LINEAR INTEGRATED CIRCUIT
Pin 1, GND, IC ground
In the case of battery reversal, resistor R4 to ground (-11) will protect the IC against damage. An integrated
protection circuit together with external resistances R2 and R4 limits the current pulses in the IC.
Pin 2, Supply voltage, VSS - Power
On the PCB connection, the arrangement of the supply connections to Pin 2 must be so as to ensure that, the
resistance of VSS to Pin 6 is lower than that to Pin 2.
Pin 3, Relay control output (driver)
The relay control output is a high-side driver with a low saturation voltage and capable to drive a typical automotive
relay with a minimum coil resistance of 60Ω.
Pin 4 and 5 Oscillator (C1 and R1)
Flashing frequency, f1, is determined by the R1 C1 components as follows (see Application Citcuit):
C1 ≤ 47μF
R1 = 6.8kΩ to 510kΩ
In case of a lamp outage, the oscillator frequency is switched to the lamp outage frequency f2 with f2 ≈ 2.2 × f1.
Duty cycle in normal flashing mode: 50%
Duty cycle in lamp outage mode: 40% (bright phase)
Pin 6, Supply voltage, Sense
A minimized layer resistance from point VS/shunt to Pin 6 is recommended to accurate monitoring via the shunt
Pin 7, Lamp outage detection
The lamp current is monitored via an external shunt resistor R3 and an internal comparator K1 with its reference
voltage of typ. 77mV (VSS = 12V). The outage of one lamp out of two lamps is detected according to the following
Nominal current of 1 lamp: 21W / (VSS = 12V): Ilamp = 1.75A
Nominal current of 2 lamps: 2 x 21W / (VSS = 12V): Ilamp = 3.5A.
The detection threshold is recommended to be set in the middle of the current range: Ioutage ≈ 2.7A.
Thus the shunt resistor is calculated as:
R3 = VT (K1) / Ioutage
R3 = 77mV / 2.7A ≈ 29mΩ.
Comparator K1‘s reference voltage is matched to the characteristics of filament lamps (see “control signal
threshold” in the data part).
The combination of shunt resistor and resistance of wire harness prevents Pin 7 from a too high voltage in case of
Pin 8, Start input
Start condition for flashing: the voltage at Pin 8 has to be less than VSS - 5V (flasher switch closed).
Humidity and dirt may decrease the resistance between 10a and GND. If this leakage resistance is > 5kΩ the IC is
still kept in its off-condition. In this case the voltage at Pin 8 is greater than VSS - 5V.
During the bright phase the voltage at Pin 8 is above the K2 threshold, during the dark phase it is below the K3
threshold. For proper start conditions a minimum lamp wattage of 10W is required.
UTC assumes no responsibility for equipment failures that result from using products at values that
exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or other
parameters) listed in products specifications of any and all UTC products described or contained herein .
UTC products are not designed for use in life support appliances, devices or systems where malfunction
of these products can be reasonably expected to result in personal injury. Reproduction in whole or in
part is prohibited without the prior written consent of the copyright owner. UTC reserves the right to
make changes to information published in this document, including without limitation specifications and
product descriptions, at any time and without notice. This document supersedes and replaces all
information supplied prior to the publication hereof.
UNISONIC TECHNOLOGIES CO., LTD
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