TDF8555J NXP Semiconductors, TDF8555J Datasheet - Page 12

• Manufacturer Part Number: TDF8555J
• Description: The TDF8555J is one of a new generation of complementary quad Bridge-Tied Load(BTL) audio power amplifiers with full I²C-bus controlled diagnostics, multiple voltageregulator and two power switches intended for automotive applications
• Manufacturer: NXP Semiconductors

NXP Semiconductors
TDF8555J
Product data sheet
7.4.1 Output protection and short-circuit protection
7.4.2 Loss-of-ground/loss of V
7.4 Protection
If a short-circuit to ground, V
only the amplifier with the short will be switched off. The channel that has a short-circuit
and the type of short-circuit can be read via the I
indicate there is a problem. The window protection prevents a restart of the channel with a
short to ground or battery. With a short across the load the amplifier is switched on again
after 15 ms to check if the short across the load is still present. If the short-circuit
conditions are still present, the channel is switched off. If several channels have a short
across the load at the same time, the channels are switched on one by one to prevent
high supply current switching with four shorts across the load at the same time. The 15 ms
cycle reduces power dissipation. To prevent audible distortion, the amplifier channel with
the short can be disabled via the I
Loss-of-ground/loss of V
not connected and the ground (or V
outputs. In this situation the supply capacitor in the set is charged through the body diode
of the output power transistor. This body diode (between the drain and the source of the
power transistor) is always present in amplifiers with MOS output stages. The capacitor
charge current depends on the series impedance of the supply lines, the output
impedance of the loss-of-ground tester and the value of the capacitor; see
simulate a worst-case condition, the loss-of-ground tester is equipped with a buffer
capacitor of 116 mF to simulate a very low output impedance. With a R
currents of more than 70 A have been measured.
Fig 5.
(1) Capacitor value can be 2200 F to 10000 F.
(2) Amplifier output stage.
Test circuit for loss-of-ground test
All information provided in this document is subject to legal disclaimers.
V P
Loss-of-ground tester
Rev. 1 — 15 September 2011
C buffer
116 mF
P
is a double-fault condition: the ground (or V
P
V pulse
P
4 45 W power amplifier with multiple voltage regulator
or across the load occurs on one or more amplifier outputs,
failure
2
C-bus.
NMOS
80N03L
P
) wire is connected to one of the loudspeaker
2200 μF
R S
(1)
2
C-bus. Pin DIAG is pulled LOW to
DUT in application
TDF8555J
P
(2)
001aam695
) wire of the set is
s
© NXP B.V. 2011. All rights reserved.
of 63 m, peak
3
5
7
9
17
19
21
23
Figure
5. To
12 of 57