MAX4063
Differential Microphone Preamplifier with
Internal Bias and Complete Shutdown
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Detailed Description
The MAX4063 is a differential microphone pre-
amplifier providing high-quality amplification, optimized
for use in computer and mobile applications. This device
features adjustable gain, very high power-supply rejec-
tion (95dB), and common-mode rejection (79dB), making
it ideal for low-noise applications. The MAX4063 provides
a differential input stage, making the device particularly
effective when layout constraints force the microphone
amplifier to be physically remote from the ECM micro-
phone.
The MAX4063 is capable of switching its output
between the differential input and an inverting single-
ended input. INT/AUX selects either the differential
input or single-ended auxiliary input. In addition, the
MAX4063 has an integrated microphone bias source,
simplifying system design and eliminating the need for
external components. The MAX4063 has a complemen-
tary output allowing CODECs and other devices with
differential inputs to be optimally driven (see
Functional
Diagram
). The MAX4063 includes a 0.3µA shutdown
mode for ultimate power savings. The differential gain
of the MAX4063 is set with a single resistor connected
between the G1 and G2 pins. The MAX4063 has an
internal default gain of 20V/V on the AUX_IN input. The
AUX_IN gain can be increased with a single external
resistor (see the
Differential-Gain Adjustment and
Auxiliary Input-Gain Adjustment
sections).
Differential Input
The main microphone amplifier is a low-noise, differen-
tial input structure. This is an almost essential element
when faced with amplification of low-amplitude analog
signals in digitally intense environments such as note-
PIN
TSSOP TQFN
NAME FUNCTION
115 G2
Gain-Selectable Input. Connect an external resistor between G1 and G2 to set the gain for
the differential amplifier (see Adjustable Differential Gain-Setting section).
216INT/AUX
Internal (Differential) or Auxiliary (Single-Ended) Input Select. Drive INT/AUX low to select
differential in or high to select auxiliary in.
31SHDN
Shutdown Input. Drive SHDN high for normal operation. Drive SHDN low for shutdown
mode.
4 2 OUT Amplifier Output. OUT is high impedance when in shutdown mode.
5 3 BIAS
External Electret Microphone Capsule Bias Output. Bypass BIAS with a 1µF capacitor to
ground.
64V
CC
Power Supply. Bypass the V
CC
to GND with a 0.1µF capacitor.
7 5 ADJ
Adjustable Gain Select for AUX_IN (see Auxiliary Input-Gain Adjustment section). Connect
a 10pF capacitor between OUT and ADJ.
87OUT Complementary Amplifier Output. OUT is high impedance in shutdown mode.
9 9 IN+ Noninverting Differential Amplifier Input. AC-couple the audio signal into IN+.
10 10 IN- Inverting Differential Amplifier Input. AC-couple the audio signal into IN-.
11 11 GND Ground
12 12 AUX_IN Single-Ended Input for Auxiliary Microphone. AC-couple the audio signal into AUX_IN.
13 6, 8, 14 N.C. No Connection. Not internally connected.
14 13 G1
Gain-Selectable Input. Connect an external resistor between G1 and G2 to set the gain for
the differential amplifier.
—— EP
Exposed Pad (TQFN Only). Internally connected to GND. Connect to a large ground plane
to maximize thermal performance. Not intended as an electrical connection point.