MC33441 ON Semiconductor, MC33441 Datasheet - Page 5

• Manufacturer Part Number: MC33441
• Description: Electroluminescent Lamp Driver IC
• Manufacturer: ON Semiconductor

will be turned off and the energy will release to the EL lamp.
And, those switches will remain off until the next clock cycle.
H−Bridge Network
network is used to charge and discharge the EL lamp. The
switching frequency of the bridge network is controlled by a
clock signal from the divider with its frequency much lower than
the one to the coil−driver. Moreover, to reduce the current
consumption, the biasing current to the two low−side switches
of the H−bridge is not activated until the coil−driver circuit
needed to release the energy to the EL lamp. Then, the biasing
circuit will be on and be ready before the main switch in the
coil−driver really starts to turn off.
External Components
and the type of the EL lamp to be used. The external resistance
(R
the lamp. The relationship between R
F
Frequency Divider.
so
F
R
EL
EL
EXT
To achieve the 140 V peak−to−peak voltage, H−bridge
System designer will base on the application to decide the size
By substitute the equation of F
EXT
= F
+ 4.341
) at RT1 pin determines the excitation frequency (F
+ 4.341
OSC
R
B 384
EXT
F
EL
10
10
7
Hz
7
W
EXT
OSC
and the frequency is:
from Oscillator &
http://onsemi.com
EL
) for
5
Á Á Á Á Á Á
Á Á Á Á Á Á
Á Á Á Á Á Á
Á Á Á Á Á Á
Á Á Á Á Á Á
Á Á Á Á Á Á
Á Á Á Á Á Á
Á Á Á Á Á Á
frequency’s TC can be kept low. The filter capacitor is to provide
a smooth and more stable output waveform for the EL lamp.
The value of this capacitor depends on the input voltage and the
coil’s inductance value. Equations below can be used to estimate
filter capacitor’s value at different input voltage.
Best Case Approximation for the Filter Capacitor:
Worst Case Approximation for the Filter Capacitor:
switch when it is on, L is the coil’s value and F
clock frequency.
= 1 mH, EL lamp = 2.2 nF and at room temperature.
Moreover, if a low TC resistor is used, the oscillator
where V
Measurement below is recorded with the condition: coil
C
C
FILTER
FILTER
1.8 V
2.0 V
2.5 V
3.0 V
VDD
IN
+ 0.026
+ 0.085
Table 1: Reference for C
is the input voltage, V
Á Á Á Á Á Á
Á Á Á Á Á Á
Á Á Á Á Á Á
Á Á Á Á Á Á
Á Á Á Á Á Á
Á Á Á Á Á Á
Á Á Á Á Á Á
Á Á Á Á Á Á
100 K−130 KW
100 K−130 KW
100 K−130 KW
100 K−130 KW
(V
(V
R
in
in
EXT
* V
* V
SW
SW
SW
Á Á Á Á Á Á
Á Á Á Á Á Á
Á Á Á Á Á Á
Á Á Á Á Á Á
Á Á Á Á Á Á
Á Á Á Á Á Á
Á Á Á Á Á Á
Á Á Á Á Á Á
)
)
2
2
is voltage across the
FILTER
(L
(L
22 nF−33 nF
10 n−22 nF
10 n−22 nF
5 n−10 nF
C
F
F
FILTER
OSC
OSC
OSC
2
2
)
)
is the