MAX9759 Maxim Integrated Products, MAX9759 Datasheet - Page 10

• Manufacturer Part Number: MAX9759
• Description: 3.2W High-Efficiency Low-EMI Filterless Class D Audio Amplifier
• Manufacturer: Maxim Integrated Products

3.2W, High-Efficiency, Low-EMI, Filterless,
Class D Audio Amplifier
The MAX9759 filterless, Class D audio power amplifier
features several improvements to switch-mode amplifier
technology. The MAX9759 offers Class AB performance
with Class D efficiency, while occupying minimal board
space. A unique modulation scheme, synchronizable
switching frequency, and SSM mode create a compact,
flexible, low-noise, efficient audio power amplifier. The
differential input architecture reduces common-mode
noise pickup, and can be used without input-coupling
capacitors. The device can also be configured as a sin-
gle-ended input amplifier.
Comparators monitor the MAX9759 inputs and com-
pare the complementary input voltages to the sawtooth
waveform. The comparators trip when the input magni-
tude of the sawtooth exceeds their corresponding input
voltage. Both comparators reset at a fixed time after the
rising edge of the second comparator trip point, gener-
10
TQFN
6, 14
9, 12
______________________________________________________________________________________
EP
10
11
13
15
16
1
2
3
4
5
7
8
PIN
TSSOP
4, 12
2, 15
EP
10
11
13
14
16
7
8
9
1
3
5
6
Detailed Description
SYNC_OUT
NAME
SHDN
PGND
MUTE
OUT+
SYNC
PV
OUT-
GND
V
IN+
IN-
G2
G1
EP
DD
DD
Operating Modes
Analog Power Supply. Bypass to GND with a 1µF ceramic capacitor.
Noninverting Audio Input
Inverting Audio Input
Analog Ground
Active-Low Shutdown Input. Drive SHDN low to shut down the MAX9759. Connect to
V
Power Ground
Frequency Select and External Clock Input:
SYNC = GND: Fixed-frequency mode with f
SYNC = FLOAT: Fixed-frequency mode with f
SYNC = V
SYNC = Clocked: Fixed-frequency mode with f
Active-Low Mute Function. Drive MUTE low to disable the H-bridge outputs. Connect to
V
H-Bridge Power Supply. Bypass to PGND with a 10µF ceramic capacitor.
Negative Speaker Output
Positive Speaker Output
Internal Clock Output. Connect SYNC_OUT to the clock input of cascaded Maxim class
D amplifiers. Float SYNC_OUT if unused.
Gain Control 2 (See the Gain Selection Section)
Gain Control 1 (See the Gain Selection Section)
Exposed Paddle. Can be left floating or tied to GND.
DD
DD
for normal operation.
for normal operation.
DD
: Spread-spectrum mode with f
ating a minimum-width pulse t
the second comparator (Figure 1). As the input voltage
increases or decreases, the duration of the pulse at
one output increases (the first comparator to trip) while
the other output pulse duration remains at t
This causes the net voltage across the speaker (V
- V
The MAX9759 features two FFM modes. The FFM
modes are selected by setting SYNC = GND for a
1.1MHz switching frequency, and SYNC = FLOAT for a
1.5MHz switching frequency. In FFM mode, the fre-
quency spectrum of the class D output consists of the
fundamental switching frequency and its associated
harmonics (see the Wideband FFT graph in the Typical
Operating Characteristics). The MAX9759 allows the
switching frequency to be changed, should the fre-
quency of one or more of the harmonics fall in a sensi-
tive band. This can be done at any time and does not
affect audio reproduction.
OUT-
) to change.
FUNCTION
Fixed-Frequency Modulation (FFM) Mode
S
S
= 1100kHz.
S
= 1200kHz ±70kHz.
S
= 1500kHz.
= external clock frequency.
ON(MIN)
Pin Description
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at the output of
ON(MIN)
OUT+
.