UGQ5140K Ver la hoja de datos (PDF) - Allegro MicroSystems
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UGQ5140K Datasheet PDF : 8 Pages
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5140
PROTECTED POWERHALL®
SENSOR:
LAMP/SOLENOID DRIVER
FIGURE 3
TYPICAL LAMP DRIVER APPLICATION
X
+12 V
V
CC
1
2
3
4
OPTIONAL LAMP TEST
(SEE TEXT)
Dwg. EH-001
FIGURE 4
LAMP CURRENT vs TIME
NORMAL LAMP IN-RUSH CURRENT
NOT TO SCALE
CURRENT LIMIT
DELTA TEMP.
LIMIT
TIME
Dwg WH-001
TYPICAL APPLICATIONS
INCANDESCENT LAMP DRIVER
High incandescent lamp turn-ON currents (com-
monly called in-rush currents) can contribute to poor lamp
reliability and destroy semiconductor lamp drivers. Warm-
ing resistors protect both driver and lamp but use signifi-
cant power when the lamp is OFF while current-limiting
resistors waste power when the lamp is ON. Lamps with
steady-state current ratings to 300 mA can be driven by
the UGQ5140K (Figure 3) without the need for warming or
current limiting resistors. In applications using several
sensor/drivers to control multiple lamps, the internal clamp
diodes may be connected together to an appropriate
current-limiting resistor and simple “lamp test†switch.
As shown in Figure 4, when an incandescent lamp is
initially turned ON, the cold filament is at minimum resis-
tance and will normally allow a 10x to12x peak in-rush
current. As the lamp warms up, the filament resistance
increases to its rated value and the lamp current is
reduced to its steady-state rating. When switching a lamp
with the UGQ5140K, the internal current-limiting circuitry
limits the peak current to approximately 900 mA. The
device will stay in the current limit and delta temperature
limit modes until the lamp resistance increases to its rated
steady-state value (Figure 4). A side-effect of this current-
limiting feature is that lamp turn-on times will increase.
Typical lamp turn-on times are shown in Figure 5.
INDUCTIVE LOAD DRIVER
Connecting the internal clamp diode (pin 3) to the
positive supply allows relays or other inductive loads to be
driven directly, as shown in Figure 6. The internal diode
prevents damage to the output transistor by clamping the
high-voltage spikes which occur when turning OFF an
inductive load. An optional external Zener diode can be
used to increase the flyback voltage, providing a much
faster inductive load turn-OFF current decay, resulting in
faster dropout (reduced relay contact arcing), and im-
proved performance. The maximum Zener voltage, plus
the load supply voltage, plus the clamp diode forward
voltage should not exceed 35 volts.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
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