19-4948; Rev 0; 9/09
MAX9820 Evaluation Kit
General Description
The MAX9820 evaluation kit (EV kit) demonstrates the
MAX9820 stereo headphone amplifier with external
gain and DirectDrive
®
outputs for portable applications.
Maxim’s DirectDrive technology eliminates the need for
bulky DC-blocking capacitors at the output of the
amplifier.
The MAX9820 EV kit is configured for a -1V/V gain and
is designed to operate from a 2.7V to 5.5V DC power
supply. The EV kit is capable of delivering up to 95mW
into a 32Ω load and achieves 0.005% THD+N.
♦
2.7V to 5.5V Operation
♦
Adjustable -1V/V Gain
♦
95mW Into a 32Ω Load
♦
0.005% THD+N
♦
Lead(Pb)-Free and RoHS Compliant
♦
Fully Assembled and Tested
Features
♦
No DC-Blocking Output Capacitors Required
Evaluates: MAX9820
Ordering Information
DirectDrive is a registered trademark of Maxim Integrated
Products, Inc.
PART
MAX9820EVKIT+
TYPE
EV Kit
+Denotes
lead(Pb)-free and RoHS compliant.
Component List
DESIGNATION QTY
C1, C2
2
DESCRIPTION
1µF ±10%, 50V X7R ceramic
capacitors (0805)
Murata GRM21BR71H105K
10µF ±10%, 10V X5R ceramic
capacitor (0805)
Murata GRM21BR61A106K
0.1µF ±10%, 16V X7R ceramic
capacitor (0603)
Murata GRM188R71C104K
1µF ±10%, 10V X5R ceramic
capacitors (0603)
Murata GRM188R61A105K
Not installed, miniature PCB test points
Stereo headphone jack (3.5mm)
DESIGNATION QTY
JU1
OUTL
OUTR
PGND
R1–R4
R5
1
1
1
1
4
1
DESCRIPTION
2-pin header
White miniature PCB test point
Red miniature PCB test point
Black miniature PCB test point
40.2kΩ ±1% resistors (0603)
10kΩ ±5% resistor (0603)
External gain headphone amplifier
(10 TDFN-EP*)
Maxim MAX9820ETB+
(Top Mark: AAU)
Shunt (JU1)
PCB: MAX9820 EVALUATION KIT+
C3
1
C4
1
U1
1
C5, C6
C1P, VSS
HPOUT
2
0
1
—
—
1
1
*EP
= Exposed pad.
Component Supplier
SUPPLIER
Murata Electronics North America, Inc.
PHONE
770-436-1300
WEBSITE
www.murata-northamerica.com
Note:
Indicate that you are using the MAX9820 when contacting this component supplier.
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
MAX9820 Evaluation Kit
Evaluates: MAX9820
Quick Start
Required Equipment
•
•
•
2.7V to 5.5V, 500mA power supply
One set of stereo headphones
Audio signal source
The EV kit’s gain for each channel is set to -1V/V. The
left- and right-channel gain can be adjusted by modify-
ing the ratio of the corresponding gain-setting resistors
(R1–R4). R1 and R4 set the left-channel gain, while R2
and R3 set the right-channel gain. The gain for either
channel can be adjusted to a minimum of -1V/V. The IC
delivers up to 95mW into a 32Ω load, while achieving
0.005% THD+N.
Test points OUTR, OUTL, and PGND are provided to
easily measure the output signals.
Procedure
The MAX9820 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 a shunt is installed on jumper JU1 (IC
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 VDD PCB pad.
5) Verify that the audio source output is disabled.
6) Connect the audio source ground, left signal, and
right signal to the GND, VINL, and VINR PCB pads,
respectively.
7) Plug the headphone into the HPOUT headphone jack.
8) Enable the power-supply output.
9) Enable the audio source.
10) Remove the shunt from jumper JU1 (IC enabled).
11) Verify that the headphones are playing the audio
source signal.
Shutdown (
SHDN
)
Jumper JU1 controls the shutdown pin (SHDN) of the
MAX9820, which enables and disables the MAX9820
IC. See Table 1 for jumper JU1 configuration.
Gain Setting
The default gain-setting resistors (R1–R4) configure the
gain for both the left and right channels to -1V/V. The
gain can be changed by replacing these resistors with
other surface-mount 0603 resistors. Resistors with a tol-
erance of 1% or better are recommended for optimum
performance. Use Table 2 and the following equations
to select new gain-setting resistors for the correspond-
ing channel.
RIN
>
1
2
π ×
20Hz
×
CIN
RFB
≥
10k
Ω
RIN
=
RFB
−
A
Detailed Description of Hardware
The MAX9820 EV kit features the MAX9820 stereo
headphone amplifier, in a 10-pin TDFN package with an
exposed pad, for portable applications. The MAX9820
IC features adjustable gain and DirectDrive outputs.
DirectDrive generates an internal negative supply
(-VDD) from the external positive supply (VDD), thus
biasing the output signal at 0V DC. Zero-voltage bias-
ing eliminates the need for bulky DC-blocking capaci-
tors at the output of the amplifier. The MAX9820 oper-
ates from a 2.7V to 5.5V, 500mA power supply.
where RIN is the respective input resistance, CIN is the
respective input capacitance, RFB is the respective
feedback resistance, A is the desired gain, and -3dB
frequency is set at 20Hz. The gain for either channel
can be adjusted to a minimum of -1V/V. Refer to the
MAX9820 IC data sheet for more details.
Table 1. Shutdown Selection (JU1)
SHUNT
POSITION
Installed
Not installed
SHDN
PIN
Connected to PGND
Connected to VDD
through resistor R5
MAX9820
FUNCTION
Disabled
Enabled
Table 2. Component Function
CHANNEL
Right
Left
RIN
R2
R1
RFB
R3
R4
CIN
C2
C1
2
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