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.