TDA8922C NXP Semiconductors, TDA8922C Datasheet - Page 9

• 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
8.3.1.2 OverTemperature Protection (OTP)
8.3.2 OverCurrent Protection (OCP)
TFB is specified at the thermal foldback activation temperature T
closed-loop voltage gain is reduced by 6 dB. The TFB range is:
T
The value of T
details.
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 TDA8922C, 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 TDA8922C amplifier distinguishes between low-ohmic short-circuit conditions and
other overcurrent conditions such as a dynamic impedance drop at the loudspeakers. The
impedance threshold (Z
How the amplifier reacts to a short circuit depends on the short-circuit impedance:
Fig 6.
act(th_fold)
•
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).
(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
5 C < T
act(th_fold)
= 6 A) due, for example, to a short-circuit to a supply line or across the
act(th_fold)
Rev. 01 — 7 September 2009
30 dB
24 dB
act(th_prot)
Gain
0 dB
(dB)
for the TDA8922C is approximately 153 C; see
th
) depends on the supply voltage.
< T
. The amplifier will resume switching approximately 100 ms
(T
th
1
act(th_fold)
act(th_prot)
: the amplifier limits the maximum output current to I
act(th_prot)
Figure
5 C)
6.
.
2
T
act(th_fold)
T
act(th_prot)
2
75 W class-D power amplifier
3
001aah656
T
j
act(th_fold)
( C)
TDA8922C
© NXP B.V. 2009. All rights reserved.
Table 8
where the
for more
9 of 40
ORM