General Description
The MAX9814 evaluation kit (EV kit) is a fully assembled
and tested PCB that is used to evaluate the single-
supply MAX9814 low-noise microphone amplifier IC.
The MAX9814 IC contains a low-noise amplifier, an out-
put amplifier, a microphone bias-voltage generator, and
automatic gain-control (AGC) internal circuitry. The
overall gain of the microphone amplifier is selectable to
40dB, 50dB, or 60dB without compression. The
MAX9814 incorporates compressor/limiter circuitry that
limits the microphone output to a set voltage.
The MAX9814 EV kit operates over a 2.7V to 5.5V
range. The EV kit also features low quiescent current,
and shutdown control to minimize power consumption.
The MAX9814 IC is available in a 14-pin TDFN (3mm x
3mm x 0.8mm) exposed paddle package.
Features
o2.7V to 5.5V Single-Supply Operation
o20dB of Dynamic Gain Compression
oSelectable Gain Control
oProgrammable Attack Time
oSelectable Attack/Release Ratio
oLow-Power Shutdown Mode
oFully Assembled and Tested
Evaluates: MAX9814
MAX9814 Evaluation Kit
________________________________________________________________________________________________________________________________
Maxim Integrated Products
1
Ordering Information
DESIGNATION
QTY
DESCRIPTION
C1 1
0.22µF ±10%, 6.3V X5R ceramic
capacitor (0402)
TDK C1005X5R0J224K
C2, C7, C9 3
0.1µF ±10%, 10V X5R ceramic
capacitors (0402)
TDK C1005X5R1A104K
C3 1
0.047µF ±10%, 25V X7R ceramic
capacitor (0402)
TDK C1005X7R1E223K
C4 1
0.022µF ±10%, 25V X7R ceramic
capacitor (0402)
TDK C1005X7R1E223K
C5 1
2.2µF ±10%, 6.3V X5R ceramic
capacitor (0603)
TDK C1608X5R0J225K
C6 1
1µF ±10%, 6.3V X5R ceramic
capacitor (0603)
TDK C1608X5R1A105KB
C8 1
0.47µF ±10%, 6.3V X5R ceramic
capacitor (0402)
TDK C1005X5R0J474K
DESIGNATION
QTY
DESCRIPTION
J1 1 Nonswitched PC-mount RCA jack,
black
J2 1 Nonswitched PC-mount RCA jack,
red
JU1, JU2, JU3
3 3-pin headers
JU4, JU5, JU6
3 2-pin headers
R1 1 150kΩ ±1% resistor (0402)
R2 1 100kΩ ±1% resistor (0402)
R3 1 2.21kΩ ±1% resistor (0402)
U1 1 MAX9814ETD+ (14-pin TDFN)
— 6 Shunts (JU1–JU6)
— 1 PCB: MAX9814 Evaluation Kit
Component List
19-0760; Rev 0; 4/07
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
+
Denotes a lead-free and RoHS-compliant EV kit.
*
EV kit PCB temperature range only.
**EP
= exposed paddle.
PART TEMP RANGE IC PACKAGE
MAX9814EVKIT+ 0°C to +70°C* 14 TDFN-EP**
SUPPLIER PHONE WEBSITE
TDK Corp. 847-803-6100 www.component.tdk.com
Component Supplier
Note: Indicate that you are using the MAX9814 when contacting
this component supplier.
Evaluates: MAX9814
MAX9814 Evaluation Kit
2______________________________________________________________________________________________________________________________________________________________________________
Quick Start
Recommended Equipment
• 5V 200mA power supply
• Function generator
• Digital multimeter (DMM)
• Oscilloscope
Procedure
The MAX9814 EV kit is fully assembled and tested.
Follow the steps listed below to verify board operation.
Caution: Do not turn on the power supply until all
connections are completed:
1) Verify that shunts are installed across pins 1-2 of
jumpers JU1 (MAX9814 enabled), JU2 (gain =
40dB), and JU3 (attack/release ratio = 1:2000).
2) Verify that a shunt is not installed across jumpers
JU4, JU5, JU6 (attack time ≈53µs).
3) Set the power supply to 5V.
4) Set the function generator’s output for a sine wave
with 10mVP-P, 1kHz frequency, and 0V offset.
5) Turn off the power supply and function generator.
6) Connect channel 1 of the oscilloscope to the
MIC_IN pad and channel 2 of the oscilloscope to
the MIC_OUT pad. Connect the ground leads of the
oscilloscope to the respective SGND_ pads.
7) Connect the 5V terminal of the power supply to the
VCC pad and the ground terminal of the power sup-
ply to the GND pad.
8) Connect the positive output of the function genera-
tor to the MIC_IN pad on the EV kit and the ground
lead of the function generator to the SGND_IN pad.
9) Connect the positive terminal of the digital multime-
ter to the TH pad and the ground terminal to the
GND pad.
10) Turn on the power supply.
11) Verify that the TH voltage is approximately 800mV.
12) Turn on the function generator.
13) Using the oscilloscope, verify that the signal at the
MIC_OUT pad is 1VP-P.
14) Increase the function generator to 50mVP-P.
15) Verify that MIC_OUT amplitude is 1.6VP-P.
Detailed Description
The MAX9814 EV kit is used to evaluate the MAX9814
low-noise microphone amplifier IC, which is designed
for single-supply applications. The power supply must
provide a minimum 200mA to the MAX9814 EV kit,
which has an operating range of 2.7V to 5.5V.
The MAX9814 IC contains a low-noise amplifier, a vari-
able gain amplifier (VGA) with automatic gain control,
an output amplifier, and a microphone bias-voltage
generator. The low-noise preamplifier gain is fixed to a
12dB gain, while the VGA has a dynamic gain from 0dB
to 20dB and the output amplifier has gains of 8dB,
18dB, and 28dB. Without compression, the sum of all of
the gain blocks result in an overall gain of 40dB, 50dB,
or 60dB. The MAX9814 IC incorporates attack-/hold-
and-release timing circuitry that limits the MICOUT pin
to a set voltage.
The MAX9814 compression circuitry monitors MICOUT
and limits the peak voltage to TH. Gain compression is
realized by the VGA, which automatically adjusts its
gain to keep the output voltage peak equal to the set
threshold. The VGA has 20dB of dynamic gain, which
results in a maximum gain compression of 20dB. The
amplifier overall gain, with the AGC disabled, can be
set to 40dB, 50dB, or 60dB using jumper JU2. With the
AGC on and the output voltage fully compressed, the
overall gain will be 20dB, 30dB, or 40dB.
The amplifier’s output is compressed when the peak
voltage amplitude at MICOUT exceeds the voltage set
at TH. The MAX9814 EV kit compression threshold is
preset at 800mV. A custom threshold voltage can be
programmed using resistors R1 and R2, and the 2V
microphone bias output MICBIAS. Removing resistor
R1 and applying a voltage source at the TH pad can
also externally control the MICOUT threshold.
The input signal can either be applied to the RCA jack
J2, or a microphone can be connected between the
MIC_IN and SGND_IN pads. The 2V microphone bias
MICBIAS is connected to the MIC_IN node via R3.
The MAX9814 attack time and attack/release ratio are
set through jumpers JU3–JU6.
Jumper Selection
Shutdown
Jumper JU1 controls the shutdown mode of the
MAX9814 EV kit . The shutdown function can be activat-
ed on the EV kit by installing a shunt across pins 2-3.
The shutdown function can also be controlled by
removing the shunt on jumper JU1 and connecting an
external controller to the SHDN pad. See Table 1 for
jumper JU1 shutdown configurations.
Gain Control
The MAX9814 maximum signal gain can be configured
to 40dB, 50dB, or 60dB. Jumper JU2 selects the overall
gain for the MAX9814 EV kit. See Table 2 for jumper
JU2 gain control configurations.
Attack/Release Ratio Setting
Jumper JU3 sets the ratio of the attack time to the release
time of the MAX9814 AGC circuit to ratios of 1:500,
1:2000, and 1:4000. See Table 3 for configuring the
desired attack/release ratio using jumper JU3 position.
Jumpers JU4, JU5, and JU6 configure the attack time.
Capacitor C4 sets the attack time to 53µs. To increase
the attack time, configure the shunts on JU4, JU5,
and/or JU6, which change the total capacitance con-
nected at the MAX9814 CT pin. See Table 4 for
jumpers JU4, JU5, and JU6 configurations. Table 5 lists
the attack/release times. The attack time can be esti-
mated using the following equation:
tAttack ≈2400 * CCT
where CCT is in farads and the total connected capaci-
tance.
Evaluates: MAX9814
MAX9814 Evaluation Kit
______________________________________________________________________________________________________________________________________________________________________________3
SHUNT POSITION SHDN PIN EV KIT FUNCTION
1-2 Connected to VCC MAX9814 enabled
2-3 Connected to GND MAX9814 disabled
— Not connected SHDN driven by
external controller
Table 1. Shutdown Configuration (JU1)
SHUNT
POSITION GAIN PIN MAXIMUM GAIN
(dB)
1-2 Connected to VCC 40
2-3 Connected to GND 50
— Not connected 60
Table 2. Gain Control Configuration (JU2)
SHUNT
POSITION
ATTACK/RELEASE
PIN
ATTACK/RELEASE
RATIO
2-3 Connected to GND 1:500
1-2 Connected to VCC 1:2000
— Not connected 1:4000
Table 3. Attack/Release Ratio
Configuration (JU3)
RELEASE TIMES (ms)
ATTACK TIME
(µs) 1:500 1:2000 1:4000
53 26.4 105.6 211.2
166 83 332 664
406 203 812 1624
937 468 1874 3748
Table 5. Attack/Release Times
JU4 SHUNT POSITION JU5 SHUNT POSITION JU6 SHUNT POSITION CT PIN CAPACITANCE
(µF)
ATTACK TIME
(µs)
Not installed Not installed Not installed 0.022 53
Installed Not installed Not installed 0.069 166
Installed Installed Not installed 0.169 406
Installed Installed Installed 0.389 937
Table 4. Attack Time Configuration (JU4, JU5, and JU6)
Evaluates: MAX9814
MAX9814 Evaluation Kit
4______________________________________________________________________________________________________________________________________________________________________________
Figure 1. MAX9814 EV Kit Schematic
VCC
R3
2.21kΩ
1%
JU1
SHDN
C4
0.022µF
VCC
C7
0.1µF
C3
0.047µF
JU4
C2
0.1µF
C5
2.2µF
C6
1µF
JU5
C1
0.22µF
JU6
VCC
MIC_OUT
GND
SGND_OUT
CT
1
2
3
2
1
J1
1
CG
3
N.C.
4
C8
0.47µF
C9
0.1µF
BIAS
N.C. 11
MICIN 8
JU2
1
2
3
VCC
GAIN 10
JU3
1
2
3
VCC
A/R 9
12
MICBIAS 13
VCC
5
MICOUT
6
GND
7
2
MAX9814
U1
SHDN
R1
150kΩ
1%
R2
100kΩ
1%
MIC_IN
TH 14 TH
SGND_IN
2
1
J2
Evaluates: MAX9814
MAX9814 Evaluation Kit
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 _____________________
5
© 2007 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.
Janet Freed
Figure 2. MAX9814 EV Kit Component Placement Guide—
Component Side
Figure 3. MAX9814 EV Kit PCB—Component Guide
Figure 4. MAX9814 EV Kit PCB—Solder Side
