D372A Datasheet, PDF (5/12 Pages) List of Unclassifed Manufacturers – Electroluminescent Lamp Driver IC

Designing With D372
I. Lamp Frequency Capacitor (CLF) Selection
Selecting the appropriate value of capacitor (CLF) for the low frequency oscillator will set the output frequency of the
D372 inverter. Figure 1 graphically represents the effect of the CLF capacitor value on the oscillator frequency at
V+ = 3.0V.
600
500
400
300
200
100
1
2
3
4
5
CLF (nF)
Figure 1: Typical Lamp Frequency vs. CLF Capacitor
The lamp frequency may also be controlled with an external clock signal. The resulting lamp frequency will be half of
the clock signal frequency. The differential output voltage will increase in magnitude during the high portion of the
clock signal and decrease during the low portion of the clock signal. Lamp frequencies of 200-500Hz are typically
used.
The selection of the CLF value can also affect the output brightness and current consumption of the driver. The EL
lamp frequency (LF) depends on lamp size, drive conditions, and mainly on the CLF value selected. Figures 2 and 3
show typical brightness and current draw of a D372 circuit at different frequencies. The data was taken with an
average 1.0mH inductor and 68 pf CHF capacitor.
9
45
8
Luminance
40
Current
7
35
6
5
30
4
25
3
20
2
15
1
0
10
0
100
200
300
400
500
600
Frequency (Hz)
9
45
8
Luminance
Current
40
7
35
6
5
30
4
25
3
20
2
15
1
0
10
0
100
200
300
400
500
600
Frequency (Hz)
Figure 2: Typical Luminance and Current
vs. Lamp Frequency
Conditions: V+ = 3.0 V, 1.5 in² EL Lamp
6
Figure 3: Typical Luminance and Current
vs. Lamp Frequency
Conditions: V+ = 5.0 V, 4.0 in² EL Lamp