AN10436 PHILIPS [NXP Semiconductors], AN10436 Datasheet - Page 16

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

NXP Semiconductors
AN10436_1
Application note
2.6.7 OverCurrent Protection (OCP)
The TDA8932B/33(B) will recover when the supply voltage is within
(8/5) V
The supply voltage at which the UBP becomes active with a symmetrical supply can be
estimated as follows:
Low threshold level:
High threshold level:
Where:
Example asymmetrical supply (use
At a supply voltage of 22 V, the voltage on HVPREF is equal to V
HVPREF voltage is buffered so the level will change only very slowly. When the supply
voltage drops quickly (dV/dt > 4 V/s), the UBP is triggered below 17.6 V. When the supply
voltage increases quickly, the UBP is triggered above 29.3 V.
Remark: With either an unregulated or a weak power supply, it might happen that this
UBP is triggered, e.g., because of a voltage drop during a transient from no load to full
load condition. See
The OCP is activated only in a fault condition when the current exceeds 4 A (TDA8932B)
or 2 A (TDA8933(B)) because of either a low ohmic short across the load or a low ohmic
short from the demodulated output (after the inductor) to either V
set low for 50 ms and the internal timer of 100 ms is started. The timer or the WP will keep
the power stage disabled for at least 100 ms. As long as the short remains across the
load, this cycle will repeat. The average power dissipation in the TDA8932B/33(B) will be
low because the short circuit current will flow only during a very small part of the timer
cycle of 100 ms.
When the current exceeds 4 A (TDA8932B) or 2 A (TDA8933(B)) during normal operation,
only the cycle-by-cycle current limiting is active without causing any audio holes
(interruptions). See also
V
V
DDA ubp
DDA ubp
V
V
V
V
HVPREF
DDA(ubp)
HVPREF
SSA
(
(
HVPREF
= negative analog supply voltage (pin 9) referenced to V
)l
)h
= half supply voltage reference (pin 11) referenced to V
(V), HVPREF is connected to GND.
=
= unbalance protection analog supply voltage. V
=
3
-- - V
5
> V
5
-- - V
3
⋅
⋅
P
SSA
SSA
> (8/3) V
Section 4.4
Rev. 01 — 12 December 2007
Section
HVPREF
for more detail.
2.6.2.
.
Equation 5
TDA8932B/33(B) Class-D audio amplifier
and
Equation
DDA
6):
HVPREF
(pin 8) referenced to
SS
HVPREF
SSA
or V
(V)
AN10436
© NXP B.V. 2007. All rights reserved.
(V)
DD
= 11 V. The
. The DIAG is
16 of 55
(7)
(8)