Zywyn
Features
•
•
•
•
+2.2V to +5.0V battery operation
10nA typical standby current
High voltage output typical 160V
PP
Internal oscillator
ZSP4423
Electroluminescent Lamp Driver
Low Power Applications
General Description
The ZSP4423 is a high voltage output DC-AC converter
that can operate from a +2.2V to +5.0V power supply. The
ZSP4423 is designed with our proprietary high voltage
BiCMOS technology and is capable of supplying up to
200V
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 capacitor is used to select the oscillator fre-
quency. The ZSP4423 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
•
•
•
•
•
PDAs
MP3 players
Cellular phones
Remote controls
Handheld computers
Ordering Information
Part Number
ZSP4423CN
ZSP4423LCN
ZSP4423CU
ZSP4423LCU
ZSP4423CX
ZSP4423NEB
ZSP4423UEB
Temperature Range
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
0°C to +70°C
n/a
n/a
Package Type
8-Pin nSOIC
8-Pin nSOIC Green
8-Pin MSOP
8-Pin MSOP Green
Die in Wafflepack
nSOIC Eval. Board
MSOP Eval. Board
Pin Configuration
HON 1
V
SS
2
COIL 3
EL2 4
8
CAP2
CAP1
V
DD
EL1
Zywyn
ZSP4423
7
6
5
Please contact the factory for pricing and availabiliy on a Tape-on-Reel
and Green Package
option.
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
January 2005
rev. 02
Zywyn Corporation
ZSP4423
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 .................................................................................................
+7.0V
Input Voltages/Currents
HON (pin 1) ................................... –0.5V to (V
DD
+0.5V)
COIL (pin3)..............................................................60mA
Lamp Output .......................................................... 230V
PP
Storage Temperature .............................. –65°C to +150°C
Operating Temperature ............................. –40°C to +85°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 environ-
ment 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 soldering. Zywyn
ships product in Dry Vapor Barrier Bags with a humidity
indicator card and desiccant pack. The humidity 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 impli-
cation or otherwise under any patent or patent rights of
Zywyn Corporation.
Electrical Characteristics
T
A
= +25°C, V
DD
= +3.0V, C
LAMP
= 6000pF, Coil = 20mH (R
S
= 70Ω); C
OSC
= 150pF, 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
= V
DD
= +5.0V
V
DD
= +3.0V, V
HON
= 0V
V
DD
= +5.0V, V
HON
= 0V
V
DD
= +3.0V, V
HON
= +3.0V
V
DD
= +5.0V, V
HON
= +5.0V
V
DD
–0.25
V
DD
– 0.25
0
V
DD
25
50
10
0.3
Condition
Min
2.2
Typ
3.0
5
12
Max
5.0
12
40
6.0
0.25
V
DD
+ 0.25
60
120
200
1
Units
V
mA
V
V
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
µA
nA
µA
Coil Frequency
Coil Duty Cycle
Peak Coil Current
Guaranteed by design
9.6
75
60
kHz
%
mA
EL Lamp Frequency
Peak-to-Peak Output Voltage
V
DD
= +3.0V
V
DD
= +3.0V
200
110
300
150
500
Hz
V
Zywyn
2
January 2005
rev. 02
Zywyn Corporation
ZSP4423
exceed max coil current specification. The majority of the
current goes through the coil and is typically much greater
than I
DD
. The f
COIL
signal controls a switch that connects
the end of the coil at pin 3 to ground or to open circuit. The
f
COIL
signal is a 75% duty cycle signal, switching at 1/8 the
oscillator frequency. For a 64kHz oscillator f
COIL
is 8kHz.
During the time when the f
COIL
signal is high, the coil is
connected from V
BATTERY
to ground and a charged mag-
netic field is created in the coil. During the low part of f
COIL
,
the ground connection is switched open, the field col-
lapses 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
steps. As the voltage potential approaches its maximum,
the steps become shorter (see
Figure 4).
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 256. For a 64kHz oscillator,
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 4 and 5 which are 180 degrees out of phase with each
other (see
Figure 6).
A differential representation of the
outputs is shown in
Figure 7.
To minimize AC interference
it is advisable to use a decoupling filter capacitor between
V
DD
and ground.
Circuit Description
The ZSP4423 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 7 and 8 allows the user to vary the oscillator frequency
from 32kHz to 400kHz. In general, increasing the C
OSC
capacitor will increase the lamp output voltage and
decrease the lamp frequency.
The suggested oscillator frequency is 64kHz
(C
OSC
=150pF). The oscillator output is internally divided
to create two internal control signals, f
COIL
and f
LAMP
. The
oscillator output is internally divided down by 8 flip-flops;
a 64kHz signal will be divided into 8 frequencies; 32, 16,
8, 4, 2, 1, 0.5, and 0.25 Hz. The 3rd flip-flop output (8kHz)
is used to drive the coil (see
Figure 1)
and the 8th flip flop
output (250Hz) 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 on-chip oscillator of the ZSP4423 can be overdriven
with an external clock source by removing the C
OSC
capacitor and connecting a clock source to pin 8 (Cap 2).
The clock should have a 50% duty cycle and range from
V
DD
to ground. An external clock signal may be desirable
in order to synchronize any parasitic switching noise with
the system clock. The maximum external clock frequen-
cies that can be supplied is 400kHz.
The coil is an external component connected from
V
BATTERY
to pin 3 of the ZSP4423. Energy is stored in the
coil according to the equation E
L
=1/2LI
2
, where I is the
peak current flowing in the inductor. The current in the
inductor is time dependent and is set by the “ON” time of
the coil switch:
I = (V
L
/L) t
ON
, where V
L
is the voltage across the inductor.
At the moment the switch closes, the current in the induc-
tor is zero and the entire supply voltage (minus the V
SAT
of the switch) is across the inductor. The current in the
inductor will then ramp up at a linear rate. As the current
in the inductor builds up, the voltage across the inductor
will decrease due to the resistance of the coil and the “ON”
resistance of the switch: V
L
= V
BATTERY
– IR
L
– V
SAT
.
Since the voltage across the inductor is decreasing, the
current ramp-rate also decreases which reduces the cur-
rent in the coil at the end of t
ON
the energy stored in the
inductor per coil cycle and therefore the light output. The
other important issue is that maximum current (saturation
current) in the coil is set by the design and manufacturer
of the coil. If the parameters of the application such as
V
BATTERY
, L, R
L
or t
ON
cause the current in the coil to
increase beyond its rated I
SAT
, excessive heat will be
generated and the power efficiency will decrease with no
additional light output. The Zywyn ZSP4423 is final tested
using a 20mH/70Ω coil from CTC. For suggested coil
sources, see
“Coil Manufacturers.”
The supply V
DD
can range from +2.2V to +5.0V. It is not
necessary that V
DD
= V
BATTERY
. V
BATTERY
should not
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 hand held equipment. Zywyn now offers low
power single-chip driver circuits specifically designed to
drive small to medium sized electroluminescent panels.
All that is required is one external inductor and capacitor.
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 than LEDs or incandescent 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. There are
many variables which can be optimized for specific appli-
cations.
4
January 2005
rev. 02
Zywyn
Microcontroller MCU
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