SP4415 Datasheet, PDF (3/10 Pages) Sipex Corporation – Electroluminescent Lamp Driver with Selectable Level Outputs

PIN DESCRIPTION
THEORY OF OPERATION
1
8
2
7
3
6
4
5
Pin 1 – NC - Float this pin..
Pin 2 – V_SS - Ground connection
Pin 3 – Coil - Coil input, connect coil from V_DD
to Pin 5.
Pin 4 – Lamp2- EL voltage output, connect
directly to EL lamp.
Pin 5 – Lamp1- EL voltage output, connect
directly to EL lamp.
Pin 6 – V - Power supply for driver, connect to
DD
system V .
DD
Pin 7 – Level Select - Selects the number of
inductor drive pulses.
Pin 8 – Clk - Clock input for charge and
discharge cycles.
The SP4415 is made up of three basic circuit
elements, a clock signal conditioner, a divider
chain, and a switched H-bridge network. The clock
signal conditioner circuit allows users to directly
connect a crystal oscillator output to the SP4415;
no buffering is necessary. The clock input features
high impedance (50 MΩ), low capacitance (2.5pF)
and 200mV sensitivity. The external clock should
range from (V_DD-1V) to ground. The SP4415 is
optimized for 32,768Hz clock signals and is allowed
to vary from 20 kHz to 60kHz.
The externally supplied clock signal provides the
circuit with a clock source used to control the
charge and discharge phases for the coil and lamp.
The suggested oscillator frequency is 32,768Hz .
This clock frequency is internally divided to create
two internal control signals, f and f . For
COIL
LAMP
example a 32,768Hz signal will be divided to
provide an 8,192Hz 75% duty cycle output to drive
the coil and a 256Hz 50% duty cycle output to
drive the lamp. Although the oscillator frequency
can be varied to optimize the lamp output, the ratio
of f_COIL to f_LAMP will always equal 32.
7
Level Select
V_DD
6
V_BATTERY
Coil 35mH/125 ohms
3
8
CLK
9 BIT COUNTER
Q
CLR
7 BIT COUNTER Q
2 BIT
COUNTER
HON LEVEL
DECODER
PULSE COUNT
DECODER
PULSE COUNT
SELECTOR
V_ss
2
f_COIL
SCR1
SCR2
f_LAMP
f_LAMP
EL Lamp
EL1
EL2
5
4
SP4415 Schematic
SP4415DS/06
SP4415 Electroluminescent Lamp Driver
3
© Copyright 1996 Sipex Corporation