TS4621ML STMICROELECTRONICS [STMicroelectronics], TS4621ML Datasheet - Page 32

• Manufacturer Part Number: TS4621ML
• Description: High-performance class-G stereo headphone amplifier
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

Application information
4.4.1
Figure 70. Incorrect ground connection for single-ended option
32/40
Audio driver
VaudioL
Right output
Left output
VaudioR
Vmc
The gain range in these configurations remains unchanged and is given by:
With reference to
Layout recommendations for single-ended operation
The connection location of each input that has to be set to ground is extremely important.
Incorrect connection location
If these inputs are connected to AGnd (the ground of the TS4621ML class-G), the output
voltage can be expressed by the following simplified equation from an AC point of view.
Equation 1
Vout = Av x (Vaudio + Vmc + Vgndnoise) + Vbatnoise x PSRR
As shown in
multiplied by the gain of the amplifier. If Vmc can be totally controlled by the design of the
audio source device (no parasitic AC voltage), it is not necessarily the case for Vgndnoise.
This noise can be significantly reduced by an adequate low impedance ground plane, but
not totally eliminated. In practice, only ten millivolts in the right frequency range are enough
to produce an audible parasitic sound in the headphone with a volume level as low as
-20 dB.
Equation
Figure
Vgndnoise
Cin
1 µF
Cin
1 µF
Cin
1 µF
Cin
1 µF
1, any ground noise and any parasitic AC voltage on Vmc is directly
69, note that the absolute phase in the audio band is 180°.
InL-
InR-
InL+
InR+
Doc ID 023181 Rev 1
VoutLR
2.2 µF
Css
PVss
Cs
2.2 µF
-
+
=
-
+
Negative
supply
VinLR Gain
AVdd
C1
Vbat
Positive
supply
detector
detector
C12
2.2 µF
Level
Level
C2
×
Sw
HpVdd
AGnd
VoutR
L1
3.3 µH
VoutL
CMS
Ct
10 µF
12 ohms min.
12 ohms min.
Rout
Rout
TS4621ML
3
2
1
Cout
0.8 nF min.
Cout
0.8 nF min.
J1
AM06154