TDA8954 NXP Semiconductors, TDA8954 Datasheet - Page 11

• 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
8.4.2 OverCurrent Protection (OCP)
In order to guarantee the robustness of the TDA8954, 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 TDA8954 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
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, OTP and signal on pin DIAG1
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
V
PULL-UP
) depends on the supply voltage.
V
DIAG1
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
T
PROT
1
) connected to pin PROT can be between
2
2 × 210 W class-D power amplifier
010aaa562
3
TDA8954
© NXP B.V. 2009. All rights reserved.
PROT
is fully
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