Datasheet SP4438EU, SP4438UEB Datasheet (Sipex Corporation)

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Page 1

Ultra-Quiet Electroluminescent Lamp Driver

For Cellular Phone Applications

■ Patent Pending Output Waveshaping

■ Waveshaped Output Optimized For Low

Acoustic Noise And Maximum Efficiency

■ Reduced Supply Current And Standby Current

■ Up to15cd/m2 For Cell Phone Sized EL Lamps (2 to 3 sq. in.)

■ Waveshaped Output And Low Frequency Operation Minimize Stress On EL Lamp To Extend Its Lifetime

■ Uses 820µH, Sub-2mm Coils

■ Gradual Rising And Falling Edges Minimizes

EMI

■ +2.7V To +3.3V Battery Operation

■ Space-Saving 8-pin MSOP package

APPLICATIONS

■ Cellular Radios

■ Wireless Communication Products

SP4438

DESCRIPTION

The SP4438 device is a low noise, high voltage output DC-AC inverter designed to drive electroluminescent lamps to backlight liquid crystal display and keypads used in cellular phones, cordless phones, 2-way radios, and other wireless communication products. The output waveform of the SP4438 device is ideal for cell phone applications requiring low acoustic noise performance. One external resistor is used to set the internal oscillator frequency and one inductor is required to generate the high voltage AC output to drive an EL lamp up to 3 square inches in size. The SP4438 operates from a +3.0V battery source and has a low power standby mode that draws less than 1µA, making it ideal for low-power cellular applications. All input pins are ESD protected with internal diodes to VDD and VSS. The SP4438 is offered in a space-saving 8-pin MSOP package.

BATT

VDD

ELEN

OSC

2 3 4

SP4438

EL1

ELEN

EL2

CINT COIL

0.1µF

714kΩ

SP4438

OSC

EL Lamp

1nF

COIL

INT

EL2EL1

820µH/14Ω

1N4148

INT

47nF

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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.

Supply Voltage (VDD to VSS)........................-0.3V, +5V

Operating Temperature.......................-40˚C to +85˚C

Storage Temperature........................-65˚C to +150˚C

Power Dissipation Per Package 8-pin MSOP

(derate 4.85mW/OC above +70OC).........................400mW

SPECIFICATIONS

VDD = +2.7V to +3.3V, L values unless otherwise noted.

= 820µH/14Ω, R

COIL

= 714kΩ, EL Lamp Load = (8nF + 2.5kΩ)/1MΩ, and T

OSC

RETEMARAP.NIM.PYT.XAMSTINUSNOITIDNOC

SCITSIRETCARAHCTUPNI

= -40OC to +85OC. T

AMB

= 25OC for typical

AMB

V,egatloVylppuS

,tnerruCylppuSI

LIOCI+DD

V,egatloVlioC

LIOC

V,egatloVtupnINELE

NELE

LE:WOL

FFO

LE:HGIH

7.20.33.3V 03AmVDDV0.3+=

52.0-

V52.0

52.0+

ecnadepmItupnINELE13MΩ

I,tnerruCnwodtuhS

DSI=LIOCI+DD

1AµV

NELE

V,WOL=

V0.3+=

EVIRDROTCUDNI

f,ycneuqerFlioC

LIOC

62 32

2334

zHk

k417= Ω T,

CSO

04-=

BMA

52+=OC

BMA

58+otC

V,C

V0.3+=

elcyCytuDlioC09%

I,tnerruClioCkaeP

LIOC-KP

001Am

TUPTUOPMALLE

f,ycneuqerFpmaLLE

PMAL

,egatloVtuptuOkaePotkaePV

P-P

091 571

031 021

052633

843

541 041

esioNelbiduA62Bd

emiTesiR55.8.00.1sm

T T

P-P

LPS

52+=

BMA BMA

BMA

V,C

04-=

52+=

04-=

52+=

58+otC

V,C

58+otC

V,C

daolhtiw,V0.3+=

1ETON,V0.3+=

,daolhtiw,V0.3+=

%09ot%01morfderusaem

NOTE 1: Audible Noise is measured inside an acoustic sound chamber. The Sound Level Meter is a B&K Mediator 2238, A-weighted with Condenser Mic type 4188 positioned 1/4 inch above the lamp in an 8 cubic inch volume. See Figure 5 on page 6.

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PINOUT

VDD

ELEN

PIN ASSIGNMENTS

Pin 1 — VDD — Positive Battery Power Supply.

Connect such that +2.7V < V

Pin 2 — ELEN — Electroluminescent Lamp

Enable. When driven HIGH, this input pin enables the EL driver outputs for EL1 and EL2. This pin has an internal pulldown resistor.

Pin 3 — R

ing a resistor to this input pin sets the frequency of the internal clock.

Pin 4 — VSS — Power Supply Common. Con-

nect to the lowest circuit potential, typically ground.

— Oscillator Resistor. Connect-

OSC

2 3 4

< +3.3V.

SP4438

Pin 6 — C

Pin 7 — EL2 — Electroluminescent Lamp Out-

Pin 8 — EL1 — Electroluminescent Lamp Out-

EL1

EL2

CINT

COIL

— Integrating Capacitor. An integrating capacitor (47nF typical) connected from this pin to ground filters out any coil switching spikes or ripple present in the output waveform to the EL lamp. Connecting a fast recovery diode from COIL to C increases the light output of the EL lamp.

put 2. This is a high voltage lamp driver output pin to connect to the EL lamp.

put 1. This is a high voltage lamp driver output pin to connect to the EL lamp.

INT

Pin 5 — COIL — The inductor for the EL lamp

is connected from VDD to this input pin.

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VBATT

VDD

ROSC

EL Lamp

ELEN

ROSC

714kΩ

0.1µF

Figure 1: Typical Operating Circuit for the SP4438. Note: C1 should be close to L1.

1nF

SP4438

VSS

820µH/14Ω

COIL

INT

EL2EL1

1N4148

INT

47nF

Page 5

OSC

714kΩ

VBATT

COIL

SP4438

OSC

CINT

820µH/14Ω

1N4148

CINT

47nF

0.1µF

1nF

ELEN

FF7

Figure 2: Internal Block Diagram of the SP4438

PMOSPMOS

BRIDGE

CONTROL

DMOS

EL1

DMOS

EL2

EL Lamp

Figure 3: EL Differential Output Waveform of the EL1 and EL2 Outputs of the SP4438

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EL Lamp Noise Measurement Set-Up

1”

2”

4”

EL Lamp

Microphone Type 4188

Photometer Tek-J17

Anechoic Chamber

Bruel & Kjaer

2238 Mediator

A-Weighting

dBSPL

Measurement

Aux 1

HP8903A Audio Analyzer - SPCL 3.1, 1.17 Preamplifier with 30kHz High Pass Filter

EL Driver

Differential Voltage Probe

Current Probe

Tek754C Digital Osciliscope Voltage Waveform Measurements

Figure 4: Dual Supply Application Circuit for the SP4438

EL Lamp Noise Measurement Set-Up

1”

2”

4”

EL Lamp

Microphone Type 4188

Photometer Tek-J17

Anechoic Chamber

Monitor

Bruel & Kjaer

2238 Mediator

A-Weighting

dBSPL

Measurement

Aux 1

HP8903A Audio Analyzer - SPCL 3.1, 1.17 Preamplifier with 30kHz High Pass Filter

Differential Voltage Probe

Current Probe

Monitor

Tek754C Digital Osciliscope Voltage Waveform Measurements

EL Driver

Figure 5. Electroluminescent Lamp Noise Measurement Setup for the SP4438

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DESCRIPTION

The SP4438 Electroluminescent Lamp Driver is a low-cost low voltage device ideal for the replacement of LED backlighting designs in cell phones, PDAs and other portable designs desiring low acoustic noise. The SP4438 contains a DC-AC inverter that can produce an AC output of 145V +3.3V input voltage. An internal block diagram

(typical) from a +2.7V to

P-P

of the SP4438 can be found in Figure 2. The SP4438 is built on Sipex's dielectrically

isolated BiCMOS process that provides the isolation required to separate the high voltage AC signal used to drive the EL lamp from the low voltage logic and signal processing circuitry. This ensures latch-up free operation in the interface between the low voltage CMOS circuitry and the high voltage bipolar circuitry. The SP4438 is ideal for applications driving EL lamps to backlight LCD displays and keypads, used in cellular radios.

in dim to dark conditions for momentary periods of time. EL lamps consume less power than LEDs or incandescent bulbs making them ideal for battery powered products. Also, EL lamps are able to evenly light an area without creating any undesirable "hot spots" in the display.

THEORY OF OPERATION

The SP4438 is a DC-AC inverter made up of:

1. The Oscillator/Frequency Divider, 2. The Coil/Boost Converter, 3. The Switched Hbridge Network, and 4. The Precision Bridge Control Logic. Further details of each element follow.

The Oscillator/Frequency Divider

The oscillator provides the SP4438 with an onchip clock used to control the coil switch (f and the H-bridge network (f oscillator frequency can be varied to optimize the lamp output, the ratio of f always equal 128.

). Although the

LAMP

COIL/fLAMP

COIL

will

)

A total of only six external components are required for the standard operation of the SP4438: an inductor, a fast recovery diode, three capacitors and a resistor. A diagram of the SP4438 in a typical application can be found in Figure 1.

Electroluminescent Technology

An EL lamp is a strip of plastic that is coated with a phosphorous material which emits light (fluoresces) when a (>40V) AC signal is applied across it. Long periods of DC voltages applied to the lamp tends 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 transformer, transistors, and several resistors and capacitors. This approach is large and bulky, and cannot be implemented in most hand held equipment. Sipex offers low power single chip driver circuits specifically designed to drive small to medium sized electroluminescent panels.

Market Applications

Electroluminescent backlighting is ideal when used with LCD displays, keypads, or other backlit readouts. Its main use is to illuminate displays

Figure 2 shows the oscillator output driving the coil and through 7 flip flops, driving the lamp. The suggested oscillator frequency is 32kHz for f

. The oscillator output is internally divided

COIL

down by 7 flip flops to create a second internal control signal at 250Hz for f

LAMP

The Coil/Boost Converter

The supply V See figure 4 on page 6. V such that I coil current specification. The majority of the

can range from +2.7V to +9V.

COIL

does not exceed the maximum

COIL

should be chosen

COIL

current goes through the coil and is typically much greater than IDD.

The inductor is an external component connected from V Energy is stored in the coil according to the

to the COIL pin of the SP4438.

COIL

equation

EL = 1/2 x L x I

where IP, to the first approximation, is the product

IP = (tON) x ((V

- VCE)/L)

BATT

where tON is the time it takes for the coil to reach its peak current, VCE is the voltage drop across the internal NPN transistor and L is the

Page 8

inductance of the coil. When the NPN transistor switch is off, the energy is forced through an internal diode which drives the switched Hbridge network. This energy recovery is directly related to the brightness of the EL lamp output. There are many variations among coils; magnetic material differences, winding differences and parasitic capacitances.

Increase EL Lamp Light Output: By connecting a fast recovery diode from COIL (pin 5) to C switched H-bridge network is bypassed resulting

(pin 6), the internal diode of the

INT

in an increase in light output at the EL lamp. We suggest a fast recovery diode, such as the industry standard 1N4148, be used for D1. This circuit connection can be found in Figure 2.

The f the coil at the COIL pin to ground or to open circuit. The f signal switching at the oscillator frequency, 32kHz. During the time when the f HIGH, the coil is connected from V and a charged magnetic field is created in the coil. When the f connection is switched open, the field collapses,

signal controls a switch that connects

COIL

signal is a 90% duty cycle

COIL

to ground

COIL

signal is LOW, the ground

COIL

signal is

and the energy in the inductor is forced to flow toward the high voltage H-bridge switches.

The Switched H-Bridge Network

Current sources and precision controlled timing of the SP4438 switched H-bridge network are designed to reduce EMI emissions, extend EL lamp life, and reduce the overall power dissipation of the device.

Current sources were added to the high and low side of the H-bridge network to ensure control of the charge and discharge of the EL lamp. The precision MOSFET timing of the SP4438 allows for controlled charging and discharging of the EL lamp to minimize EMI and audible noise. Refer to Figure 7 for the single ended and differential output waveforms to the EL lamp.

The Precision Bridge Control Circuitry

This circuitry is driven by the internal oscillator to control the timing of the charge and discharge of the EL lamp to eliminate EMI and noise concerns. This control circuitry drives the Hbridge timing. Refer to Figure 2 for the internal block diagram of the SP4438.

Fine Tuning Performance

Circuit performance of the SP4438 can be improved with some of the following suggestions:

Split Power Supplies: Instead of driving both the logic and power circuitry of the SP4438 from a single battery supply, two supplies can be implemented, one to drive the IC and the other to drive the inductor.

The +2.7V to +3.3V power supply is connected to VCC. This power supply can be used to power the oscillator and control logic. The current draw on this power supply will be minimal, typically <1mA for SP4438.

When selecting a separate +2.7V to +9.0V power supply connected to the inductor to drive the IC power circuitry, it is essential that the proper inductor is selected. The peak current draw of the inductor should not exceed maximum conditions over the entire input voltage operating range.

If the inductor selected is too large, the power current may rise too slowly. At low input voltages, this will not allow the peak current to rise to the set peak current trip point. At high input voltages, the power current might rise too quickly and overshoot the set peak current trip point. These conditions will prevent optimal light output at the EL lamp. Excessive currents may permanently affect the normal operation of the SP4438.

Changing the EL Lamp Output Voltage Waveform: Designers can alter the trapezoidal

output voltage waveform to the EL Lamp. Changing the capacitance of the integrating capacitor, C waveform making it appear more sinusoidal.

, will ideally integrate the output

INT

This will minimize any noise inherent to the application.

Page 9

Audio Noise Considerations: A system can have different sources of audio noise. The coil, the filter capacitor, and the EL lamp itself may be a source of audio noise if operated in the audio frequency range.

emitted is a function of the voltage applied to the lamp, the frequency at which it is applied, the lamp material and the lamp size. Sipex supplies characterization charts to aid the designer in selecting the optimum circuit configuration.

Designers should select either the coil or coil frequency such that the coil is not in continous mode as this will greatly decrease efficiency and contribute to noise.

Close attention should be given to the mounting of the filter capacitor where the mounting can act as an amplifier, such as in a speaker box. Film capacitors do not exhibit audio noise concerns but certain ceramic capacitors subjected to a high voltage source can exhibit a piezoelectric effect. This can be a source of concern in the audio range.

The EL lamp itself can also exhibit audible noise as a result of high voltage swings at frequencies within the audio range. Close attention should be given to the physical mounting of the EL lamp to diminish this concern that can generate both EMI and audio noise.

Electromagnetic Interference (EMI) Considerations: Electromagnetic Interferenc

Electromagnetic Interference (EMI) concerns are rooted in uncontrolled high voltage swings on the EL lamp. The controlled charging and dischanging of the EL lamp by the SP4438 minimizes EMI effects.

Sipex will perform customer application evaluations, using the customer's actual EL lamp to determine the optimum operating conditions for specific applications. For customers considering an EL backlighting solution for the first time, Sipex is able to offer retrofitted solutions to the customer's existing LED or nonbacklit product for a thorough electrical and cosmetic evaluation. Refer to Figure 6 for an enlargement and actual size evaluation board layout. Please contact your local Sales Representative for Sipex or the Sipex factory directly to initiate this valued service.

Printed Circuit Board Layout Suggestions: The SP4438's high voltage

operation makes PC layout important for minimizing ground bounce and noise. Keep the IC's GND pin and the ground leads of C1 and C

less than 0.2 in (5mm) apart. Also keep the

INT

connections to COIL as short as possible. To maximize output power and efficiency and minimize output ripple voltage, use a ground plane and solder the IC's V ground plane.

directly to the

EL Lamp Driver Design Challenges

There are many variables which can be optimized for specific applications. The amount of light

Page 10

EVALUATION BOARD LAYOUT (ENLARGED)

EVALUATION BOARD LAYOUT (ACTUAL SIZE)

Figure 6. Evaluation Board Layout for the SP4438.

Page 11

Figure 7. Single Ended and Differential Output Waveforms for the SP4438 CH.1 and CH.2 are single ended waveform SP4438 CH.4 is differential SP4438 waveform.

Page 12

IDD (mA)

1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3

Supply Current vs. Lamp Size

Lamp Size (in2)

Figure 1

200

180

160

140

120

100

Output Voltage (Vp-p)

1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3

Lamp Size (in2)

Figure 2

Output Voltage vs. Lamp Size

Page 13

Luminance vs.Lamp Size

Luminance (cd/m^2)

11.522.53

280

Lamp Size (in2)

Figure 3

Lamp Frequency vs. V

275

270

265

Lamp Freq-(Hz)

260

255

250

2.5 2.7 2.9 3.1 3.3 3.5 3.7

VDD (volts)

Figure 4

Page 14

180

170

160

150

140

Lamp Voltage (V-p-p)

130

120

2.5 2.7 2.9 3.1 3.3 3.5 3.7

Lamp Voltage vs. V

VDD (volts)

Figure 5

(mA)

2.5 2.7 2.9 3.1 3.3 3.5 3.7

VDD (volts)

Figure 6

Page 15

300

Luminance vs. V

Luminance (cd/m^2)

2.5 2.7 2.9 3.1 3.3 3.5 3.7

VDD (volts)

Figure 7

290

280

270

260

250

240

230

Lamp Frequency (Hz)

220

210

200

-40 -20 0 20 40 60 80

Temp (ºC)

Figure 8

Page 16

Peak Lamp Voltage vs. Temp

160

155

150

145

140

135

130

Peak Lamp Voltage (Volts)

125

120

-40 -20 0 20 40 60 80

Temp (ºC)

Figure 9

(total part current) vs. Temp

Total Part Current

-40 -20 0 20 40 60 80

Temp (ºC)

Figure 10

Page 17

Coil Manufacturers

Hitachi Metals Material Trading Division 2101 S. Arlington Heights Road, Suite 116 Arlington Heights, IL 60005-4142 Phone: 1-800-777-8343 Ext. 12 (847) 364-7200 Ext. 12 Fax: (847) 364-7279

Hitachi Metals Ltd. Europe Immernannstrasse 14-16, 40210 Dusseldorf, Germany Contact: Gary Loos Phone: 49-211-16009-0 Fax: 49-211-16009-29

Hitachi Metals Ltd. Kishimoto Bldg. 2-1, Marunouchi 2-chome, Chiyoda-Ku, Tokyo, Japan Contact: Mr. Noboru Abe Phone: 3-3284-4936 Fax: 3-3287-1945

Hitachi Metals Ltd. Singapore 78 Shenton Way #12-01, Singapore 079120 Contact: Mr. Stan Kaiko Phone: 222-8077 Fax: 222-5232

Hitachi Metals Ltd. Hong Kong Room 1107, 11/F., West Wing, Tsim Sha. Tsui Center 66 Mody Road,Tsimshatsui East, Kowloon, Hong Kong Phone: 2724-4188 Fax: 2311-2095

Panasonic 6550 Katella Ave Cypress, CA 90630-5102 Phone: (714) 373-7366 Fax: (714) 373-7323

Sumida Electric Co., LTD. 5999, New Wilke Road, Suite #110 Rolling Meadows, IL,60008 U.S.A. Phone: (847) 956-0666 Fax: (847) 956-0702

Sumida Electric Co., LTD. 4-8, Kanamachi 2-Chrome, Katsushika-ku, Tokyo 125 Japan Phone: 03-3607-5111 Fax: 03-3607-5144

Sumida Electric Co., LTD. Block 15, 996, Bendemeer Road #04-05 to 06, Singapore 339944 Republic of Singapore Phone: 2963388 Fax: 2963390

Sumida Electric Co., LTD. 14 Floor, Eastern Center, 1065 King's Road, Quarry Bay, Hong Kong Phone: 28806688 Fax: 25659600

Murata 2200 Lake Park Drive, Smyrna Georgia 30080 U.S.A. Phone: (770) 436-1300 Fax: (770) 436-3030

Murata European Holbeinstrasse 21-23, 90441 Numberg, Postfachanschrift 90015 Phone: 011-4991166870 Fax: 011-49116687225

Murata Taiwan Electronics 225 Chung-Chin Road, Taichung, Taiwan, R.O.C. Phone: 011 88642914151 Fax: 011 88644252929

Murata Electronics Singapore 200 Yishun Ave. 7, Singapore 2776, Republic of Singapore Phone: 011 657584233 Fax: 011 657536181

Murata Hong Kong Room 709-712 Miramar Tower, 1 Kimberly Road, Tsimshatsui, Kowloon, Hong Kong Phone: 011-85223763898 Fax: 011-85223755655

Polarizers/transflector Mnfg.

Nitto Denko Yoshi Shinozuka Bayside Business Park 48500 Fremont, CA. 94538 Phone: 510 445 5400 Fax: 510 445-5480

Top Polarizer- NPF F1205DU Bottom - NPF F4225 or (F4205) P3 w/transflector

Transflector Material Astra Products Mark Bogin P.O. Box 479 Baldwin, NJ 11510 Phone (516)-223-7500 Fax (516)-868-2371

EL Lamp manufacturers

Leading Edge Ind. Inc. 11578 Encore Circle Minnetonka, MN 55343 Phone 1-800-845-6992

Midori Mark Ltd. 1-5 Komagata 2-Chome Taita-Ku 111-0043 Japan Phone: 81-03-3848-2011

Luminescent Systems inc. (LSI) 101 Etna Road Lebanon, NH. 03766-9004 Phone: (603) 448-3444 Fax: (603) 448-3452

NEC Corporation Yumi Saskai 7-1, Shiba 5 Chome, Minato-ku, Tokyo 108-01, Japan Phone: (03) 3798-9572 Fax: (03) 3798-6134

Seiko Precision Shuzo Abe 1-1, Taihei 4-Chome, Sumida-ku, Tokyo, 139 Japan Phone: (03) 5610-7089 Fax: (03) 5610-7177

Gunze Electronics 2113 Wells Branch Parkway Austin, TX 78728 Phone: (512) 752-1299

Page 18

All package dimensions in inches

0.020

0.0965 ±0.003

0.020 1

0.013 ±0.005

0.0256

0.116

±0.004

0.118

±0.004

BSC

0.118

±0.004

0.004

±0.002

0.034

±0.004

0.040

±0.003

0.012

±0.003

0.16

R .003

12.0˚ ±4˚

0.01

12.0˚ ±4˚

0.008

0.0215 ±0.006

0.037 Ref

±0.004

0.116

0.118

±0.004

0˚ - 6˚

0.006

±0.006

0.006

±0.006

3.0˚ ±3˚

Page 19

ORDERING INFORMATION

Model Operating Temperature Range Package Type

SP4438EU .............................................. -40˚C to +85˚C ..........................................8-Pin MSOP

SP4438UEB........................................................................................................ Evaluation Board

Corporation

SIGNAL PROCESSING EXCELLENCE

Sipex Corporation

Headquarters and Sales Office

22 Linnell Circle Billerica, MA 01821 TEL: (978) 667-8700 FAX: (978) 670-9001 e-mail: sales@sipex.com

233 South Hillview Drive Milpitas, CA 95035 TEL: (408) 934-7500 FAX: (408) 935-7600

Sipex Corporation reserves the right to make changes to any products described herein. Sipex does not assume any liability arising out of the application or use of any product or circuit described hereing; neither does it convey any license under its patent rights nor the rights of others.

Datasheet SP4438EU, SP4438UEB Datasheet (Sipex Corporation)

Specifications and Main Features

Frequently Asked Questions

User Manual