MAX4295 Maxim, MAX4295 Datasheet - Page 10

• Manufacturer Part Number: MAX4295
• Description: Mono/Stereo 2W Switch-Mode (Class-D) Audio Power Amplifiers
• Manufacturer: Maxim

The MAX4295/MAX4297 switch-mode, Class-D audio
power amplifiers are intended for portable multimedia
and general-purpose audio applications. Linear ampli-
fiers in the 1W to 2W output range are inefficient; they
overheat when operated near rated output power lev-
els. The efficiency of linear amplifiers is <50% when the
output voltage is equal to 1/2 the supply. The
MAX4295/MAX4297 Class-D amplifiers achieve effi-
ciencies of 87% or greater and are capable of deliver-
ing up to 2W of continuous maximum power to a 4Ω
load. The lost power is due mainly to the on-resistance
of the power switches and ripple current in the output.
In a Class-D amplifier, a PWM controller converts the
analog input to a variable pulse-width signal. The pulse
width is proportional to the input voltage, ideally 0% for
Mono/Stereo 2W Switch-Mode (Class-D)
Audio Power Amplifiers
10
MAX4295
______________________________________________________________________________________
1, 12
2, 15
4, 13
10
11
14
16
—
—
—
—
—
—
—
—
3
5
6
7
8
9
PIN
4, 9, 16, 21
6, 7, 18, 19
MAX4297
3, 23
10
13
11
12
22
14
15
20
17
24
—
—
—
—
5
8
2
1
Detailed Description
OUT+R
AOUTR
OUT+L
AOUTL
OUT-R
NAME
OUT-L
PGND
SHDN
OUT+
AOUT
PV
OUT-
GND
VCM
V
FS1
FS2
INR
INL
SS
IN
CC
CC
Analog Ground
H-Bridge Power Supply
Positive H-Bridge Output
Positive Left-Channel H-Bridge Output
Positive Right-Channel H-Bridge Output
Power Ground
Analog Power Supply
Audio Input Common-Mode Voltage. Do not connect. Minimize parasitic
coupling to this pin.
Audio Input
Left-Channel Audio Input
Right-Channel Audio Input
Input Amplifier Output
Left-Channel Input Amplifier Output
Right-Channel Input Amplifier Output
Active-Low Shutdown Input. Connect to V
leave floating.
Frequency Select Input 1
Frequency Select Input 2
Negative H-Bridge Output
Negative Left-Channel H-Bridge Output
Negative Right-Channel H-Bridge Output
Soft-Start
a 0V input signal and 100% for full-scale input voltages.
A passive lowpass LC network filters the PWM output
waveform to reconstruct the analog signal. The switch-
ing frequency is selected much higher than the maxi-
mum input frequencies so that intermodulation
products are outside the input signal bandwidth.
Higher switching frequencies also simplify the filtering
requirements.
The MAX4295/MAX4297 consist of an inverting input
operational amplifier, a PWM ramp oscillator, a con-
troller that converts the analog input to a variable pulse
width signal, and a MOSFET H-bridge power stage
(Figures 1a and 1b). The control signal is generated by
the PWM comparator; its pulse width is proportional to
the input voltage. Ideally the pulse width varies linearly
between 0% for a 0V input signal and 100% for full-
scale input voltages (Figure 2). This signal controls the
FUNCTION
CC
for normal operation. Do not
Pin Description