Datasheet

External Synchronization
The SYNC function allows the MAX9759 to allocate
spectral components of the switching harmonics to
insensitive frequency bands and facilitates synchroniza-
tion to a system clock (allowing for a fully synchronous
system). Applying an external TTL clock of 1000kHz to
1600kHz to SYNC synchronizes the switching frequency
of the MAX9759. The period of the SYNC clock can be
randomized, enabling the MAX9759 to be synchronized
to another MAX9759 operating in SSM mode.
Cascading Amplifiers
The SYNC_OUT function of the MAX9759 allows for
multiple Maxim Class D amplifiers to be cascaded and
frequency locked. Synchronizing multiple Class D
amplifiers ensures that no beat frequencies within the
audio spectrum occur on the power-supply rails. Any
intermodulation distortion due to the interference of
several modulation frequencies is minimized as a
result. Leave the SYNC_OUT pin of the MAX9759 float-
ing if the SYNC_OUT function is not applicable.
Filterless Modulation/Common-Mode Idle
The MAX9759 uses Maxim’s unique modulation
scheme that eliminates the LC filter required by tradi-
tional Class D amplifiers, improving efficiency, reduc-
ing component count, and conserving board space
and system cost. Conventional Class D amplifiers out-
put a 50% duty-cycle square wave when no signal is
present. With no filter, the square wave appears across
the load as a DC voltage, resulting in finite load current,
increasing power consumption. When no signal is pre-
MAX9759
3.2W, High-Efficiency, Low-EMI,
Filterless, Class D Audio Amplifier
12 ______________________________________________________________________________________
V
OUT+
- V
OUT-
t
SW
t
SW
t
SW
t
SW
V
IN-
V
IN+
OUT+
OUT-
t
ON(MIN)
Figure 2. MAX9759 Outputs with an Input Signal Applied (SSM Mode)