Datasheet

Detailed Description
The MAX9737 filterless, mono class D audio power
amplifier offers Class AB audio performance and Class
D efficiency with minimal board space. The device
operates from an 8V to 28V supply range.
The MAX9737 features filterless, spread-spectrum
modulation, externally set gain and a low-power shut-
down mode that reduces supply current to less than
1µA. Comprehensive click-and-pop suppression and
precharge circuitry reduce noise into and out of shut-
down or mute within 10ms.
Spread-Spectrum Modulation
The MAX9737 features a unique spread-spectrum
switching modulation that flattens EMI wideband spec-
tral components, reducing radiated emissions from the
speaker and cables. The switching frequency of the
Class D amplifier varies randomly by ±4kHz around the
300kHz center frequency. Instead of a large amount of
spectral energy present at multiples of the switching
frequency, the energy is spread over a bandwidth that
increases with frequency. Above a few MHz, the wide-
band spectrum looks like white noise for EMI purposes.
A proprietary amplifier topology ensures this white
noise does not corrupt the noise floor in the audio
bandwidth.
Efficiency
The high efficiency of a Class D amplifier is due to the
output transistors acting as switches and therefore con-
sume negligible power. Power loss associated with the
Class D output stage is due to the MOSFET I
2
R losses,
switching losses, and quiescent current.
Although the theoretical best efficiency of a linear
amplifier is 78% at peak output power, under typical
music reproduction levels, the efficiency falls to below
40%. The MAX9737 exhibits > 80% efficiency under the
same conditions (Figure 1).
Shutdown
The MAX9737 features a shutdown mode that reduces
power consumption to less than 1µA (typ), extending
battery life in portable applications. Drive SHDN low to
place the device in low-power shutdown mode. In shut-
down mode, the outputs are high impedance and the
common-mode voltage at the output decays to zero.
MAX9737
Mono 7W Class D Amplifier
_______________________________________________________________________________________ 7
Pin Description
PIN NAME FUNCTION
1, 17, 18 PVDD
Power Supply. Bypass PVDD to PGND with a 1µF capacitor connected to pin 1 and a 1µF capacitor
connected to pins 17 and 18.
2 CHOLD Charge-Pump Output. Connect a 1µF capacitor to PVDD.
3, 10, 11 AGND Analog Ground
4 MUTE Mute Input. Drive MUTE low to place the device in mute mode.
5 SHDN Shutdown Input. Drive SHDN low to place the part in shutdown mode.
6PC
Input Capacitor Precharge Connection. Connect between input resistor, R
IN
, and input coupling
capacitor, C
IN
.
7 IN Op Amp Inverting Input.
8 PRE Op Amp Output. PRE is the output of the input operational amplifier.
9 COM Internal 2.0V Bias. Bypass COM to AGND with a 1µF capacitor.
12 REG Internal 4.2V Bias. Bypass REG to AGND with a 1µF capacitor.
13, 14 V
S
Internal 5.0V Bias. Bypass V
S
to AGND with a 1µF capacitor.
15 C1N Charge-Pump, Flying-Capacitor Negative Terminal. Connect C1N to C1P through a 0.1µF capacitor.
16 C1P Charge-Pump, Flying-Capacitor Positive Terminal. Connect C1P to C1N through a 0.1µF capacitor.
19, 20 OUT- Negative Speaker Output
21, 22 PGND Power Ground
23, 24 OUT+ Positive Speaker Output
— EP Exposed Pad. Must be externally connected to PGND.