TDA8954 NXP Semiconductors, TDA8954 Datasheet - Page 12

• Manufacturer Part Number: TDA8954
• Description: The TDA8954 is a stereo or mono high–efficiency Class D audio power amplifier in asingle IC featuring low power dissipation
• Manufacturer: NXP Semiconductors

NXP Semiconductors
TDA8954_1
Product data sheet
When OCP is activated, the active power transistor is turned off and the other power
transistor is turned on to reduce the current (C
operation is resumed at the next switching cycle (C
discharge each time OCP is activated during a switching cycle. If the fault condition that
caused OCP to be activated persists long enough to fully discharge C
will switch off completely and a restart sequence will be initiated.
After a fixed period of 100 ms, the amplifier will attempt to switch on again, but will fail if
the output current still exceeds the OCP threshold. The amplifier will continue trying to
switch on every 100 ms. The average power dissipation will be low in this situation
because the duty cycle is short.
Switching the amplifier on and off in this way will generate unwanted ‘audio holes’. This
can be avoided by increasing the value of C
switch-off. C
frequency-dependent impedance drops at the speakers.
The amplifier will switch on, and remain in Operating mode, once the overcurrent
condition has been removed. OCP ensures the TDA8954 amplifier is fully protected
against short-circuit conditions while avoiding audio holes.
Table 4.
[1]
Pin DIAG2 pin can be used to:
When a short circuit occurs between the load and the supply voltage, the current will
increase rapidly to I
switching frequency will be transmitted on pin DIAG2 to indicate that OCP is active. If the
short circuit condition persists long enough to cause the OCP circuit to shut down the
amplifier, the DIAG2 signal will be transmitted continuously until the amplifier has started
up again and has commenced switching (see
Type
TDA8954 +41/−41
1. Monitor the OCP status - a pulsed signal at the switching frequency is generated on
2. Monitor the protection status - a pulsed signal with a minimum width of typically
OVP can be triggered by supply pumping; see
DIAG2 when current limiting has been enabled.
100 ms will be generated on pin DIAG2 to indicate that the amplifier has been
switched off by one of the protection circuits (see
generated at start-up before the amplifier output starts switching.
V
Current limiting behavior during low output impedance conditions at different
values of C
DD
PROT
/V
SS
will also prevent the amplifier switching off due to transient
(V) V
ORM
Rev. 01 — 24 December 2009
PROT
500
, when current limiting will be activated. A pulsed signal at the
I
(mV, p-p) f (Hz) C
20
1000
20
1000
1000
Section
(pF)
10
10
15
15
220
PROT
PROT
Figure
PROT
14.6.
(up to 220 pF) to delay amplifier
PWM output stops
Short
(Z
yes
yes
yes
yes
no
PROT
is partially discharged). Normal
th
9).
2 × 210 W class-D power amplifier
[1]
[1]
Table
= 0 Ω)
is recharged). C
5). This signal is also
Short
(Z
yes
no
yes
no
no
th
[1]
[1]
= 0.5 Ω)
PROT
TDA8954
© NXP B.V. 2009. All rights reserved.
PROT
, the amplifier
Short
(Z
yes
no
yes
no
no
is partially
th
[1]
[1]
= 1 Ω)
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