MAX9789/MAX9790
Windows Vista-Compliant, Stereo Class AB Speaker
Amplifiers and DirectDrive Headphone Amplifiers
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Detailed Description
The MAX9789/MAX9790 combine a 2W BTL speaker
amplifier with an 100mW DirectDrive headphone amplifi-
er. These devices feature comprehensive click-and-pop
suppression and programmable four-level speaker ampli-
fier gain control. The MAX9789/MAX9790 feature high
+90dB PSRR, low 0.002% THD+N, industry-leading click-
and-pop performance, low-power shutdown mode, and
excellent RF immunity. The MAX9789 incorporates an
integrated LDO that serves as a clean power supply for a
CODEC or other circuits.
The MAX9789/MAX9790 is Microsoft Windows Vista com-
pliant. See Table 1 for a comparison of the Microsoft
Windows Vista premium mobile specifications and
MAX9789/MAX9790 specifications.
The speaker amplifiers use BTL architecture, doubling the
voltage drive to the speakers and eliminating the need for
DC-blocking capacitors. The output consists of two sig-
nals, identical in magnitude, but 180° out of phase.
The headphone amplifiers use Maxim’s DirectDrive
architecture to eliminate the bulky output DC-blocking
capacitors required by traditional headphone ampli-
fiers. A charge pump inverts a positive supply (CPVDD)
to create a negative supply (CPVSS). The headphone
amplifiers operate from these bipolar supplies with their
outputs biased about GND. The benefit of the GND
bias is that the amplifier outputs no longer have a DC
component (typically VDD / 2). This feature eliminates
the large DC-blocking capacitors required with conven-
tional headphone amplifiers to conserve board space
and system cost, as well as improve low-frequency
response.
The MAX9789/MAX9790 feature programmable speak-
er amplifier gain, allowing the speaker gain to be set by
the logic voltages applied to GAIN1 and GAIN2, while
the headphone amplifiers feature a fixed 3.5dB gain.
Both amplifiers feature an undervoltage lockout that
prevents operation from an insufficient power supply
and click-and-pop suppression that eliminates audible
transients on startup and shutdown. The amplifiers
include thermal overload and short-circuit protection.
An additional feature of the speaker amplifiers is that
there is no phase inversion from input to output.
Low-Dropout Linear Regulator
(MAX9789 Only)
The MAX9789’s low-dropout (LDO) linear regulator can
be used to provide a clean power supply to a CODEC
or other circuitry. The LDO can be enabled indepen-
dently of the audio amplifiers. Set LDO_EN = VDD to
enable the LDO or set LDO_EN = GND to disable the
LDO. The LDO is capable of providing up to 120mA
continuous current and features Maxim’s Dual Mode
feedback, easily enabling a fixed 4.75V output or a
user-adjustable output. When LDO_SET is connected
to GND, the output is internally set to 4.75V. The output
voltage can be adjusted from 1.21V to 4.75V by con-
necting two external resistors as a voltage divider, at
LDO_SET (Figure 1).
Note: THD+N, DYNAMIC RANGE, and CROSSTALK should be measured in accordance with AES-17 audio measurements standards.
Table 1. Windows Premium Mobile Vista Specifications vs. MAX9789/MAX9790
Specifications
DEVICE TYPE
REQUIREMENT
WINDOWS PREMIUM MOBILE Vista
SPECIFICATIONS
MAX9789/MAX9790
TYPICAL PERFORMANCE
THD+N
≤ -65dB FS
[20Hz, 20kHz]
-94dB FS
[20Hz, 20kHz]
Dynamic range with
signal present
≤ -80dB FS,
A-weighted
-97dB FS,
A-weighted
Analog Line Output
Jack (RL = 10k
Ω,
FS = 0.707VRMS)
Line output crosstalk
≤ -50dB
[20Hz, 20kHz]
-77dB
[20Hz, 20kHz]
THD+N
≤ -45dB FS
[20Hz, 20kHz]
-77dB FS
[20Hz, 20kHz]
Dynamic range with
signal present
≤ -60dB FS,
A-weighted
-89dB FS,
A-weighted
Analog Headphone
Out Jack (RL = 32
Ω,
FS = 0.300VRMS)
Headphone output
crosstalk
≤ -50dB
[20Hz, 20kHz]
-74dB
[20Hz, 20kHz]
Dual Mode is a trademark of Maxim Integrated Products, Inc.