AN10436 PHILIPS [NXP Semiconductors], AN10436 Datasheet - Page 14

• Manufacturer Part Number: AN10436
• Description: TDA8932B/33(B) Class-D audio amplifier
• Manufacturer: PHILIPS [NXP Semiconductors]

NXP Semiconductors
Table 2.
[1]
[2]
[3]
AN10436_1
Application note
Feature
OCP
Low ohmic short
across the load
OTP
WP threshold level at V
DIAG is active low for at least 50 ms.
UBP threshold level at V
Overview of all the limiting and protection features inside the TDA8932B/33(B)
2.6.1 Thermal Foldback (TF)
2.6.2 Cycle-by-cycle current limiting
2.6.3 Window Protection (WP)
TDA8932B
TDA8933(B) 2.0 A
-
When the junction of the TDA8932B/33(B) exceeds 140 °C, the TF will gradually reduce
the gain, limiting the power dissipation. This means that the device will not switch off, but
will continue to operate at a slightly lower gain, causing no audio holes (interruptions). The
maximum junction temperature will not go beyond the absolute maximum temperature.
Therefore, a heat sink is not required and the thermal design becomes less critical and
less temperature head room requires to be taken into account since audio holes will not
occur and the device will always stay within the Safe Operating Area (SOA).
When the output current of the device exceeds either 4 A (TDA8932B) or
2 A (TDA8933(B)), the cycle-by-cycle current limitation becomes active. This means the
device will not switch off, but continue to operate while limiting the current without causing
audio holes (interruptions). The maximum output current will not go beyond the absolute
maximum current.
Remark: When the cycle-by-cycle current limiting becomes active, it will cause distortion.
See
the supply voltage and the speaker impedance.
WP checks the voltage at the PWM outputs (OUT1 pin 27 and OUT2 pin 22) before the
power stage is enabled (transition from SLEEP mode to MUTE / OPERATING mode). To
avoid large currents flowing, the WP is activated (power stage stays floating) in the event
of a short from the PWM output to either V
50 ms.
The PWM output voltage where the WP becomes active at an asymmetrical supply can be
calculated as follows:
Low threshold level:
P
V
P
= 22 V. See
O wp
= 22 V. See
(
Section 3.2
)l
155 °C
Trigger level
Min
4.0 A
=
11
----- - V
32
Equation 3
Equation 5
⋅
DDA
for information on how to calculate the peak output current, depending on
Typ
5.0 A
2.3 A
-
and
Rev. 01 — 12 December 2007
and
Equation 4
Equation 6
Max
-
-
160 °C
for the threshold level versus the supply voltage.
for the threshold level versus the supply voltage.
DIAG
output
low
low
[2]
[2]
DD
or V
TDA8932B/33(B) Class-D audio amplifier
Remark
Power stage becomes floating entering
FAULT mode. (See
Power stage becomes floating entering
FAULT mode. (See
SS
. The DIAG is set to low for at least
…continued
Section
Section
AN10436
© NXP B.V. 2007. All rights reserved.
2.6.7)
2.6.8)
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