L497 STMicroelectronics, L497 Datasheet - Page 3

• Manufacturer Part Number: L497
• Description: HALL EFFECT PICKUP IGNITION CONTROLLER
• Manufacturer: STMicroelectronics

PIN FUNCTIONS (refer to fig. 4)
N
10
11
12
13
1
2
3
4
5
6
7
8
9
HALL-EFFECT INPUT
CURRENT SENSING
MAX CONDUCTION
DWELL CONTROL
DWELL CONTROL
RECOVERY TIME
POWER SUPPLY
BIAS CURRENT
RPM OUTPUT
SIGNAL GND
AUX. ZENER
TIMER
Name
TIME
GND
N.C.
This pin must be connected to ground.
This pin must be connected to ground.
Supply Voltage Input. An internal 7.5 V (typ) zener zener limits the voltage
at this pin. The external resistor R
high supply voltages.
This pin must be connected to ground or left open.
Hall-effect Pickup Signal Input. This input is dwell control circuit output in
order to enable the current driving into the coil. The spark occurs at the
high-to-low transition of the hall-effect pickup signal.
Furthermore this input signal enables the slow recovery and permanent
conduction protection circuits. The input signal, supplied by the open
collector output stage of the Hall effect sensor, has a duty-cycle typically
about 70 %. V
Open collector output which is at a low level when current flows in the
ignition coil. For high voltages protection of this output, connection to the
pin 7 zener is recommended.
In this situation R
current if RPM module pad is accidentally connected to V
A 21 V (typ) General Purpose Zener. Its current must be limited by an
external resistor.
A capacitor connected between this pin and ground sets the slope of the
dwell time variation as it rises from zero to the correct value. This occurs
after the detection of I
hall-effect signal pulse.
The duration of the slow recovery is given by :
t
where R
capacitor at pin 8 (in F).
A capacitor connected between this pin and ground determines the
intervention delay of the permanent conduction protection. After this delay
time the coil current is slowly reduced to zero.
Delay Time T
T
where R
capacitor at pin 9 (in F).
A capacitor C
HAll effect output is High and is discharged at the High to Low transition of
the Hall effect signal.
The recommended value is 100 nF using a 62 K
The average voltage on the capacitor CW connected between this pin and
ground depends on the motor speed and the voltage supply. The
comparison between V
dwell control. For the optimized operation of the device C
recommended value is 100 nF using a 62 K
A resistor connected between this pin and ground sets the internal current
used to drive the external capacitors of the dwell control
(pin 10 and 11) permanent conduction protection (pin 9) and slow recovery
time (pin 8). The recommended value is 62 K .
Connection for the Coil Current Limitation. The current is measured on the
sensing resitor R
limitation value is given by :
I
src
sens
p
=16 C
= 12,9 R
0.32
7
7
p
is the biasing resistor at pin 12 (in K ) and C
R
is the biasing resistor at pin 12 (in K ) and C
7
7
R
p
R
T
C
(ms)
5
10
S
src
is given by :
connected between this pin and ground is charged when the
is internally clamped to V
R
(ms)
S
8
R
11
11
must limit the zener current, too, and R
and taken through the divider R
coll
CW
and V
94 % I
Function
CT
5
nom
limits the current through the zener for
voltage determines the timing for the
, just before the low transition of the
3
and ground by diodes
resistor at pin 12.
resistor at pin 12.
10
S
/R
.
11
src
P
. The current
1
T
is the delay
is the delay
limits pin 6
= C
W
L497
; the
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