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Электронный компонент: L484D1013TR

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L484
September 2003
MAGNETIC PICKUP IGNITION CONTROLLER
.
DIRECT DRIVING OF THE EXTERNAL DAR-
LINGTON
.
OPERATES WITH A WIDE RANGE OF MAG-
NETIC PICKUP TYPES
.
CHARGING ANGLE (DWELL) CONTROL
.
COIL CURRENT PEAK LIMITATION
.
CONTINUOUS COIL CURRENT PROTECTION
.
TACHOMETER SIGNAL OUTPUT
.
EXTERNAL DARLINGTON OVERVOLTAGE
PROTECTION
.
LOAD DUMP AND REVERSE BATTERY PRO-
TECTION
.
POSSIBILITY OF SPARK POINT DELAYING
(ANTI KNOCK SYSTEM)
DESCRIPTION
The L484 is an integrated circuit designed for use
with an NPN darlington in breakerless ignition sys-
tems with magnetic pickup sensors and high energy
ignition coils.
A key feature of the L484 is flexibility. It can be used
with a wide variety of magnetic sensors thanks to the
special design which has two input pins from the
pickup ; the first is the zero crossing detector for the
ignition command and the second pin is used to cal-
culate the dwell time. Moreover another pin is used
to adapt the L484 to various pickup types.
Other features of the device include darlington over-
voltage protection, dump protection, a supply volt-
age range of 6-28 V.
DIP16
ORDERING NUMBERS : L484 (DIP16)
L484D1 (SO16)
SO16
BLOCK DIAGRAM
1/11
ABSOLUTE MAXIMUM RATINGS
Symbol
Parameter
Value
Unit
V
R
Reverse Battery Voltage
14
V
V
D
Dump Voltage
100
V
P
tot
Power Dissipation at T
amb
= 90
C
0.75
W
T
j
, T
stg
Junction and Storage Temperature Range
55 to 150
C
THERMAL DATA
Symbol
Parameter
Value
Unit
R
th j-amb
Thermal Resistance Junction-ambient (DIP16)
Max
80
C/W
R
th j-al
Thermal Resistance Junction-alumina (SO16)
Max
50
C/W
PIN CONNECTION
L484
2/11
PIN FUNCTIONS (refer to fig. 2)
N
Name
Function
1
CURRENT SENSING
INPUT
Connection for Coil Current Limitation. The current is measured on the
sense resistor R
SENS
and divided on R1/R2. The current limitation value is
given by :
I
SENS
=
R1
+
R2
R
SENS
R2
2
PICKUP INPUT
Magnetic Pickup Signal Input. This pin sets the dwell time, i.e. the max
negative pickup voltage value starting from which the device can drive the
current into the coil. The real dwell time will be a function of the dwell
control logic. Increasing the resistor R11 the maximum conduction time
increases. The max input current foreseen is 2mA.
3
PERMANENT
CONDUCT.
PROTECTION TIMER
A capacitor C1 connected between this pin and ground sets the delay of the
permanent conduction protection in the coil current. Using a 50nF capacitor
the typical desaturation time delay for the protection is 75ms.
4
PERMANENT CONDUCT.
PROTECTION INHIBIT
A low level on this input (max 0.7V) disables the protection, irrespective of
the state of pin 3. If the protection is used this pin must be left open.
5
RPM OUTPUT
Open collector output signal which is at a low level when the final darlington
is in ON status. The current is internally limited at 10mA.
6
DWELL TIME ADJUST
At high motor rotation speeds, i.e. when the peak value of the magnetic
pick-up signal exceedes 6V using R12 = 100K
, this pin may be used to
vary the dwell ratio. Adding a resistor in series R
a
between this pin and pin
11 the desaturation time is reduced. It is therefore possible to use this pin to
adapt the L484 to various pickup types. The maximum value of the resistor
R
a
is 200K
.
7
DWELL CONTROL
TIMER
A capacitor C2 connected between this pin and ground sets the timing for
the dwell control. The recommended value is 100nF. The resistors R
b
/R
c
provide an hysteresis to confirm ON state and avoid spurious sparks.
8
ZERO CROSSING
INPUT
Zero cross detector input of the magnetic pickup signal for the ignition
actuation. At high motor rotation speeds, the external resistor R12 may be
used to vary the desaturation time ratio, to adapt the L484 to various
signal waveforms of time magnetic pick-up. Reducing the resistor value the
dwell time increases. Typically the range of values for resistor R12 is from
50K
to 150K
..
9
POWER-ON INPUT
A low level on this pin forces the external darlington into conduction
particularly useful in anti knock system. This function is particularly useful in
antiknock system because provides a spark time delay. Anyway the current
limitation, the permanent conduction protection and the dump protection
are operating even when pin 9 is at a low level. If this function is not used it
must be left open.
10
SIGNAL GROUND
This pin must be connected to ground.
11
POWER SUPPLY
Supply Voltage Input. A 7V (typ) zener is present at the input. The external
resistor R9 limits the current through the zener for higher supply voltages.
12
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:
V
Dth
=
8.5
R8
+
R9
R9
+
5
10
-
4
R8
(the resistor R9 value must be higher than 4K
).
* this function is particularly useful in antiknock systeme because provides a spark time delay. anyway the current limitation, the pemanent con
duction protection and the dump protection are operating even when pin 9 is at a low level.
L484
3/11
PIN FUNCTIONS (continued)
N
Name
Function
14
DRIVER COLLECTOR
INPUT
The collector current for the internal driver which drives the external
darlington is supplied through this pin. The external resistor R10 limits the
dissipation in the IC. The value this resistor depends on the darlington used
and on the limiting current in the coil.
15
OVERVOLTAGE
LIMITATION
The external darlington is protected against overvoltage by means of an
internal zener available at this pin. The external divider R5/R6 defines the
limitation value, typically given by :
V
ovp
=
30
R5
+
5
10
-
3
R6
+
30
16
DRIVING STAGE
OUTPUT
Current Driver for the External Darlington. To ensure stability on the current
limitation loop a capacitor C3 (typically 2.2nF, this value depending on the
darlington used) must be connected between this pin and the current
sensing input (pin 1).
ELECTRICAL CHARACTERISTICS (V
S
= 14.4V ; T
J
= - 40 to 125
C unless otherwise specified ; referred
to the test circuit)
Symbol
Parameter
Test Conditions
Min.
Typ.
Max.
Unit
V
S
Operating Supply Voltage
6
28
V
V
IS
Input Stage Voltage (pin 2 with
10K
resistor)
160
200
240
mV
V
TH
On Pick-up Thresh. Voltage at LOW RPM
(pin 2)
V
IS
30
V
IS
+30
mV
V
SENS
Current Limitation Sensing Voltage (pin 1)
V
S
= 6 to 16V
200
320
mV
V
ZC
Zero Crossing Thresh. Voltage (pin 8)
3
20
60
mV
V
H
Hysteresis Voltage (pin 8)
100
200
mV
I
7C
I
7D
I
7D
/I
7C
C
D WELL
Charge Current
C
D WELL
Discharge Current
at LOW RPM
V
pick-up
= 0.5V ;
or pin 6 not connected
(*) Note 1
0.7
7
7
3
30
15
A
A
I
7C
I
7D
I
7D
/I
7C
C
D WELL
Charge Current
C
D WELL
Discharge Current
at HIGH RPM
V
pick-up
= 9V
(**) Note 2
8
13
0.7
33
44
3.2
A
A
V
pin3
I
3
Threshold Voltage
Output Current
T
amb
= 25
C
(***) Note 3
0.85
4
3
V
A
V
Cp
Continuous Coil Current Protection Inhibit
LOW Voltage (pin 4).
0
0.7
V
V
CEsat
Series Darlington Driver
Saturation Voltage (V
pin 14 - 16
)
I
pin14
= 150mA
I
pin14
= 50mA
0.4
1
0.6
V
V
V
Z
Zener Volt. Pin 11
I
pin11
= 140mA
6.5
8.8
V
V
OVZ
External Darlington Overvoltage Protection
Zener Voltage
T
amb
= 25
C ;
I
pin15
= 5 to 15mA
25
35
V
I
09
Pin 9 Output Current in Low Status
V
9
= 0V
3
mA
V
CH
I
CH
Tachometer Signal Output LOW Voltage.
(pin5)
Output Leakage (pin 5)
ON Condition
I
sink
= 0.5mA
OFF Condition
V
pin5
= 5V
0.7
10
V
A
L484
4/11
DUMP PROTECTION
Symbol
Paramater Test
Conditions
Min.
Typ.
Max.
Unit
V
DZ
Zener Dump (pin 12)
I
pin12
= 2mA
7.5
9.5
V
(*) Note 1 : TD/T is given by the formula :
TD
1
=
T
1 + I7D/I7C
(**) Note 2 :
TD
K
=
T
1 + I7D/I7C
K value depends on the pickup used in the application ; typically K = 0.1
(***) Note 3 : the permanent conduction protection is guaranteed over the full temperature range
CIRCUIT OPERATION
The L484 controls the charging angle (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 keeps the output stage in its
active region during current limitation. The time the
output stage is operating in the active region (de-
saturation time), is sufficient to compensate for
possible variation in the energy stored due to the ac-
celeration of the motor ; moreover this time is limited
to avoid excessive power dissipation.
MAGNETIC PICKUP CHARACTERISTICS
The typical magnetic pickup waveforms are shown
in fig. 1, the amplitude of the signal being a function
of the frequency. However on the market there are
many types of magnetic pickup, of which the wave-
forms may differ very much. Adjusting the value of
the resistor R
11
on pin 2 and/or adding a resistor R
a
between the pin 6 (dwell adjust) and pin 11, as
shown in the application circuit, it is possible to adapt
the L484 to a wide range of magnetic pickup wave-
forms.
Particularly by means of the resistor R
11
on pin 2 it
is possible to define the maximum advance of the
conduction start into the coil . This is very useful at
high pickup frequency.
CONTROL OF THE DWELL ANGLE
The dwell angle control circuit defines the conduc-
tion time of the output darlington, versus the speed
of rotation, the supply voltage and the charac-
teristics of the coil.
In each cycle the time the transistor operates in the
active region is compared with a reference time and
the error signal amplified to advance or delay the
conduction in the next cycle. To limit the power dissi-
pation the desaturation time is typically fixed
to 10% of the period T.
At very low frequencies the ON thershold is fixed at
200mV of the input signal and the desaturation time
is mainly determined by the peak waveform. This
positive threshold also prevents permanent conduc-
tion when the motor is stopped. When the input fre-
quency increases the dwell control gradually sets
the desaturation time to 10% of the period. At higher
frequencies the ON threshold becomes negative to
permit a conduction angle of more than 50% always
keeping desaturation time to 10% of the period.
CURRENT LIMITING
The current in the coil is measured by means of a
voltage drop across a suitable resistor in the emitter
lead of the power transistor. When the threshold
voltage (260mV typ) is reached, the coil current is
kept constant via a feedback loop.
L484
5/11
DARLINGTON OVERVOLTAGE LIMITATION
The darlington is protected against overvoltage by
means of an external divider R
5
/R
6
(pin 15) and an
internal zener. This zener drives the external dar-
lington in order to limit the collector voltage.
CHARGING ANGLE SIGNAL OUTPUT
This signal is intended for tachometer applications
(pin 5). It consists of an open collector stage with
current internally limited at 10mA
"POWER ON" SIGNAL INPUT
In the low status this input forces the external dar-
lington into conduction (pin 9). This control input can
be used together with the conduction time informa-
tion coming from pin 5 to bypass the normal dwell
time calculation. When an external logic control is
used to recognize particular engine condition (as in
anti Knock system).
PROTECTION CIRCUITS
PERMANENT CONDUCTION PROTECTION
This function is intended to prevent continuous cur-
rent conduction in the final stage when the magnetic
pickup is open or intermittent. The duration of the in-
tervention is set by means of a capacitor 1 at pin 3.
Grounding pins 3 or 4, this protection is eliminated.
The inhibit function at pin 4 is particularly useful
when an external logic control is used to disable the
permanent conduction protection.
REVERSE BATTERY AND DUMP PROTECTION
Due to the external resistors R
6
, R
7
, R
8
, R
10
the de-
vice is protected against reverse battery. The load
dump protection withstands up to 100V with a decay
time
300ms. The intervention threshold for load
dump is fixed by means of an external divider con-
nected to pin 11.
OTHER APPLICATION INFORMATION
If the supply is voltage disconnected - or the battery
wire is broken - while the current is flowing through
the coil, the external diode D
1
keeps the coil current
from recirculating into the device : in this way both
device and darlington are protected.
The zener diode Dz, connected between pin 14 and
GND, allows to withstand positive spikes up to 200V.
The device - used in the recommended application
circuit - satisfies the ISO/DP 7637/1 overvoltage
standard.
Figure 1 : Typical Magnetic Pickup Waveform and L484 Response at low and high
fequency.
L484
6/11
Figure 1 : Typical Magnetic Pick-up Waveform and L484 Response at Low and High Frequency
(continued).
L484
7/11
Figure 2 : Application Circuit.
L484
8/11
DIP16
DIM.
mm
inch
MIN.
TYP.
MAX.
MIN.
TYP.
MAX.
a1
0.51
0.020
B
0.77
1.65
0.030
0.065
b
0.5
0.020
b1
0.25
0.010
D
20
0.787
E
8.5
0.335
e
2.54
0.100
e3
17.78
0.700
F
7.1
0.280
I
5.1
0.201
L
3.3
0.130
Z
1.27
0.050
OUTLINE AND
MECHANICAL DATA
L484
9/11
SO16 Narrow
DIM.
mm
inch
MIN.
TYP.
MAX.
MIN.
TYP.
MAX.
A
1.75
0.069
a1
0.1
0.25
0.004
0.009
a2
1.6
0.063
b
0.35
0.46
0.014
0.018
b1
0.19
0.25
0.007
0.010
C
0.5
0.020
c1
45 (typ.)
D (1)
9.8
10
0.386
0.394
E
5.8
6.2
0.228
0.244
e
1.27
0.050
e3
8.89
0.350
F (1)
3.8
4
0.150
0.157
G
4.6
5.3
0.181
0.209
L
0.4
1.27
0.016
0.050
M
0.62
0.024
S
(1) D and F do not include mold flash or protrusions. Mold flash or potrusions shall not exceed 0.15mm (.006inch).
OUTLINE AND
MECHANICAL DATA
8(max.)
0016020
Weight: 0.20gr
L484
10/11
Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the conse-
quences 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 STMicroelectronics. Specifications mentioned in this
publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. STMi-
croelectronics products are not authorized for use as critical components in life support devices or systems without express written
approval of STMicroelectronics.
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L484
11/11