max9706etxt Maxim Integrated Products, Inc., max9706etxt Datasheet - Page 14

• Manufacturer Part Number: max9706etxt
• Description: 3-channel, 2.3w, Filterless Class D Amplifiers With Active Crossover
• Manufacturer: Maxim Integrated Products, Inc.

3-Channel, 2.3W, Filterless Class D Amplifiers
with Active Crossover
Spread-spectrum modulation and synchronizable switch-
ing frequency significantly reduce EMI emissions.
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. Both
comparators reset at a fixed time after the rising edge of
the second comparator trip point, generating a minimum-
width pulse (t
ond comparator (Figure 2). 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 speaker
(V
helps the device to achieve high levels of linearity.
Figure 2. Outputs with an Input Signal Applied (FFM Mode)
14
OUT+
______________________________________________________________________________________
V
- V
OUT_+
V
V
IN+
IN-
OUT-
- V
ON(MIN)
OUT_-
) to change. The minimum-width pulse
OUT+
OUT-
,100ns typ) at the output of the sec-
Class D Speaker Amplifier
t
ON(MIN)
t
SW
The MAX9706/MAX9707 feature two fixed-frequency
modes. Connect SYNC_IN to GND to select a 1.1MHz
switching frequency. Float SYNC to select a 1.34MHz
switching frequency. The frequency spectrum of the
MAX9706/MAX9707 consists of the fundamental
switching frequency and its associated harmonics (see
the Wideband Output Spectrum graph in the Typical
Operating Characteristics). Program the switching fre-
quency so the harmonics do not fall within a sensitive
frequency band (Table 1). Audio reproduction is not
affected by changing the switching frequency.
Fixed-Frequency (FFM) Mode
Operating Modes