MAX9742ETX+ Maxim Integrated Products, MAX9742ETX+ Datasheet - Page 22

• Manufacturer Part Number: MAX9742ETX+
• Description: IC AMP AUDIO PWR 20.5W D 36TQFN
• Manufacturer: Maxim Integrated Products
• Type: Class Dr

Specifications of MAX9742ETX+

• Output Type: 2-Channel (Stereo)
• Max Output Power X Channels @ Load: 20.5W x 2 @ 8 Ohm
• Voltage - Supply: 20 V ~ 40 V, ±10 V ~ 20 V
• Features: Depop, Differential Inputs, Mute, Short-Circuit and Thermal Protection, Shutdown
• Mounting Type: Surface Mount
• Package / Case: 36-TQFN Exposed Pad
• Product: Class-D
• Output Power: 16 W
• Thd Plus Noise: 0.08 %
• Supply Current: 15 mA
• Maximum Power Dissipation: 2.86 W
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Audio Load Resistance: 4 Ohms
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

To maximize the performance of the differential output
filter and minimize EMI radiation, keep the ground con-
nections of the C
PCB and place the filter near the MAX9742.
The component ratings for C
requirements mentioned in the Single-Ended LC Output
Filter Design (L
For speaker loads that have appreciable amounts of
voice coil inductance (> 33µH), peaking in the frequen-
cy response of the output may occur near the cutoff fre-
quency of the LC filter, which may cause the device to
go into current limit at high output powers. This peaking
is due to the resonant circuit formed by the LC output
filter and complex impedance of the speaker. To nullify
the peaking in the frequency response, connect a
Zobel network (series RC circuit) in parallel with the
speaker load as shown in Figure 10. The Zobel circuit
reduces the peaking by dampening the reactive behav-
ior of the speaker. For the single-ended output configu-
ration, use the following equations to calculate the
component values for the Zobel network:
where R
the value of the Zobel capacitor, R
tance of the speaker, and f
Single-/Dual-Supply, Stereo 16W,
Class D Amplifier with Differential Inputs
Figure 9. BTL LC Output Filter
22
______________________________________________________________________________________
ZBL
C
BRIDGE-TIED-LOAD (BTL) OUTPUT FILTER
OUTL
OUTR
ZBL
R
is the value of the Zobel resistor, C
ZBL
F
and C
=
F
=
2
capacitors close together on the
π
1.2
F
×
) section.
L
L
F
F
×
R
SPKR
R
C
1
SPKR
C
C
F
is the cutoff frequency of
F
F
and L
×
SPKR
( )
f
Ω
C
F
( )
F
follow the same
R
Zobel Network
is the DC resis-
SPKR
ZBL
is
the LC filter. For the BTL configuration, use half of the
BTL resistance for the Zobel network calculations.
Connect a ground-terminated Zobel network on each
side of the BTL resistance to prevent excessive peak-
ing in the common-mode response of the output filter.
For most applications, R
power rating of 1/4W or greater. C
voltage rating greater than or equal to V
Table 3. Recommended Differential LC
Filter Component Values for an 8Ω BTL
Speaker Load (f
Figure 10. Zobel Network Connections for High-Inductance
Speakers
NOTE: AN OUTPUT-COUPLING CAPACITOR (C
SINGLE-ENDED OUTPUT CONFIGURATION.
OUT_
OUTL
OUTR
DC Resistance of Speaker (Ω)
8
L
L
L
F
F
F
C
C
C
C
= 40kHz)
F
F
F
ZBL
C
C
C
R
R
R
OUT
ZBL
ZBL
ZBL
should have a minimum
ZBL
ZBL
ZBL
) IS NEEDED FOR SINGLE-SUPPLY,
ZBL
L
R
R
F
L
L
SPKR
SPKR
SPKR
SPKR
22
DD
(µH)
should have a
.
SPEAKER
SPEAKER
LOAD
LOAD
C
F
0.68
(µF)