Datasheet TK65929MTL, TK65928MTL, TK65927MTL, TK65926MTL, TK65925MTL Datasheet (TOKO)

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TK6592x

20P

MEDIUM EL LAMP DRIVER

FEATURES

■ High Ratio of Brightness / Input Power

■ Constant Brightness Versus Input Supply Changes

■ Optimized for 9 nf to 27 nf Panel Capacitance

■ Panel Voltage Slew Rates Controlled for Life

Enhancement

■ Panel Peak to Peak Voltage Independent of Input

Voltage and Temperature

■ Panel Peak to Peak Frequency Independent of

Input Voltage and Temperature

■ Miniature Package (SOT23L-6)

■ Operates with Miniature Coil

■ Minimum External Components

■ Laser-Trimmed Fixed Frequency Operation

■ PWM Control Method

■ Adjustable Output Voltage

■ Lower Noise (Audio and EMI)

■ Split Power Supply Application

DESCRIPTION

The TK6592x Electroluminescent (EL) Lamp Driver has been optimized for battery controlled systems where power consumption and size are primary concerns. The miniature device size (SOT23L-6), together with the miniature Toko EL coils (D32FU, D31FU, D52FU), further helps system designers reduce the space required to drive the small EL panels.

The proprietary architecture (detailed in the Theory of Operation section) of the TK6592x provides a constant output power to the lamp, independent of variations in the battery voltage. This architecture allows the output voltage to remain relatively constant as battery voltages decay, without the need for directly sensing the high voltage output of the EL driver.

ORDERING INFORMATION

TK6592 MTL

Lamp Frequency Code

LAMP FREQUENCY CODE

TK65920 175 Hz TK65921* 200 Hz TK65922 225 Hz TK65923* 250 Hz TK65924 275 Hz

TK65925* 300 Hz TK65926 325 Hz TK65927* 350 Hz TK65928 375 Hz TK65929* 400 Hz

* Consult factory for availability of other frequencies.

TAPE/REEL CODE

TL: Tape Left

APPLICATIONS

■ Battery Powered Systems

■ Cellular Telephones

■ Pagers

■ LCD Modules

■ Wrist Watches

■ Consumer Electronics

The oscillator circuits for the boost converter and lamp driver are both internally generated in the TK6592x, without the need for external components. The clock frequency of the boost converter is laser-trimmed to ensure good initial accuracy that is relatively insensitive to variations in temperature and supply voltage. The clock frequency of the lamp driver tracks the frequency of the boost converter by a constant scaling factor.

Furthermore, the drive architecture of the TK6592x has been designed to limit peak drive current delivered to the lamp. This approach limits the slew rate of the voltage across the lamp and has the potential to improve lamp life and decrease RF interference.

The TK6592x is available in a miniature, 6-pin SOT23L-6 surface mount package

TK6592x

BLOCK DIAGRAM

HV BOOST

CONTROL

OSCILLATOR

BRIDGE

GND

IND

GND

May 2000 TOKO, Inc. Page 1

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TK6592x

ABSOLUTE MAXIMUM RATINGS

VCC Pin.................................................................... 6.5 V

All Pins Except V

and GND ...............................V

CLAMP

Power Dissipation (Note 1) ................................ 600 mW

TK6592x ELECTRICAL CHARACTERISTICS

VCC = 3.6 V, TA = Tj = 25 °C, unless otherwise specified.

SYMBOL PARAMETER TEST CONDITIONS MIN TYP MAX UNITS

Storage Temperature Range ................... -55 to +150 °C

Operating Temperature Range ...................-30 to +80 °C

Junction Temperature ........................................... 150 °C

PEAK

LAMP

BOOST

CLAMP

(MAX)

OUT

CONV

Note 1: Power dissipation is 600 mW when mounted as recommended (200 mW In Free Air). Derate at 4.8 mW/°C for operation above 25 °C. Note 2: Converter supply current is dependent upon the DC resistance of inductor L1. Lower DC resistances will result in lower supply currents. Note 3: When using test circuit below. Gen. Note: Refer to “INDUCTOR VALUE SELECTION” and “INDUCTOR TYPE SELECTION” of Design Considerations Section for choosing

inductor.

Input Supply Range 2.7 3.6 6 V

Quiescent Current Current into pin 6 200 µA Peak Current Threshold 44 52 60 mA Lamp Frequency See Table 1 Hz

Boost Frequency See Table 2 kHz Boost Clamp Voltage Force 100 µA into HV pin 90 105 120 V Maximum Duty Cycle 88 92 96 % Peak to Peak Lamp Voltage (Note 3) 125 140 155 V

Converter Supply Current (Notes 2, 3) See Table 3 mA

TEST CIRCUIT

680 µH

CONV

12 nF

HV GND

47 nF

IND

Note: L1 = Toko Low Profile D52FU Series: 875FU-681 M D1 = DIODES INC. DL4148 C1 = AVX 12061C473KAT2A

Page 2 May 2000 TOKO, Inc.

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TK6592x ELECTRICAL CHARACTERISTICS

VIN = 3.6 V, TA = Tj = 25 °C, unless otherwise specified.

TABLE 1: LAMP FREQUENCY

TOKO PART NO. MIN. TYP. MAX.

TK65920 157 Hz 175 Hz 193 Hz TK65921 180 Hz 200 Hz 220 Hz TK65922 202 Hz 225 Hz 248 Hz TK65923 225 Hz 250 Hz 275 Hz TK65924 247 Hz 275 Hz 303 Hz TK65925 270 Hz 300 Hz 330 Hz TK65926 292 Hz 325 Hz 358 Hz TK65927 315 Hz 350 Hz 385 Hz TK65928 337 Hz 375 Hz 413 Hz TK65929 360 Hz 400 Hz 440 Hz

TABLE 2: OSCILLATOR FREQUENCY

TK6592x

TOKO PART NO. MIN. TYP. MAX.

TK65920 20.1 kHz 22.4 kHz 24.7 kHz TK65921 23.0 kHz 25.6 kHz 28.2 kHz TK65922 25.9 kHz 28.8 kHz 31.7 kHz TK65923 28.8 kHz 32.0 kHz 35.2 kHz TK65924 31.6 kHz 35.2 kHz 38.8 kHz TK65925 34.5 kHz 38.4 kHz 42.3 kHz TK65926 37.4 kHz 41.6 kHz 45.8 kHz TK65927 40.3 kHz 44.8 kHz 49.3 kHz TK65928 43.2 kHz 48.0 kHz 52.8 kHz TK65929 46.1 kHz 51.2 kHz 56.3 kHz

TABLE 3: CONVERTER SUPPLY CURRENT

TOKO PART NO. MIN. TYP. MAX.

TK65920 - 7.8 mA 15.6 mA TK65921 - 9.0 mA 18.0 mA TK65922 - 10.1 mA 20.2 mA TK65923 - 11.2 mA 22.4 mA TK65924 - 12.3 mA 24.6 mA TK65925 - 13.4 mA 26.8 mA TK65926 - 14.5 mA 29.0 mA TK65927 - 15.6 mA 31.2 mA TK65928 - 16.8 mA 33.6 mA TK65929 - 17.9 mA 35.8 mA

May 2000 TOKO, Inc. Page 3

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TK6592x

(V)

TYPICAL PERFORMANCE CHARACTERISTICS

USING TEST CIRCUIT

TK65929 Voltage Waveform Across 12 nF LampTK65921 Voltage Waveform Across 12 nF Lamp

PEAK TO PEAK LAMP VOLTAGE

160

150

140

OUT

130

120

2.5 3 3.5 4 4.5 5 5.5 6

230

220

210

(Hz)

TK65921

vs. SUPPLY VOLTAGE

L1 = 680 µH

L1 = 560 µH

VCC (V)

TK65921

LAMP FREQUENCY

vs. SUPPLY VOLTAGE

PEAK TO PEAK LAMP VOLTAGE

160

150

140

OUT

130

120

2.5 3 3.5 4 4.5 5 5.5 6

460

440

420

(Hz)

TK65929

vs. SUPPLY VOLTAGE

L1 = 680 µH

L1 = 560 µH

VCC (V)

TK65929

LAMP FREQUENCY

vs. SUPPLY VOLTAGE

200

LAMP

190

180

2.5 3 3.5 4 4.5 5 5.5 VCC (V)

400

LAMP

380

360

2.5 3 3.5 4 4.5 5 5.5 6 VCC (V)

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TYPICAL PERFORMANCE CHARACTERISTICS (CONT.)

USING TEST CIRCUIT

TK6592x

AVERAGE CONVERTER SUPPLY CURRENT vs. SUPPLY VOLTAGE

18 16 14 12

(mA)

CONV

6 4 2 0

2.5 3 3.5 4 4.5 5 5.5

PEAK CURRENT THRESHOLD

(mA)

PEAK

TK65921

VCC (V)

TK65921

vs. SUPPLY VOLTAGE

AVERAGE CONVERTER SUPPLY

CURRENT vs. SUPPLY VOLTAGE

26 24 22 20

(mA)

18 16

CONV

14 12 10

2.5 3 3.5 4 4.5 5 5.5 6

PEAK CURRENT THRESHOLD

(mA)

PEAK

TK65929

VCC (V)

TK65929

vs. SUPPLY VOLTAGE

2.5 3 3.5 4 4.5 5 5.5 6 VCC (V)

TK65921

QUIESCENT CURRENT

vs. SUPPLY VOLTAGE

2.5 3 3.5 4 4.5 5 5.5 6 VCC (V)

(µA) I

200

150

100

2.5 3 3.5 4 4.5 5 5.5 6 VCC (V)

TK65929

QUIESCENT CURRENT

vs. SUPPLY VOLTAGE

2.5 3 3.5 4 4.5 5 5.5 6

VCC (V)

(µA) I

200

150

100

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TK6592x

(V)

)

(°C)

TYPICAL PERFORMANCE CHARACTERISTICS (CONT.)

USING TEST CIRCUIT

PEAK TO PEAK LAMP VOLTAGE

160

150

140

OUT

130

120

110

-50 -25 0 25 50 75 100 125

220

210

200

TK65921

vs. TEMPERATURE

VCC = 3.6 V

VCC = 2.7 V

TEMPERATURE (°C)

TK65921 LAMP FREQUENCY vs. TEMPERATURE

PEAK TO PEAK VOLTAGE

160

150

140

OUT

130

120

110

-50 -25 0 25 50 75 100 125

440

420

400

TK65929

vs. TEMPERATURE

VCC = 3.6 V

VCC = 2.7 V

TEMPERATURE (°C)

TK65929 LAMP FREQUENCY vs. TEMPERATURE

LAMP

190

180

170

-50 -25 0 25 50 75 100 125 TEMPERATURE (°C)

AVERAGE CONVERTER SUPPLY

CURRENT vs. TEMPERATURE

(mA)

CONV

-50 -25 0 25 50 75 100 12

TK65921

TEMPERATURE (°C)

LAMP

380

360

340

-50 -25 0 25 50 75 100 125 TEMPERATURE (°C)

AVERAGE CONVERTER SUPPLY

CURRENT vs. TEMPERATURE

(mA)

CONV

-50 -25 0 25 50 75 100 125

TK65929

TEMPERATURE

Page 6 May 2000 TOKO, Inc.

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TYPICAL PERFORMANCE CHARACTERISTICS (CONT.)

(

A) I

(

USING TEST CIRCUIT

TK6592x

PEAK CURRENT THRESHOLD

58 56 54

PEAK

48 46 44

-50 -25 0 25 50 75 100 125

100

TK65921

vs. TEMPERATURE

VCC = 3.6 V

VCC = 2.7 V

TEMPERATURE (°C)

TK65921

QUIESCENT CURRENT

vs. TEMPERATURE

PEAK CURRENT THRESHOLD

58 56

54 52

PEAK

48 46

44 42

-50 -25 0 25 50 75 100 125

100

TK65929

vs. TEMPERATURE

VCC = 2.7 V

TEMPERATURE (°C)

TK65929

QUIESCENT CURRENT

vs. TEMPERATURE

VCC = 3.6 V

-50 -25 0 25 50 75 100 125 TEMPERATURE (°C)

May 2000 TOKO, Inc. Page 7

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TK6592x

TYPICAL PERFORMANCE CHARACTERISTICS (CONT.)

USING D

TEST CIRCUIT

(MAX)

TK65921

MAXIMUM DUTY CYCLE

(%)

(MAX)

(%)

vs. SUPPLY VOLTAGE

2.5 3 3.5 4 4.5 5 5.5 6 VCC (V)

TK65921

MAXIMUM DUTY CYCLE

vs. TEMPERATURE

MAXIMUM DUTY CYCLE

(%)

(MAX)

2.5 3 3.5 4 4.5 5 5.5 6

(%)

TK65929

vs. SUPPLY VOLTAGE

VCC (V)

TK65929

MAXIMUM DUTY CYCLE

vs. TEMPERATURE

(MAX)

-50 -25 0 25 50 75 100 125

TEMPERATURE (°C)

HV GND

TEST CIRCUIT

(MAX)

IND

(MAX)

-50 -25 0 25 50 75 100 125 TEMPERATURE (°C)

Note: R1 = 470 Ω

Page 8 May 2000 TOKO, Inc.

Page 9

THEORY OF OPERATION

TK6592x

An Electroluminescent (EL) Lamp is a strip of plastic, coated with a phosphorous material that emits light when a high voltage AC signal is applied to the terminals of the device. EL panels have the ability to light the entire panel uniformly. Because of this, they are gradually becoming more popular and widespread than LEDs. The amount of light emitted from an EL Lamp is typically proportional to the magnitude of the voltage applied to the lamp. Furthermore, the color of the light emitted by an EL Lamp is somewhat dependent upon the frequency of the applied drive signal. For most applications, a peak-to-peak voltage of 100 to 170 V, with a drive frequency of 175 to 400 Hz, provides optimal trade-off between lamp intensity and power consumption.

The capacitance of the EL Panel is typically proportional to the size of the lamp (a 1 square inch EL Panel typically exhibits approximately 5 nF of capacitance load). The TK6592x series of devices has been optimized to drive EL panels, which are approximately 2-4 square inches in size.

The Boost section of the TK6592x consists of a controller for stepping up a relatively low voltage (2.7 to 6 V) to a much higher voltage (50 to 90 V) needed to drive the EL Lamp. The boost section of the TK6592x uses a proprietary architecture which provides a relatively constant output power, independent of the input supply, without the need for sensing the high voltage output of the boost converter. By controlling the peak current through the switching element of the boost converter, the boost section provides a constant output power independent of the input supply.

The H-Bridge section of the TK6592x switches the high voltage output of the boost converter to the two terminals of the EL Lamp. By alternately switching the terminals of the lamp between the high voltage supply and ground, the peak-to-peak voltage developed across the lamp is effectively twice the high voltage generated by boost converter. Furthermore, the TK6592x limits the magnitude of the drive currents through the H-Bridge switches in order to minimize the edge rates developed across the EL Lamp. This approach protects the EL Panel from large current spikes and reduces the likelihood of high frequency noise components being injected into neighboring circuitry.

The Oscillator section of the TK6592x generates a fixed frequency clock source for the previously described Boost and H-Bridge sections, without the need for external components. The high frequency output of the oscillator is used for driving the boost controller. A lower frequency

clock is generated by dividing the high frequency clock by 128; this lower frequency clock corresponds to the drive frequency of the EL Lamp. The laser-trimmed oscillators are relatively insensitive to variations in temperature and supply voltage. Therefore, they provide good control of the lamp color emitted by the panel.

The circuit below illustrates a typical application where the TK6592x is driving a 2-square-inch EL Lamp with a capacitance of approximately 12 nF.

12 nF

HV GND

47 nF

IND

FIGURE 1: TYPICAL APPLICATION

By keeping the ratio of the boost frequency and the HBridge frequency constant, the peak-to-peak output voltage from the TK6592x becomes primarily dependent upon the capacitance of the EL Lamp, the peak current threshold of the boost converter, and the value of the inductive element used in the boost converter. For the TK6592x, the peak current threshold is laser-trimmed to 52 mA. The capacitive load of the EL Lamp is a function of panel size and is typically fixed. Therefore, the high voltage output of the boost converter can be set to a desired voltage by selecting the appropriate value of the inductive element used in the boost converter.

= Boost Peak Current Threshold (52 mA)

PEAK

= Capacitance of EL Lamp

L = Inductance Value

VHV = (I

/ 2) x (L /CEL) x 128

PEAK

May 2000 TOKO, Inc. Page 9

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TK6592x

HVP HVP

UL UR

EL Panel

LL LR

Current Source 1

Current Source 2

THEORY OF OPERATION (CONT.)

With properly selected components, the TK6592x will nominally support peak output voltages to 90 V (180 V from the driver outputs, the removal of the load can cause the output voltage to increase beyond 90 V. To protect against this fault condition, a clamp circuit exists on the high voltage output which nominally limits the output voltage to a typical value of 105 V (210 V

H-BRIDGE SECTION OPERATION

). Should the EL Panel become disconnected

PK-PK

DETAILS CONCERNING THE

In an effort to extend EL lamp life, reduce EMI emissions, and reduce the power draw of the IC, current sources to control the charging and discharging of the EL lamp panel and special sequencing control of the H-bridge FETs were added to the H-bridge of TK659xx.

Current sources were added between ground and the sources of the low-side N-channel FETs (Figure 2). Therefore, the current into and out of the EL panel is controlled and limited.

The FETs are turned off and on in the sequence shown in Figure 3. As is noted in Figure 3, there is a period of time when both of lower N-channel FETs are turned on and both of upper P-channel FETs are turned off. This provides a

period of time to discharge the EL panel capacitance completely; before starting to recharge it again with current

from HV voltage rail. Therefore, this special sequencing method prevents taking current off the HV voltage rail during the discharge of EL panel capacitance and operates more efficiently.

FIGURE 2: H-BRIDGE SCHEMATIC

BOTH OFF

OFF

BOTH ON

OFF

Discharging

EL Panel

Capacitance

OFF

Page 10 May 2000 TOKO, Inc.

FIGURE 3: H-BRIDGE SEQUENCING WAVEFORMS

Page 11

TK6592x

PIN DESCRIPTIONS

SUPPLY PIN (VCC)

This pin is the positive input supply for the TK6592x. Good design practices dictate capacitive decoupling to the ground pin.

GROUND PIN (GND)

The pin provides the ground connection for the IC.

IND PIN

This pin is periodically pulled to ground by a power transistor acting as an internal switch to the TK6592x. Externally, this pin is typically connected to an inductor and a rectifying diode. By modulating the switching action of the internal switch, the TK6592x can boost the relatively low voltage of the battery to the high voltage required to drive the EL Lamp.

HV PIN

This pin is connected to the filter capacitor and the cathode of the rectifying diode in order to generate a high voltage supply. This high voltage supply is switched to the terminals of the EL Lamp through the H-Bridge.

This pin is connected to one side of the EL Panel.

EL- PIN

This pin is connected to the other side of the EL Panel. Note: Measuring the voltage across the EL lamp (EL+ pin to EL- pin) should be done with balanced scope probes using

differential measurement techniques to obtain a true waveform of the voltage across the EL lamp.

May 2000 TOKO, Inc. Page 11

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TK6592x

DESIGN CONSIDERATIONS

INDUCTOR VALUE SELECTION

Designing an EL Driver utilizing the TK6592x is a very simple task. The primary component affecting the behavior of the converter is the inductor. Essentially, the entire design task primarily consists of selecting the proper inductor value and type given the operating conditions of the EL Panel (e.g., lamp capacitance, frequency, output voltage, supply range). The following tables and charts are intended to simplify the selection of the inductor.

Given the capacitance of the EL Lamp, and the peak output voltage requirements, the following table can be utilized to select the value of the inductive component.

TABLE 4: PEAK OUTPUT VOLTAGE VS. INDUCTOR VALUE AND LAMP CAPACITANCE

INDUCTOR

VALUE

180 µH 42 V 36 V 32 V 29 V 27 V 25 V 24 V

220 µH 46 V 40 V 36 V 33 V 30 V 28 V 27 V 330 µH 56 V 49 V 44 V 40 V 37 V 34 V 33 V

390 µH 61 V 53 V 47 V 43 V 40 V 37 V 35 V 470 µH 67 V 58 V 52 V 48 V 44 V 41 V 39 V

560 µH 73 V 64 V 57 V 52 V 48 V 45 V 42 V 680 µH 81 V 70 V 63 V 57 V 53 V 50 V 47 V

820 µH 89 V 77 V 69 V 63 V 58 V 54 V 51 V

1000 µH 85 V 76 V 69 V 64 V 60 V 57 V 1200 µH 83 V 76 V 70 V 66 V 62 V

1500 µH 85 V 79 V 74 V 69 V 1800 µH 86 V 81 V 76 V

2200 µH 89 V 84 V

Note: The voltages indicated in the table above may not be achievable under certain circumstances (i.e., low battery or higher drive frequencies).

Refer to the charts on page 12 to determine which output voltage/coil combination can be supported by the EL driver.

9.0 nF LAMP

Close to 100 V operation check capacitor C1 voltage rating

12.0 nF LAMP

15.0 nF LAMP

18.0 nF LAMP

21.0 nF LAMP

24.0 nF LAMP

27.0 nF LAMP

As an example as to how the above table is to be used, assume that we have a 2-square-inch panel (12 nF capacitance) and we would like the peak-to-peak voltage across the lamp to be 140 V. The peak voltage on either terminal would be 70 V (140 V / 2). Referring to the table above, we can see that using a 680 µH coil the peak voltage developed across a 12 nF Lamp would be approximately 70 V. In this particular example, the inductive component should have a value of 680 µH.

INDUCTOR TYPE SELECTION

After the value of the inductor has been selected, an appropriate coil type needs to be selected taking into account such factors as DC resistance and current capability. The following charts can be utilized for selecting the proper family of Toko Coils. Furthermore, the following charts will also indicate if the TK6592x is the appropriate driver given the frequency and input supply requirements. If the TK6592x does not have sufficient drive capability given the input supply and frequency

Page 12 May 2000 TOKO, Inc.

Page 13

TK6592x

INDUCTOR

VALUE

(

INDUCTOR

VALUE

(

INDUCTOR

VALUE

(

INDUCTOR

VALUE

(

INDUCTOR

VALUE

(

DESIGN CONSIDERATIONS (CONT.)

requirements, the following charts will suggest the TK6593x family of EL Drivers which have higher drive capabilities. To utilize the following charts in selecting an appropriate coil, perform the following steps:

1) From the following charts, select the chart that matches the part number of the Toko EL Driver that will be used in the application. The part number of the Toko EL Driver will be dependant upon the desired frequency of the EL panel (e.g., TK65921 = 200Hz).

2) Determine input supply voltage range (e.g., 4 to 6 V). The x-axis of the following charts represent the minimum expected supply voltage. Below this minimum supply voltage the EL Driver output may begin to droop. On the appropriate chart, draw a vertical line upward from the minimum supply voltage represented on the x-axis (e.g., 4V).

3) Draw a horizontal line passing through the chosen inductor value on the y-axis (e.g., 680 µH).

4) The vertical and horizontal lines drawn in steps 2 and 3 respectively will intersect at a point. This point will lie in one of four regions of the chart (e.g., D31FU). These four regions suggest which family of Toko Coils to use.

Of the three coil families suggested in these charts, the D31FU has the smallest physical size but also has higher DC resistance. The D52FU series of coils has the largest physical size and the lowest DC resistance. The D52FU or the D32FU can be used as a reasonable substitute for the D31FU. Similarly, the D52FU can be used as a replacement for the D32FU. Substituting a coil with lower DC resistance will generally result in a system that will consume less power supply current.

2200 1800

1500 1200 1000

2200 1800

1500 1200 1000

820 680 560

470 390

180

820 680 560

470 390

TK65920, TK65921

USE TK6593X

D31FU

3 4 5 6

MINIMUM SUPPLY (V)

TK65926, TK65927

USE TK6593X

D31FU

D52FU

D32FU

D52FU

D32FU

2200 1800

1500 1200 1000

2200 1800

1500 1200 1000

820 680 560

470 390

180

820 680 560

470 390

TK65922, TK65923

USE TK6593X

D52FU

D32FU

D31FU

3 4 5 6

MINIMUM SUPPLY (V)

TK65928, TK65929

USE TK6593X

D52FU

D32FU

D31FU

2200 1800

1500 1200 1000

820 680 560

470 390

180

TK65924, TK65925

USE TK6593X

D52FU

D32FU

D31FU

3 4 5 6

MINIMUM SUPPLY (V)

180

3 4 5 6

MINIMUM SUPPLY (V)

180

3 4 5 6

MINIMUM SUPPLY (V)

May 2000 TOKO, Inc. Page 13

Page 14

TK6592x

SPLIT SUPPLY APPLICATION

APPLICATION INFORMATION

The split power supply application of this EL driver IC is a circuit configuration (see Figure 4) in which the V (V

) is separated or split away from the main power input (V

control

C 5 nF

HV GND

22 nF

) supplying current to the inductor.

power

IND

control

from

2.7 to 6 V max. 200 µA

power

from

0.9 to 20 V

FIGURE 4: SPLIT SUPPLY APPLICATION CIRCUIT

IC power

The voltage supplied to the VCC pin of the IC (V draw on this power supply rail of the system would be very small (under 200 µA). This V off the EL lamp driver, which permits the V

power

) needs to be maintained in the 2.7 V to 6.0 V range, but the current

control

can be used to turn on and

control

to be connected to the battery or other power source directly with the

least amount of resistance in the power path as possible.

Now with the VCC power for the IC (V

) being supplied from a different source, the main power (V

control

) can be any

power

voltage between 0.9 V and 20 V. But it is critical to properly select the inductor such that the proper peak current regulation is maintained over the input voltage operating range of the converter.

If the inductor value is too large the current will rise too slowly and not have time to reach its set peak current trip point at low input voltages, but at high input voltage the current might rise too quickly and overshoot the set peak current trip point.

The primary battery applications for this part are in a dual cell alkaline or dual cell Li-Ion system (such as a GPS or smart cell phones). These systems are assumed to have a minimum useable input voltage of 1.8 V for the dual cell alkaline system and 5.4 V for the dual cell Li-Ion system.

For low converter input voltages (1.8 V and 5.4 V minimum input voltages), Table 5 shows the recommended maximum inductance value for a given device part number (therefore a given frequency of operation) and a minimum input voltage. Each cell in the table gives three inductance values; each value (in µH) corresponds to each type of specialized Toko EL driver inductors (D31FU, D32FU, and D52FU types of Toko inductors).

Page 14 May 2000 TOKO, Inc.

Page 15

APPLICATION INFORMATION (CONT.)

TABLE 5: DUAL CELL ALKALINE AND DUAL CELL LI-ION INDUCTANCE SELECTION TABLE

TK6592x

PART NO.

f lamp f converter

min.Vp L type

D31FU

1.8V D32FU D52FU

D31FU

5.4V D32FU D52FU

TK65920 175 Hz

22.4 kHz

390 µH 560 µH 680 µH

1000 µH 1200 µH

2700 µH

TK65921 200 Hz

25.6 kHz

390 µH 560 µH 680 µH

1000 µH 1200 µH

2200 µH

TK65922 225 Hz

28.8 kHz

390 µH 470 µH 560 µH

1000 µH 1200 µH

2200 µH

TK65923 250 Hz

32.0 kHz

390 µH 470 µH 560 µH

1000 µH 1200 µH

1800 µH

TK65924

275 Hz

35.2 kHz

390 µH 470 µH 560 µH

1000 µH 1200 µH

1800 µH

TK65925 300 Hz

38.4 kHz

390 µH 470 µH 470 µH

1000 µH 1200 µH

1800 µH

TK65926 325 Hz

41.6 kHz

390 µH 390 µH 470 µH

1000 µH 1200 µH

1500 µH

TK65927 350 Hz

44.8 kHz

330 µH 390 µH 470 µH

1000 µH 1200 µH

1500 µH

TK65928 375 Hz

48.0 kHz

330 µH 390 µH 390 µH

1000 µH 1200 µH

1500 µH

TK65929 400 Hz

51.2 kHz

330 µH 330 µH 390 µH

1000 µH 1200 µH

1200 µH

After selecting the inductor type and value, Table 4 of the TK6592X data sheet can be used to determine the typical output voltage for a given loading of EL lamp capacitance. If you wish to reduce this output voltage, just reduce the inductor’s inductance value.

NOISE CONSIDERATIONS

There are two specific noise types relevant to the user when it comes to choosing EL Drivers: the Audio Noise and the Electromagnetic Interference (EMI) Noise.

The EMI Noise would most likely come from the boost converter/coil section. The Toko EL Driver has specifically been designed to address this issue.

The device runs at a fixed frequency and the frequency is controlled tightly in order to avoid interference. Furthermore, the panel frequency is forced to be a 128 submultiple of the boost frequency avoiding any type of beating

frequencies. By choosing shielded coils, the EMI noise problem can further be reduced. The Audio Noise can come from several components which make up the system. The coil, if operated in the audio range would be a source of noise. The Toko EL Driver was carefully designed to give

the user the choice of 10 frequencies such that the coil frequency will always be above audio range. Since the device operates at a fixed frequency in discontinuous conduction mode, there are no possible submultiples which would cause audible noise.

The filter capacitor can be a source of audio noise. Furthermore, depending on how this cap is mounted, the mounting can act as an amplifier (as a speaker box). Certain ceramic caps driven from a high voltage source as in the EL Driver case, demonstrate a PIEZOELECTRIC effect which is distinguishable in the Audio Range.

Other types of caps, such as film type do not denote an audio noise. The panel itself, being operated well into the Audio Range (175 Hz to 400 Hz) and of a capacitive nature driven from high

voltage may also display Audible Noise. Mounting of this panel can enhance or diminish this natural effect of the panel.

May 2000 TOKO, Inc. Page 15

Page 16

TK6592x

LAYOUT

Actual Size

SPLIT SUPPLY LAYOUT

Actual Size

Page 16 May 2000 TOKO, Inc.

Page 17

NOTES

TK6592x

May 2000 TOKO, Inc. Page 17

Page 18

TK6592x

NOTES

Page 18 May 2000 TOKO, Inc.

Page 19

NOTES

TK6592x

May 2000 TOKO, Inc. Page 19

Page 20

TK6592x

(

)

PACKAGE OUTLINE

SOT23L-6

Dimensions are shown in millimeters Tolerance: x.x = ± 0.2 mm

+0.15

0.4

- 0.05

123

0.95

+0.3

- 0.1

3.5

(3.4)

unless otherwise specified

0.32 5 PL

Marking Information

Marking

TK65920 B0

0.1

+0.15

- 0.05

Marking

0.1

0.3

1.2

1.4 max

+0.15

- 0.05

0 - 0.1

0.15

0.6

1.0

Recommended Mount Pad

3.3

0.95

3.0 e1

0.95

2.2

15 max

+ 0.3

0.4

TK65921 B1 TK65922 B2 TK65923 B3 TK65924 B4 TK65925 B5 TK65926 B6 TK65927 B7 TK65928 B8 TK65929 B9

Toko America, Inc. Headquarters 1250 Feehanville Drive, Mount Prospect, Illinois 60056 Tel: (847) 297-0070 Fax: (847) 699-7864

TOKO AMERICA REGIONAL OFFICES

Midwest Regional Office Toko America, Inc. 1250 Feehanville Drive Mount Prospect, IL 60056 Tel: (847) 297-0070 Fax: (847) 699-7864

Western Regional Office Toko America, Inc. 2480 North First Street , Suite 260 San Jose, CA 95131 Tel: (408) 432-8281 Fax: (408) 943-9790

Eastern Regional Office Toko America, Inc. 107 Mill Plain Road Danbury, CT 06811 Tel: (203) 748-6871 Fax: (203) 797-1223

Semiconductor Technical Support Toko Design Center 4755 Forge Road Colorado Springs, CO 80907 Tel: (719) 528-2200 Fax: (719) 528-2375

Visit our Internet site at http://www.tokoam.com

The information furnished by TOKO, Inc. is believed to be accurate and reliable. However, TOKO reserves the right to make changes or improvements in the design, specification or manufacture of its products without further notice. TOKO does not assume any liability arising from the application or use of any product or circuit described herein, nor for any infringements of patents or other rights of third parties which may result from the use of its products. No license is granted by implication or otherwise under any patent or patent rights of TOKO, Inc.

Page 20 May 2000 TOKO, Inc.

IC-xxx-TK6592x

0798O0.0K