TDA8922C NXP Semiconductors, TDA8922C Datasheet - Page 10

• Manufacturer Part Number: TDA8922C
• Description: The TDA8922C is a high-efficiency Class D audio power amplifier
• Manufacturer: NXP Semiconductors

NXP Semiconductors
TDA8922C_1
Product data sheet
8.3.3 Window Protection (WP)
The value of the protection capacitor (C
10 pF and 220 pF (typically 47 pF). While OCP is activated, an internal current source is
enabled that will discharge C
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 TDA8922C amplifier is fully protected
against short-circuit conditions while avoiding audio holes.
Table 4.
[1]
Window Protection (WP) checks the conditions at the output terminals of the power stage
and is activated:
Type
TDA8922C
•
•
Short-circuit impedance < Z
and at the same time discharges the capacitor on pin PROT. When C
discharged, the amplifier shuts down completely and an internal timer is started.
Tested using three samples and an external clock.
During the start-up sequence, when the TDA8922C is switching from Standby to
Mute.
Current limiting behavior during low output impedance conditions at different
values of C
PROT
V
(V)
+29.5/
29.5
DD
/V
will also prevent the amplifier switching off due to transient
SS
Rev. 01 — 7 September 2009
PROT
V
500
I
(mV, p-p) f (Hz) C
[1]
PROT
th
: the amplifier limits the maximum output current to I
.
20
1000
20
1000
1000
PROT
10
10
15
15
220
PROT
PROT
) connected to pin PROT can be between
PROT
(pF)
(up to 220 pF) to delay amplifier
PROT
is partially discharged). Normal
PWM output stops
Short
(Z
yes
yes
yes
yes
no
2
th
is recharged). C
= 0 )
75 W class-D power amplifier
Short
(Z
yes
yes
yes
no
no
TDA8922C
th
= 0.5 )
PROT
© NXP B.V. 2009. All rights reserved.
PROT
PROT
, the amplifier
is partially
is fully
Short
(Z
yes
yes
yes
no
no
th
= 1 )
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