L497 ,HALL EFFECT PICKUP IGNITION CONTROLLERABSOLUTE MAXIMUM RATINGSSymbol Parameter Value UnitI D.C. Supply current 200 mA3Transient Supply Cu ..
L4970 ,10A SWITCHING REGULATORABSOLUTE MAXIMUM RATINGSSymbol Parameter Value UnitV Input Voltage 55 V9V Input Operating Voltage 5 ..
L4970A ,10A SWITCHING REGULATORL4970A®10A SWITCHING REGULATOR10A OUTPUT CURRENTMULTIPOWER BCD TECHNOLOGY5.1V TO 40V OUTPUT VOLTAGE ..
L4971 ,1.5A STEP DOWN SWITCHING REGULATORL4971®1.5A STEP DOWN SWITCHING REGULATORUP TO 1.5A STEP DOWN CONVERTEROPERATING INPUT VOLTAGE FROM ..
L4971. ,1.5A STEP DOWN SWITCHING REGULATORFeatures of this new generations of DC-DC con-DESCRIPTIONverter include pulse-by-pulse current limi ..
L4971D ,1.5A STEP DOWN SWITCHING REGULATORL4971®1.5A STEP DOWN SWITCHING REGULATORUP TO 1.5A STEP DOWN CONVERTEROPERATING INPUT VOLTAGE FROM ..
LBE63C , Power TOPLED with Lens Enhanced Optical Power LED (ATON)
LBE67C , Power TOPLED® Enhanced optical Power LED (ATON®)
LBG6SP , Advanced Power TOPLED Enhanced optical Power LED
LBH1000 , 1.6×0.8×0.4 mm(L×W×H) small size surface mount type SMD
LBH1000 , 1.6×0.8×0.4 mm(L×W×H) small size surface mount type SMD
LBL293 , SmartLED® 0603 Hyper-Bright LED Lead (Pb) Free Product - RoHS Compliant
L497
HALL EFFECT PICKUP IGNITION CONTROLLER
L497March 1998
HALL EFFECT PICKUP IGNITION CONTROLLER DIRECT DRIVING OF THE EXTERNAL
POWER DARLINGTON. COIL CURRENT CHARGING ANGLE (dwell)
CONTROL. PROGRAMME COIL CURRENT PEAK LIMITA-
TION. PROGRAMMABLE DWELL RECOVERY TIME
WHEN 94 % NOMINAL CURRENT NOT
REACHED. RPM OUTPUT. PERMANENT CONDUCTION PROTECTION. OVERVOLTAGE PROTECTION FOR EXTER-
NAL DARLINGTON. INTERNAL SUPPLY ZENER. REVERSE BATTERY PROTECTION
DESCRIPTIONThe L497 is an integrated electronic ignition control-
ler for breakerless ignition systems using Hall effect
sensors.
The device drives an NPN external darlington to
control the coil current providing the required stored
energy with low dissipation.
A special feature of the L497 is the programmable
time for the recovery of the correct dwell ratio Td/T
when the coil peak current fails to reach 94 % of the
nominal value. In this way only one spark may have
an energy less than 94 % of the nominal one during
fast acceleration or cold starts.
BLOCK DIAGRAM1/11
ABSOLUTE MAXIMUM RATINGS
PIN CONNECTION (top view)
THERMAL DATA(*) Thermal resistance junction-aluminia with the device soldered on the middle of an aluminia supporting substrate mesuring
15 x 20 ; 0.65 mm thickness.
L4972/11
PIN FUNCTIONS (refer to fig. 4)
L4973/11
PIN FUNCTIONS (continued)
ELECTRICAL CHARACTERISTICS (VS = 14.4 V, – 40 °C < Tj < 125 °C unless otherwise specified)
L4974/11
ELECTRICAL CHARACTERISTICS (continued)
Figure 1 : Main Waveforms.
APPLICATION INFORMATION
Notes :1.
td/t desaturation ratio is given by: td = 1
1 + I11C ⁄ I11D
Isense = Icoil when the external Darlington is in the active region.
L4975/11
DWELL ANGLE CONTROL
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 characteristics of the coil.
On the negative edge of the Hall-effect input signal
the capacitor CW begins discharging with a constant
current l11D. When the set peak value of the coil cur-
rent is reached, this capacitor charges with a con-
stant current I11C = 13.3 x I11D, and the coil current
is kept constant by desaturation of the driven stage
and the external darlington.
The capacitor CT starts charging on the posi-
tive.edge of the Hall-effect input signal with a con-
stant current I10C. The dwell angle, and conse-
quently the starting point of the coil current conduc-
tion, is decided by the comparison between V10 and
V11.
A positive hysteresis is added to the dwell compa-
rator to avoid spurious effects and CT is rapidly dis-
charged on the negative edge of Hall-effects input
signal.
In this way the average voltage on CW increases if
the motor speed decreases and viceversa in order
to maintain constant the ratio td 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.
DESATURATION TIMES IN STATIC
CONDITIONS
In static conditions and if CT = CW as recommended
and if the values of the application circuit of fig.4 are
used. = 1
1 + I11C / I11D
DESATURATION TIMES IN LOW AND HIGH
FREQUENCY OPERATION
Due to the upper limit of the voltage range of pin 11,
if the components of fig.4 are used, below 10 Hz
(300 RPM for a 4 cylinder engine) the OFF time
reaches its maximum value (about 50 ms) and then
the circuit gradually loses control of the dwell angle
because D = T – 50 ms.
Over 200 Hz (6000 RPM for a 4 cylinder engine) the
available time for the conduction is less than 3.5 ms.
If the used coil is 6 mH, 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 condition of acceleration and decel-
eration of the motor below 80Hz/s. These conditions
can be simulated by means of a signal gene-rator
with a linearly modulated frequency between 1 Hz
and 200 Hz (this corresponds to a change between
30 and 6000 RPM for a 4 cylinders engine).
CURRENT LIMIT
The current in the coil is monitored by measuring the
Isense current flowing in the sensing resistor Rs on
the emitter of the external darlington. Isense is given
by :
Isense = Icoil + I14When the voltage drop across Rs reaches the inter-
nal comparator threshold value the feedback loop is
activated and Isense kept constant (fig.1) forcing the
external darlington in the active region. In this con-
dition :
Isense = IcoilWhen a precise peak coil current is required Rs must
be trimmed or an auxiliary resistor divider (R10, R11)
added :
Icpeak (A) = 0.320
RS) ⋅
R10
R11 + 1
SLOW RECOVERY CONTROL (fig. 2)
If Isense has not reached 94 % of the nominal value
just before the negative edge of the Hall-effect input
signal, the capacitor Csrc and CW are quickly dis-
charged as long as the pick-up signal is "low". At the
next positive transition of the input signal the load
current starts immediately, producing the maximum
achievable Tdesat; then the voltage on CSRC in-
creases linearly until the standby is reached. During
this recovery time the CSRC voltage is converted into
a current which, substrated from the charging cur-
rent of the dwell capacitor, produces a Tdesat modu-
lation. This means that the Tdesat decreases slowly
until its value reaches, after a time TSRC, the nominal
7% value.
The time TSRC is given by:
Trsc = 12.9 R7 CSRC (ms)
where R7 is the biasing resistor at pin 12 (in KΩ) and
Csrc the capacitor at pin 8 (in μF).
L4976/11
