AN10436 PHILIPS [NXP Semiconductors], AN10436 Datasheet - Page 42

• Manufacturer Part Number: AN10436
• Description: TDA8932B/33(B) Class-D audio amplifier
• Manufacturer: PHILIPS [NXP Semiconductors]

NXP Semiconductors
AN10436_1
Application note
4.3 Low frequency supply pumping effect
A Single Ended (SE) Class-D amplifier will deliver energy back to the supply line (V
during the negative part of the audio signal. Because most power supplies are not capable
of sinking energy, the supply voltage will increase especially when driving the amplifier at
low audio frequencies. This phenomenon is often called the pumping effect.
The voltage increase caused by the pumping effect depends on:
This voltage increase might trigger the OVP of the audio amplifier and/or cause incorrect
control behavior of the regulated power supply.
The most effective way to overcome the pumping effect in a stereo SE application is to
apply one of the input signals to the negative input to invert the phase of that particular
output (see
Fig 39. Supply GND connection
•
•
•
•
•
•
The speaker impedance.
The supply voltage.
The audio signal frequency.
The capacitance value of the supply line.
The source/sink current of other channels (including the quiescent current of the
amplifier).
The current drawn from other circuits attached to the same supply line.
POWER SUPPLY
LEAVE FLOATING
FROM GROUND
(OR USE RC)
GND
Figure
GND
40).
Rev. 01 — 12 December 2007
PROCESSOR
SOUND
GND
DAC
OUT
FERRITE
BEAD
STAR GROUND
AMPLIFIER SIDE
TDA8932B/33(B) Class-D audio amplifier
DIFFERENTIAL INPUT
100nF
SOLID GROUND PLANE
AMPLIFIER TDA8932B/33(B)
LP
FILTER
AN10436
© NXP B.V. 2007. All rights reserved.
GND
SPEAKER
010aaa079
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