TDF8555J NXP Semiconductors, TDF8555J Datasheet - Page 16

• 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
In the first stage an offset is generated across the load. To avoid plop-noise, the offset is
generated in 15 ms, next the actual load measurement is done. Finally, the offset across
the load is reduced again after 15 ms. The complete start-up measurement cycle lasts for
t
If the voltage of the outputs is more than 3.5 V during the first stage, the start-up
diagnostic is switched off to avoid damage to the amplifier. This can happen with a door
slam or with a short to V
valid after the first stage. If only 1 or 2 channels report not valid after the first stage, a short
to V
over-voltage during the start-up diagnostic cycle can be assumed.
The start-up diagnostics has a built-in spike filter to remove disturbances caused by
switching relays in the wiring harness or EMC. The door-slam processor filters out
disturbances caused when the car door closes: car door-slam can cause the speakers to
move slowly which disturbs the measurement. With these filter techniques, reliable load
detection is performed in a single start-up diagnostics cycle.
If required, the start-up diagnostics can be repeated. Only the first stage, where the
speaker load is determined, is sensitive to disturbance and can be repeated. When the
start-up diagnostics start, the invalid bits are set, and “the start-up diag busy bit” (bit
DB4[D6]) indicates that the start-up diagnostic is not yet completed. When the start-up is
completed, or interrupted by a POR, the “start-up diag busy bit” is reset.
sudiag
Fig 10. Start-up with start-up diagnostics
P
.
(1) First stage: open load/load/line driver short across the load.
(2) Second stage: amplifier start plus short to ground/V
or of those channels can be assumed. If all 4 channels report not valid, an under- or
turn on diagnostic
All information provided in this document is subject to legal disclaimers.
amplifier
IB1[D1]
enable
output
STB
Rev. 1 — 15 September 2011
P
. If a short to V
4 45 W power amplifier with multiple voltage regulator
P
t
sudiag
is applied, the shorted channel will report not
(1)
t
d(sudiag-on)
P
t
(2)
amp_on
speaker fault.
TDF8555J
001aam699
© NXP B.V. 2011. All rights reserved.
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