L482

November 1991

HALLEFFECT PICKUP IGNITION CONTROLLER

DIRECT DRIVING OF THE EXTERNAL PO-
WER DARLINGTON

COIL CURRENT CHARGING ANGLE (DWELL)
CONTROL

COIL CURRENT PEAK VALUE LIMITATION

CONTINUOUS COIL CURRENT PROTECTION

CONDUCTION AND DESATURATION TIME
OUTPUT SIGNALS

PERMANENT CONDUCTION PROTECTION
RESET OUTPUT SIGNAL

OVERVOLTAGE PROTECTION FOR EXTER-
NAL DARLINGTON

LOAD DUMP PROTECTION

DESCRIPTION

The L482 is an integrated circuit designed for use
with an NPN darlington in breakerless ignition sy-
stems with hall-effect pickup sensors and high ener-
gy ignition coils.

It controls the energy stored in the ignition coil and
the desaturation time of the external darlington to
limit the power dissipation.

DIP16

ORDERING NUMBERS : L482 (DIP16)

L482D1 (SO16)

PIN CONNECTIONS (top views)

DIP16

SO16

The L482 is also particularly suitable for use as igni-
tion control and driving stage in more sophisticated
car electronic systems which employ microproces-
sor circuits.

SO16

1/11

PIN FUNCTIONS (refer to fig. 3 for DIP16 package)

Name

Function

CONDUCTION TIME

SIGNAL

A low level on this output signal indicates when the external darlington is in
the ON condition i.e. when the current flows through the coil (ton in fig.1)

HALL-EFFECT INPUT

Hall-effect Pickup Input. A high level on this pin enables the current driving
into the coil. The effective coil charge will be a function of the dwell control
logic. A High to Low transition from the Hall-effect pickup is the signal for
ignition actuation. The input signal, supplied by the open collector output
stage of the Hall-effect sensor, has a duty cycle typically about 70%.

DWELL CONTROL

The average voltage on the capacitor C

connected between this pin and

ground depends on the motor speed and the voltage supply. The
comparison between V

and V

voltages determines the timing for the

dwell control. The recommended value is 100nF using a 100K

resistor at

pin 7. For the optimized operation of the device, C2 = C5.

DWELL CONTROL TIMER

The capacitor C5 connected between this pin and ground is charged when
the Hall-effect output is high and is discharged at the High to Low transition
of the Hall-effect signal. The recommended value is 100nF using a 100K

resistor at pin 7.

HALL SENSOR SUPPLY

This pin can be used to project the Hall-effect pickup against the voltage
transients, The resistor R

limits the current into the internal zener.

DESATURATION TIME

SIGNAL

Open Collector Output Signal. This output is high when the external
darlington is in desaturation condition (current limitation), see t

pulse in fig.

REFERENCE VOLTAGE

A resistor R11 connected between this pin and ground sets the internal
current used to drive the external capacitors of the dwell control (C

and

) and permanent conduction protection (C

). The recommended value is

100K

PERMANENT CONDUCT.

PROTECTION TIMER

A capacitor C1 connected between this pin and ground determines the
intervention delay of the permanent conduction protection, t

of the figure 2.

With a 1

F capacitor and 100K

resistor R

at pin 7 the typical delay is 1s.

PERMANENT CONDUCT.

RESET OUTPUT

(no available in

Micropackage) (*)

A low pulse on this output detects the intervention of the permanent
conduction protection, as shown in figure 2. Typically the duration of the
time t

is more than 100

CURRENT SENSING

INPUT (*)

Connection for Coil Current Limitation. The current is measured on the
sense resistor R

and divided on R

. The current limitation value is

given by :

SENS

DUMP PROTECTION

(*)

The device is protected against the load dump. In load dump condition an
internal circuit,

based on a zener diode and a darlington transistor,

switches off the external darlington and short circuits the supply.
By means of the external divider R8/R9 the protection threshold can be
changed and is given as first approximation by:

Dth

8.5

(the resistor R9 value must be higher than 4K

POWER SUPPLY (*)

Supply Voltage Input. A 7V (typ) zener is present at the input. The external
resistor R

limits the current through the Zener for high supply voltages.

L482

3/11

(*) These pins refer only to the DIP package type.

For the SO 16 version the permanent conduction reset output signal is not available and the pin 9 becomes the current sensing input. Pin 10
replaces the pin 11 function, pin 11 becomes the power supply input and pin 12 is used as the signal ground.

ELECTRICAL CHARACTERISTICS (V

= 14 V, 40

125

C referred to application circuit of

figure 3 regarding DIP-16 package version)

Symbol

Parameter

Test Conditions

Min.

Typ.

Max.

Unit

Operating Supply Voltage

Supply Current

= 4.5V

Zener Voltage (pin 12)

= 80mA

6.5

8.8

Sensor Input (pin 2)
LOW Voltage
HIGH

2.5

0.5

V
V

Sensor Input Current (pin 2)

= LOW

= 6 to 16V

Hall-cell Supply Zener Voltage
(pin5)

= 10mA

Hall-cell Supply Zener Current
(pin5)

t = 10ms
T

AMB

= 25

100

CE sat

)

Series

Darlington Driver Sat.

Voltage

= 70mA

= 150mA

0.4

0.6
1.0

V
V

SENS

Current Limit. Sensing Voltage
(pin10)

= 6 to 16V

200

400

C2 Discharge Current
C2 Charge Current

= 6 to 16V

(*) Note 1

0.2

5
6

3.4

20
35

OVZ

External Darlington Overvoltage
Protection Zener Voltage

OVZ

= 5mA to 15mA

AMB

= 25

Reference Voltage

2.5

3.5

Desaturation Time

f = 40Hz V

= 14V

0.6

1.2

1.57

PIN FUNCTIONS (continued)

Name

Function

GROUND

This pin must be connected to ground.

DRIVER COLLECTOR

The collector current for the internal driver which drives the external
darlington is supplied through this pin. The external resistor R

limits the

dissipation in the IC. The value of the resistor depends is a function of the
darlington used and on the limiting current in the coil.

OVERVOLTAGE

LIMITATION

The external is protected against overvoltage by means of an internal
zener available at this pin. The external divider R

defines the limitation

value, given as first approximation by:

ovp

30
R

DRIVING STAGE

OUTPUT

Current Driver for the External Darlington. To ensure stability and precision
of Tdesat C

and R

must be used. Recommended value for R3 is 2K

order not to change the open loop gain of the system.
R

may be added to C

to obtain greater flexibility in various application

situations.
C

and RC values ranges are 1 to 100nF and 5 to 30K

depending on the

external darlington type.

L482

4/11

Figure 4 : Application Circuit (SO16).

CIRCUIT OPERATION

The L482control the conduction time (dwell) and the
peak value of the primary current in the coil over the
full range of operating conditions.

The coil current is limited to a predetermined level
by means of a negative feedback circuit including a
current sensing resistor, a comparator, the driver
stage and the power switch.

The dwell control circuit maintains the output stage
in its active region during current limitation. The time
the output stage is in the active region (desaturation
time) is sufficient to compensate for possible varia-
tions in the nergy stored due to the acceleration of
the motor ; moreover this time is limited to avoid ex-
cessive power dissipation.

CONTROL OF THE DWELL ANGLE (fig. 1 and 4)

The dwell angle control circuit calculates the con-
duction time D for the output transistor in relation to
the speed of rotation, to the supply voltage and to
the characteristic of the coil.

On the negative edge of the Hall-effect input signal
the capacitor C

begins discharging with a constant

current I

. When the set peak value of the coil cur-

rent is reached, this capacitor charges with a con-
stant current I

= 13.3 x I

and the coil current is

kept constant by desaturating the driver stage and
the external darlington.

The capacitor C

starts charging on the positive

edge of the Hall-effect input signal with a constant
current I

The dwell angle, and consequentlythe starting point
of the coil current production, is decided by the com-
parison between V

and V

. A positive hysteresis

is added to the dwell comparator to avoid spurious
effects and C

is rapidly discharged on the negative

edge of Hall-effects input signal.

In this way the average voltage on C

increases if

the motor speed decreases and viceversa in order
to maintain constant the ratiotd at any motor speed.

td is kept constant (and not d = cost) to control the
power dissipation and to have sufficient time to
avoid low energy sparks during acceleration.

The charging time D td depends on the coil and
the voltage supply.

DESATURATION TIMES IN STATIC CONDI-
TIONS.In static conditions, if C

= C

as recommen-

ded and if the values of the application circuit of fig.
3, 4 are used.

1 + I

L482

7/11

DESATURATION TIMES IN LOW AND HIGH FRE-
QUENCY OPERATION.Due to the upper limit 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 change between 30 and 6000RPM
for a 4 cylinders engine.

CURRENT LIMIT. The current in the coil is monito-
red by measuring the I

sense

current flowing in the

sensingresistor R

on the emitter of the externaldar-

lington. I

sense

is given by :

sense

= I

coil

+ I

When the voltage drop across R

reaches the inter-

nal comparator threshold value the feedbackloop is
activated and I

sense

kept constant (fig. 1) forcing the

external darlington in the active region. In this con-
dition :

sense

= I

coil

When a precise peak coil current is required R

must

be trimmed or an auxiliary resistor divider (R

, R

)

added :

SENS

Icpeak (A)

(

+ 1)

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 duration of the intervention is set
by means of a capacitor C

at pin 8 = 1

F, and

= 100k

, when the input signal is high for more

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.

DARLINGTON OVERVOLTAGE LIMITATION

The darlington is protected against overvoltage by
means of an external divider R

(pin 15) and an

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

300ms. The intervention thre-

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

must be used.

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 this reason L482 provides the following outputs:

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

) as shown in figure 1. This

signal must be TTL compatible.

a TTL compatible output from the timing circuit
(V

in figure 2). This pulse, available only using

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

) i.e. when the

current flows through the coil, see fig. 1.

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

keeps the coil current

from recirculating into the device : in this way both
device and darlington are protected.

L482

8/11

Information furnished is believed to be accurate and reliable. However, SGS-THOMSON Microelectronics assumes no responsibility for
the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its
use. No license is granted by implication or otherwise under any patent or patent rights of SGS-THOMSON Microelectronics. Specifica-
tions mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information pre-
viously supplied. SGS-THOMSON Microelectronics products are not authorized for use as critical components in life support devices or
systems without express written approval of SGS-THOMSON Microelectronics.

SGS-THOMSON Microelectronics GROUP OF COMPANIES

Australia - Brazil - France - Germany - Hong Kong - Italy - Japan - Korea - Malaysia - Malta - Morocco - The Netherlands - Singapore -

Spain - Sweden - Switzerland - Taiwan - Thaliand - United Kingdom - U.S.A.

L482

11/11

Ð­Ð»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: L482D1

ÐÐ»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: L482D1