LM4947TL National Semiconductor, LM4947TL Datasheet - Page 28

• Manufacturer Part Number: LM4947TL
• Manufacturer: National Semiconductor

Specifications of LM4947TL

• Operational Class: Class-D
• Audio Amplifier Output Configuration: 1-Channel Mono/2-Channel Stereo
• Audio Amplifier Function: Headphone/Speaker
• Single Supply Voltage (typ): Not RequiredV
• Dual Supply Voltage (typ): 3/5V
• Power Supply Requirement: Triple
• Rail/rail I/o Type: No
• Power Supply Rejection Ratio: 76dB
• Single Supply Voltage (min): Not RequiredV
• Single Supply Voltage (max): Not RequiredV
• Dual Supply Voltage (min): 2.2/2.7V
• Dual Supply Voltage (max): 5.5V
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 25
• Package Type: uSMD
• Lead Free Status / Rohs Status: Not Compliant

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Note: L and R are selected by modes from Table 4.
On initial POWER ON, the default mode is 000
M = Mono
R = R
L = L
SD = Shutdown
MUTE = Mute Mode
G
G
G
NATIONAL 3D ENHANCEMENT
The LM4947 features a stereo headphone, 3D audio en-
hancement effect that widens the perceived soundstage from
a stereo audio signal. The 3D audio enhancement creates a
perceived spatial effect optimized for stereo headphone lis-
tening. The LM4947 can be programmed for a “narrow” or
“wide” soundstage perception. The narrow soundstage has a
more focused approaching sound direction, while the wide
soundstage has a spatial, theater-like effect. Within each of
these two modes, four discrete levels of 3D effect that can be
programmed: low, medium, high, and maximum (Table 2),
each level with an ever increasing aural effect, respectively.
The difference between each level is 3dB.
The external capacitors, shown in Figure 6, are required to
enable the 3D effect. The value of the capacitors set the cutoff
frequency of the 3D effect, as shown by Equations 1 and 2.
Note that the internal 20kΩ resistor is nominal (±25%).
M
R
L
= Left stereo volume control gain
= Right stereo volume control gain
Number
= Mono volume control gain
Output
IN
Mode
IN
0
1
2
3
4
5
6
7
FIGURE 5. External 3D Effect Capacitors
MC2
0
0
0
0
1
1
1
1
MC1
0
0
1
1
0
0
1
1
MC0
0
1
0
1
0
1
0
1
G
Handsfree Mono Output
L
x L + G
TABLE 6. Output Mode Selection
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G
G
L
R
2 x G
x L + G
x R + G
R
x R + 2(G
SD
SD
SD
SD
M
x M
R
L
x R
x L
28
M
x M)
Optional resistors R
7) to affect the -3dB frequency and 3D magnitude.
FIGURE 6. External RC Network with Optional R
f
f
3DR(-3dB)
3DL(-3dB)
Right HP Output
G
R
f
f
3DR(-3dB)
3DL(-3dB)
x R + G
G
G
G
MUTE
MUTE
MUTE
M
R
R
= 1 / 2π * (20kΩ + R
SD
= 1 / 2π * 20kΩ + R
x M
x R
x R
3DL
= 1 / 2π * 20kΩ * C
= 1 / 2π * 20kΩ * C
M
R
x M
and R
3DR
Resistors
3DR
can also be added (Figure
3DR
3DL
G
Left HP Output
) * C
) * C
3DL
3DR
L
x L + G
G
MUTE
MUTE
MUTE
G
G
3DR
3DL
M
SD
L
L
x M
x L
x L
M
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x M
3DL
and
(1)
(2)
(3)
(4)