BA3899F Просмотр технического описания (PDF) - ROHM Semiconductor
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BA3899F Datasheet PDF : 8 Pages
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Standard ICs
•Operation notes
(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-
mined by fSW2 and the charging and discharging timing
by fSW1.
tSW1 (fSW1)
BA3899F
(4) Q1, Q2, and D1
The VO (Max.) shown in Figure 4 is applied to the output
VO, so if using any transistor other than that recom-
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
fSW2.
VO (Max.)
t1
Charge
t2
Discharge
Fig.4
(2) Setting fSW1
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.
C1 =
1
×1
VC1 × ( 1 + 1 )
fSW1
I1
I2
= (3.14E – 6) × 1
fSW1
(VCC = 5V)
(5) RX (resistor for adjusting light volume)
With a configuration like that shown in Figure 5, the
volume of light can be adjusted. However, RX should
be set so that IX satisfies the following condition.
Ix ( = Vx – 0.2V ) < 40µA
Rx
If IX > 40µA, LSI dispersion, temperature fluctuation,
and other elements can cause oscillation of the C2 pin
to stop. Be sure the above condition is satisfied.
The recommended setting range for fSW1 is 40Hz to
800Hz. However, the VO (Max.) shown in Figure 4 is
determined by fSW1, so caution is required concerning
the pressure withstand values of Q1, Q2, and D1.
C2
4
Rx
Vx
(3) fSW2
fSW2 is the switching pressure rise frequency, and is
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.
6
Ix
1500pF
Fig.5
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