Features

■ IC regulator for 12 V type alternator

■ Fixed frequency regulation loop

■ 130 mhigh side field driver

■ Fail safe device with double sensing of battery

voltage (VB and VS)

■ Load response control (LRC) function activates

after an initial time delay

■ Self start function from phase frequency

■ “Z” shaped regulation curve compliant with VW

specification.

■ Key recognition from L input

■ Field driver, lamp driver and relay driver short

protection

■ Complex diagnostics

■ Thermal shutdown at 175 °C

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.