MAX9708ETN+TD Maxim Integrated Products, MAX9708ETN+TD Datasheet - Page 13

• Manufacturer Part Number: MAX9708ETN+TD
• Description: IC AMP AUDIO PWR 42W STER 56TQFN
• Manufacturer: Maxim Integrated Products
• Type: Class Dr

Specifications of MAX9708ETN+TD

• Output Type: 1-Channel (Mono) or 2-Channel (Stereo)
• Max Output Power X Channels @ Load: 42W x 1 @ 4 Ohm; 21W x 2 @ 8 Ohm
• Voltage - Supply: 10 V ~ 18 V
• Features: Depop, Differential Inputs, Mute, Short-Circuit and Thermal Protection, Shutdown
• Mounting Type: Surface Mount
• Package / Case: 56-TQFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

TEMP returns high once the junction temperature cools
below the set threshold minus the thermal hysteresis. If
TEMP is connected to either MUTE or SS, the audio
output resumes. The temperature threshold is set by
the TH0, TH1, and TH2 inputs as shown in Table 1. An
RC filter may be used to eliminate any transient at the
TEMP output as shown in Figure 3.
The MAX9708 features four pin-selectable gain settings;
see Table 2.
Figure 3. An RC Filter Eliminates Transient During Switching
Table 1. MAX9708 Junction Temperature
Threshold Setting
Table 2. MAX9708 Gain Setting
TEMPERATURE
JUNCTION
High
High
Low
Low
G1
(°C)
100
110
120
129
139
150
80
90
TEMP
V
DIGITAL
______________________________________________________________________________________
10kΩ
20W/40W, Filterless, Spread-Spectrum,
High
High
High
High
TH2
Low
Low
Low
Low
High
High
Low
Low
10kΩ
G2
High
High
High
High
TH1
Low
Low
Low
Low
Gain Selection
0.1μF
Mono/Stereo, Class D Amplifier
GAIN (dB)
29.5
22
25
36
TO DIGITAL
INPUT
High
High
High
High
TH0
Low
Low
Low
Low
The MAX9708 features three switching frequencies in
the FFM mode (Table 3). In this mode, the frequency
spectrum of the Class D output consists of the funda-
mental switching frequency and its associated harmon-
ics (see the Wideband Output Spectrum graph in the
Typical Operating Characteristics). Select one of the
three fixed switching frequencies such that the harmon-
ics do not fall in a sensitive band. The switching fre-
quency can be changed at any time without affecting
audio reproduction.
The MAX9708 features a unique spread-spectrum
(SSM) mode that flattens the wideband spectral com-
ponents, improving EMI emissions that may be radiated
by the speaker and cables. This mode is enabled by
setting FS1 = FS2 = high. In SSM mode, the switching
frequency varies randomly by ±4% around the center
frequency (200kHz). The modulation scheme remains
the same, but the period of the triangle waveform
changes from cycle to cycle. Instead of a large amount
of spectral energy present at multiples of the switching
frequency, the energy is now spread over a bandwidth
that increases with frequency. Above a few megahertz,
the wideband spectrum looks like white noise for EMI
purposes. SSM mode reduces EMI compared to fixed-
frequency mode. This can also help to randomize visu-
al artifacts caused by radiated or supply-borne
interference in displays.
The MAX9708 SYNCIN input allows the Class D amplifi-
er to switch at a frequency defined by an external clock
frequency. Synchronizing the amplifier with an external
clock source may confine the switching frequency to a
less sensitive band. The external clock frequency range
is from 600kHz to 1.2MHz and can have any duty cycle,
but the minimum pulse must be greater than 100ns.
SYNCOUT is an open-drain clock output for synchro-
nizing external circuitry. Its frequency is four times the
amplifier’s switching frequency, and it is active in either
internal or external oscillator mode.
Table 3. Switching Frequencies
FS1
0
0
1
1
FS2
Spread-Spectrum Modulation (SSM) Mode
0
1
0
1
Fixed-Frequency Modulation (FFM) Mode
FREQUENCY (kHz)
SYNCOUT
200 ±4
Synchronous Switching Mode
200
250
160
Operating Modes
Spread-Spectrum
Fixed-Frequency
Fixed-Frequency
Fixed-Frequency
MODULATION
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