SP4425NEB データシートの表示（PDF） - Signal Processing Technologies
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SP4425NEB Datasheet PDF : 14 Pages
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PIN DESCRIPTION
1
8
2
7
3
6
4
5
Pin 1 – COSC- Capacitor input 1, connect Capacitor
from VSS to Pin 1 to set COSC frequency.
Pin 2 – V - Power supply common, connect to
SS
ground.
Pin 3 – Coil- Coil input, connect coil from VDD
to pin 3.
Pin 4 – D1- Diode Cathode connection.
– CINT- Integrator capacitor, connect capacitor
from pin 4 to ground to minimize coil glitch energy.
Pin 5 – Lamp- Lamp driver output2, connect to
EL lamp.
Pin 6 – Lamp- Lamp driver output1, connect to
EL lamp.
Pin 7 – VDD- Power supply for driver, connect to
system VDD.
Pin 8 – HON- Enable for driver operation,
high = active; low = inactive.
THEORY OF OPERATION
The SP4425 is made up of three basic circuit
elements, an oscillator, coil, and switched H-bridge
network. The oscillator provides the device with
an on-chip clock source used to control the charge
and discharge phases for the coil and lamp. An
external capacitor connected between pins 1 and
VSS allows the user to vary the oscillator frequency.
For a given choice of coil inductance there will be
an optimum COSC Capacitor value that gives the
maximum light output.
The suggested oscillator frequency is 25.6kHz
(COSC=180pF). The oscillator output is internally
divided to create the control signal for fLAMP. The
oscillator output is internally divided down by 6
flip flops, a 25.6kHz signal will be divided into 6
frequency levels: 12.8kHz, 6.4kHz, 3.2kHz,
1.6kHz, 800Hz, and 400Hz. The oscillator output
(25.6kHz) is used to drive the coil (see figure 2 on
page 11) and the sixth flip flop output (300Hz) is
used to drive the lamp. Although the oscillator
frequency can be varied to optimize the lamp
output, the ratio of fCOIL/fLAMP will always equal 64.
The coil is an external component connected from
VBATTERY to pin 3 of the SP4425. VBATTERY= 1.5
VDC with a 470µH/4Ω coil are typical conditions.
Energy is stored in the coil according to the equation
EL=1/2LI2, where I is the peak current flowing in
Low ESR
decoupling
VDD
capacitor
.1µF
7
VDD
180pF
1 COSC
OSC
Cap1
FF1
SP4425 Schematic
SP4425DS/20
VBATTERY
1MΩ
8
HON
470µH/4Ω
IN4148
3
Coil
fCOIL
SCR1
CINT=1800pF typ
4
D1
SCR2
Q
FF6
Q
VSS
2
fLAMP
fLAMP
EL2
EL1
5
6
EL Lamp
SP4425 Electroluminescent Lamp Driver
4
© Copyright 2000 Sipex Corporation
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