6

Standard ICs

BA3899F

(1) EL drive output

As shown in Figure 4, the EL drive output consists of

charging (rise in voltage caused by switching) and dis-

charging waveforms. The switching frequency is deter-

(4) Q1, Q2, and D1

mended, caution is required concerning the pressure

withstand value. Also, Q2 must have characteristics

which allow it to keep pace with the switching speed of

Charge

Discharge

Fig.4

The oscillation frequency is determined by charging

and discharging of the external capacitance of the C1

pin. The value for C1 should be set based on the fol-

lowing equation.

With a configuration like that shown in Figure 5, the

C1 =

×

= (3.14E – 6)

×

(

+

)

×

1

11

1

1

Ix ( =

) < 40

µA

Vx – 0.2V

Rx

µA, LSI dispersion, temperature fluctuation,

and other elements can cause oscillation of the C2 pin

to stop. Be sure the above condition is satisfied.

the pressure withstand values of Q1, Q2, and D1.

determined by the external capacitance of the C2 pin.

This value (1500pF) is determined by the inductance

value and the Q2 transistor capability. When changing

this value, the drive capability of Q2 must be taken into

consideration in order to avoid the possibility of mal-

function.

4

C2

1500pF

Vx

Rx

Ix

Fig.5