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L9407F

February 2003

This is preliminary information on a new product now in development. Details are subject to change without notice.

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FULLY MONOLITHIC DESIGN

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LOW SIDE FIELD DRIVER

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THERMAL PROTECTION

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FIELD SHORT CIRCUIT PROTECTION

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PROTECTED DIAGNOSTIC LAMP DRIVER

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PROTECTED HIGH SIDE RELAY DRIVER

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COMPLEX DIAGNOSTICS

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LOAD RESPONSE CONTROL

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DFM OUTPUT (FIELD MONITOR)

DESCRIPTION

The L9407F is a monolithic multifunction alternator

voltage regulator intended for use in automotive ap-

plication. It includes the control section, the field pow-

er stage, fault diagnostic circuit which drives a

warning lamp, and the protection against short cir-

cuits.

CIRCUIT OPERATION

The alternator's voltage regulator performs the fol-

lowing main functions:

– 1) voltage regulation

– 2) protection

– 3) control fault diagnosis

– 4) load response control

VOLTAGE REGULATION

The alternator voltage is compared with a reference

voltage in an amplifier, whose output determines the

switching frequency of output power MOS whose

current excites the coil of the alternator; as the regu-

lators are a self-oscillating type this frequency de-

pends on the whole system parameter set including

the alternator characteristics. The regulators have an

integrated filter in the voltage sensing path guaran-

teeing the correct behaviour of the devices also when

the rectifier diodes feature very high switching

spikes. The internal filtering allows the usage of the

device also with very long cables connecting the al-

ternator to the battery with an impedance so high to

cause a superimposed ripple on the alternator volt-

age higher than 5-6V. Consequently it doesn't need,

in the standard application, any external component.

Anyway an external application (2.2uF or 2.7uF)

must be inserted between A+ and ground when using

the device with very long cables.

PROTECTION

It is present a protection against short circuits of the

lamp and the relay power drivers (D+) and of the field

power driver (DF), a thermal drivers shutdown pro-

tection and an overvoltage protection of D+ power

drivers.

DIAGNOSIS

The circuit detects fault conditions related to the

phase and DF status and receives informations from

one of the three alternator phases. In order to prevent

spurious indications, fault warnings are not displayed

immediately but are dalayed by a fixed time.

LOAD RESPONSE CONTROL

The internal circuit regulates the soft start character-

istics (activated always at engine start) and the soft

attack characteristics.

Multiwatt 8

ORDERING NUMBER: L9407F

PRODUCT PREVIEW

CAR ALTERNATOR VOLTAGE REGULATOR