TDF8554J NXP Semiconductors, TDF8554J Datasheet - Page 21

• 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
8.1 Standby regulator output
8.2 Backup capacitor
8.3 Backup function
The quiescent current has a very low level of 150 A (typical value) with only regulator 2
active. Due to the low voltage operation of the application, low dropout voltage regulators
are used.
All the regulators, except for the standby regulator, can be controlled by the I
device has in addition to the regulators, two I
capable of delivering 400 mA continuous current. This device has several fail-safe
protection modes. This module conforms to peak transient tests and protects against high
continuous voltage (24 V), short-circuits and thermal stress. The standby regulator will
maintain output as long as possible even in thermal shutdown or any other fault condition.
During overvoltage stress, all outputs except regulator 2will shut off and the device is able
to supply a minimum current for an indefinite amount of time allowing sustained memory
for a microprocessor. Also, there is a provision for use of a reserve supply capacitor that
will hold enough energy for regulator 2 to allow a microprocessor to prepare for loss of
voltage.
Regulator 2 is intended as a supply for a microcontroller. It has a low quiescent current
and cannot be switched. This regulator will not shut down with the switched regulators and
cannot be controlled by the I
transients or high temperature protection.
The backup capacitor (C
the battery supply voltage (V
A backup function is implemented by a switch which behaves like an ideal diode between
pins V
flowing through it. This function allows regulator 2 to be supplied during brief periods when
no supply voltage is present on pin V
pin BUCAP and ground. When the supply voltage is present on pin V
be charged to a level of V
when V
The delay time (t
Example: V
and C
When an overvoltage condition occurs, the voltage on pin BUCAP is limited to
approximately 24 V.
t
delay
backup
P
=
P
and BUCAP. The forward voltage of this ideal diode depends on the current
C
is absent for a short time.
backup
P
= 100 F providing a t
= 14.4 V, V
All information provided in this document is subject to legal disclaimers.

delay
R
L
) can be calculated using

Rev. 1 — 31 August 2011


V
----------------------------------------------
REG2
backup
P
P
–
 0.3 V. This charge can now be used to supply regulator 2
2
P

C-bus. This regulator will not shut down during load dump
(voltage on pin REG2) = 5.0 V (N2) or 3.3 V (N4), R
4 45 W power amplifier with multiple voltage regulator
V
) is used as a backup supply for the regulator 2 output when
) cannot support the regulator 2 voltage.
V
REG2
REG2
delay
–
P
. It requires an external capacitor connected to
0.5
of 178 ms (N2) or 321 ms (N4).



2
C-controlled power switches which are
Equation
1:
TDF8554J
P
this capacitor will
© NXP B.V. 2011. All rights reserved.
2
C-bus. The
L
= 1 k
21 of 56
(1)