L482 STMicroelectronics, L482 Datasheet - Page 8

• Manufacturer Part Number: L482
• Description: HALL.EFFECT PICKUP IGNITION CONTROLLER
• Manufacturer: STMicroelectronics

DESATURATION TIMES IN LOW AND HIGH FRE-
QUENCY OPERATION.Due to the upperlimit of the
voltage range of pin 3, if the components of fig. 3, 4
are used, below 10Hz (300RPM for a 4 cylinder en-
gine) the OFF time reaches its maximum value
(about50ms) and then the circuit graduallyloses the
control of the dwell angle because D = T – 50ms
Over 200Hz (6000RPM for a 4 cylinder engine) the
available time for the conduction is less than 3.5ms.
If the used coil is 6mH, 6A, the OFF time is reduced
to zero and the circuit loses the dwell angle control.
TRANSIENT RESPONSE. The ignition system
must deliver constant energy even during the con-
dition of acceleration and deceleration of the motor
below 80Hz/s. These conditions can be simulated
by means of a signal generator with a linearly mo-
dulated frequency between 1Hz and 200Hz (this
correspondsto a changebetween 30 and 6000RPM
for a 4 cylinders engine.
CURRENT LIMIT. The current in the coil is monito-
red by measuring the I
sensingresistor R
lington. I
When the voltage drop across R
nal comparator threshold value the feedbackloop is
activated and I
external darlington in the active region. In this con-
dition :
When a precise peak coil current is required R
be trimmed or an auxiliary resistor divider (R
added :
Icpeak (A)
PROTECTION CIRCUIT
PERMANENT CONDUCTION PROTECTION
The battery voltage is applied to ignition module by
means of the ignition key. In these conditions, with
the motor stopped, it is necessary that there is no
permanent conduction in the ignition coil irrespecti-
ve of the polarity of the input signal.
The L482 incorporates a timing circuit to implement
this protection ; the durationof the intervention is set
by means of a capacitor C
R
than 1 s, the coil current gradually decreases down
to zero to avoid spurious sparks (see fig. 2).
This timing allows normal operation of the module
above 30RPM.
L482
8/11
11
= 100k , when the input signal is high for more
sense
=
is given by :
sense
I
V
sense
s
SENS
I
R
sense
on the emitter of the externaldar-
kept constant (fig. 1) forcing the
S
= I
sense
= I
coil
(
coil
+ I
1
R
R
current flowing in the
at pin 8 = 1 F, and
16
1
2
s
reaches the inter-
+ 1)
5
1
must
, R
2
)
DARLINGTON OVERVOLTAGE LIMITATION
The darlington is protected against overvoltage by
means of an external divider R
internal zener. This zener drives the external darlin-
gton in order to limit the collector voltage.
REVERSE BATTERY PRTOTECTION. Due to the
presence of external impedance at pin 5, 10, 11, 14,
15, L482 is protected against reverse battery volt-
age.
DUMP PROTECTION.
The load dump protection withstands up to 100V
with a decay time
shold for load dump is fixed by means of an external
divider connected to pin 11 (DIP-16 package ver-
sion) or to pin 10 using a Micropackage type.
NEGATIVE SPIKE PROTECTION.If correct opera-
tion is requested also during short negative spikes,
the diode DS and capacitor C
USE OF THE IC ELECTRONIC ADVANCE SY-
STEM
When the device is digitally controlled the control
unit transmits a suitable input signal to the power
module, receiving in turn information that allows the
control of the dwell and the on time of the final tran-
sistor.
For thisreason L482 provides the following outputs:
.
.
.
OTHER APPLICATION INFORMATION
If the supply voltage is disconnected - or the battery
wire is broken - while the current is flowing through
the coil, the external diode D
from recirculating into the device : in this way both
device and darlington are protected.
a time signal equal to the time in which the final
Darlington is in the active region i.e. when the coil
current is limited (V
signal must be TTL compatible.
a TTL compatible output from the timing circuit
(V
the DIP-16 package version is present after the
protection against cranking transients.
a time signal equal to the time in which the final
Darlington, is in ”on” condition (V
current flows through the coil, see fig. 1.
rs
in figure 2). This pulse, available only using
300ms. The intervention thre-
ds
) as shown in figure 1. This
1
s
keeps the coil current
5
must be used.
/R
6
on
(pin 15) and an
) i.e. when the