Zywyn
ZSP4412A
Electroluminescent Lamp Driver
Super Low Standby Current
General Description
Features
•
•
•
•
•
+2.2V to +3.6V battery operation
50nA maximum standby current (10nA typical)
High voltage output typical 160V
PP
External oscillator required
Enable control pin
The ZSP4412A is a high voltage output DC-AC converter
that can operate from a +2.2V to +3.6V power supply. The
ZSP4412A is designed with our proprietary high voltage
BiCMOS technology and is capable of supplying up to
250V
PP
signals, making it ideal for driving small electrolu-
minescent lamps. The device features 10nA (typical)
standby current, for use in low power portable products.
An inductor is used to generate the high voltage, and an
external oscillator is needed as a clock source. The
ZSP4412A is offered in an 8-pin narrow SOIC package or
an 8-pin MSOP package. For delivery in die form, please
consult the factory.
Applications
• Watches
• Pagers
• Backlit LCD displays
Ordering Information
Part Number
Temperature Range
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
n/a
n/a
Package Type
8-Pin nSOIC
8-Pin MSOP
8-Pin MSOP Green
Die in Wafflepack
Die in Wafer Form
nSOIC Eval. Board
MSOP Eval. Board
Pin Configuration
ZSP4412ACN
ZSP4412ACU
ZSP4412ALCU
ZSP4412ACX
ZSP4412ACW
ZSP4412ANEB
ZSP4412AUEB
HON 1
NC 2
OSC Input 3
V
SS
4
8
V
DD
EL2
EL1
COIL
Zywyn
ZSP4412A
7
6
5
Please contact the factory for pricing, availabiliy on Tape-and-Reel, and
Green Package
options.
8-Pin nSOIC/MSOP
Please contact the factory for EL driver design support and availability
of custom-made evaluation demo boards.
See our web site for Application Note
AN007
regarding requirements
for custom-made evaluation demo boards.
Zywyn Corporation • Tel (408) 733-3225 • Fax (408) 733-3206 • Email sales@zywyn.com • www.zywyn.com
specifications subject to change without notice
January2005
rev. 03
Zywyn Corporation
ZSP4412A
Absolute Maximum Ratings
These are stress ratings only and functional operation of
the device at these ratings or any other above those
indicated in the operation sections of the specifications is
not implied. Exposure to absolute maximum rating condi-
tions for extended periods of time may affect reliability.
V
DD .................................................................................................
+5.0V
Input Voltages/Currents
HON (pin 1) ................................... –0.5V to (V
DD
+0.5V)
COIL (pin 5)......................................................... 60mA
Lamp Output .......................................................... 250V
PP
Storage Temperature .............................. –65°C to +150°C
Operating Temperature ............................... –0°C to +70°C
Power Dissipation Per Package
8-pin nSOIC (derate 6.14mW/°C above +70°C) .. 500mW
8-pin µSOIC (derate 4.85mW/°C above +70°C) .. 390mW
Storage Considerations
Storage in a low humidity environment is preferred. Large
high density plastic packages are moisture sensitive and
should be stored in Dry Vapor Barrier Bags. Prior to
usage, the parts should remain bagged and stored below
40°C and 60%RH. If the parts are removed from the bag,
they should be used within 48 hours or stored in an
environment at or below 20%RH. If the above conditions
cannot be followed, the parts should be baked for four
hours at 125°C in order remove moisture prior to solder-
ing. Zywyn ships product in Dry Vapor Barrier Bags with
a humidity indicator card and desiccant pack. The humid-
ity indicator should be below 30%RH.
The information furnished by Zywyn has been carefully
reviewed for accuracy and reliability. Its application or
use, however, is solely the responsibility of the user. No
responsibility of the use of this information become part of
the terms and conditions of any subsequent sales agree-
ment with Zywyn. Specifications are subject to change
without the responsibility for any infringement of patents
or other rights of third parties which may result from its
use. No license or proprietary rights are granted by
implication or otherwise under any patent or patent rights
of Zywyn Corporation.
Electrical Characteristics
T
A
= +25°C, V
DD
= +3.0V, C
LAMP
= 2000pF, Coil = 30mH at 125Ω; External Oscillator = 32,768Hz unless otherwise noted.
Symbol
V
DD
I
COIL
+ I
DD
V
COIL
V
HON
Parameter
Supply Voltage
Supply Current
Coil Voltage
HON Input Voltage
LOW: EL off
HIGH: EL on
HON Current
Shutdown Current
V
HON
= V
DD
= +3.0V
V
HON
= 0V
Input Oscillator = 32768Hz
V
HON
= V
DD
= +3.0V
V
DD
–0.25
V
DD
– 0.25
1
0
V
DD
10
10
Condition
Min
2.2
Typ
3.0
5
Max
3.6
20
3.6
0.25
V
DD
+ 0.25
100
50
Units
V
mA
V
V
µA
nA
I
HON
I
SD
= I
COIL
+ I
DD
INDUCTOR DRIVE
f
COIL
= f
LAMP
x 32
I
PK-COIL
EL LAMP OUTPUT
f
LAMP
V
PP
Coil Frequency
Coil Duty Cycle
Peak Coil Current
8192
75
Hz
%
60
mA
Guaranteed by design
EL Lamp Frequency
Peak-to-Peak Output Voltage
Input Oscillator = 32768Hz
120
256
160
Hz
V
PP
Zywyn
2
January 2005
rev. 03
Zywyn Corporation
ZSP4412A
steps. As the voltage potential approaches its maximum,
the steps become shorter (see
Figure 3).
The H-bridge consists of two proprietary low on-resis-
tance high voltage switches. These two switches control
the polarity of how the lamp is charged. The high voltage
switches are controlled by the f
LAMP
signal which is the
oscillator frequency divided by 128. For a 32kHz oscilla-
tor, f
LAMP
= 250Hz.
The direction of current flow is determined by which high
voltage switch is enabled. One full cycle of the H-bridge
will create 16 voltage steps from ground to 80V (typical)
on pins 6 and 7 which are 180 degrees out of phase with
each other (see
Figure 5).
A differential view of the
outputs is shown in
Figure 6.
Circuit Description
The ZSP4412A 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. If a clock frequency other than
32kHz is used, the output of the driver as well as the
amount of current used, will be affected.
The suggested oscillator frequency is 32,768Hz. This
clock frequency is internally divided to create two internal
control signals, f
COIL
and f
LAMP
. The output is internally
divided down by 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 (8kHz)
is used to drive the coil (see
Figure 4
) and the seventh flip
flop output (256Hz) 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.
The external clock should have a 50% duty cycle and
range from V
DD
to ground. The maximum external clock
frequency is 128kHz. The coil is an external component
connected from V
BATT
to pin 5 of the ZSP4412A. Energy
is stored in the coil according to the equation
E
L
= 1/2(LI
P
)
2
where I
P
, to the first approximation, is the
product I
P
= (t
ON
)((V
BATT
– V
CE
)/L), where t
ON
is the time
it takes for the coil to reach its peak current, V
CE
is the
voltage drop across the internal NPN switch transistor,
and L is the inductance of the coil. When the NPN
transistor switch is off, the energy is forced through an
internal diode which drives the switched H-bridge net-
work. This energy recovery is directly related to the
brightness of the EL lamp output. There are many varia-
tions among coils; magnetic material differences, winding
differences and parasitic capacitances. The Zywyn
ZSP4412A is final tested using a 30mH/125Ω coil. For
suggested coil sources see,
“Coil Manufacturers.”
The f
COIL
signal controls a switch that connects the end of
the coil at pin 5 to ground or to open circuit. The f
COIL
signal is a 75% duty cycle square wave, switching at 1/4
the oscillator frequency, (for a 32kHz oscillator f
COIL
is
8kHz). During the time when the f
COIL
signal is high, the
coil is connected from V
BATT
to ground and a charged
magnetic field is created in the coil. During the low part of
f
COIL
, the ground connection is switched open, the field
collapses, and the energy in the inductor is forced to flow
toward the high voltage H-bridge switches. f
COIL
will send
16 of these charge pulses to the lamp, each pulse in-
creases the voltage drop across the lamp in discrete
Electroluminescent Technology
What is electroluminescence?
An EL lamp is basically a strip of plastic that is coated with
a phosphorous material which emits light (fluoresces)
when a high voltage (>40V) which was first applied across
it, is removed or reversed. Long periods of DC voltages
applied to the material tend to breakdown the material and
reduce its lifetime. With these considerations in mind, the
ideal signal to drive an EL lamp is a high voltage sine
wave. Traditional approaches to achieving this type of
waveform included discrete circuits incorporating a trans-
former, transistors, and several resistors and capacitors.
This approach is large and bulky, and cannot be imple-
mented in most hand held equipment. Zywyn now offers
low power single chip driver circuits specifically designed
to drive small to medium sized electroluminescent pan-
els. All that is required is an external inductor and an
external clock signal. Electroluminescent backlighting is
ideal when used with LCD displays, keypads, or other
backlit readouts. Its main use is to illuminate displays in
dim to dark conditions for momentary periods of time. EL
lamps typically consume less current than LEDs or incan-
descent bulbs making them ideal for battery powered
products. Also, EL lamps are able to evenly light an area
without creating “hot spots” in the display. The amount of
light emitted is a function of the voltage applied to the
lamp, the frequency at which it is applied, the lamp
material used and its size, and lastly, the inductor used.
There are many variables which can be optimized for
specific applications.
Zywyn
4
January 2005
rev. 03
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