MAX9779ETI+ Maxim Integrated Products, MAX9779ETI+ Datasheet - Page 10
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MAX9779ETI+
Manufacturer Part Number
MAX9779ETI+
Description
IC AMP AUDIO PWR 2.6W AB 28TQFN
Manufacturer
Maxim Integrated Products
Series
DirectDrive™r
Type
Class ABr
Datasheet
1.MAX9779ETI.pdf
(19 pages)
Specifications of MAX9779ETI+
Output Type
2-Channel (Stereo) with Stereo Headphones
Max Output Power X Channels @ Load
2.6W x 2 @ 3 Ohm; 110mW x 2 @ 16 Ohm
Voltage - Supply
4.5 V ~ 5.5 V
Features
Depop, Short-Circuit and Thermal Protection, Shutdown
Mounting Type
Surface Mount
Package / Case
28-TQFN Exposed Pad
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
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 DirectDrive
architecture that eliminates the bulky output DC-block-
ing capacitors required by traditional headphone ampli-
fiers. A charge pump inverts the positive supply
(CPV
headphone amplifiers operate from these bipolar sup-
plies 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
10
______________________________________________________________________________________
IN_
BIAS
DD
), creating a negative supply (CPV
Detailed Description
BIAS
BIAS
GND
HPOUT_
OUT_+
OUT_-
SS
). The
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 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