Rainbow Electronics MAX9768 - Manual (Page 12)

Detailed Description
The MAX9768 10W, Class D audio power amplifier with
spread-spectrum modulation provides a significant step
forward in switch-mode amplifier technology. The
MAX9768 offers Class AB performance with Class D
efficiency and a minimal board space solution. This
device features a wide supply voltage operation (4.5V to
14V), analog or digitally adjusted volume control, exter-
nally set input gain, shutdown mode, SYNC input and
output, speaker mute, and industry-leading click-and-
pop suppression.
The MAX9768 features a 64-step, dual-mode (analog or
I
2 C programmed) volume control and mute function. In
analog volume control mode, voltage applied to
SDA/VOL sets the volume level. Two address inputs
(ADDR1, ADDR2) set the volume control function
between analog and I
2 C and set the slave address. In
I 2 C mode there are three selectable slave addresses
allowing for multiple devices on a single bus.
Spread-spectrum modulation and synchronizable
switching frequency significantly reduce EMI emis-
sions. The outputs use Maxim’s low-EMI modulation
scheme with minimum pulse outputs when the audio
inputs are at the zero crossing. As the input voltage
increases or decreases, the duration of the pulse at
one output increases while the other output pulse dura-
tion remains the same. This causes the net voltage
across the speaker (V
OUT+ - V OUT- ) to change. The
minimum-width pulse topology reduces EMI and
increases efficiency.
MAX9768
10W Mono Class D Speaker
Amplifier with Volume Control
12 ______________________________________________________________________________________
MUTE
VOLUME
CONTROL
CLASS D
SHUTDOWN
CONTROL
OSCILLATOR
SYNCOUT
BIAS
14
V DD
V DD
PV DD
C BIAS
2.2 μF
7
8
1, 2
4
17, 18
15
10
13
FB
R F
30k Ω
R IN
20k Ω
C
IN
0.47 μF C1
0.1
μF
C2
0.1
μF
1 μF 1 μF
IN
20
19
6
5
24
23
GND PGND
OUT+
BOOT+
OUT-
BOOT-
BIAS
12
3, 16
9, 11 21, 22
2.7V to 3.6V 4.5V to 14V
SYNC
MUTE
SHDN
SDA/VOL
SCLK
ADDR1
ADDR2
I 2 C
ANALOG
CONTROL
MAX9768
(SHOWN IN ANALOG VOLUME CONTOL MODE, A
V
= 23.5dB, f
-3dB
= 17Hz, SPREAD-SPECTRUM MODULATION MODE, FILTERLESS MODULATION MODE, MUTE OFF)
Functional Diagram/Typical Application Circuit