TDA3602 datasheet(19/26 Pages) PHILIPS

19 / 26 page

July 1994

Philips Semiconductors

Product speciﬁcation

Multiple output voltage regulator

TDA3602

A reset by the hold function can only be created when the

state control pin remains LOW. This is accomplished by

means of transistor T1 when Port P0,0 is high ohmic.

Because of resistors R2, R3 and R5 the transistor will

switch off when Vignition falls below a level of 5.0 V. During

an engine start, when Vignition reaches voltages as low as

5 V, the transistor will switch off. Regulators 1 and 2 are

already switched of by means of the VP Schmitt-trigger,

causing the HOLD output to go LOW. When Vignition again

increases the transistor will be switched on again (Port

P0,0 has to be open = logic 1), thereby switching the state

control pin to 0 V. As Vignition continues to increase above

7.6 V (Vrise of the VP1 Schmitt-trigger) Regulators 1 and 2

will again switch on causing the HOLD output to go HIGH,

creating a new reset pulse.

The set can also be switched off by opening the ignition

key, causing transistor T1 to switch off. When the ignition

key is closed again, the set will restart to the original

situation that existed before the ignition key was opened.

The charge time of C6 equals 3

× R4 × C6 = 14ms. This is

less than the reset time tresres(rise). To avoid the TDA3602

switching to coma mode before the microprocessor is

awakened, a double function has been given to T1. During

a reset pulse T1 is on (because of resistor R7), thus Vsc will

remain 0 V provided a reset occurs. After the reset pulse

has disappeared, the microprocessor is able to fully

control Vsc by mean of Port P0,0 or Port P1,1.

Security code circuitry

When the set is off and it is pulled out of RETRACK,

×3 and

×4 are disconnected thereby switching the base of

transistor T1 to the output voltage of Regulator 3 (using

resistors R5 and R6). Transistor T1 is starting to conduct

and a RESET pulse is generated. The microprocessor is

activated and checks if Port P1,0 = logic 1. If this is so, the

microprocessor knows that the set is pulled out of

RETRACK and that time is limited to finish the program

correctly (because the microprocessor is operating on the

charge of capacitor C3). The security flag has to be set in

an EEPROM and the microprocessor can switch to

power-down before Regulator 3 switches to power-off.

Another possibility is that the set was running and pulled

out of RETRACK. Now a hold is generated, and the hold

interrupt routine has to check the security in Port P1,0.

R6 is an internal resistor in the microprocessor. An

external resistor limits however the spread.

Bulb circuitry

The lights are switched on provided the RESET output of

the TDA3602 is HIGH. This normally occurs when the set

is switched on. Only at first connection (power-off) will the

RESET output be HIGH when the set is off. In this event

the lights are also switched on. This is not a problem

because the required time for initializing the

microprocessor will be very short.

When a load dump occurs, the RESET output will go LOW,

disabling the lights. With the aid of this feature it is possible

to prevent the light bulbs being damaged at load dump.

Noise.

Regulators 1 and 2 are loaded with a 47

µF/16 V load

capacitor because of output noise. With this value the

output noise will be lower than 220

µV for Regulator 1 and

lower than 120

µV for Regulator 2 (see Table 3 and

associated text).

To minimize the noise on the supply line, capacitors C1

and C2 should be placed as close as possible across the

supply and ground pins of the TDA3602.

Timing diagram

In the timing diagram all of the situations which can occur

are shown (see Fig.12). A HIGH of switch S1 indicates that

S1 is pressed. A HIGH on Port P0,0 indicates that Port

P0,0 is high ohmic (Port P0 is an open-collector output). If

no open-collector output is available another port can be

used, but an extra diode has to be added in series with this

port to prevent T1 being switched on by this port. A HIGH

for the microprocessor indicates that the microprocessor is

operating, a LOW indicates that the microprocessor is in

standby mode.

The following situations are covered in the timing diagram:

1. Initialization of the microprocessor (TDA3602 in

power-off mode)

2. Switching the ignition with the set off (Port P0,0 =

logic 0)

3. Switching the set on/off/on by pressing S1 sequentially

(ignition available)

4. Switching behaviour at engine start and load dump

(set on)

5. Switching the set off and on again by switching the

ignition.

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