 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
SP4426 Datasheet(PDF) 4 Page - Sipex Corporation |
|
||||||||||||||||||||||||||||||
SP4426 Datasheet(HTML) 4 Page - Sipex Corporation |
|
|
4 / 11 page 
SP4426DS/01 SP4426 Electroluminescent Lamp Driver © Copyright 1997 Sipex Corporation 4 duty cycle and range from Vdd-1V to ground. An external clock signal may be desirable in order to synchronize any parasitic switching noise with the system clock. The maximum external clock frequency that can be supplied is 400kHz. The coil is an external component connected from V battery to pin 9 of the SP4426. Energy is stored in the coil according to the equation E L=1/2LI 2 where I, the the first approximation is (V bat-VCE)RL. Where V CE is approximately ) 0.5 volts for the internal coil driver transistor, and R L is the series resistance of the inductor. In order to maximize the energy stored in the inductor and subsequently recovered during the switching off of the coil transistor, it is expedient to use the highest value battery, the largest inductor with the smallest series resistance that the system constraints will permit. This energy recovery is directly related to the brightness of the lamp output. There are great variations among coils; caused by magnetic material differences, winding differences and parasitic capacitance. The Sipex SP4426 is final tested using a 9mH/35 Ω coil from Hitachi. For suggested coil sources see page 8. The supply Vdd can range from 2.2 to 6.0V. It is not necessary that Vdd=V battery. Vbattery should not exceed max coil current specification. The majority of the current goes through the coil and is typically much greater than Idd. Optional 1800pF Cosc Coil D1 EL1 Vdd N/C N/C EL2 Switch 3 Volt Battery + - N/C C2 Vss N/C N/C C1 HON 6 SQ. IN. EL LAMP 1 IN418 180pF The F coil signal controls a switch that connects the end of the coil at pin 5 to ground or to open circuit. The F coil signal is a 94% duty cycle signal switching at the oscillator frequency. During the time when the F coil signal is high, the coil is connected from V battery to ground and a charged magnetic field is created in the coil. During the low part of F coil , the ground connection is switched open, the field collapses and the energy in the inductor is forced to flow toward the lamp. F coil will send 16 of these charge pulses (see figure 2 page 8) to the lamp, each pulse increases the voltage drop across the lamp in discrete steps. As the voltage potential approaches its maximum, the steps become smaller (see figure 1 page 8). For maximum performance a fast recovery diode is recommended and should be connected between pins 5 and 6 (cathode side). The low reverse voltage capacitance of the fast recovery diode minimizes the voltage that is charged and discharged across it and this increases the energy transferred to the lamp. The H-bridge consists of two SCR structures that act as high voltage switches. These two switches control the polarity of how the lamp is charged. The SCR switches are controlled by the F lamp signal which is the oscillator frequency divided by 64. For a 20kHz oscillator, F lamp=300Hz. PDA Application Typical SP4426 Application Circuit |
English ▼
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
