Philips TDA8920B, Product Data Sheet

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TDA8920B_2 © Koninklijke Philips Electronics N.V. 2005. All rights reserved.
Product data sheet Rev. 02 — 07 November 2005 10 of 34
Philips Semiconductors
TDA8920B
2
×
100 W class-D power amplifier
8.3.4 Supply voltage protections
If the supply voltage drops below
±
12.5 V, the UnderVoltage Protection (UVP) circuit is
activated and the system will shut-down correctly. If the internal clock is used, this
switch-off will be silent and without pop noise. When the supply voltage rises above the
threshold level, the system is restarted again after 100 ms. If the supply voltage exceeds
±
33 V the OverVoltage Protection (OVP) circuit is activated and the power stages will
shut-down. It is re-enabled as soon as the supply voltage drops below the threshold level.
So in this case no timer of 100 ms is started.
An additional UnBalance Protection (UBP) circuit compares the positive analog (V
DDA
)
and the negative analog (V
SSA
) supply voltages and is triggered if the voltage difference
between them exceeds a certain level. This level depends on the sum of both supply
voltages. An expression for the unbalanced threshold level is as follows:
V
th(ub)
≈
0.15
×
(V
DDA
+ V
SSA
).
When the supply voltage difference drops below the threshold level, the system is
restarted again after 100 ms.
Example: With a symmetrical supply of
±
30 V, the protection circuit will be triggered if the
unbalance exceeds approximately 9 V; see also Section 13.7 .
In Table 4 an overview is given of all protections and the effect on the output signal.
[1] Hysteresis of 20
°
C will influence restart timing depending on heatsink size.
[2] Only complete shut-down of amplifier if short-circuit impedance is below threshold of 1
Ω
. In all other cases
current limiting: resulting in clipping output signal.
[3] Fault condition detected during (every) transition between standby-to-mute and during restart after
activation of OCP (short to one of the supply lines).
Table 4: Overview of TDA8920B protections
Protection name Complete shut-down Restart directly Restart every 100 ms
OTP Y Y
[1]
N
[1]
OCP N
[2]
Y
[2]
N
[2]
WP Y
[3]
Y N
UVP Y N Y
OVP Y Y N
UBP Y N Y