NCP5603GEVB High Efficiency Charge Pump Converter/White LED Driver Evaluation Board User's Manual http://onsemi.com EVAL BOARD USER’S MANUAL Abstract On the other hand, combining three functions in the same system creates a special case since the converter must be capable of driving the wide current load needed for the different functions. The typical currents used to drive the LED, summarized in Table 1, range from a low 1 mA to 350 mA when the flash is activated. Moreover, unlike the xenon photo flash, the LED system must have a relatively long pulse of light to properly illuminate the scene. Typically, a xenon pulse has a 1 ms flash duration, the LED system being in the 100 ms to 200 ms range. Consequently, the converter must be designed to support such a large demand. High powered LED capable to sustaining up to 800 mA are under development and drivers for these devices should be available within a few months. This evaluation board describes a multi-functional system, capable of generating and controlling the power needed to utilized three features available in modern cellular phones. In addition to larger displays, with full color capability, flash and torch features have now been added to support the embedded camera and the night path finder. These features are made possible by using an ultra bright LED powered by standard battery cells. Basic Circuit Description Since the LED have a forward drop voltage ranging from 3 V to 4.5 V, depending upon the forward current, a straightforward connection to a standard battery is not feasible as depicted Figure 2. A boost structure must be used to make the power supply voltage compatible with the LED. Figure 1. NCP5603GEVB Semiconductor Components Industries, LLC, 2012 October, 2012 − Rev. 0 1 Publication Order Number: EVBUM2140/D NCP5603GEVB Battery Voltage = F(Capacity) @ TA = +20C OSRAM − LWY87S @10 mA−3.8 V 100 CITIZEN− CL590S @20 mA−3.9 V 90 NICHIA−NECWB205 @20 mA−4.0 V Absorbed Capacity (%) 80 OSRAM − LWT67C @20 mA−4.1 V 70 60 Vout−3 Cell Alkaline Vout−Li−ion 50 Vout−2 cell Alkaline 40 30 20 10 0 2 2.5 MB−JUNE 2004 2.0 X 3 3.5 1.5 X 4 4.5 1.33 X 5 Vout (V) 1.0 X Figure 2. Typical Lithium-Ion Battery Voltage and White LED Table 1. WHITE LED TYPICAL APPLICATIONS Backlight Torch Flash OSRAM LWY85S LED 1 mA – 10 mA − − OSRAM – LWT67C 1 mA – 20 mA − − − 100 mA − OSRAM – LWW5SG − − 350 mA CITIZEN − CL590S 1 mA – 20 mA − − NICHIA−NECWB205 1 mA – 20 mA − − − − 800 mA OSRAM LUMILED http://onsemi.com 2 NCP5603GEVB ambient thermal resistance is limited by the packaging of the LED, a good thermal contact to a dedicated layer on the printed board is essential. The LWW5SG specifications give a maximum 9C/W junction-to-case thermal resistance, capable of limiting the temperature of the silicon to the 100C maximum specified in the OSRAM data sheet. After dissipating 1.6 W, the maximum thermal to air resistance acceptable by the chip can be calculated as: Along with the amount of current the converter provides, it is worthwhile to note the thermal behavior of both the silicon and the power LED. According to the OSRAM’s data sheet, the Dragon LED (LWW5SG) should have a maximum 4.5 V forward drop with 350 mA current. The power absorbed by the load will be 1.57 W and, assuming a 75% efficiency of the DC/DC converter, will translate to almost 2 W of input power. Consequently, some 400 mW will be dissipated as heat into the silicon and, according to the NCP5603 data sheet, the chip temperature will increase by RqJA Pin = 85 0.4 = 34DC. Such a temperature increase is acceptable since, even under the worst case +85C ambient temperature, the junction will be below the maximum rating defined for this chip. However, we must take into account the low battery situation: in this case, the efficiency of the converter can decrease and we end up with 60% efficiency, yielding almost 54DC temperature increases. At this point, the silicon can rise above 125C, under extreme high ambient temperature, and the global long-term reliability of the chip will be impaired. This can be avoided by either reducing the thermal resistance (using a heatsink by means of the PCB layer) or by ensuring the duty cycle is short enough to properly cool off the chip between pulses. Generally speaking, the High Intensity LED are power limited and care must be observed to avoid any thermal run out during normal operation. This is particularly true for the flash mode in which, as depicted above, nearly 1.6 W are dissipated into the LED junctions. Because the junction to R qJA T jmax T amb P chip 100 85 9.37° CW 1.6 Since the RqJC is 9C/W, it is practically impossible to achieve a 0.38C/W case to ambient thermal resistance and the only alternative is to limit the operating ambient temperature. Assuming Tamb = 60C, then RqJA = (100−60) / 1.6 = 25C/W. In this case, the case-to-ambient thermal resistance is 25 − 9 = 16C/W, a value more realistic, although not so easy to achieve with a room limited PCB. NCP5603 operates without special treatment in terms of thermal sinking and a simple copper flag is built underneath the QFN package as depicted Figure 6. The schematic of the multiple application, Figure 3, illustrates the three functions: Backlight four LED in parallel, dimming capability Torch one LED, no output adjustment Flash one power LED, pulse width adjustable http://onsemi.com 3 NCP5603GEVB TP2 1 GND C3 1.0 mF/16 V ISENSE R9 D4 TP1 LW67C 1 82 W Vout GND R8 D3 LW67C 82 W R7 D2 LW67C 82 W R6 D1 LW67C 82 W 1 GND 8 Vsel 6 4 5 Fsel EN/PWM Vout C1N C1 9 C1P GND S3 Vsel + 3 4 PK1 2 x 1.5 V VCC R2 3 100 k 6 S1 NL27WZ14 U2B NL27WZ14 U2A 1 4 Q Q RC 15 C 12 A 11 B 13 CLR GND R11 1.5 k D5 PWM Z3 GND GROUND Figure 3. NCP5603G Evaluation Board Schematic http://onsemi.com 9 10 5 3 33 nF 4 R1 14 U3B MC14538B 7 Q A B CLR 4 1 C GND 100 nF GND GND 2 C5 C8 GND GND 1 + GND 100 nF − + 4 mm Q C6 S4 POWER R10 10 k CNT/PWM 10 k VCC Adjust PWM RC R3 2 GND U3A MC14538B 6 10 k P1 200 kA J2 R5 Fsel C4 4.7 mF/16 V VCC 10 k GND VCC VCC S2 Fsel VCC 1 mF/16 V 4 mm R4 Vsel C7 100 nF J1 GND GND 2 Vbat 3 U1 NCP5603 C2N C1P 7 10 C2 1 mF/16 V GND NCP5603GEVB Figure 4. Top Layer Figure 5. Bottom Layer Figure 6. Silk Layer (Top View) http://onsemi.com 5 NCP5603GEVB switch S1 is flipped to the Vcc position, the RESET of U5A is released and the EN pin is clocked High/Low by the clock generated by U2A/U2B. Simultaneously, diode LED D7 turns ON to identify the PWM mode of operation. The duty cycle of the U5A/Q output is manually adjusted by potentiometer P1 to set the brightness of the four associated LED. The efficiency of the system has been evaluated at room temperature (see Table 2), the results being fully within the NCP5603 data sheet specifications. The system is powered by two AA cells in series, assembled in a standard battery holder, the operating mode being selected by the S1, S5 and S6 switches. Since the total current is limited by the DC/DC converter, the backlights LEDs are automatically deactivated when either the Torch or the Flash are selected. Moreover, the Flash is not available while the Torch is running. An extra feature, backlight dimming, is provided by switch S1 is associated with potentiometer P1. When the switch is connected to ground, the NCP5603 enabling pin EN is high and the brightness is maximized. When the Table 2. EVALUATION BOARD EFFICIENCY Vbat Ibat Vout Iout/LED Iout Total Yield Comments No Load 3.50 V 2.3 mA 0V 0 mA 0 mA − 3.50 V 132 mA 4.42 V 16.5 mA 66 mA 63.14% 3.50 V 170 mA 4.92 V 21.4 mA 85.6 mA 70.78% 3.10 V 131 mA 4.42 V 16.5 mA 66 mA 71.83% 3.10 V 169 mA 4.92 V 21.4 mA 85.6 mA 80.38% 3.10 V 300 mA 4.92 V 142 mA 142 mA 75.12% Torch operation The inrush current is internally limited by the chip, as depicted Figure 7, and no uncontrolled current takes place when the system starts up from scratch. Figure 8. Typical Digital Dimming Although there is no dedicated pin, the LED brightness can be dimmed by means of the EN digital control. The waveform captured in Figure 8 illustrate this behavior, the PWM being intentionally arranged out of the audio band for a portable system. Figure 7. Typical Startup Timing With a startup time well below 1 ms (from zero to full Vout, see Figure 7), the NCP5603 is fast enough to accommodate a flash application as shown in the demo board. http://onsemi.com 6 NCP5603GEVB TEST PROCEDURE Test Conditions 2. Insert two 1.5 V, AA type cell in the holder. Make sure the polarity is properly respected 3. Toggle switch S4 to turn on the system System Operation: 4. Select the Output Voltage (4.5 V or 5.0 V) by toggling the switch S3, B1 5. Select the operating frequency (260 kHz or 630 kHz) by toggling the switch S2, FSEL. Note: turn system off before switching frequency. 6. Select the Normal or PWM mode by toggling the switch S1. A RED LED turns On when the PWM mode is activated. The brightness of the LED (if necessary) can be adjusted (when the PWM mode is activated) by means of the potentiometer P1. The evaluation board can operate with either an external power supply, or with two dry cell 1.5 V, AA type, and battery. The mechanical switch S4 is used to select one of the two power sources. The system is not designed to run the two power sources simultaneously and such connection must be avoided. Using an External Power Supply: 1. Select a DC power supply with 500 mA output current capability (minimum), adjust the output voltage to 3.60 V 2. Connect the positive wire to the RED socket, connect the negative wire to the BLACK socket 3. Toggle switch S4 to turn on the system Using Dry Cell Battery: 1. Make sure no external power supply is attached to the RED and BLACK sockets Table 3. BILL OF MATERIALS FOR THE NCP5603 EVALUATION BOARD Designator Qty. Description Value Tolerance Footprint Manufacturer Manufacturer Part Number Substitution Allowed RoHS Compliant U1 1 NCP5603 Charge Pump NA NA QFN10 ON Semiconductor NCP5603MNR2G No Yes U2 1 Dual Schmitt Trigger Inverter NA NA TSOP−6 ON Semiconductor NL27WZ14DTT1G No Yes U3 1 Dual Retriggable One Shot NA NA SOIC−16 ON Semiconductor MC14538BDG No Yes R1, R2 2 Resistor 100 kW 5% 0805 Vishay CRCW08051040JNEA Yes Yes R3, R4, R5, R10 6 Resistor 10 kW 5% 0805 Vishay CRCW08051030JNEA Yes Yes R6, R7, R8, R9 4 Resistor 82 W 5% 0805 Vishay CRCW080582R0JNEA Yes Yes R11 1 Resistor 1.5 kW 5% 0805 Vishay CRCW08051530JNEA Yes Yes C1, C2, C3 3 Ceramic Capacitor 1 mF, 10 V 10% 0805 Murata GRM219R61A105KC01D Yes Yes C4 1 Ceramic Capacitor 4.7 mF, 10 V 10% 0805 Murata GRM219R61A475KE19D Yes Yes C5 1 Ceramic Capacitor 33 nF, 50 V 10% 0805 Kemet C0805C333K5RACTU Yes Yes C6, C7, C8 3 Ceramic Capacitor 100 nF, 50 V 10% 0805 Kemet C0805C104K5RACTU Yes Yes J1 1 Banana Socket NA − PLUG_4MM Deltron Components 571−0500 Yes Yes J2 1 Banana Socket NA − PLUG_4MM Deltron Components 571−0100 Yes Yes D1, D2, D3, D4 4 LW Y87S White LED NA NA OSRAM_LED Osram Q65110A1709 Yes Yes D5 1 HYPER MINI TOPLED NA NA OSRAM_LED Osram Q65110A2364 Yes Yes TP1, TP2 2 Test Point NA NA TEST_POINT Keystone 5005 Yes Yes P1 1 ADJ. Potentiometer 200 kW NA VR−4 Bourns 3386F−1−204LF Yes Yes PK2 1 AA Battery Pack NA NA BPACK2 Keystone 2223 Yes Yes S1 1 Manual Switch NA NA APEM_CMS APEM TL36WS84000 Yes Yes S2, S3, S4 3 Manual Switch NA NA SIP3 EAO 09.03290.01 Yes Yes Z3 1 Ground NA NA GND_TEST Harwin D3082−05 Yes Yes http://onsemi.com 7 NCP5603GEVB ON Semiconductor and are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC owns the rights to a number of patents, trademarks, copyrights, trade secrets, and other intellectual property. A listing of SCILLC’s product/patent coverage may be accessed at www.onsemi.com/site/pdf/Patent−Marking.pdf. SCILLC reserves the right to make changes without further notice to any products herein. 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