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TDA3681ATH
Multiple voltage regulator with switch and ignition buffer
Philips Semiconductors Product specification
Multiple voltage regulator with
switch and ignition buffer TDA3681A
FEATURES
General Extremely low noise behaviour and good stability with
very small output capacitors Second supply pin for regulators 3 and 4 to reduce
power dissipation (e.g. via a DC-to-DC converter) Three VP-state controlled regulators (regulators1,3
and 4) and a power switch Regulator2, reset and ignition buffer operational during
load dump and thermal shutdown Combined control pin for switching regulators 1 and3 Separate control pins for switching regulator 4 and the
power switch Supply voltage range from −18Vto +50V Low quiescent current in standby mode (when
regulators1,3 and4 and power switch are switchedoff
and ignition input is low) Hold output for low VP, load dump and temperature
protection Reset (push-pull output stage) for regulator 2 and hold
output (open-collector output) Adjustable reset delay time High supply voltage ripple rejection Backup capacitor for regulator2 One independent ignition buffer (active HIGH).
Protections Reverse polarity safe (down to −18 V without high
reverse current) Able to withstand voltages up to 18 V at the outputs
(supply line may be short-circuited) ESD protection on all pins Thermal protections Load dump protection Foldback current limit protection for regulators1,2,3
and4 Delayed second current limit protection for the power
switch (at short circuit) The regulator outputs and the power switch are short-circuit safe to ground and supply (VP).
GENERAL DESCRIPTIONThe TDA3681Aisa multiple output voltage regulator with power switch andan ignition buffer.Itis intendedfor use
in car radios with or without a microcontroller.
The TDA3681A contains the following: Four fixed voltage regulators with a foldback current
protection (regulators1,2,3 and4). Regulator2, which
is intended to supply a microcontroller, also operates
during load dump and thermal shutdown Regulators3 and 4 have a second supply pin that can
be connected to a lower supply voltage (> 6.5 V) to
reduce the power dissipation A power switch with protection, operated by a control
input Reset and hold outputs that can be used to interface
with the microcontroller; the reset signal canbe usedto
call up the microcontroller Both supply pins can withstand load dump pulses and
negative supply voltages Regulator 2, which is in regulation at a backup voltage
above 6.5VA provisionfor the useofa reserve supply capacitor that
will hold enough energyfor regulator2(5V continuous)
to allow a microcontroller to prepare for loss of voltage An ignition input Schmitt trigger with push-pull output
stage.
ORDERING INFORMATION
Philips Semiconductors Product specification
Multiple voltage regulator with
switch and ignition buffer TDA3681A
QUICK REFERENCE DATA
Philips Semiconductors Product specification
Multiple voltage regulator with
switch and ignition buffer TDA3681A
BLOCK DIAGRAM
Philips Semiconductors Product specification
Multiple voltage regulator with
switch and ignition buffer TDA3681A
PINNING
Note The pin is used for final test purposes. In the
application it should be connected directly to ground.
Philips Semiconductors Product specification
Multiple voltage regulator with
switch and ignition buffer TDA3681A
FUNCTIONAL DESCRIPTIONThe TDA3681Aisa multiple output voltage regulator with
a power switch, intended for use in car radios with or
without a microcontroller. Because of the low voltage
operationof the car radio, low voltage drop regulators are
used.
Regulator 2 is in regulation when the backup voltage
exceeds 6.5 V for the first time. When regulator 2 is
switched on and its output voltage is within its voltage
range, the reset output is disabled to release the
microcontroller. The reset delay time before release can
be extended by an external capacitor (CCRES). This
start-up featureis includedto securea smooth start-upof
the microcontrollerat first connection, without uncontrolled
switching of regulator 2 during the start-up sequence.
The chargeon the backup capacitor canbe usedto supply
regulator 2 for a short period when the external supply
voltage dropsto0V (the time dependson the valueof the
backup capacitor).
The output stages of all switchable regulators have an
extremely low noise behaviour and good stability, evenfor
small values of the output capacitors.
When both regulator 2 and the supply voltages (VP1 and
VP2> 4.5 V) are available, regulators1 and 3 can be
operated by means of one enable input.
Regulator4 and the power switch havea separate enable
input.
Pin HOLDis normally HIGH butis active LOW. Pin HOLD connectedtoan open-collector NPN transistor and must
have an external pull-up resistor to operate. The hold
outputis controlledbya low battery voltage (VP1) detection
circuit which, when activated, pulls the hold output LOW
(enabled).
The hold circuit is also controlled by the temperature and
load dump protection. Activating the temperature or load
dump protection causesa hold (LOW) during the time that
the protection is activated.
The hold circuit is enabled at low battery voltages. This
indicates that it is not possible to get regulator 1 into
regulationwhen switchingit on: regulator1 has the highest
output voltage (8.5 V) of all switchable regulators.
Therefore, regulator 1 is the most critical regulator with
respect to an out of regulation condition caused by a low
battery voltage.
The hold function includes hysteresisto avoid oscillations
when the battery voltage crosses the hold threshold levels
for low VP and load dump. The block diagram of the hold
function is illustrated in Fig.3.
All output pins are fully protected. The regulators are
protected against load dump (regulators1,3 and4 switch
off at supply voltages >18 V) and short-circuit (foldback
current protection).
The power switch containsa current protection. However,
this protectionis delayedat short-circuitby the reset delay
capacitor (it should be noted that this is the second
function of the reset delay capacitor CCRES). During this
time, the output current is limited to a peak value of at
least3A (aftera delay, the power switch can deliver 1.8A
continuous if VP≤18V).
In a normal situation, the voltage on the reset delay
capacitor is approximately 3.5 V (depending on the
temperature). The power switch output is approximately− 0.4 V. At operating temperature, the power switch
can deliver at least 3 A. At high temperature, the switch
can deliver approximately 2A.
Philips Semiconductors Product specification
Multiple voltage regulator with
switch and ignition buffer TDA3681A
During an overload condition or a short circuit
(VSW
capacitor rises 0.6V above the voltageof regulator2. This
rise time depends on the capacitor connected to
pin CCRES. During this time, the power switch can deliver
more than 3 A. When regulator 2 is out of regulation and
generates a reset, the power switch can only deliver 2A
and will immediately go into foldback protection. supply voltages>17V, the power switchis clampedat V maximum (to avoid externally connected circuits
being damaged by an overvoltage) and the power switch
will switch off at load dump.
Interfacing with the microcontroller (simple full or semi
on/off logic applications) can be realized with an
independent ignition Schmitt trigger and ignition output
buffer (push-pull output).
The timing diagrams are illustrated in Figs4 and5.
The second supply voltage VP2is usedfor the switchable
regulators3 and4. This input canbe connectedtoa lower
supply voltageof≥6Vto reduce the power dissipationof
the TDA3681A. A DC-to-DC converter could be used for
this purpose.
Philips Semiconductors Product specification
Multiple voltage regulator with
switch and ignition buffer TDA3681A
Philips Semiconductors Product specification
Multiple voltage regulator with
switch and ignition buffer TDA3681A
LIMITING VALUES
In accordance with the Absolute Maximum Rating System (IEC 60134).
THERMAL CHARACTERISTICS
QUALITY SPECIFICATION
In accordance with “General Quality Specification For Integrated Circuits (SNW-FQ-611)”.
Philips Semiconductors Product specification
Multiple voltage regulator with
switch and ignition buffer TDA3681A
CHARACTERISTICS
VP1 =VP2= 14.4 V; Tamb =25 °C; measured in test circuit of Fig.8; unless otherwise specified.
Philips Semiconductors Product specification
Multiple voltage regulator with
switch and ignition buffer TDA3681A
