max9752aetit Maxim Integrated Products, Inc., max9752aetit Datasheet - Page 12

• Manufacturer Part Number: max9752aetit
• Description: 2.2w, Low-emi, Stereo, Class D Power Amplifiers With Directdrive Headphone Amplifiers
• Manufacturer: Maxim Integrated Products, Inc.

The MAX9752/MAX9753/MAX9754 combine a 2.2W,
Class D speaker amplifier and a 62mW DirectDrive
headphone amplifier with integrated headphone sens-
ing and comprehensive click-and-pop suppression.
The speaker amplifiers offer Class AB performance with
Class D efficiency, while occupying minimal board
space. A unique filterless modulation scheme and
spread-spectrum switching create a compact, flexible,
low-noise, efficient audio power amplifier.
The MAX9752 features an analog volume control, BEEP
input, and four-level gain control. The MAX9753 fea-
tures a 2:1 input stereo multiplexer and two-level gain
control. The MAX9754 has only the Class D amplifiers
and the headphone amplifiers.
An input amplifier sets the gain of the signal path, and
feeds both the speaker and headphone amplifier
(Figure 1). The speaker amplifier uses a low-EMI, Class
D architecture to drive the speakers, eliminating the
need for an external filter for short speaker cables.
The headphone amplifiers use Maxim’s patented
DirectDrive architecture eliminating the bulky output DC-
blocking capacitors required by traditional headphone
amplifiers. A charge pump inverts the positive supply
(CPV
phone amplifiers operate from these bipolar supplies
with their outputs biased about GND (Figure 2). The
2.2W, Low-EMI, Stereo, Class D Power Amplifiers
with DirectDrive Headphone Amplifiers
Figure 1. MAX9752/MAX9753/MAX9754 Signal Path
12
VOL
IN_
______________________________________________________________________________________
DD
BIAS
), creating a negative supply (CPV
MAX9752 ONLY
CONTROL
VOLUME
Detailed Description
BIAS
BIAS
GND
SS
). The head-
HPOUT_
OUT_+
OUT_
amplifiers have almost twice the supply range compared
to other single-supply amplifiers, nearly quadrupling the
available output power. The benefit of the GND bias is
that the amplifier outputs no longer have a DC compo-
nent (typically V
blocking capacitors required with conventional
headphone amplifiers, removing the dominant source of
click and pop, conserving board space, system cost,
and improving frequency response.
An undervoltage lockout prevents operation from an
insufficient power supply. The amplifiers include ther-
mal-overload and short-circuit protection, and can with-
stand ±8kV ESD strikes on the headphone amplifier
outputs (IEC Air-Gap Discharge). An additional feature
of the speaker amplifiers is that there is no phase inver-
sion from input to output.
The MAX9752/MAX9753/MAX9754 feature a unique,
patented spread-spectrum mode that flattens the wide-
band spectral components, improving EMI emissions
that may be radiated by the speaker and cables. The
switching frequency varies randomly by ±90kHz around
the center frequency (1200kHz). Instead of a large
amount of spectral energy present at multiples of the
switching frequency, the energy is now spread over a
bandwidth that increases with frequency. Above a few
megahertz, the wideband spectrum looks like white
noise for EMI purposes (Figure 3).
Figure 2. Traditional Amplifier Output vs. DirectDrive Output
CONVENTIONAL DRIVER-BIASING SCHEME
DD
DirectDrive BIASING SCHEME
/ 2). This eliminates the large DC-
Class D Speaker Amplifier
V
OUT
V
GND
GND
V
+V
-V
DD
DD
DD
DD
/ 2