TDA3681ATH Просмотр технического описания (PDF) - Philips Electronics

Номер в каталоге

Компоненты Описание

Список матч

TDA3681ATH

Multiple voltage regulator with switch and ignition buffer

Philips Electronics 

Philips Semiconductors

Multiple voltage regulator with

switch and ignition buffer

Product specification

TDA3681A

FUNCTIONAL DESCRIPTION

The TDA3681A is a multiple output voltage regulator with

a power switch, intended for use in car radios with or

without a microcontroller. Because of the low voltage

operation of 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 feature is included to secure a smooth start-up of

the microcontroller at first connection, without uncontrolled

switching of regulator 2 during the start-up sequence.

The charge on the backup capacitor can be used to supply

regulator 2 for a short period when the external supply

voltage drops to 0 V (the time depends on the value of the

backup capacitor).

The output stages of all switchable regulators have an

extremely low noise behaviour and good stability, even for

small values of the output capacitors.

When both regulator 2 and the supply voltages (VP1 and

VP2 > 4.5 V) are available, regulators 1 and 3 can be

operated by means of one enable input.

Regulator 4 and the power switch have a separate enable

input.

Pin HOLD is normally HIGH but is active LOW. Pin HOLD

is connected to an open-collector NPN transistor and must

have an external pull-up resistor to operate. The hold

output is controlled by a 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 causes a 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

regulation when switching it on: regulator 1 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 hysteresis to 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 (regulators 1, 3 and 4 switch

off at supply voltages > 18 V) and short-circuit (foldback

current protection).

The power switch contains a current protection. However,

this protection is delayed at short-circuit by 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

least 3 A (after a delay, the power switch can deliver 1.8 A

continuous if VP ≤ 18 V).

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

VP − 0.4 V. At operating temperature, the power switch

can deliver at least 3 A. At high temperature, the switch

can deliver approximately 2 A.

handbook, full pagewidth

low battery

VP1

internal

detector

voltage reference

TDA3681A

TEMPERATURE

PROTECTION

LOAD DUMP

OR

HOLD

buffer

Fig.3 Block diagram of the hold circuit.

MGU564

2003 Aug 29

6

Share Link: