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
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
OUT
L
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-
be calculated by the following equation:
J(MAX)
A
D(MAX)
JA
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
Figure 1. BTL Configuration
+1
VOUT(P-P)
2 x VOUT(P-P)
-1