TDA8953 NXP Semiconductors, TDA8953 Datasheet - Page 10

• Manufacturer Part Number: TDA8953
• Description: The TDA8953 is a stereo or mono high-efficiency Class D audio power amplifier in a single IC featuring low power dissipation
• Manufacturer: NXP Semiconductors

NXP Semiconductors
TDA8953_1
Product data sheet
8.3.2 OverCurrent Protection (OCP)
In order to guarantee the robustness of the TDA8953, the maximum output current
delivered at the output stages is limited. OCP is built in for each output power switch.
OCP is activated when the current in one of the power transistors exceeds the OCP
threshold (I
load.
The TDA8953 amplifier distinguishes between low-ohmic short-circuit conditions and
other overcurrent conditions such as a dynamic impedance drop at the loudspeaker. The
impedance threshold (Z
How the amplifier reacts to a short circuit depends on the short-circuit impedance:
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.
Fig 8.
•
•
Short-circuit impedance > Z
but the amplifier does not shut down the PWM outputs. Effectively, this results in a
clipped output signal across the load (behavior very similar to voltage clipping).
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.
(1) Duty cycle of PWM output modulated according to the audio input signal.
(2) Duty cycle of PWM output reduced due to TFB.
(3) Amplifier is switched off due to OTP.
Behavior of TFB and OTP
ORM
= 12 A) due, for example, to a short-circuit to a supply line or across the
Rev. 01 — 24 December 2009
Gain
[dB]
th
) depends on the supply voltage.
PROT
30
24
0
th
th
: the amplifier limits the maximum output current to I
: the amplifier limits the maximum output current to I
.
T
PROT
1
) connected to pin PROT can be between
PROT
PROT
is partially discharged). Normal
2
2 × 210 W class-D power amplifier
is recharged). C
010aaa620
3
PROT
TDA8953
© NXP B.V. 2009. All rights reserved.
PROT
PROT
, the amplifier
is partially
is fully
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ORM
ORM