參數(shù)資料
型號: SP4428
英文描述: Electroluminescent Lamp Driver High Drive Capability for Low Voltage Applications
中文描述: 電致發(fā)光燈驅(qū)動器驅(qū)動能力高低壓應(yīng)用
文件頁數(shù): 3/11頁
文件大?。?/td> 107K
代理商: SP4428
SP4428DS/16
SP4428 Electroluminescent Lamp Driver
3
Copyright 2000 Sipex Corporation
THEORY OF OPERATION
The
SP4428
is made up of three basic circuit
elements, an oscillator, coil, driver 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 V
allows the user to vary the oscillator
frequency. For a given choice of coil inductance
there will be an optimum C
Capacitor value that
gives the maximum light output in a given lamp.
The suggested oscillator frequency is 28.8kHz
(C
=180pF). The oscillator output is internally
divided to create the control signal f
.
The oscillator output is internally divided down
by 6 flip flops, a 28.8kHz signal will be divided
into 6 frequency levels; 14.4kHz, 7.2kHz, 3.6kHz,
1.8kHz, 900Hz, and 450Hz. The oscillator output
(28.8kHz) is used to drive the coil (see
figure 2
on
page 7
) 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 f
COIL
/f
LAMP
will always equal 64.
The coil is an external component connected from
V
to pin 3 of the
SP4428
. Energy is
developed in the coil according to the equation
E
=1/2LI
2
where the current I is defined as
I=(V
BATTERY
-IR-V
OL
)/R
T
. In order to maximize the
PIN DESCRIPTION
Pin 1 – C
- Connect CAP from V
SS
to Pin 1 to
set Oscillator frequency.
Pin 2 – V
SS
- Power supply common, connect to
ground.
Pin 3 – Coil- Coil input, connect coil from
V
BATTERY
to Pin 3.
Pin 4 – D1- Diode cathode connection.
Pin 5 – EL2- Lamp driver output1, connect to
EL lamp.
Pin 6 – EL1- Lamp driver output2, connect to
EL lamp.
Pin 7 – V
DD
- Power supply for driver, connect to
system V
DD
.
Pin 8 – HON- Enable for driver operation,
high = active; low = inactive.
1
2
3
4
8
7
6
5
S
SP4428 Schematic
Q
Q
HON
SCR1
SCR2
OSC
FF1
FF6
EL Lamp
1M
V
DD
Coil
5
6
EL1
EL2
1
Cap1
2
V
SS
V
BATTERY
V
DD
7
3
470
μ
H/4.9
8
180pF
IN4148
Optional
1,800pF
4
D1
.1
μ
F
C
OSC
f
COIL
f
LAMP
f
LAMP
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