L9686(1995) Просмотр технического описания (PDF) - STMicroelectronics
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L9686 Datasheet PDF : 7 Pages
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L9686
ELECTRICAL CHARACTERISTICS (– 20°C < Tamb <, 100°C, 8V < VS < 18V unless otherwise speci-
fied.)
Symbol
VS
V2 – V1
V2 – V3
R2
KN
CT
Parameter
Operating Voltage
Clamping Voltage
Output Saturation Voltage
Starter Resistance
Oscillator Constant KN (normal
Operation)
Temperature Coefficient of Kn
Test Condition
see note 1
IRL = 250mA
see note 2
Fn = 1/KnRoCo
Osc. Frequency
See Note 3
D.C.
KC
DCLF
IQ
Vth
Duty Cycle (normal operation)
Oscillator Constant KC
(lamp failure detection)
Duty Cicle (lamp failure
detection)
Current Consumption Relay off
Ipin 1
Lamp Failure Threshold
(see note 4)
FC = 1KcRoCo
Osc. Frequency
VS = 8V
VS = 13.5V
VS = 18V
R3 = 220Ω
VS = 13.5V
–20 < Tamb < 100°C
Min. Typ. Max. Unit
8
18
V
27
34
V
1.7
V
3.6
KΩ
1.27
1.74
–1.5 ⋅
1/°C
10-3
45
50
55
%
0.53
0.74
35
40
45
%
2.2
3.9
mA
2.7
4.3
mA
3.3
4.7
mA
65
85
95
mV
Notes : 1.
2.
3.
4.
5.
This voltage is the threshold used to protect the circuit against overvoltage : if Vbat is > than this threshold, the relay will be on
and the voltage across the circuit will maintain constant increasing the current in the protective resistor R3.
This is the maximum value for operation. This value must be higher than 1 K Ohms in order to limit the current in pin 8 during
dumps. A recommended value for application should be 1,5 K Ohms.
The external leakage from the blinker unit to ground must be with an equivalent resistor higher than 5,6 K Ohms to avoid para-
sitic operation when the switch S1 is off.
This temperature coefficient is usefull to compensate the drift of the external timing network (R1, C1).
This threshold is calculated for a 20 m Ohm shunt. The threshold is dependant of Vbat as the bulb current.
FUNCTIONAL DESCRIPTION
The circuit is designed to drive the direction indi-
cator flasher relay. The application circuit shows
the typical system configuration with the external
components. Its consists of a network (R1 C1) to
determine the oscillator frequency, shunt resistor
(RS) to detect defective bulbs and two current lim-
iting resistors (R2/R3) to protect the IC against
load dump transients.
The lightbulbs L2, L3, L4, L5, are the turn signal in-
dicators with the dashboard-light L6. The S1
switch position is sensed across resistor R2
and Rlamp by input 8. The flashing cycle is started
by closing S1 : then, after a delay time td typically
equal to 1.5 ms, the relay is actuated and the pin
3 goes high switching on the corresponding
lamps L2, L3, (or L4, L5). These lamps will flash at
the oscillator frequency not depending on the bat-
tery voltage value (8 - 18 V). The flashing cycle
stops and the circuit is reset to the initial position
when the switch S1 is open.
The lamp failure detection function senses the
current through the shunt resistor RS. When one
of the lightbulbs is defective the voltage drop
across RS is reduced to a half and the failure is
indicated by doubling the flashing frequency.
3/7
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