D355B Datasheet, PDF (5/14 Pages) List of Unclassifed Manufacturers – Electroluminescent Lamp Driver IC

Designing With D355B
I. Lamp Frequency Capacitor (CLF) Selection
Selecting the appropriate value of capacitor for the low frequency oscillator (CLF) will set the output frequency
of the D355 inverter. Figure 1 graphically represents the inversely proportional relationship between the
CLF capacitor value and the oscillator frequency. In this example at V+=3.0V, LF = 1600 nF-Hz/CLF.
900
800
700
600
500
400
300
200
100
0
0 1 2 3 4 5 6 7 8 9 10
CLF (nF)
Figure 1: Typical Lamp Frequency vs. CLF Capacitor
Alternatively, the lamp frequency may also be controlled with an external clock signal with a 50% duty
cycle. The output lamp frequency will be the same frequency as the input clock signal. For example, if a
250Hz input clock signal is used, the resulting lamp frequency will be 250Hz. The clock signal input voltage
should not exceed V+.
The selection of the CLF value can also affect the brightness of the EL lamp because of its control of the
lamp frequency (LF). Although input voltage and lamp size can change EL lamp frequency as well, LF
mainly depends on the CLF value selected or the frequency of the input clock signal to CLF. The luminance
of various sizes of Durel 3 Blue-green EL lamp driven by a D355B at V+ = 3.0V using the same inductor
value is shown in Figure 2 with respect to lamp frequency.
8
7
6
2in² EL Lamp
5
4
4in² EL Lamp
3
2
6in² EL Lamp
1
0
0
200
400
600
800 1000
Lamp Frequency (Hz)
Figure 2: Typical Lamp Luminance vs. Lamp Frequency
6