOL

) of the output

amplifiers.

Use the Gain Setting slide bar to adjust A

V_VOL

Bass Boost Select

The MAX9723 includes a bass-boost feature that com-

pensates for the headphone’s poor bass response by

increasing the amplifier gain at low frequencies

V_BOOST

). The bass-boost setting is customized by

adjusting R5, R6, and C9 for the left channel and R4,

R6, and C10 for the right channel. See the

Detailed

Description of Hardware

section.

Checking the Bass Boost Select checkbox (Figure 4)

enables bass boost. The output has additional gain

V_BOOST

) on top of the overall gain (A

V_VOL

). The

default A

V_BOOST

is +8.8dB for bass frequencies. The

absolute gain at low frequencies is equal to:

V_TOTAL

= A

V_VOL

+ A

V_BOOST

Powered Up Checkbox and Close Button

Uncheck the Powered Up checkbox (Figure 5), while

SHDN is pulled high, to shut down the MAX9723. The

EV kit software powers up in the state shown in Figure

5. Clearing the Powered Up checkbox does not reset

the internal registers.

Press the Close button (Figure 5) to quit the

MAX9723D EV kit software.

Evaluate: MAX9723A/MAX9723B/MAX9723C/MAX9723D

MAX9723D Evaluation Kit/Evaluation System

4 _______________________________________________________________________________________

Figure 3. Gain Range Checkbox and Gain Setting Slide Bar for

MAX9723 Gain Adjustments

Figure 5. Powered Up Checkbox and Close Button

VERSION GAIN RANGE (dB)

MAX9723A -5 or 0

MAX9723B -5 or 0

MAX9723C +1 or +6

MAX9723D* +1 or +6

EV kit IC version.

Table 2. MAX9723 Gain Range

Figure 4. MAX9723 Bass-Boost Feature

Evaluate: MAX9723A/MAX9723B/MAX9723C/MAX9723D

_______________________________________________________________________________________ 5

MAX9723D Evaluation Kit/Evaluation System

Detailed Description of Hardware

BassMax Component Selection

PCB components R5, R6, and C9 set the bass boost for

the left channel, while components R4, R3, and C10 set

the bass boost for the right channel (see Figure 6). The

default bass boost is +8.8dB. Changing the components

listed above modifies the bass-boost gain and frequency

response. For example, when bass boost is enabled, the

ratio of R5 and R6 sets the left-channel bass boost gain

V_BOOST_

) that is calculated using the following equa-

tion. Adjust resistors R4 and R3 to set the right-channel

bass boost.

To maintain circuit stability, the ratio:

must not exceed 1/2 (a ratio of 1/3 is recommended).

The switch that shorts BB_ to SGND, when BassMax is

disabled, can have an on-resistance as high as 300Ω.

Choose a value for R5 (R3) greater than 40kΩ to ensure

that positive feedback is negligible when BassMax is

disabled. Table 3 contains a list of R6 (R3) values, with

R5 (R4) = 47kΩ, and the corresponding low-frequency

gain.

The low-frequency boost attained by the BassMax cir-

cuit is added to the gain realized by the volume setting.

Select the BassMax gain so that the output signal

remains within the dynamic range of the MAX9723.

Output signal clipping occurs at low frequencies if the

BassMax gain boost is excessively large (refer to the

Output Dynamic Range

section in the MAX9723 data

sheet).

56+

V BOOSTL_

log=×

⎛

⎝

⎜

⎞

⎠

⎟

−

MAX9723D

OUT_

BB_

(R4)

*REFERENCE DESIGNATORS IN PARENTHESIS INDICATE RIGHT-CHANNEL COMPONENTS.

(R3)

AUDIO INPUT

BASSMAX

ENABLE

(C10)

Figure 6. Bass Boost External Components for Left Channel

R6 (R3) (kΩ) AV GAIN (dB)

39 20.6

33 15.1

27 11.3

22 8.8

15 5.7

10 3.7

Note: Reference designators in parenthesis indicate right-

channel components.

Table 3. BassMax Gain Examples—R5

(R4) = 47kΩ

GAIN PROFILE WITH AND

WITHOUT B

ASSMAX

FREQUENCY (Hz)

V_TOTAL

(dB)

10,0001000100

-2

POLE

ZERO

WITH BASSMAX

MAX9723D

R5(R3) = 47kΩ

R6 (R4) = 22.1kΩ

C9 (C10) = 0.1µF

V_VOL

= +6dB

WITHOUT BASSMAX

-4

10 100,000

Figure 7. BassMax, Gain Profile Example for A

V_VOL

= +6dB

For the left channel, capacitor C9 creates a pole and a

zero according to the following equations:

POLE

is the frequency that the gain boost begins to roll

off. f

ZERO

is the frequency that the bass-boost gain no

longer affects the transfer function and the volume-control

gain dominates. Table 4 lists capacitor values and the

corresponding poles and zeros for a given DC gain.

See Figure 7 for an example of a gain profile using

BassMax. Set the right-channel frequency response by

adjusting R4, R3, and C10.

MAX9723D EV System

The MAX9723D EV system (MAX9723DEVCMODU+ or

MAX9723DEVCMOD2+) is a complete stereo

DirectDrive headphone amplifier system consisting of

the MAX9723D EV kit and Maxim’s system command

module (CMODUSB+ or CMOD232+).

The MAX9723D EV kit provides a proven layout for

evaluating the MAX9723 and comes with the

MAX9723DETE+ installed.

CMODUSB+ and CMOD232+

Command Module

The CMODUSB+ and CMOD232+ use a proprietary

design to provide SPI- and I

C-compatible interfaces to

demonstrate various Maxim devices. Maxim reserves

the right to change the implementation of this module at

any time with no advance notice.

CMODUSB+ Power Supply

The CMODUSB+ board uses a MAX1658 linear regula-

tor. Jumper J1 selects between the 5VDC voltage that

comes from the USB connector and the MAX1658’s

regulated 3.3V output voltage. Set the CMODUSB+

jumper J1 at position 2-3 to have 3.3V output voltage to

evaluate the MAX9723D EV kit.

CMOD232+ Power Supply

The CMOD232+ board uses a MAX1659 linear regula-

tor. Jumper J1 selects either the MAX1659’s 5V default

output voltage or 3.3V output voltage. Set the

CMOD232+ jumper J1 at position 1-2 to have 3.3V out-

put voltage to evaluate the MAX9723D EV kit.

MAX9723D EV Kit Stand-Alone Operation

The MAX9723D EV kit operates without the system

command module, but the functions are limited to

power-on reset-default settings listed below:

• BassMax enabled

• Maximum gain range:

0dB for MAX9723A/MAX9723B or +6dB for

MAX9723C/MAX9723D

• Maximum gain setting

• Device enabled

Input Mode

The audio input terminals on the MAX9723D EV kit

accept stereo single-ended inputs (INR and INL).

MAX9723 I

C Address

The MAX9723 device is an I

C/SMBus™ slave and is

write only. Versions A and C have a fixed slave address

of 1001100X, and versions B and D have a fixed slave

address of 1001101X. See Table 1 for details.

CRR

POLE

ZERO

×××

−56

2 956

Evaluate: MAX9723A/MAX9723B/MAX9723C/MAX9723D

MAX9723D Evaluation Kit/Evaluation System

6 _______________________________________________________________________________________

C9 (C10) (nF) f

POLE

(Hz) f

ZERO

(Hz)

100 38 106

82 47 130

68 56 156

56 68 190

47 81 230

22 174 490

10 384 1060

Note: Reference designators in parenthesis indicate right-

channel components. Simply substitute R4 for R5, R3 for R6,

and C10 for C9 for right-channel equations.

Table 4. BassMax Pole and Zero

Examples for a Gain Boost of 8.8dB—R5

(R4) = 47kΩ and R6 (R3) = 22kΩ

SMBus is a trademark of Intel Corp.

P1-P3 P4-P6 P7-P9 P10-P10

MAX9723DEVKIT+

Mfr. #:

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Manufacturer:

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Description:

Audio IC Development Tools MAX9723A/B/C/D Eval Kit

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