MAX9776 Maxim Integrated Products, MAX9776 Datasheet - Page 19

• Manufacturer Part Number: MAX9776
• Description: (MAX9775 / MAX9776) Stereo Class D Audio Subsystem
• Manufacturer: Maxim Integrated Products

www.datasheet4u.com
The MAX9775/MAX9776 ultra-low-EMI, filterless, Class D
audio power amplifiers feature several improvements to
switch-mode amplifier technology. The MAX9775/
MAX9776 feature active emissions limiting circuitry to
reduce EMI. Zero dead-time technology maintains state-
of-the-art efficiency and THD+N performance by allowing
the output FETs to switch simultaneously without cross-
conduction. A unique filterless modulation scheme and
spread-spectrum modulation create compact, flexible,
low-noise, efficient audio power amplifiers while
occupying minimal board space. The differential input
architecture reduces common-mode noise pickup with or
without the use of input-coupling capacitors. The
MAX9775/MAX9776 can also be configured as single-
ended input amplifiers without performance degradation.
The MAX9775/MAX9776 feature three fully differential
input pairs (INA_, INB_, INC_) that can be configured
as stereo single-ended or mono differential inputs. I
provides control for input configuration, volume level,
and mixer configuration. The MAX9775’s 3D enhance-
ment feature widens the stereo sound field to improve
stereo imaging when stereo speakers are placed in
close proximity.
Figure 1. Outputs with an Input Signal Applied
V
V
V
IN+
OUT+
IN-
2 x 1.5W, Stereo Class D Audio Subsystem
- V
OUT-
OUT+
OUT-
______________________________________________________________________________________
Detailed Description
with DirectDrive Headphone Amplifier
t
ON(MIN)
t
SW
2
C
DirectDrive allows the headphone and mono receiver
amplifiers to output ground-referenced signals from a
single supply, eliminating the need for large DC-block-
ing capacitors. Comprehensive click-and-pop suppres-
sion minimizes audible transients during the turn-on
and turn-off of amplifiers.
Comparators monitor the audio inputs and compare the
complementary input voltages to a sawtooth waveform.
The comparators trip when the input magnitude of the
sawtooth exceeds their corresponding input voltage. The
active emissions limiting circuitry slightly reduces the
turn-on rate of the output H-bridge by slew-rate limiting
the comparator output pulse. Both comparators reset at
a fixed time after the rising edge of the second compara-
tor trip point, generating a minimum-width pulse
(t
parator (Figure 1). As the input voltage increases or
decreases, the duration of the pulse at one output
increases while the other output pulse duration remains
the same. This causes the net voltage across the speak-
er (V
helps the devices to achieve high levels of linearity.
ON(MIN)
OUT+
,100ns typ) at the output of the second com-
- V
OUT-
) to change. The minimum-width pulse
Class D Speaker Amplifier
19