Class h operation, Headphone ground sense (hpsns), Figure 28. traditional amplifier output – Rainbow Electronics MAX98089 User Manual
Page 108: Class h operation headphone ground sense (hpsns)
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MAX98089
Low-Power, Stereo Audio Codec
with FlexSound Technology
Class H Operation
A Class H amplifier uses a Class AB output stage with
power supplies that are modulated by the output signal.
In the case of the ICs, two nominal power-supply differ-
entials of 1.8V (+0.9V to -0.9V) and 3.6V (+1.8V to -1.8V)
are available from the charge pump. Figure 29 shows the
operation of the output-voltage-dependent power supply.
Headphone Ground Sense (HPSNS)
HPSNS senses the ground return for the headphone
load. For optimal performance, connect HPSNS to the
ground pole of the jack through an isolated trace, as
shown in Figure 30. If HPSNS is not used, connect to the
analog ground plane.
Figure 28. Traditional Amplifier Output vs. DirectDrive Output
Figure 29. Class H Operation
Figure 30. HPSNS configurations
V
DD
V
DD
/2
GND
CONVENTIONAL AMPLIFIER BIASING SCHEME
DirectDrive AMPLIFIER BIASING SCHEME
+V
DD
GND
-V
DD
(V
SS
)
HPL
HPR
HPSNS
CONFIGURATION FOR OPTIMAL PERFORMANCE
HEADPHONE
JACK
HPL
HPR
HPSNS
CONFIGURATION FOR WHEN NOT USING HPSNS
HEADPHONE
JACK
32ms
32ms
1.8V
0.9V
V
TH_H
V
TH_L
-0.9V
-1.8V
HPVDD
HPVSS
OUTPUT
VOLTAGE