���������������������������������������������������������������� Maxim Integrated Products  10

MAX98309/MAX98310

Mono 1.4W Class AB Audio Amplifiers

Detailed Description

The MAX98309/MAX98310 mono 1.4W Class AB audio

amplifiers offer low quiescent current while maintaining

excellent SNR and low 0.008% THD+N. Both ICs feature

excellent 90dB PSRR and state-of-the-art click-and-pop

suppression.

The ICs are offered with an internally fixed 0dB, 3dB,

6dB, and 9dB gain (MAX98310) or an externally set gain

(MAX98309) through external resistors.

The MAX98309 features a 10ms or 100ms pin-selectable

turn-on time, while the MAX98310 has a preset 5ms turn-

on time.

Bias

The ICs operate from a single 2.5V to 5.5V power supply

and feature an internally generated common-mode bias

voltage of VDD/2 reference to ground. BIAS provides both

click-and-pop suppression and sets the DC bias level

for the audio outputs. Choose the value of the bypass

capacitor as described in the BIAS Capacitor section. Do

not connect external loads to BIAS as this can affect the

overall performance.

Turn-On Time

The MAX98309 external gain amplifier features a select-

able turn-on time for optimized click-and-pop perfor-

mance. Connect TON to GND for a 10ms turn-on time.

Connect TON to VDD for a 100ms turn-on time. The

MAX98310 has a preset 5ms turn-on time.

Shutdown Mode

The ICs feature a 1.8FA low-power shutdown mode

that reduces quiescent current consumption. When the

active-low shutdown mode is entered, the ICs’ internal

bias circuitry is disabled, the amplifier outputs go high

impedance, and BIAS is driven to GND.

Click-and-Pop Suppression

The ICs feature Maxim’s industry-leading click-and-

pop suppression circuitry. During startup, the amplifier

common-mode bias voltage ramps to the DC bias point.

When entering shutdown, the amplifier outputs are high

impedance between both outputs. This scheme mini-

mizes the energy present in the audio band.

Applications Information

BTL Amplifier

The ICs are designed to drive a load differentially, a

configuration referred to as bridge-tied load, or BTL. The

BTL configuration (Figure 1) offers advantages over the

single-ended configuration, where one side of the load

is connected to ground. Driving the load differentially

doubles the output voltage compared to a single-ended

amplifier under similar conditions.

Substituting 2 x VOUT(P-P) for VOUT(P-P) into the following

equations yields four times the output power due to

doubling of the output voltage:

OUT (P P)

RMS

RMS

OUT

L

V

V

2 2

V

2

P

R

−

=

=

Because the differential outputs are biased at midsupply,

there is no net DC voltage across the load. This elimi-

nates the need for DC-blocking capacitors required for

single-ended amplifiers. These capacitors can be large,

expensive, consume board space, and degrade low-

frequency performance.

Power Dissipation and Heatsinking

Under normal operating conditions, the ICs dissipate a

significant amount of power. The maximum power dissi-

pation is given in the Absolute Maximum Ratings or can

be calculated by the following equation:

J(MAX)

A

D(MAX)

JA

T

T

P

−

=

θ

where TJ(MAX) is +150NC, TA is the ambient temperature,

and BJA is the reciprocal of the derating factor in C/W as

specified in the Absolute Maximum Ratings.

Figure 1. BTL Configuration

+1

VOUT(P-P)

VOUT(P-P)

2 x VOUT(P-P)

-1