TDA8950 NXP Semiconductors, TDA8950 Datasheet - Page 9

• Manufacturer Part Number: TDA8950
• Description: The TDA8950 is a high-efficiency Class D audio power amplifier
• Manufacturer: NXP Semiconductors

NXP Semiconductors
TDA8950_2
Product data sheet
8.3.1.2 OverTemperature Protection (OTP)
8.3.2 OverCurrent Protection (OCP)
If TFB fails to stabilize the temperature and the junction temperature continues to rise, the
amplifier will shut down as soon as the temperature reaches the thermal protection
activation threshold, T
after the temperature drops below T
The thermal behavior is illustrated in
In order to guarantee the robustness of the TDA8950, the maximum output current that
can be 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 TDA8950 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 6.
•
•
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
= 9.2 A) due, for example, to a short-circuit to a supply line or across the
30 dB
24 dB
act(th_prot)
Gain
0 dB
(dB)
Rev. 02 — 11 June 2009
th
) depends on the supply voltage.
PROT
. The amplifier will resume switching approximately 100 ms
(T
th
th
1
act(th_fold)
: the amplifier limits the maximum output current to I
: the amplifier limits the maximum output current to I
.
act(th_prot)
Figure
PROT
5 C)
6.
) connected to pin PROT can be between
.
2
T
act(th_fold)
T
act(th_prot)
2
150 W class-D power amplifier
3
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T
j
( C)
TDA8950
© NXP B.V. 2009. All rights reserved.
PROT
is fully
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ORM
ORM