max9779etit Maxim Integrated Products, Inc., max9779etit Datasheet - Page 10

• Manufacturer Part Number: max9779etit
• Description: Max9779 2.6w Stereo Audio Power Amplifier And Directdrive Headphone Amplifier
• Manufacturer: Maxim Integrated Products, Inc.

The MAX9779 combines a 2.6W BTL speaker amplifier
and a 110mW DirectDrive headphone amplifier with
integrated headphone sensing and comprehensive
click-and-pop suppression. The MAX9779 features four-
level gain control. The device features high 90dB PSRR,
low 0.01% THD+N, industry-leading click-pop perfor-
mance, and a low-power shutdown mode.
Each signal path consists of an input amplifier that sets
the gain of the signal path and feeds both the speaker
and headphone amplifier (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
2.6W Stereo Audio Power Amplifier and
DirectDrive Headphone Amplifier
Figure 1. MAX9779 Signal Path
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______________________________________________________________________________________
IN_
BIAS
DD
), creating a negative supply (CPV
Detailed Description
BIAS
BIAS
GND
HPOUT_
OUT_+
OUT_-
SS
).
GND bias is that the amplifier outputs no longer have a
DC component (typically V
large DC-blocking capacitors required with convention-
al headphone amplifiers, conserving board space and
system cost, and improving frequency response.
The device features an undervoltage lockout that pre-
vents operation from an insufficient power supply and
click-and-pop suppression that eliminates audible tran-
sients on startup and shutdown. The amplifiers include
thermal-overload and short-circuit protection, and can
withstand ±8kV ESD strikes on the headphone amplifier
outputs (IEC air discharge). An additional feature of the
speaker amplifiers is that there is no phase inversion
from input to output.
Conventional single-supply headphone amplifiers have
their outputs biased about a nominal DC voltage (typi-
cally half the supply) for maximum dynamic range.
Large coupling capacitors are needed to block this DC
bias from the headphones. Without these capacitors, a
significant amount of DC current flows to the headphone,
resulting in unnecessary power dissipation and possible
damage to both headphone and headphone amplifier.
Maxim’s patented DirectDrive architecture uses a charge
pump to create an internal negative supply voltage. This
Figure 2. Traditional Headphone Amplifier Output Waveform
vs. DirectDrive Headphone Amplifier Output Waveform
CONVENTIONAL DRIVER-BIASING SCHEME
DirectDrive BIASING SCHEME
V
OUT
DD
/ 2). This eliminates the
V
GND
GND
V
+V
-V
DD
DD
DD
DD
DirectDrive
/ 2