SP4425Q Datasheet, PDF (9/12 Pages) Sipex Corporation – Electroluminescent Lamp Driver for Low Noise Applications

The following scope photos show the affect the tuning resistors (QR1 and QR2) have on the output
waveform. Figure 11 implements only 5KΩ of series resistance introducing only a slight amount of
filtering of the discharge edge. Figure 12 shows that if the values are increased to 10KΩ the discharge
edge is reduced even further. A 20KΩ example is shown in Figure 14 and represents the most amount
of filtering needed. Again, the balance in light output and audible noise must be observed for each
application.
V_BATTERY
Coil=Toko 1.2mH/19Ohm
V_DD
C_INT=1800pF
C_OSC=270pF
SP4425Q
QR1=5K-20KΩ
QR2=5K-20KΩ
EL Lamp
Figure 11.
QR1=QR2=5KΩ
V_PP=196V_PK-PK, F_LAMP=269Hz
Low noise suppression level
Figure 12.
QR1=QR2=10KΩ
V_PP=187V_PK-PK, F_LAMP=268Hz
Low noise suppression level
Figure 13.
QR1=QR2=15KΩ
V_PP=177V_PK-PK, F_LAMP=269Hz
High noise suppression level
Figure 14.
QR1=QR2=20KΩ
V_PP=168V_PK-PK, F_LAMP=266Hz
High noise suppression level
SP4425QDS/12
SP4425Q Electroluminescent Lamp Driver
9
© Copyright 1998 Sipex Corporation