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Part: SP4428NEB
Category:
Interface and Interconnect
Description: Electroluminescent Lamp Driver High Drive Capability For Lowvoltage Applications
Company: Sipex Corporation
Datasheet: Download SP4428NEB datasheet File size : 77 kB
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®
SP4428
Electroluminescent Lamp Driver High Drive Capability for Low Voltage Applications
s Low Power +1.1V to +1.7V Single Cell Operation s Low-Cost EL Driver Ideal for Backlighting s DC-to-AC Inverter Generates High Voltage AC to Drive EL Lamps s Externally Adjustable Oscillator s Low Current Standby Mode APPLICATIONS s Pagers s Watches s Backlit LCD Displays
DESCRIPTION
The SP4428 is a high voltage output DC-AC converter that can operate from a single 1.5 VDC power supply. The SP4428 is capable of supplying 200 VPP (typical), making it ideal for driving electroluminescent lamps. The device features 1µA (typical) standby current, for use in low power portable products. One external inductor is required to generate the high voltage charge, and one external capacitor is used to produce a clock signal that generates the coil and lamp frequencies. The SP4428 is ideal for PDAs, pagers, and other low power portable applications using LCDs in dim or low light environments. The SP4428 is offered in an 8-pin narrow SOIC. For delivery in die form, please consult the factory.
COSC VSS COIL D1
1 2 3 4 SP4428
8 7 6 5
HON VDD EL1 EL2
Block Diagram
SP4428DS/16 SP4428 Electroluminescent Lamp Driver © Copyright 2000 Sipex Corporation
1
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 below is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability. TA= +25°C unless otherwise noted VDD...5V Input Voltages/Currents HON (pin1)........-0.5V to (VDD+0.5V) COIL (pin3)...100mA Lamp Outputs...........230VPP Storage Temperature....-65°C to +150°C Power Dissipation Per Package 8-pin NSOIC (derate 6.14mW/oC above +70oC).........500mW
The information furnished herein by Sipex has been carefully reviewed for accuracy and reliability. Its application or use, however, is solely the responsibility of the user. No responsibility for the use of this information is assumed by Sipex, and this information shall not explicitly or implicitly become part of the terms and conditions of any subsequent sales agreement with Sipex. Specifications are subject to change without prior notice. By the sale or transfer of this information, Sipex assumes no responsibility for any infringement of patents or other rights of third parties which may result from its use. No license or other proprietary rights are granted by implication or otherwise under any patent or patent rights of Sipex Corporation.
SPECIFICATIONS
(T= 25°C; VDD = 1.5V; Lamp Capacitance = 4.7nF; Coil = 470µH at 4.9 Ohms; COSC = 180pF unless otherwise noted) CINT = 1800pF
PARAMETER Supply Voltage, VDD Supply Current, ICOIL+IDD Coil Voltage, VCOIL HON Input Voltage, VHON LOW: EL off HIGH: EL on HON Current, EL on Shutdown Current, ISD=ICOIL+IDD INDUCTOR DRIVE Coil Frequency, fCOIL Coil Duty Cycle Peak Coil Current, IPK-COIL EL LAMP OUTPUT EL Lamp Frequency, fLAMP
MIN. 1.1
TYP. 1.5 35 45
MAX. 1.7 50 80 1.7
UNITS V mA V
CONDITIONS
VDD=1.1V, VHON=1.1V VDD=1.5V, VHON=1.5V
VDD -0.25 VDD-0.25 0 VDD 3 0.5
0.25V VDD+0.25 15 10
V µA µA
internal pulldown, VHON=VDD=1.5V VHON=0V
28.8 90 100
kHz % mA Guaranteed by design.
150 300 150 90 120
450
500 550 750
Hz
TAMB=+25OC, VDD=1.1V TAMB=+25OC, VDD=1.5V TAMB=-40OC to +85OC, VDD=1.5V VDD=1.1V VDD=1.5V
Peak to Peak Output Voltage
120 160
VPP
SP4428DS/16
SP4428 Electroluminescent Lamp Driver
© Copyright 2000 Sipex Corporation
2
PIN DESCRIPTION
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 VSS allows the user to vary the oscillator frequency. For a given choice of coil inductance there will be an optimum COSC Capacitor value that gives the maximum light output in a given lamp. The suggested oscillator frequency is 28.8kHz (COSC=180pF). The oscillator output is internally d i v i d e d to create the control signal f LAMP . 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 fCOIL/fLAMP will always equal 64. The coil is an external component connected from VBATTERY to pin 3 of the SP4428. Energy is developed in the coil according to the equation E L=1/2LI 2 where the current I is defined as I=(VBATTERY-IR-VOL)/RT. In order to maximize the
1 2 3 4
8 7 6 5
Pin 1 COSC- Connect CAP from VSS to Pin 1 to set Oscillator frequency. Pin 2 VSS- Power supply common, connect to ground. Pin 3 Coil- Coil input, connect coil from VBATTERY 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 VDD- Power supply for driver, connect to system VDD. Pin 8 HON- Enable for driver operation, high = active; low = inactive.
SP4428
VDD
VBATTERY 470µH/4.9 IN4148 8 HON 1M 1 COSC 180pF fLAMP
Q
Optional 1,800pF 4 D1
.1µF
7 VDD
3 Coil
OSC Cap1 fCOIL
SCR1 SCR2
FF1
FF6
Q
fLAMP EL1 5 EL2 6
VSS 2
EL Lamp
SP4428 Schematic
SP4428DS/16 SP4428 Electroluminescent Lamp Driver © Copyright 2000 Sipex Corporation
3
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