Evaluates: MAX9791A
MAX9791A Evaluation Kit
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Quick Start
Recommended Equipment
Before beginning, the following equipment is needed:
• One 5V, 3A DC supply
• Two 4Ω speakers
• One stereo headphone
• Two audio signal sources
Procedure
The MAX9791A EV kit is fully assembled and tested.
Follow the steps below to verify board operation.
Caution: Do not turn on the power supply until all
connections are completed.
1) Verify that shunts are installed as follows:
JU1: Pins 2-3 (speaker amplifier enabled)
JU2: Pins 1-2 (headphone amplifier enabled)
JU3: Pins 1-2 (LDO enabled)
JU4: Installed (HPVDD connected to AVDD)
JU6: Installed (wake-on-beep function disabled)
2) Set the power-supply output to 5V.
3) Disable the power-supply output.
4) Connect the power-supply ground to the PGND
PCB pad and the power-supply positive output to
the AVDD PCB pad.
5) Verify that the audio source output is disabled.
6) Connect the audio sources’ right channels to the
SPINR and HPINR phono jacks and the left chan-
nels to the SPINL and HPINL phono jacks.
7) Plug the headphone into the HPOUT headphone jack.
8) Connect one speaker across the SPOUTL+ and
SPOUTL- PCB pads and the other speaker across
the SPOUTR+ and SPOUTR- PCB pads.
9) Enable the power-supply output.
10) Enable the audio source.
11) Verify that the headphones and speakers are playing
the audio source signal.
Detailed Description of Hardware
The MAX9791A evaluation kit (EV kit) demonstrates the
MAX9791A IC in a 28-pin TQFN package. The IC com-
bines a stereo Class D amplifier, a stereo DirectDrive
headphone amplifier, and a 120mA, 4.75V low-dropout
regulator (LDO) for notebook, tablet PC, and portable
media player applications. Maxim’s DirectDrive technol-
ogy eliminates the need for bulky DC-blocking capaci-
tors at the headphone amplifier output. The IC features
adjustable gain.
The EV kit is configured for a 12dB speaker amplifier
gain and 0dB headphone amplifier gain. The gains can
be adjusted by modifying the corresponding gain-set-
ting resistors R1–R4. R1 and R2 set the speaker amplifi-
er gain while R3 and R4 set the headphone amplifier
gain. The EV kit is designed to operate from a 4.5V to
5.5V speaker supply and an optional separate 2.7V to
5.5V headphone supply. The EV kit is capable of deliv-
ering up to 2W into a pair of 4Ω speakers, 180mW into a
32Ω headphone load, and 120mA from the LDO output.
In applications where speaker leads exceed 225mm,
replace resistors R5–R8 with a surface-mount 0805 fer-
rite bead and install surface-mount 0603 capacitors for
C11–C14. The speaker outputs do not require an output
filter as the MAX9791A relies on the inherent inductance
of the speaker coil and the natural filtering of an attached
speaker. For optimum results, use a speaker with a
series inductance > 10µH. The EV kit layout shows an
optional speaker output filter for evaluation purposes.
Shutdown
Jumpers JU1, JU2, and JU3 enable or disable the speaker
amplifier (SPKR_EN), the headphone amplifier (HP_EN),
and the LDO (LDO_EN), respectively. See Tables 1, 2,
and 3 for jumper JU1, JU2, and JU3 configuration.
Table 1. Speaker Amplifier (Jumper JU1)
