Philips Semiconductors
Product specication
I2C-bus controlled 4 45 Watt power
amplier and multiple voltage regulator
TDA8589J; TDA8589xJ
V
(V)
V
P
V
BUCAP
V
O(REG2)
t (sec)
t
out of regulation
backup
VP – VO REG2 – 0.5
----------------------------------------------------
IL
tbackup = Cbackup
Fig.5 Backup capacitor function.
Reset output
Power switches
A reset pulse is generated at pin RST when the output
voltage of regulator 2 rises above the reset threshold
value. The reset output is a push-pull output that both
sources and sinks current. The output voltage can switch
between ground and VO(REG2), and operates at a low
regulator 2 voltage or VBUCAP. The RST signal is controlled
by a low-voltage detection circuit which, when activated,
pulls pin RST LOW (reset active) when VO(REG2) is
Vth(rst). If VO(REG2) Vth(rst), pin RST goes HIGH. The
reset pulse is delayed by 40 s internally. To extend the
delay and to prevent oscillations occurring at the threshold
voltage, an external capacitor can be connected to
pin RESCAP. Note that a reset pulse is not generated
when VO(REG2) falls below the reset threshold value.
There are two power switches that provide an unregulated
DC voltage output for amplifiers and an aerial motor
respectively. The switches have internal protection for
over-temperature conditions and are activated by setting
bits D2 and D3 of instruction byte IB1 to logic 1. The
regulated outputs will supply pulsed current loads that can
contaminate the line with high frequency noise, so it is
important to prevent any cross-coupling between the
regulated outputs, particularly with the 8.3 V audio supply,
and the unregulated outputs.
In the ON state, the switches have a low impedance to the
battery voltage. When the battery voltage is higher than
22 V, the switches are switched off. When the battery
voltage is below 22 V the switches are set to their original
condition.
Reset delay capacitor
A Reset Delay Capacitor (RDC) connected to
pin RESCAP can be used to extend the delay period of the
reset pulse and to ensure that a clean reset signal is sent
to the microcontroller. The RDC is charged by a current
source. The reset output (pin RST) will be released
(pin RST goes HIGH) when the RDC voltage crosses the
RDC threshold value.
2004 Feb 24
12
NXP [ NXP ]
