MAX4061/MAX4062

The MAX4062 has a lower bias voltage and low-imped-

ance outputs (optimum electret bias resistor can then be

set externally). This gives a low-noise, flexible solution

that can run from 2.4V to 5.5V, suitable for handheld

devices such as PDAs that typically have audio power

supplies in the 3V region (see Figure 3).

In applications where the differential microphone is placed

some distance from the MAX4060/MAX4061/MAX4062,

using a remote differential bias scheme as shown in

Figure 4 can provide improved noise rejection.

Output

MAX4060/MAX4061 DC Bias

The output voltage has a DC-bias voltage independent

of the power supplies, resulting in superior PSRR perfor-

mance. The MAX4061 output is high impedance when the

part is in shutdown mode. AC-coupling the output into the

next audio stage (e.g., CODEC) is recommended.

Applications Information

Shutdown Mode

The MAX4061 features a low-power, complete shutdown

mode. When SHDN goes low, the supply current drops

to 0.3μA, the output enters a high-impedance state, and

the bias current to the microphone is switched off. Driving

SHDN

high enables the amplifier. SHDN should not be

left unconnected.

Power Supplies and Layout

The MAX4060 operates from a 4.5V to 5.5V single sup-

ply and the MAX4061/MAX4062 operate from a 2.4V to

5.5V single supply. Bypass the power supply with a 0.1μF

capacitor to ground. In systems where analog and digital

grounds are available, the MAX4060/MAX4061 should be

connected to the analog ground.

Figure 2. MAX4060 Used for Biasing a Microphone

IN-

IN+

6

5

4

VCC

4.5V TO 5.5V

MAX4060

INT/AUX 1

OUT 2

GND

7

x10

VBIAS

x10

BIAS

3

AUX_IN

MICROPHONE

INPUT

8

RBIAS

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Analog Devices │ 11

MAX4060/MAX4061/

MAX4062

Differential Microphone Preamplifiers with

Internal Bias and Complete Shutdown