SP4412A Datasheet, PDF (3/10 Pages) Sipex Corporation – Electroluminescent Lamp Driver

PIN DESCRIPTION
1
8
2
7
3
6
4
5
Pin 1 – HON- Enable for driver operation,
high = active; low = inactive.
Pin 2 – NC
Pin 3 – Oscillator clock input
Pin 4 – V_SS - Power supply common, connect to
ground.
Pin 5 – Coil - Coil input, connect coil from V
DD
to Pin 3.
Pin 6 – Lamp- Lamp driver output1, connect to
EL lamp.
Pin 7 – Lamp- Lamp driver output2, connect to
EL lamp.
Pin 8 – V_DD - Positive supply.
THEORY OF OPERATION
The SP4412A is made up of three basic circuit
elements, a divider chain, a coil, and a switched
H-bridge network. The countdown chain
provides the circuit with a clock source used to
control the charge and discharge phases for the
coil and lamp. An external oscillator is required
and is delivered to pin 3 of the SO-8 package or
to the "Osc in" pad of the bare die. The chart on
page 6 shows the effect of variations in coil
values used. If a clock frequency other than
32kHz is used, the output of the driver as well as
the amount of current used, will be effected.
The suggested oscillator frequency is 32,768Hz.
This clock frequency is internally divided to
create two internal control signals, f and
COIL
f . The output is internally divided down by
LAMP
7 flip flops; therefore, a 32,768Hz signal will be
divided into the following frequencies; 32, 16,
8, 4, 2, 1, 0.5 and 0.25kHz. The second flip flop
output (8 kHz) is used to drive the coil (see
figure 2 on page 7) and the seventh flip flop
output (256 Hz) 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 32.
V_DD
8
V_DD
1
HON
V_BATTERY or V_DD
30 mH at 125Ω
5
Coil
External
Clock
Clock
3
Divider
Chain
FF1
2 NC
Q
FF2
Q
V_SS
4
f_COIL
f_LAMP
f_LAMP
EL1
EL2
6
7
EL Lamp
SP4412A Schematic
SP4412ADS/12
SP4412ACN Electroluminescent Lamp Driver
3
© Copyright 2000 Sipex Corporation