TDF8554J NXP Semiconductors, TDF8554J Datasheet - Page 19

• Manufacturer Part Number: TDF8554J
• Description: The TDF8554J 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
TDF8554J
Product data sheet
7.5.4 Distortion (clip-) detection
7.6 Line driver mode and low gain mode
If the amplifier output clips to the supply voltage or ground, the output signal becomes
distorted. If the distortion per channel exceeds a selectable threshold (2 %, 5 % or 10 %),
pin DIAG is activated.
The clip detection level can be programmed via the I
blocked below a supply voltage of 10 V to avoid false clip detection during engine start, or
can be programmed to operate at the low voltage detection level of 7.2 V or 5.5 V.
Since it is possible to have different amplifier gain settings between the front and rear
channels and there is only one clip reference current, the clip detect levels are only
accurate for the channels with the highest gain. In line driver mode the DC-output voltage
is 0.24V
The TDF8554J amplifier can be used as a line driver or as a low gain amplifier. In both
situations, the gain needs to be set to 16 dB via I
independently set for front channels (1 and 3) and rear channels (2 and 4). The main
difference between the line driver mode and low gain mode is the DC-output voltage.
In line driver mode the TDF8554J can be used to drive a separate amplifier or booster. In
this mode the DC output voltage is set to 0.23  battery voltage and is filtered with the
capacitor connected to pin SVR (V
half the battery voltage is to allow engine starts at a battery voltage as low as 6 V. The DC
output voltage remains approximately 3 V during engine start. If the DC output voltage is
set to half the battery voltage, with an engine start the common mode voltage will change
quickly from 7 V to 3 V. This drives the input stage of the booster below the ground level.
If the TDF8554J amplifier is used as a low gain amplifier in a booster, the DC output
voltage is set to half of the supply voltage to ensure maximum undistorted output power.
The line driver and low gain modes can be selected with I
Fig 13. AC-load impedance as a function of peak output voltage (low current AC-load
P
detection)
and clip detection will still indicate a clip, but the levels will not be accurate.
All information provided in this document is subject to legal disclaimers.
(W)
Z
Rev. 1 — 31 August 2011
L
50
40
30
20
10
0
0
4 45 W power amplifier with multiple voltage regulator
l
2
C-bus bits not set
no load detected,
SVR
). The reason to not set the DC output voltage to
2
trip level
2
C-bus (IB3[D5:D6]) and can be
4
load detected,
l
2
C-bus bits set
2
C-bus. The clip information is
V
oM
001aam702
(V)
2
C-bus IB4[D4].
6
TDF8554J
© NXP B.V. 2011. All rights reserved.
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