max9758etjt Maxim Integrated Products, Inc., max9758etjt Datasheet - Page 13

• Manufacturer Part Number: max9758etjt
• Description: 2.3w Stereo Speaker Amplifiers And Directdrive Headphone Amplifiers With Automatic Level Control
• Manufacturer: Maxim Integrated Products, Inc.

The MAX9756/MAX9757/MAX9758 combine dual, 2W
BTL stereo audio power amplifiers with a DirectDrive
headphone amplifier in a single device. The stereo
power amplifiers deliver up to 2.3W per channel into a
3Ω speaker from a 5V supply and the stereo head-
phone amplifiers deliver up to 130mW per channel into
a 16Ω headphone from a 5V supply.
The MAX9756/MAX9757 feature ALC that automatically
controls output power to the speaker, preventing loud-
speaker, overload and provides optimized dynamic
range.
The MAX9756/MAX9757/MAX9758 feature 31-step ana-
log volume control and a BEEP input. The amplifier
gain is pin programmable. These devices feature click-
and-pop suppression, eliminating the need for discrete
muting circuitry. Speaker and headphone outputs have
short-circuit and thermal protection.
The MAX9756/MAX9758s’ internal LDO features
Maxim’s Dual Mode™ feedback. The LDO output volt-
age is either fixed at 4.65V (SET = GND), or adjusted
between 1.23V and 5V using a resistive divider at SET.
The LDO delivers up to 150mA of continuous current,
and can be enabled independently from the audio
amplifiers. Short-circuit and thermal-overload protec-
tion are provided for the LDO.
Figure 1. MAX9756/MAX9757 Signal Path
Dual Mode is a trademark of Maxim Integrated Products, Inc.
Headphone Amplifiers with Automatic Level Control
VOL
IN_
BIAS
CONTROL
VOLUME
2.3W Stereo Speaker Amplifiers and DirectDrive
______________________________________________________________________________________
Detailed Description
ALC
BIAS
BIAS
GND
OUT_+
OUT_-
HP_
All devices feature a single-supply voltage, a shut-
down mode, logic-selectable gain, and a headphone
sense input. Industry-leading click-and-pop suppres-
sion eliminates audible transients during power and
shutdown cycles.
Each signal path consists of an input amplifier that sets
the signal-path gain and feeds both the speaker and
headphone amplifiers (Figure 1). The speaker amplifier
uses a BTL architecture, doubling the voltage drive to
the speakers and eliminating the need for DC-blocking
capacitors. The output consists of two signals, identical
in magnitude, but 180° out of phase.
The headphone amplifiers use Maxim’s patented
DirectDrive architecture that eliminates the bulky output
DC-blocking capacitors required by traditional head-
phone amplifiers. A charge pump inverts the positive
supply (CPV
The headphone amplifiers operate from these bipolar
supplies with their outputs biased about GND (Figure 2).
The amplifiers have almost twice the supply range
compared to other single-supply amplifiers, nearly qua-
drupling the available output power. The benefit of the
GND bias is that the amplifier outputs do not have a DC
component (typically V
DC-blocking capacitors required with conventional
headphone amplifiers, conserving board space and
system cost while improving frequency response.
Figure 2. Traditional Headphone Amplifier Output Waveform
vs. DirectDrive Headphone Amplifier Output Waveform
DD
CONVENTIONAL DRIVER-BIASING SCHEME
), creating a negative supply (CPV
DirectDrive BIASING SCHEME
DD
V
OUT
/2). This eliminates the large
V
GND
GND
V
+V
-V
DD
DD
DD
DD
/2
SS
13
).