TK6591x SMALL EL LAMP DRIVER FEATURES APPLICATIONS ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ High Ratio of Brightness / Input Power Constant Brightness Versus Input Supply Changes Optimized for 3.5 nf to 12.5 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 TK6591x 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. 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 TK6591x, 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 TK6591x 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 TK6591x is available in a miniature, 6 pin SOT23L-6 surface mount package. TK6591x 20 P The proprietary architecture (detailed in the Theory of Operation section) of the TK6591x 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. EL+ VCC HV GND EL- IND BLOCK DIAGRAM IND ORDERING INFORMATION VCC HV BOOST CONTROL GND TK6591 MTL Lamp Frequency Code HV OSCILLATOR EL+ H BRIDGE TAPE/REEL CODE LAMP FREQUENCY CODE TK65910 TK65911* TK65912 TK65913* TK65914 175 Hz 200 Hz 225 Hz 250 Hz 275 Hz TK65915* TK65916 TK65917* TK65918 TK65919* May 2000 TOKO, Inc. 300 Hz 325 Hz 350 Hz 375 Hz 400 Hz EL- TL: Tape Left * Consult factory for availability of other frequencies. Page 1 TK6591x ABSOLUTE MAXIMUM RATINGS VCC Pin .................................................................... 6.5 V All Pins Except VCC and GND ............................... VCLAMP Power Dissipation (Note 1) ................................ 600 mW Storage Temperature Range ................... -55 to +150 °C Operating Temperature Range ...................-30 to +80 °C Junction Temperature ........................................... 150 °C TK6591x ELECTRICAL CHARACTERISTICS VCC = 3.6 V, TA = Tj = 25 °C, unless otherwise specified. SYMBOL PARAMETER TEST CONDITIONS MIN TYP MAX UNITS 2.7 3.6 6 V 200 µA 38 mA V CC Input Supply Range IQ Quiescent Current IPEAK Peak Current Threshold FLAMP Lamp Frequency See Table 1 Hz FBOOST Boost Frequency See Table 2 kHz V CLAMP Boost Clamp Voltage D(MAX) Maximum Duty Cycle V OUT Peak to Peak Lamp Voltage (Note 3) ICONV Converter Supply Current (Notes 2, 3) Current into pin 6 26 Force 100 µA into HV pin 32 90 105 120 V 88 92 96 % 125 140 155 V See Table 3 mA 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. TEST CIRCUIT EL + VCC HV GND ICONV VCC CEL 5 nF EL - IND L1 820 µH C1 22 nF Page 2 D1 Note: L1 = Toko Low Profile D32FU Series: 887FU-821 M D1 = DIODES INC. DL4148 C1 = AVX 12061C223KAT2A May 2000 TOKO, Inc. TK6591x TK6591x ELECTRICAL CHARACTERISTICS VIN = 3.6 V, TA = Tj = 25 °C, unless otherwise specified. TABLE 1: LAMP FREQUENCY TOKO PART NO. TK65910 TK65911 TK65912 TK65913 TK65914 TK65915 TK65916 TK65917 TK65918 TK65919 MIN. 157 Hz 180 Hz 202 Hz 225 Hz 247 Hz 270 Hz 292 Hz 315 Hz 337 Hz 360 Hz TYP. 175 Hz 200 Hz 225 Hz 250 Hz 275 Hz 300 Hz 325 Hz 350 Hz 375 Hz 400 Hz MAX. 193 Hz 220 Hz 248 Hz 275 Hz 303 Hz 330 Hz 358 Hz 385 Hz 413 Hz 440 Hz MIN. 20.1 kHz 23.0 kHz 25.9 kHz 28.8 kHz 31.6 kHz 34.5 kHz 37.4 kHz 40.3 kHz 43.2 kHz 46.1 kHz TYP. 22.4 kHz 25.6 kHz 28.8 kHz 32.0 kHz 35.2 kHz 38.4 kHz 41.6 kHz 44.8 kHz 48.0 kHz 51.2 kHz MAX. 24.7 kHz 28.2 kHz 31.7 kHz 35.2 kHz 38.8 kHz 42.3 kHz 45.8 kHz 49.3 kHz 52.8 kHz 56.3 kHz TYP. 3.2 mA 3.6 mA 4.1 mA 4.5 mA 5.0 mA 5.4 mA 5.8 mA 6.3 mA 6.7 mA 7.2 mA MAX. 6.4 mA 7.2 mA 8.2 mA 9.0 mA 10.0 mA 10.8 mA 11.6 mA 12.6 mA 13.4 mA 14.4 mA TABLE 2: OSCILLATOR FREQUENCY TOKO PART NO. TK65910 TK65911 TK65912 TK65913 TK65914 TK65915 TK65916 TK65917 TK65918 TK65919 TABLE 3: CONVERTER SUPPLY CURRENT TOKO PART NO. TK65910 TK65911 TK65912 TK65913 TK65914 TK65915 TK65916 TK65917 TK65918 TK65919 May 2000 TOKO, Inc. MIN. - Page 3 TK6591x TYPICAL PERFORMANCE CHARACTERISTICS USING TEST CIRCUIT TK65911 Voltage Waveform Across 5 nF Lamp 150 TK65919 Voltage Waveform Across 5 nF Lamp TK65911 PEAK TO PEAK LAMP VOLTAGE vs. SUPPLY VOLTAGE 150 TK65919 PEAK TO PEAK LAMP VOLTAGE vs. SUPPLY VOLTAGE L1 = 820 µH 130 L1 = 680 µH 120 110 100 2.5 L1 = 820 µH 140 VOUT (V) VOUT (V) 140 130 120 L1 = 680 µH 110 3 3.5 4 4.5 5 5.5 100 2.5 6 3 3.5 VCC (V) TK65911 LAMP FREQUENCY vs. SUPPLY VOLTAGE 230 FLAMP (Hz) FLAMP (Hz) 5 5.5 6 5.5 6 440 210 200 420 400 380 190 3 3.5 4 4.5 VCC (V) Page 4 4.5 TK65919 LAMP FREQUENCY vs. SUPPLY VOLTAGE 460 220 180 2.5 4 VCC (V) 5 5.5 6 360 2.5 3 3.5 4 4.5 5 VCC (V) May 2000 TOKO, Inc. TK6591x TYPICAL PERFORMANCE CHARACTERISTICS (CONT.) USING TEST CIRCUIT TK65911 AVERAGE CONVERTER SUPPLY CURRENT vs. SUPPLY VOLTAGE 18 16 16 14 14 ICONV (mA) ICONV (mA) 18 12 10 8 10 8 6 4 4 2 2 2.5 35 3 3.5 4 4.5 5 5.5 0 6 2.5 3 3.5 4 4.5 5 5.5 VCC (V) VCC (V) TK65911 PEAK CURRENT THRESHOLD vs. SUPPLY VOLTAGE TK65919 PEAK CURRENT THRESHOLD vs. SUPPLY VOLTAGE 35 6 33 IPEAK (mA) 33 IPEAK (mA) 12 6 0 31 29 31 29 27 27 25 25 2.5 200 3 3.5 4 4.5 5 5.5 2.5 6 3.5 4 4.5 5 5.5 VCC (V) TK65911 QUIESCENT CURRENT vs. SUPPLY VOLTAGE TK65919 QUIESCENT CURRENT vs. SUPPLY VOLTAGE 200 6 150 IQ (µA) 100 100 50 50 0 2.5 3 VCC (V) 150 IQ (µA) TK65919 AVERAGE CONVERTER SUPPLY CURRENT vs. SUPPLY VOLTAGE 3 3.5 4 4.5 VCC (V) May 2000 TOKO, Inc. 5 5.5 6 0 2.5 3 3.5 4 4.5 5 5.5 6 VCC (V) Page 5 TK6591x TYPICAL PERFORMANCE CHARACTERISTICS (CONT.) USING TEST CIRCUIT 140 TK65911 PEAK TO PEAK LAMP VOLTAGE vs. TEMPERATURE 140 V IN = 3.6 V VIN = 3.6 V 130 120 V IN VOUT (V) VOUT (V) 130 = 2.7 V 110 100 120 VIN = 2.7 V 110 100 90 -50 -25 220 0 25 50 75 90 100 125 -50 -25 50 75 TK65911 LAMP FREQUENCY vs. TEMPERATURE TK65919 LAMP FREQUENCY vs. TEMPERATURE 440 100 125 FLAMP (Hz) 420 200 190 400 380 360 170 340 -50 -25 0 25 50 75 100 125 -50 -25 TEMPERATURE (°C) 0 25 50 75 100 125 TEMPERATURE (°C) TK65919 AVERAGE CONVERTER SUPPLY CURRENT vs. TEMPERATURE TK65911 AVERAGE CONVERTER SUPPLY CURRENT vs. TEMPERATURE 6 10 5 9 ICONV (mA) ICONV (mA) 25 TEMPERATURE (°C) 180 4 3 8 7 6 2 5 1 -50 -25 0 25 50 75 TEMPERATURE (°C) Page 6 0 TEMPERATURE (°C) 210 FLAMP (Hz) TK65919 PEAK TO PEAK LAMP VOLTAGE vs. TEMPERATURE 100 125 -50 -25 0 25 50 75 100 125 TEMPERATURE (°C) May 2000 TOKO, Inc. TK6591x TYPICAL PERFORMANCE CHARACTERISTICS (CONT.) USING TEST CIRCUIT 35 34 34 33 33 VIN = 3.6 V 32 31 IPEAK (mA) IPEAK (mA) 35 TK65911 PEAK CURRENT THRESHOLD vs. TEMPERATURE 30 VIN = 3.6 V 32 31 VIN = 2.7 V 30 29 29 VIN = 2.7 V 28 -50 -25 0 25 50 75 28 -50 -25 100 125 0 25 50 75 100 125 TEMPERATURE(°C) TEMPERATURE (°C) TK65911 QUIESCENT CURRENT vs. TEMPERATURE TK65919 QUIESCENT CURRENT vs. TEMPERATURE 100 100 90 90 IQ (µA) IQ (µA) TK65919 PEAK CURRENT THRESHOLD vs. TEMPERATURE 80 80 70 70 60 60 50 50 -50 -25 0 25 50 75 TEMPERATURE (°C) May 2000 TOKO, Inc. 100 125 -50 -25 0 25 50 75 100 125 TEMPERATURE (°C) Page 7 TK6591x TYPICAL PERFORMANCE CHARACTERISTICS (CONT.) USING D(MAX) TEST CIRCUIT TK65911 MAXIMUM DUTY CYCLE vs. SUPPLY VOLTAGE 95 95 94 D(MAX) (%) D(MAX) (%) 94 93 92 91 93 92 91 90 90 2.5 3 3.5 4 4.5 5 5.5 6 2.5 3 3.5 4 4.5 5 5.5 VCC (V) VCC (V) TK65911 MAXIMUM DUTY CYCLE vs. TEMPERATURE TK65919 MAXIMUM DUTY CYCLE vs. TEMPERATURE 95 95 94 94 D(MAX) (%) D(MAX) (%) TK65919 MAXIMUM DUTY CYCLE vs. SUPPLY VOLTAGE 93 92 6 93 92 91 91 90 90 -50 -25 0 25 50 75 -50 -25 100 125 0 25 50 75 100 125 TEMPERATURE (°C) TEMPERATURE(°C) D(MAX) TEST CIRCUIT EL + VCC HV GND VCC EL - IND R1 Note: R1 = 470 Ω Page 8 May 2000 TOKO, Inc. TK6591x THEORY OF OPERATION 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 TK6591x series of devices has been optimized to drive EL panels, which are approximately 1-2 square inches in size. The Boost section of the TK6591x 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 TK6591x 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 TK6591x 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 TK6591x 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 TK6591x 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 May 2000 TOKO, Inc. 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 TK6591x is driving a 1-square-inch EL Lamp with a capacitance of approximately 5 nF. EL + VCC HV GND VIN CEL 5 nF EL - IND L1 C1 22 nF D1 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 TK6591x 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 TK6591x, the peak current threshold is laser-trimmed to 32 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. IPEAK = Boost Peak Current Threshold (32 mA) CEL = Capacitance of EL Lamp L = Inductance Value VHV = (IPEAK / 2) x (L /CEL) x 128 Page 9 TK6591x THEORY OF OPERATION (CONT.) With properly selected components, the TK6591x will nominally support peak output voltages to 90 V (180 VPK-PK). Should the EL Panel become disconnected 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 VPK-PK). DETAILS CONCERNING THE H-BRIDGE SECTION OPERATION 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. HV HVP UL UR HVP EL+ ELEL Panel LL LR Current Source 2 Current Source 1 FIGURE 2: H-BRIDGE SCHEMATIC BOTH OFF UL OFF ON OFF OFF UR OFF OFF BOTH ON OFF ON LL ON OFF ON ON LR ON ON ON OFF VEL- VEL+ Discharging EL Panel Capacitance VEL = VEL+ - VEL- FIGURE 3: H-BRIDGE SEQUENCING WAVEFORMS Page 10 May 2000 TOKO, Inc. TK6591x PIN DESCRIPTIONS SUPPLY PIN (VCC) This pin is the positive input supply for the TK6591x. 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 TK6591x. Externally, this pin is typically connected to an inductor and a rectifying diode. By modulating the switching action of the internal switch, the TK6591x 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. EL+ PIN 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 TK6591x DESIGN CONSIDERATIONS INDUCTOR VALUE SELECTION Designing an EL Driver utilizing the TK6591x 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 3.5 nF LAMP 5.0 nF LAMP 6.5 nF LAMP 8.0 nF LAMP 9.5 nF LAMP 11.0 nF LAMP 12.5 nF LAMP 220 µH 45 V 38 V 33 V 30 V 28 V 26 V 24 V 270 µH 50 V 42 V 37 V 33 V 30 V 28 V 26 V 330 µH 52 V 44 V 38 V 34 V 32 V 29 V 28 V 390 µH 57 V 47 V 42 V 37 V 34 V 32 V 30 V 470 µH 62 V 52 V 46 V 41 V 38 V 35 V 33 V 560 µH 68 V 57 V 50 V 45 V 41 V 38 V 36 V 680 µH 75 V 63 V 55 V 49 V 45 V 42 V 40 V 820 µH 82 V 69 V 60 V 54 V 50 V 46 V 43 V 1000 µH 76 V 67 V 60 V 55 V 51 V 48 V 1200 µH 83 V 73 V 66 V 60 V 56 V 53 V 1500 µH 82 V 73 V 67 V 63 V 59 V 1800 µH 89 V 80 V 74 V 69 V 64 V 89 V 82 V 76 V 71 V 90 V 84 V 79 V 2200 µH 2700 µH 3300 µH Close to 100 V operation check capacitor C1 voltage rating 87 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. As an example as to how the above table is to be used, assume that we have a 1-square-inch panel (5 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 820 µH coil the peak voltage developed across a 5 nF Lamp would be approximately 69 V. In this particular example, the inductive component should have a value of 820 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 TK6591x is the appropriate driver given the frequency and input supply requirements. If the TK6591x does not have sufficient drive capability given the input supply and frequency Page 12 May 2000 TOKO, Inc. TK6591x DESIGN CONSIDERATIONS (CONT.) requirements, the following charts will suggest the TK6592x 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., TK65911 = 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., 820 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. TK65910, TK65911 D52FU 2200 1800 D32FU 1500 1200 1000 820 X D31FU 680 3900 3300 2700 2200 1800 1500 3 4 D52FU D32FU D31FU 330 6 4 5 MINIMUM SUPPLY (V) TK65916, TK65917 TK65918, TK65919 D52FU D32FU D31FU 3900 3300 2700 5 MINIMUM SUPPLY (V) May 2000 TOKO, Inc. 6 6 USE TK6592X D52FU 2700 2200 1800 1500 1200 1000 820 680 D32FU D31FU 3 4 5 MINIMUM SUPPLY (V) USE TK6592X D52FU 2200 1800 1500 D32FU 1200 1000 820 680 330 4 3900 3300 330 3 USE TK6592X 3 USE TK6592X MINIMUM SUPPLY (V) 1200 1000 820 680 330 5 INDUCTOR VALUE (µH) INDUCTOR VALUE (µH) 330 3900 3300 2700 2200 1800 1500 1200 1000 820 680 TK65914, TK65915 INDUCTOR VALUE (µH) USE TK6592X 3300 2700 INDUCTOR VALUE (µH) INDUCTOR VALUE (µH) 3900 TK65912, TK65913 D31FU 3 4 5 6 MINIMUM SUPPLY (V) Page 13 6 TK6591x APPLICATION INFORMATION LOW VOLTAGE SPLIT SUPPLY APPLICATION The split power supply application of this EL driver IC is a circuit configuration (see Figure 4) in which the VCC IC power (Vcontrol) is separated or split away from the main power input (Vpower) supplying current to the inductor. CEL 5 nF EL + VCC HV GND EL - Vcontrol from 2.7 to 6 V max. 200 µA IND L1 C1 22 nF Vpower from 0.9 to 20 V D1 FIGURE 4: SPLIT SUPPLY APPLICATION CIRCUIT The voltage supplied to the VCC pin of the IC (Vcontrol) needs to be maintained in the 2.7 V to 6.0 V range, but the current draw on this power supply rail of the system would be very small (under 200 µA). This Vcontrol can be used to turn on and off the EL lamp driver, which permits the Vpower 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 (Vcontrol) being supplied from a different source, the main power (Vpower) can be any 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 low voltage battery applications for this part are in a single cell or a dual cell alkaline system (such as a pager or PDA). These systems are assumed to have a minimum useable input voltage of 0.9 V for the single cell system and 1.8 V for the dual cell system. For low converter input voltages (0.9 V and 1.8 V minimum input voltages), the following 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. TK6591x APPLICATION INFORMATION (CONT.) TABLE 5: INDUCTANCE SELECTION TABLE FOR SINGLE AND DUAL CELL ALKALINE SYSTEMS PART NO. TK65910 f lamp 175 Hz f converter 22.4 kHz min.Vp L type TK65911 TK65912 200 Hz 225 Hz 25.6 kHz 28.8 kHz TK65913 TK65914 TK65915 250 Hz 275 Hz 300 Hz 32.0 kHz 35.2 kHz 38.4 kHz TK65916 TK65917 325 Hz 350 Hz 41.6 kHz 44.8 kHz TK65918 375 Hz 48.0 kHz TK65919 400 Hz 51.2 kHz 0.9V D31FU D32FU D52FU 330 µH 390 µH 560 µH 270 µH 390 µH 470 µH 270 µH 390 µH 470 µH 270 µH 330 µH 390 µH 270 µH 330 µH 390 µH 220 µH 330 µH 390 µH 220 µH 330 µH 330 µH 220 µH --330 µH 220 µH --330 µH 220 µH --330 µH 1.8V D31FU D32FU D52FU 680 µH 1000 µH 1200 µH 680 µH 820 µH 1200 µH 680 µH 820 µH 1000 µH 680 µH 820 µH 1000 µH 680 µH 680 µH 820 µH 560 µH 680 µH 820 µH 560 µH 680 µH 820 µH 560 µH 680 µH 820 µH 560 µH 680 µH 680 µH 470 µH 560 µH 680 µH After selecting the inductor type and value, Table 4 of the TK6591X 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. The TK6591X is the recommended part type to use in the low voltage single cell (0.9 V input) split supply application because it has the lowest peak current set point of the TK659XX family of EL drivers. This, therefore, restricts the size of EL panels that can be driven to those with smaller capacitance values. 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 TK6591x LAYOUT Actual Size 2x SPLIT SUPPLY LAYOUT Actual Size 2x Page 16 May 2000 TOKO, Inc. TK6591x NOTES May 2000 TOKO, Inc. Page 17 TK6591x NOTES Page 18 May 2000 TOKO, Inc. TK6591x NOTES May 2000 TOKO, Inc. Page 19 TK6591x PACKAGE OUTLINE Marking Information SOT23L-6 TK65910 TK65911 TK65912 TK65913 TK65914 TK65915 TK65916 TK65917 TK65918 TK65919 +0.15 0.4 - 0.05 0.1 M 0.6 6 e1 3.0 1.0 Marking 1 2 3 0.32 e 5 PL e 3.5 +0.15 - 0.05 0.1 e 0.95 M 0.95 0.95 Marking A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 e 0.95 Recommended Mount Pad +0.3 - 0.1 2.2 max 15 1.2 0.15 Dimensions are shown in millimeters Tolerance: x.x = ± 0.2 mm (unless otherwise specified) +0.15 - 0.05 0 - 0.1 1.4 max 0.3 (3.4) 0.4 + 0.3 3.3 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 © 1999 Toko, Inc. All Rights Reserved May 2000 TOKO, Inc. IC-xxx-TK6591x 0798O0.0K Printed in the USA