TDA8920B NXP Semiconductors, TDA8920B Datasheet - Page 19

• Manufacturer Part Number: TDA8920B
• Description: The TDA8920B is a high efficiency class-D audio power amplifier with very lowdissipation
• Manufacturer: NXP Semiconductors

Philips Semiconductors
TDA8920B_2
Product data sheet
13.7 Pumping effects
In this way the TDA8920B amplifier is fully robust against short circuit conditions while at
the same time so-called audio holes as a result of loudspeaker impedance drops are
eliminated.
In a typical stereo half-bridge SE application the TDA8920B class-D amplifier is supplied
by a symmetrical voltage (e.g V
in a SE configuration, a so-called ‘pumping effect’ can occur. During one switching
interval, energy is taken from one supply (e.g. V
delivered back to the other supply line (e.g. V
source cannot sink energy, the voltage across the output capacitors of that voltage supply
source will increase: the supply voltage is pumped to higher levels. The voltage increase
caused by the pumping effect depends on:
The pumping effect should not cause a malfunction of either the audio amplifier and/or the
voltage supply source. For instance, this malfunction can be caused by triggering of the
undervoltage or overvoltage protection or unbalance protection of the amplifier.
Best remedy for pumping effects is to use the TDA8920B in a mono full-bridge application
or in case of stereo half-bridge application adapt the power supply (e.g. increase supply
decoupling capacitors).
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A typical value for the capacitor on the PROT pin is 220 pF. After a fixed time of
100 ms the amplifier is switched on again. If the requested output current is still too
high the amplifier will switch-off again. Thus the amplifier will try to switch to the
Operating mode every 100 ms. The average dissipation will be low in this situation
because of this low duty cycle. If the overcurrent condition is removed the amplifier will
remain in Operating mode once restarted.
Speaker impedance
Supply voltage
Audio signal frequency
Value of decoupling capacitors on supply lines
Source and sink currents of other channels
Rev. 02 — 07 November 2005
DD
= +27 V and V
SS
) and visa versa. When the voltage supply
DD
SS
), while a part of that energy is
= 27 V). When the amplifier is used
2
100 W class-D power amplifier
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
TDA8920B
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