Detailed Description

The MAX9892 is the second-generation click-and-pop

eliminator designed to be used with conventional head-

phone amplifiers. The MAX9892 works by adding a low-

impedance current path from the headphone side of

the DC-blocking capacitor to ground. Drive MUTE low

when turning off the amplifier, and high when enabling

the amplifier. A short turn-on time allows the switches in

the MAX9892 to close before the DC-blocking capaci-

tors have significantly discharged, eliminating clicks

and pops at amplifier turn-off. An adjustable turn-off

time allows the delay to be set to mask all clicks and

pops during amplifier turn-on.

Setting the Turn-Off Time

The MAX9892 features a SET input that allows the turn-

off time to be adjusted from 1ms to 1000ms to match

the click-and-pop profile of the amplifier startup. The

value of an external capacitor sets the switch open

delay, as shown in the following equation:

When the headphone amplifier is enabled, the

MAX9892 automatically waits the set delay time before

opening the analog switches. This allows amplifier turn-

on click and pop to be eliminated.

Applications Information

Setting the Supply Voltage

The MAX9892 operates from 1.7V to 3.6V supply volt-

age. The inputs, INL and INR, accept voltage swings

headphone is ground biased, meaning that the signal

swings just as much negative as positive. Since the

to pass the audio signal when the switch is open

(Figure 2).

A voltage-divider can be used to scale down an avail-

able supply voltage as shown in Figure 3. The voltage-

divider allows the creation of a supply voltage for the

MAX9892 that is low enough to allow the negative por-

tion of the audio signal to pass. When using large resis-

tances for the voltage-divider, the supply current

to 1M

Ω for a given supply voltage. Use the following

ence to GND, the MAX9892 supply can be set from 2V

to 3.5V.

Selecting Series Resistors

Operating Circuit, is necessary to achieve optimal click-

graph in the

Typical Operating Characteristics for

details on how much click-and-pop reduction to expect

for a given series resistor.

Layout Considerations

bypass capacitor should be positioned as close as

solid system ground plane to ensure optimum perfor-

mance.

Refer to the MAX9892 Evaluation Kit for a proven PCB

layout.

R

VV

II

AMP

DD

DD

1

2

=

−

+

()

Shunt Mode Audio Click-and-Pop Eliminator

_______________________________________________________________________________________

5

IN_

GND

IN_

GND

A

B

Figure 2. Proper Supply Selected for a Given Input Signal.

A: Supply Voltage with a Large Signal;

B: Supply Voltage with a Small Signal