TDA3629 데이터 시트보기 (PDF) - Philips Electronics

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TDA3629

Light position controller

Philips Electronics 

Philips Semiconductors

Light position controller

Product specification

TDA3629

FUNCTIONAL DESCRIPTION

The device is intended to control the elevation of the light

beam of a head light of a passenger car. The driver can

control the elevation of the light beam by rotating a

potentiometer on the dashboard (the setting

potentiometer). The device adapts the elevation of the light

beam by activating the control motor. The elevation of the

head light is fed back to the device by a second

potentiometer (the feedback potentiometer).

This feedback potentiometer is mechanically coupled to

the motor.

The device operates only when the supply voltage is within

certain limits. The device is switched off outside these

boundaries. The under voltage detection detects whether

the supply voltage is below the under voltage threshold.

The motor will not be activated when this occurs, but it

remains short-circuited by the output stages.

The over voltage will switch off the total device when the

supply voltage is higher than the over voltage threshold.

A thermal protection circuit becomes active if the junction

temperature exceeds a value of approximately 160 °C.

This circuit will reduce the motor current, which will result

in a lower dissipation and hence a lower chip temperature.

This condition will only occur when the motor is blocked at

high ambient temperature.

A detection of a broken wire of the slider of the setting

potentiometer is included because it will be connected to

the device by a wire several meters long. This detection

circuit prevents the motor from rotating when the wire is

broken. In this event the brake will remain active.

The protection of VSET to VP circuit prevents the motor

from rotating when the voltage at the VSET input is above

the threshold value. This can be used to detect whether

the wire from the slider of the setting potentiometer is

short-circuited to the battery line. A protection of VSET

short-circuited to ground is also present. The motor will be

stopped if VSET becomes lower than the threshold level.

The shaded areas in Fig.4 represent the parts where the

short-circuit protection stages are active. Figure 4 shows

that a position of 0 mm can not be reached, neither can a

position of 100%. The minimum position that can be

reached depends on the battery voltage Vb, although the

maximum position does not.

handbook, halfpage

100

position

(%)

MGE635

0

0 VSET(min)

VSET(max) Vb VSET (V)

Fig.4 Conversion gain.

The device is protected against electrical transients which

may occur in an automotive environment. The device will

shut off when positive transients on the battery line occur

(see Figs 7 and 8). The motor will not be short-circuited in

this event. The flyback diodes, illustrated in Fig.1, will

remain present. The state of the output stages at the

moment when the transient starts is preserved by internal

flip-flops. Negative transients on the battery line

(see Figs 7 and 8) will result in a set short-circuited to

ground fault detection, because it will result in a voltage at

the setting input which is below the short-circuited to

ground threshold. The device however discharges the

electrolytic capacitor during these transients. It will stop

functioning when the resulting supply voltage becomes too

low.

1996 Sep 04

5

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