September 2013

Doc ID 022665 Rev 2

1/13

13

L9409

Alternator voltage regulator with load response control

Features

voltage (VB and VS)

after an initial time delay

specification.

protection

Description

The L9409 is a monolithic multifunction alternator

voltage regulator intended for use in automotive

applications.

The device regulates the output of an automotive

generator by controlling the field winding current

by means of either an analog fixed frequency

PWM signal or digital fixed frequency PWM signal

(LRC). The Load Response Control function is

activated in order to eliminate IC engine speed

fluctuation and vibrations caused by the insertion

of sudden electrical loads during alternator low

speed operations (f < 310 Hz). Both the analog

and digital duty cycle are applied to a high side

driver.

The device is able to regulate the voltage either

using a feedback signal from B pin or from S pin

depending on application needs. S pin is intended

to have a clear direct connection with the positive

terminal of the car battery. If this connection gets

lost the device will regulate voltage using B pin

giving a fail safe functionality.

Using L pin is possible to sense key switch and a

pre-excitation duty cycle is applied on the field coil

in order to start phase voltage sensing. In the

case L connection gets lost, device starts to

generate using residual magnetism of the

generator.

Field, lamp and relay drivers are protected

against short circuit.

Order codes

Multiwatt8

Table 1. Device summary

Order code

Junction temp range,

CPackage

Packing

L9409F

-40 to 150

Multiwatt8

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