MAX9810 Maxim Integrated Products, MAX9810 Datasheet - Page 7

• Manufacturer Part Number: MAX9810
• Description: Electret Condenser Microphone Cartridge Preamplifier
• Manufacturer: Maxim Integrated Products

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The MAX9810 replaces the FET commonly used in
ECMs with a high-gain, low-noise, low-output-impedance
amplifier, offering improved performance over the tradi-
tional FET solution. The MAX9810 features high PSRR
(82dB at 1kHz), and is available in three gain options
(24dB, 27dB, and 30dB). ECMs with FET impedance
converters require additional amplification (Figure 1).
The high gain of the MAX9810 eliminates the need for an
external preamplifier, allowing the ECM cartridge to be
directly connected to front-end devices such as
CODECs or ADCs (Figure 2). The MAX9810 also fea-
tures excellent RF immunity (see the RF Noise Rejection
section).
When operated from a 3V supply, the internal 1.5V DC
bias point provides symmetrical, rail-to-rail operation
where the output can swing to within 15mV of either rail
into a 10kΩ load. The 1.5V bias point is independent of
supply, so when operated from supplies other than 3V,
the MAX9810 output can run out of headroom on one of
the supplies (Figure 3). This limits the peak-to-peak out-
put to approximately:
The MAX9810 shows no phase reversal when the
device is overdriven. If the device output is driven into
clipping, the overload behavior is predictable.
BUMP
A1
A2
B1
B2
V
V
OUT(P-P)
OUT(P-P)
Electret Condenser Microphone Cartridge
NAME
GND
OUT
V
IN
DD
_______________________________________________________________________________________
Detailed Description
= V
= 3V for V
Amplifier Power Supply
Amplifier Output
Amplifier Input
Ground
DD
for V
Pin Description
Rail-to-Rail Output
DESCRIPTION
DD
DD
> 3V
< 3V
The MAX9810 features excellent RF rejection at com-
mon cellular-phone operating frequencies. Figure 4
shows the modulation products of a high-frequency
signal coupling into the device power supply, while the
device is driven with a 1kHz input. At 1GHz, the
MAX9810 exhibits 82dB of rejection.
Unlike FETs, the MAX9810 requires a separate power
source (Figures 1 and 2). V
2.3V to 5.5V power supply external to the ECM car-
tridge, thus the MAX9810 ECM solution requires three
electrical connections instead of the two commonly
found in current FET solutions.
For optimum performance, bypass the MAX9810 as
close to the device as possible (inside the cartridge).
This yields the best RF rejection and PSRR and is ideal
for applications such as cell phones where high-fre-
quency noise is present. The device operates properly if
the bypass capacitor is placed on the circuit board out-
side the cartridge; however, RF rejection is slightly
degraded in this configuration (Figure 4). This is well
suited for applications where there is less high-frequen-
cy interference such as PDAs and notebook computers.
For land pattern and suggested layout of the 4-bump
UCSP, see the JEDEC website at www.ipc.org/html/
framesetcatseg.html.
Applications Information
Preamplifier
DD
RF Noise Rejection
must be connected to a
Supply Bypassing
UCSP Layout
7