TDF8590TH_2 © NXP B.V. 2007. All rights reserved.
Product data sheet Rev. 02 — 23 April 2007 8 of 30
NXP Semiconductors
TDF8590TH
2 × 80 W SE (4 Ω) or 1 × 160 W BTL (8 Ω) class-D amplifier
6.4.4 Window protection
The WP checks the conditions at the output terminals of the power stage and is activated:
• During the start-up sequence, when pin MODE is switched from standby to mute. In
the event of a short-circuit at one of the output terminals to V
DD
or V
SS
the start-up
procedure is interrupted and the TDF8590TH waits until the short to the supply lines
has been removed. Because the test is done before enabling the power stages, no
large currents will flow in the event of a short-circuit.
• When the amplifier is completely shut down due to activation of the OCP because a
short to one of the supply lines is made, then during restart (after 100 ms) the window
protection will be activated. As a result the amplifier will not start up until the short to
the supply lines is removed.
6.4.5 Supply voltage protections
If the supply voltage drops below ±12.5 V, the UVP circuit is activated and the
TDF8590TH switch-off will be silent and without pop noise. When the supply voltage rises
above ±12.5 V, the TDF8590TH is restarted again after 100 ms.
If the supply voltage exceeds ±33 V the OVP circuit is activated and the power stages will
shut down. It is re-enabled as soon as the supply voltage drops below ±33 V. So in this
case no timer of 100 ms is started. The maximum operating supply voltage is ±29 V and if
the supply voltage is above the maximal allowable voltage of ±34 V (see Section 7), the
TDF8590TH can be damaged, irrespective of an activated OVP. See Section 12.6
“Pumping effects” for more information about the use of the OVP.
An additional 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
the unbalance threshold level, which is expressed as follows:
V
When the supply voltage difference V
DDA
− V
SSA
exceeds V
th(unb)
, the TDF8590TH
switches off and is restarted again after 100 ms.
Example: With a symmetrical supply of V
DDA
= 20 V and V
SSA
= −20 V, the unbalance
protection circuit will be triggered if the unbalance exceeds approximately 6 V.
In Table 4 an overview is given of all protections and the effect on the output signal.
[1] Amplifier gain will depend on junction temperature and heat sink size.
[2] Thermal foldback will influence restart timing depending on heat sink size.
Table 4. Overview protections TDF8590TH
Protection name Complete shut down Restart directly Restart every 100 ms DIAG
TF N Y
[1]
NN
OTP Y Y
[2]
N
[2]
N
OCP N
[3]
Y
[3]
N
[3]
Y
WP Y
[4]
YN Y
UVP Y N Y N
OVP Y Y N N
UBP Y N Y N
V
th unb()
0.15 V
DDA
V
SSA
–()×≈
