MC33441 Datasheet, PDF (7/12 Pages) ON Semiconductor – Electroluminescent Lamp Driver IC

MC33441
APPLICATION INFORMATION
EL Lamp Selection
EL lamps are a laminate which exhibit a capacitance on
the order of 2.5nF to 3.5nF per square inch. The light will
emit as the high voltage is applied across the electrodes of
this capacitance. The color of the emitted light is determined
by the type of chemical used and the frequency of the
excitation voltage. On the other hand, the lamp brightness
increases approximately the square of the applied voltage
and nearly linear to the excitation frequency. Once a lamp
has been selected, the operating frequency and the essential
voltage for the optimum performance is determined. Then,
the driver circuit can begin to design.
Inductor Selection (L1)
Use a 1mH/0.15A inductor for MC33441. Higher
inductor values can be used to reduce the peak transient coil
current from the battery supply. As the value of the inductor
(L1), increases, the resistor (R1) value may need to increase
correspondingly to provide optimum performance. While a
lower inductor values lead to smaller physical size, it will
generate a higher peak coil current. A lower resistor (R1)
value should be used when a lower inductance coil is being
used.
The inductor must have a saturation current rating equal
to or bigger than the peak coil current which is 150mA.
Filter Capacitor Selection (C2)
See Table 1 for the estimated value of the filter capacitors
based on the input voltage supply. Since the maximum
voltage of the filter capacitor can reach 70V or even 80V,
capacitor with high voltage rating will be required.
Resistor Selection (R1)
Since the fundamental frequency of the oscillator is set by
the external resistor (R1), the temperature coefficient of the
frequency is dominated by the value of this resistor. A low
temperature coefficient (TC) resistor is suggested to use for
keeping the variation of oscillator’s frequency low against the
operation temperature range. (See Page 4, Fig. 3 & Fig. 4)
+ + W R1
REXT
4.341 10⁷
FEL
Layout
The MC33441 is high output voltage operation make PC
board layout critical to minimize ground bounce and noise.
Locate input bypass capacitor, filter capacitor and
oscillator’s resistor as close to the device pins as possible.
BATTERY
C1
0.1µF
PB1
ENABLE
L1
1mH
U1
1 _VDD
EL1 ⁸
2 _ENB
3 _RT1
EL2 ⁷
FILTER ⁶
4 _VSS
COIL ⁵
R1
130K
MC33441 (TSSOP–8)
EL–LAMP
C2
27nF/100V
Figure 10. MC33441 Demo Board Schematic
COMPONENT SUPPLIER
Supplier
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Part Number
Part# CC–0012
Part# CRCH664–
102K–831015
Description
EL–Lamp: 14.5mm x 47mm Color:
Yellow–Green
Inductor: 1mH / 0.15A
Phone
(886)–2–22692827
(852)–2341–5539
http://onsemi.com
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