L9407F Datasheet, PDF (1/11 Pages) STMicroelectronics – CAR ALTERNATOR VOLTAGE REGULATOR

L9407F
CAR ALTERNATOR VOLTAGE REGULATOR
PRODUCT PREVIEW
s FULLY MONOLITHIC DESIGN
s LOW SIDE FIELD DRIVER
s THERMAL PROTECTION
s FIELD SHORT CIRCUIT PROTECTION
s PROTECTED DIAGNOSTIC LAMP DRIVER
s PROTECTED HIGH SIDE RELAY DRIVER
s COMPLEX DIAGNOSTICS
s LOAD RESPONSE CONTROL
s DFM OUTPUT (FIELD MONITOR)
Multiwatt 8
ORDERING NUMBER: L9407F
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.
February 2003
This is preliminary information on a new product now in development. Details are subject to change without notice.
1/11