Differential Microphone Preamplifiers with

Internal Bias and Complete Shutdown

8

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Pin Description

PIN

MAX4060

MAX4061

MAX4062

NAME

FUNCTION

1—

2

INT/AUX

Internal (Differential) or Auxiliary (Single-Ended) Input Select. Drive INT/AUX low

to select internal or high to select auxiliary microphone input.

23

3

OUT

Amplifier Output. OUT is high impedance when in shutdown mode.

3—

—

BIAS

External Electret Microphone Capsule Bias Output. BIAS has a greater than

2k

Ω output impedance.

44

5

55

6

IN+

Noninverting Differential Amplifier Input. AC-couple the audio signal into IN+.

66

7

IN-

Inverting Differential Amplifier Input. AC-couple the audio signal into IN-.

77

8

GND

Ground

8—

9

AUX_IN

Single-Ended Input for Auxiliary Microphone. AC-couple the audio signal into

AUX_IN.

—1

1

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.)

—2

—

SHDN

Shutdown Input. Drive SHDN high for normal operation. Drive SHDN low for

shutdown mode.

——

4

BIAS

External Electret Microphone Capsule Bias Output Bypass BIAS with 1µF

Capacitor to Ground

—8

10

G1

Gain-Selectable Input. Connect an external resistor between G1 and G2 to set

the gain for the differential amplifier.

Detailed Description

The MAX4060/MAX4061/MAX4062 are differential micro-

phone preamplifiers providing high-quality audio, opti-

mized for use in computer and mobile applications.

These devices feature rail-to-rail outputs, very high

power-supply rejection, and common-mode rejection,

making them ideal for low-noise applications. The

MAX4060/MAX4061/MAX4062 are particularly effective

when layout constraints force the microphone amplifier to

be physically remote from the ECM microphone and/or

the rest of the audio circuitry.

The MAX4060/MAX4062 are capable of switching their

output between the differential input and an inverting

single-ended input. INT/AUX selects either the differen-

tial input or single-ended auxiliary input. In addition, the

MAX4060/MAX4061 have an internal bias generator to

bias the microphone in either differential or single-

ended modes. The MAX4061 includes a complete

0.3µA shutdown mode for ultimate power savings. The

differential gain of the MAX4061/MAX4062 is set with a

single resistor connected between the G1 and G2 pins.

The MAX4060 has a fixed gain of 10V/V.

Differential Input

The main microphone input is a low-noise, differential

input structure. This is an almost essential element

when faced with amplification of low-amplitude analog

signals in digitally intense environments such as note-

book PCs or PDAs. Used correctly, the advantages

over a single-ended solution are:

• Better power-supply noise rejection.

• Less degradation from noise in PC board ground

planes.

• The microphone and preamplifier can be placed

physically further apart, easing PC board layout

restrictions.