Data Sheet Rev. 1.00 / December 2011 ZLED7015 1.0MHz Boost Converter with Internal 35V Switch ZLED7015 1.0MHz Boost Converter with Internal 35V Switch Brief Description Features Integrated 35V power switch Wide input range: 6VDC to 30VDC The ZLED7015, one of our ZLED family of LED control ICs, is a constant current boost converter with an internal high-power 35V switch. It is optimal for driving multiple white LEDs connected in series so that the LED current is uniform for better brightness and color control. It can also drive devices that require a constant voltage and is capable of operating efficiently with voltage supplies ranging from 6VDC to 30VDC. It is ideal for diverse lighting applications requiring low supply voltages such as SELV applications. Typically, smaller, less expensive external components can be used since the ZLED7015 switches at 1.0MHz (typical). Over-temperature protection Over-voltage (open LED string) protection adjusted via external resistor divider Under-voltage lockout ensures reliable circuit operation Control of output current during start-up via internal “soft-start” Switching frequency: 1.0MHz Single pin on/off or brightness control via PWM, microcontroller, or DC voltage control signal input MSOP-10 package The ZLED7015 output current is adjustable via an external current sense resistor RS connected from the FB pin to ground. Benefits High efficiency: up to 95% efficiency Few small, low-profile components needed for operation The ZLED7015 improves efficiency and minimizes power losses in the current setting resistor RS by use of an internal 0.3V feedback reference voltage. Small form-factor package Available Support Dimming can be controlled using a pulse-width modulation (PWM) waveform or a DC voltage applied to the FB pin. Evaluation Kit Physical Characteristics The ZLED7015 provides a “soft-start” function to prevent excessive in-rush current on start-up and ensures a controlled rise of the output voltage. Operating temperature: -40°C to 85°C RoHS-compliant Over-voltage protection is adjustable via external resistors R1 and R2. ZLED7015 Typical Application Circuit VOUT VIN = 6 to 30 VDC L1 D1 REN R1 CIN RVDD C1 EN C2 LX OVP VDD R2 CVDD ZLED7015 PGND LED String FB COVP COUT VP AGND CVP RS © 2011 Zentrum Mikroelektronik Dresden AG — Rev. 1.00 All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. The information furnished in this publication is subject to changes without notice. ZLED7015 1.0MHz Boost Converter with Internal 35V Switch ZLED7015 Block Diagram 6 to 30 VDC VIN L1 RVDD CIN ZLED7015 9 REN CVDD C1 D1 2 LDO C2 VP VDD Bias & Reference Bandgap COUT CVP 7 – FB 10 R + LX RS VREF Oscillator S n LED Ramp Gen ∑ 4 R1 Q COVP R2 Slope Compensation Shutdown RS EN Current Sense OVP 6 Over-Voltage Protection Thermal Protection Current Limit PGND 1 AGND 3, 5 Typical Applications Low-Voltage Retro-fit Lighting Architectural/Building Lighting MR16 Lights Replacement Tubes SELV Lighting LED Backlighting Signage and Outdoor Lighting General Purpose Low-Voltage Industrial and Consumer Applications Ordering Information Product Sales Code Description Package ZLED7015-ZI1R ZLED7015 – 1.0MHz Boost Converter with Internal 35V Switch MSOP-10 (Tape & Reel) ZLED7015KIT-E1 ZLED7015-E1 Evaluation Board, 1 ZLED-PCB10, and 5 ZLED7015 ICs Kit Sales and Further Information www.zmdi.com [email protected] Zentrum Mikroelektronik Dresden AG Grenzstrasse 28 01109 Dresden Germany ZMD America, Inc. 275 South 5th Avenue Pocatello, ID 83201 USA Zentrum Mikroelektronik Dresden AG, Japan Office 2nd Floor, Shinbashi Tokyu Bldg. 4-21-3, Shinbashi, Minato-ku Tokyo, 105-0004 Japan ZMD FAR EAST, Ltd. 3F, No. 51, Sec. 2, Keelung Road 11052 Taipei Taiwan Zentrum Mikroelektronik Dresden AG, Korean Office POSCO Centre Building West Tower, 11th Floor 892 Daechi, 4-Dong, Kangnam-Gu Seoul, 135-777 Korea Phone +49.351.8822.7.533 Fax +49.351.8822.8.7533 Phone +1.208.478.7200 Fax +1.208.478.7200 Phone +81.3.6895.7410 Fax +81.3.6895.7301 Phone +886.2.2377.8189 Fax +886.2.2377.8199 Phone +82.2.559.0660 Fax +82.2.559.0700 DISCLAIMER: This information applies to a product under development. Its characteristics and specifications are subject to change without notice. Zentrum Mikroelektronik Dresden AG (ZMD AG) assumes no obligation regarding future manufacture unless otherwise agreed to in writing. The information furnished hereby is believed to be true and accurate. However, under no circumstances shall ZMD AG be liable to any customer, licensee, or any other third party for any special, indirect, incidental, or consequential damages of any kind or nature whatsoever arising out of or in any way related to the furnishing, performance, or use of this technical data. ZMD AG hereby expressly disclaims any liability of ZMD AG to any customer, licensee or any other third party, and any such customer, licensee and any other third party hereby waives any liability of ZMD AG for any damages in connection with or arising out of the furnishing, performance or use of this technical data, whether based on contract, warranty, tort (including negligence), strict liability, or otherwise. © 2011 Zentrum Mikroelektronik Dresden AG — Rev. 1.00 All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. ZLED7015 1.0MHz Boost Converter with Internal 35V Switch Contents 1 2 3 4 IC Characteristics .......................................................................................................................................................... 6 1.1 Absolute Maximum Ratings ................................................................................................................................... 6 1.2 Operating Conditions ............................................................................................................................................. 6 1.3 Electrical Parameters ............................................................................................................................................. 7 1.4 Typical Operating Characteristics .......................................................................................................................... 8 1.5 Characteristic Waveforms .................................................................................................................................... 10 Circuit Description ....................................................................................................................................................... 12 2.1 EN Pin, VP Pin, and Soft-Start Function .............................................................................................................. 12 2.2 Output Current Control......................................................................................................................................... 12 2.2.1 Output Current and RS .................................................................................................................................. 12 2.2.2 Dimming via External DC Voltage Control .................................................................................................... 13 2.2.3 Dimming via PWM Control............................................................................................................................ 14 2.2.4 Microcontroller LED Control .......................................................................................................................... 15 2.2.5 Constant Voltage Application ........................................................................................................................ 15 Application Circuit Design ........................................................................................................................................... 17 3.1 External Component – RS .................................................................................................................................... 17 3.2 External Component – Inductor L1 ....................................................................................................................... 17 3.3 External Components – Input Decoupling Capacitors C1 and CIN ........................................................................ 17 3.4 External Component –Output Capacitors C2 and COUT ........................................................................................ 17 3.5 External Component – Diode D1 .......................................................................................................................... 17 3.6 Additional External Components .......................................................................................................................... 17 Operating Conditions................................................................................................................................................... 18 4.1 Under-Voltage Lockout ........................................................................................................................................ 18 4.2 Over-Voltage Threshold and Open-Circuit Protection .......................................................................................... 18 4.3 Over-Temperature Protection .............................................................................................................................. 18 5 ESD/Latch-Up-Protection ............................................................................................................................................ 19 6 Pin Configuration and Package ................................................................................................................................... 19 7 Layout Requirements .................................................................................................................................................. 21 7.1 General Considerations and Ground Traces ....................................................................................................... 21 7.2 Layout Considerations for C1, CIN, C2 and COUT ................................................................................................... 21 7.3 Layout Considerations for the EN Pin .................................................................................................................. 21 7.4 Layout Considerations for the LX Pin, L1 External Coil, and D1 Diode ................................................................. 21 7.5 Layout Considerations for the External Current Sense Resistor (R S) .................................................................. 21 7.6 Layout Considerations for CVP and CVDD .............................................................................................................. 21 7.7 Layout Considerations for the Thermal Pad......................................................................................................... 21 8 Glossary of Terms ....................................................................................................................................................... 22 9 Ordering Information ................................................................................................................................................... 22 10 Document Revision History ......................................................................................................................................... 22 Data Sheet December 20, 2011 © 2011 Zentrum Mikroelektronik Dresden AG — Rev. 1.00 All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. The information furnished in this publication is subject to changes without notice. 4 of 22 ZLED7015 1.0MHz Boost Converter with Internal 35V Switch List of Figures Figure 1.1 IOUT vs. VIN with RS = 0.42Ω ............................................................................................................................ 8 Figure 1.2 IOUT vs. VIN with RS = 0.88Ω ............................................................................................................................ 8 Figure 1.3 IOUT vs. VOUT with RS = 0.42Ω ......................................................................................................................... 8 Figure 1.4 IOUT vs. VOUT with RS = 0.88Ω ......................................................................................................................... 8 Figure 1.5 Efficiency vs. VIN with RS = 0.42Ω .................................................................................................................. 8 Figure 1.6 Efficiency vs. VIN with RS = 0.88Ω .................................................................................................................. 8 Figure 1.7 Efficiency vs. VOUT with RS = 0.42Ω ................................................................................................................ 9 Figure 1.8 Efficiency vs. VOUT with RS = 0.88Ω ................................................................................................................ 9 Figure 1.9 VFB Reverence Voltage vs. VIN ....................................................................................................................... 9 Figure 1.10 IOUT vs. PWM Duty Cycle ................................................................................................................................ 9 Figure 1.11 VOUT, VIN, and IL1 during Soft Start ................................................................................................................ 10 Figure 1.12 VOUT, VLX, and IOUT during Typical Operation ................................................................................................ 10 Figure 1.13 VOUT, VLX, and IL1 when Over-Voltage Protection (OVP) Threshold is Exceeded ......................................... 11 Figure 2.1 Typical Application Circuit ............................................................................................................................ 13 Figure 2.2 Example Circuit for Controlling Output Current via an External DC Control Voltage .................................... 13 Figure 2.3 Example Circuit for Controlling Output Current via a PWM Control Signal ................................................... 14 Figure 2.4 Example Circuit for Constant Voltage Source Applications .......................................................................... 16 Figure 6.1 ZLED7015 Pin Configuration—MSOP-10 Package...................................................................................... 19 Figure 6.2 MSOP-10 Package Dimensions for the ZLED7015 ...................................................................................... 20 List of Tables Table 1.1 Absolute Maximum Ratings ............................................................................................................................ 6 Table 1.2 Operating Conditions ...................................................................................................................................... 6 Table 1.3 Electrical Parameters ..................................................................................................................................... 7 Table 6.1 Pin Description MSOP-10............................................................................................................................. 19 Data Sheet December 20, 2011 © 2011 Zentrum Mikroelektronik Dresden AG — Rev. 1.00 All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. The information furnished in this publication is subject to changes without notice. 5 of 22 ZLED7015 1.0MHz Boost Converter with Internal 35V Switch 1 IC Characteristics Note: Exceeding the maximum ratings given in this section could cause operation failure and/or cause permanent damage to the ZLED7015. Exposure to these conditions for extended periods may affect device reliability. 1.1 Absolute Maximum Ratings Table 1.1 Absolute Maximum Ratings No. PARAMETER SYMBOL 1.1.1 Supply voltage on VDD pin (also see specification 1.2.2) VDD 1.1.2 LX pin output voltage VLX 1.1.3 All other pins 1.1.4 ESD Performance Human Body Model CONDITIONS MIN TYP MAX UNIT -0.3 40.0 V -0.3 40.0 V -0.3 6.0 V High voltage pins: 1, 4, 5, 9, and 10 ±2.5 kV Low voltage pins: 2, 3, 6, 7, and 8 ±4 kV 1.1.5 Junction temperature Tj MAX -40 150 °C 1.1.6 Storage temperature TST -65 150 °C 1.1.7 Lead soldering temperature 260 °C 1.1.8 Junction-to-ambient thermal resistance 60 °C/W MAX UNIT 1.2 10 seconds maximum RθJA Operating Conditions Table 1.2 Operating Conditions No. PARAMETER SYMBOL CONDITIONS MIN TYP 1.2.1 Operating temperature TOP -40 +85 °C 1.2.2 Supply voltage on VDD pin (also see absolute maximum specification 1.1.1) VDD 6 30 V Data Sheet December 20, 2011 © 2011 Zentrum Mikroelektronik Dresden AG — Rev. 1.00 All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. The information furnished in this publication is subject to changes without notice. 6 of 22 ZLED7015 1.0MHz Boost Converter with Internal 35V Switch 1.3 Electrical Parameters Test conditions for the following specifications are T amb = 25°C (typical) and VDD = 12V, unless otherwise noted. Production testing of the ZLED7015 is performed at 25°C unless otherwise stated. Functional operation of the ZLED7015 and specified parameters at other temperatures are guaranteed by design, characterization, and process control. Table 1.3 Electrical Parameters No. PARAMETER SYMBOL CONDITIONS MIN Continuous switching 1.3.1 Supply current IDD TYP MAX UNIT 2 mA Quiescent: no switching 1.1 mA Shutdown: no switching; VEN=0V 15 µA 1.3.2 Shutdown current ISD 1.3.3 LX switching frequency fOCS 1 MHz 1.3.4 Maximum duty cycle DLX 90 % 1.3.5 EN pin ON threshold voltage VENon Rising VEN 1.3.6 EN pin OFF threshold voltage VENoff Falling VEN 1.3.7 Internal feedback reference voltage 1.3.8 Integrated switch ON resistance RDSon 1.3.9 Integrated switch current limit ISWlimit Duty cycle = 90% 1.3.10 Integrated switch leakage current ISWleak VLX = 40V 1.3.11 Internal regulator 1.3.12 Over-temperature protection (OTP) threshold 1.3.13 OTP threshold hysteresis 1.3.14 Under-voltage lock-out threshold (UVLO) 1.3.15 UVLO hysteresis 1.3.16 Internal over-voltage threshold reference voltage 1.3.17 Over-voltage protection threshold hysteresis Data Sheet December 20, 2011 VFB VP 1.4 0.285 6V<VDD<30V, CVP=10μF 1.8 4.5 V 0.4 V 0.3 0.315 V 0.8 1.2 Ω 2.1 2.4 A 1 µA 5.5 V 5.0 TOTP 150 °C TOTP_HYS 50 °C 2.9 V VUVLO_HYS 100 mV VOVP_TH 0.9 V VOVP_TH_HYS 10 mV VUVLO Falling VDD © 2011 Zentrum Mikroelektronik Dresden AG — Rev. 1.00 All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. The information furnished in this publication is subject to changes without notice. 7 of 22 ZLED7015 1.0MHz Boost Converter with Internal 35V Switch 1.4 Typical Operating Characteristics The curves are valid for the typical application circuit and Tamb = 25°C unless otherwise noted. IOUT vs. VIN with RS = 0.42Ω Figure 1.2 730 360 720 355 710 350 IOUT (mA) IOUT (mA) Figure 1.1 700 IOUT vs. VIN with RS = 0.88Ω 345 340 690 335 680 VOUT=30V,RS=0.88,L1=10H VOUT=30V,RS=0.42,L1=10H 330 670 18 20 22 24 26 10 28 15 20 VIN (V) IOUT vs. VOUT with RS = 0.42Ω Figure 1.4 730 360 720 355 710 350 IOUT (mA) IOUT (mA) Figure 1.3 700 690 30 IOUT vs. VOUT with RS = 0.88Ω 345 340 335 680 VIN=12V,RS=0.88,L1=10H VIN=24V,RS=0.42,L1=10H 330 670 25 26 27 28 29 12 30 15 18 Figure 1.5 21 24 27 30 VOUT (V) VOUT (V) Efficiency vs. VIN with RS = 0.42Ω Figure 1.6 100 100 90 90 Efficiency (%) Efficiency (%) 25 VIN (V) 80 70 Efficiency vs. VIN with RS = 0.88Ω 80 70 60 60 VOUT=30V,RS=0.88,L1=10H VOUT=30V,RS=0.42,L1=10H 50 50 18 20 22 24 VIN (V) Data Sheet December 20, 2011 26 28 10 15 20 25 30 VIN (V) © 2011 Zentrum Mikroelektronik Dresden AG — Rev. 1.00 All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. The information furnished in this publication is subject to changes without notice. 8 of 22 ZLED7015 1.0MHz Boost Converter with Internal 35V Switch Efficiency vs. VOUT with RS = 0.42Ω Figure 1.8 100 100 90 90 Efficiency (%) Efficiency (%) Figure 1.7 80 70 Efficiency vs. VOUT with RS = 0.88Ω 80 70 60 60 VIN=12V,RS=0.88,L=10H VIN=24V,RS=0.42,L=10H 50 50 25 26 27 28 29 12 30 15 18 VOUT (V) Figure 1.9 VFB Reverence Voltage vs. VIN Figure 1.10 24 27 30 IOUT vs. PWM Duty Cycle (For details of PWM dimming, see section 2.2.3.) 320 400 310 350 300 500Hz 10KHz 300 290 IOUT (mA) Reference Voltage (mV) 21 VOUT (V) 280 270 250 200 150 260 100 250 50 6 10 14 18 VIN (V) 22 26 30 0 0 20 40 60 80 100 PWM Duty Cycle (%) Data Sheet December 20, 2011 © 2011 Zentrum Mikroelektronik Dresden AG — Rev. 1.00 All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. The information furnished in this publication is subject to changes without notice. 9 of 22 120 ZLED7015 1.0MHz Boost Converter with Internal 35V Switch 1.5 Characteristic Waveforms Figure 1.11 VOUT, VIN, and IL1 during Soft Start VOUT 10V/Div VIN 10V/Div IL1 Inductor Current 1A/Div VIN = 12VDC, RS = 0.88Ω, L1 = 10µH, VOUT = 28V Figure 1.12 VOUT, VLX, and IOUT during Typical Operation VOUT 20V/Div VLX 20V/Div IOUT 20mA/Div VIN = 12VDC, RS = 0.88Ω, L1 = 10µH, VOUT = 28V 2μs/Div Data Sheet December 20, 2011 © 2011 Zentrum Mikroelektronik Dresden AG — Rev. 1.00 All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. The information furnished in this publication is subject to changes without notice. 10 of 22 ZLED7015 1.0MHz Boost Converter with Internal 35V Switch Figure 1.13 VOUT, VLX, and IL1 when Over-Voltage Protection (OVP) Threshold is Exceeded VOUT 20V/Div VLX 20V/Div IL1 500mA/Div VIN = 12VDC, RS = 0.88Ω, L1 = 10µH, VOUT = 28V, VOVP = 33V Data Sheet December 20, 2011 © 2011 Zentrum Mikroelektronik Dresden AG — Rev. 1.00 All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. The information furnished in this publication is subject to changes without notice. 11 of 22 ZLED7015 1.0MHz Boost Converter with Internal 35V Switch 2 Circuit Description The ZLED7015 is a constant-current boost converter that can also function as a constant voltage driver for LED applications. The boost converter topology features an internal 35V power switch and feedback circuit to control the output to the LED string. Optimal performance is achieved by operating in continuous conduction mode within the application’s load current range; i.e., the current through inductor L1 is always above 0A. The output current is set by an external resistor and the device supports DC linear or PWM dimming. Additional device features include selectable open-load/over-voltage protection, over-temperature protection, undervoltage lockout, and an automatic soft-start function to minimize the inrush current during startup. 2.1 EN Pin, VP Pin, and Soft-Start Function The EN pin can be used to enable or disable the ZLED7015. When the voltage on the EN pin rises above the ON threshold voltage VENon specified in Table 1.3, the ZLED7015 begins its “soft-start.” When the voltage at EN falls below the OFF threshold voltage VENoff, the ZLED7015 shuts down. There is a hysteresis between VENon and VENoff to prevent intermittent operation. The ZLED7015’s internal “soft-start” function ensures a smooth device start-up by preventing excessive inrush current and providing a controlled rise in the output current. When the soft-start function is initiated, the internal circuitry clamps the internal switch current threshold to zero during a 1millisecond delay. The soft-start function then gradually increases the internal switch current threshold over a 4-5 msec period. See Figure 1.11 for an illustration of typical waveforms during start-up. Important: The EN pin requires termination. If the EN pin is not used to control operation, connect it to the positive power supply through a 100kΩ resistor. Do not allow the EN pin to float. The VP pin is connected to the ZLED7015’s internal power regulator and requires an external bypass capacitor, CVP, to ensure correct device operation. 2.2 Output Current Control The LED current is determined by the voltage across the external sense resistor RS, which is fed back to the input FB. Internally, this is compared with the internal feedback reference voltage, VFB (see typical application shown on page 2), and the duty cycle of the internal power switch is adjusted to reduce or increase the output current IOUT. Selection of RS is discussed in section 2.2.1, and other external components are discussed in section 3. Dimming can be controlled by superimposing a DC or filtered pulse-width modulated (PWM) signal on the feedback voltage from RS. Refer to sections 2.2.2 and 2.2.3, respectively, for more details. 2.2.1 Output Current and RS The ZLED7015 continually adjusts the output current, IOUT, in order to maintain the voltage level at the FB pin equal to the internal feedback reference voltage, VFB. Equation (1) shows the basic relationship between IOUT, VFB, and RS for the basic application shown in Figure 2.1. I OUT VFB 0.3V RS RS (1) Where IOUT = Average output current through the LED(s) in amperes VFB = Internal feedback reference voltage (see Table 1.3, parameter 1.3.7) Data Sheet December 20, 2011 © 2011 Zentrum Mikroelektronik Dresden AG — Rev. 1.00 All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. The information furnished in this publication is subject to changes without notice. 12 of 22 ZLED7015 1.0MHz Boost Converter with Internal 35V Switch Figure 2.1 Typical Application Circuit VOUT VIN = 6 to 30 VDC L1 D1 REN R1 CIN RVDD C1 EN C2 LX OVP VDD R2 CVDD ZLED7015 FB COVP COUT VP AGND PGND 2.2.2 LED String CVP RS Dimming via External DC Voltage Control The LED output current can be set below the nominal average value defined on section 2.2.1 by using an external DC voltage control signal superimposed on the FB pin as shown in the example circuit in Figure 2.2. As the DC control signal, VDC, increases, the current through R3 increases with a subsequent increase in the voltage at the FB pin. This causes the ZLED7015 to compensate by reducing the output current through the LED string. Consequently, the output current is inversely proportional to the DC control voltage. Note: It is important to ensure that the LED output voltage VOUT remains higher than the input voltage VIN in dimming applications. Figure 2.2 Example Circuit for Controlling Output Current via an External DC Control Voltage VIN = 6 to 30 VDC VOUT L1 D1 REN R1 CIN RVDD C1 EN C2 LX VDD OVP R2 CVDD ZLED7015 PGND LED String FB COVP R3 COUT VP AGND CVP R4 RS DC Control Signal VDC = 0 to 5V Data Sheet December 20, 2011 © 2011 Zentrum Mikroelektronik Dresden AG — Rev. 1.00 All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. The information furnished in this publication is subject to changes without notice. 13 of 22 ZLED7015 1.0MHz Boost Converter with Internal 35V Switch The output current controlled by the DC voltage on FB can be calculated using equation (2): I OUT Where R VDC VFB VFB 3 R4 RS (2) IOUT = Output current through the LED(s) with a DC control voltage VFB = Internal feedback reference voltage (Table 1.3, parameter 1.3.7) VDC = External DC control voltage 2.2.3 Dimming via PWM Control An external pulse-width modulated (PWM) signal input can be used to control the LED output current by driving the output current to a value below the nominal average value defined in section 2.2.1. A microcontroller can be used to generate the PWM signal. See Figure 2.3 for an example circuit. The PWM signal is superimposed on the feedback voltage from RS at the FB pin via the input filter R 5/C3 and R4, which produces a DC voltage with a ripple. This method of controlling dimming is similar to the external DC voltage control described in section 2.2.2. The duty cycle of the PWM signal regulates the filtered DC voltage level, which inversely controls the LED output current level. When the duty cycle is at 100%, the output current is at the minimum. With a 0% duty cycle, the output current is at the maximum. Recommendation: With a PWM signal of 0 to 5V, use an R3 value of 10kΩ and a PWM frequency of >2kHz to minimize the filtered PWM voltage ripple. Note: It is important to ensure that the LED output voltage VOUT remains higher than the input voltage VIN in dimming applications. Figure 2.3 Example Circuit for Controlling Output Current via a PWM Control Signal VIN = 6 to 30 VDC L1 D1 REN R1 CIN RVDD C1 EN C2 LX VDD OVP R2 CVDD ZLED7015 PGND LED String FB COVP R3 COUT VP AGND CVP RS R4 C3 5V Microcontroller PMW Signal Data Sheet December 20, 2011 R5 0V © 2011 Zentrum Mikroelektronik Dresden AG — Rev. 1.00 All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. The information furnished in this publication is subject to changes without notice. 14 of 22 ZLED7015 1.0MHz Boost Converter with Internal 35V Switch The output current controlled by the PWM voltage on FB can be calculated using equation (3): I OUT Where R VPWM DPWM VFB VFB 3 R4 R5 RS (3) IOUT = Output current through the LED(s) with a PWM control voltage VFB = Internal feedback reference voltage (see Table 1.3, parameter 1.3.7) VPWM = External PWM control voltage DPWM = Duty cycle of the PWM control signal 2.2.4 Microcontroller LED Control A microcontroller can control the LED output current by providing a PWM control signal to the FB pin as described in section 2.2.3. Depending on the application, the microcontroller can also be used to control the shutdown circuitry via the EN pin (see section 2.1) providing a fast and smooth transition to shutdown. 2.2.5 Constant Voltage Application In addition to functioning as a constant-current boost converter for driving an LED string, the ZLED7015 can be configured as a constant-voltage boost converter for other applications. Figure 2.4 demonstrates a typical circuit for this application. The output voltage controlled by the values of R3 and RS can be calculated using equation (4): VOUT VFB ( R3 RS ) RS (4) Where VOUT = Output voltage to the load VFB = Internal feedback reference voltage (Table 1.3, parameter 1.3.7) Data Sheet December 20, 2011 © 2011 Zentrum Mikroelektronik Dresden AG — Rev. 1.00 All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. The information furnished in this publication is subject to changes without notice. 15 of 22 ZLED7015 1.0MHz Boost Converter with Internal 35V Switch Figure 2.4 Example Circuit for Constant Voltage Source Applications VIN = 6 to 30 VDC L1 D1 REN R1 CIN RVDD C1 CVDD EN LX VDD FB ZLED7015 PGND C2 December 20, 2011 Load OVP COUT VP AGND CVP Data Sheet R3 R2 COVP RS © 2011 Zentrum Mikroelektronik Dresden AG — Rev. 1.00 All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. The information furnished in this publication is subject to changes without notice. 16 of 22 ZLED7015 1.0MHz Boost Converter with Internal 35V Switch 3 Application Circuit Design The following sections cover selection of the external components shown in the typical application on page 2. 3.1 External Component – RS Recommendation: Use precision resistors (±1% or better tolerance) for the RS resistor to ensure accurate control of the LED current. See section 2.2.1 for the equation for selecting the value of RS, which sets the nominal current output. 3.2 External Component – Inductor L1 Designing the circuit so that the current through inductor L 1 is always above 0V (i.e., continuous mode) typically gives the best performance due to improved load regulation and reduced output ripple. Select an inductor that has a saturation current and a current rating greater than the mean input current. The inductor value selection requires trade-offs between unwanted ripple current and parasitic effects. A larger value inductor reduces inductor ripple current, resulting in less output ripple voltage; however, higher values also increase parasitic resistance, which can degrade performance. For most applications, a 10µH inductor with a saturation current >2.5A is adequate. See section 7.4 for layout restrictions. 3.3 External Components – Input Decoupling Capacitors C1 and CIN The input capacitors C1 and CIN minimize the input voltage noise and ripple. Recommendation: use a 22µF or larger low-ESR electrolytic capacitor for CIN in parallel with a 1µF ceramic capacitor rated at greater than the input voltage plus a safety margin for C1. 3.4 External Component –Output Capacitors C2 and COUT The output capacitors C2 and COUT minimize the output voltage ripple. Recommendation: use a 22µF or larger low-ESR electrolytic capacitor for COUT in parallel with a 1µF ceramic capacitor rated at greater than the output voltage plus a safety margin for C2. 3.5 External Component – Diode D1 For the diode D1, select a high-speed, low-capacitance Schottky diode with low reverse leakage at the maximum operating voltage and temperature to ensure maximum efficiency and performance. Important: Choose diodes with a continuous current rating higher than the maximum output load current and a peak current rating above the peak coil current. When operating above 85°C, the reverse leakage of the diode must be addressed because it can cause excessive power dissipation in the diode, especially when the output voltage is relatively high. Its reverse breakdown voltage must be greater than the over-voltage protection level VOVP (see section 4.2). Note: Silicon diodes have higher forward voltage and higher voltage overshoot before they start conducting, which can increase the peak voltage on the LX output. Ensure that the total voltage appearing on the LX pin, including supply ripple, is within the specified range (see Table 1.1). 3.6 Additional External Components For the VDD input, connect resistor RVDD to the positive power supply and connect ceramic capacitor C VDD to ground. Recommendations: use 1µF for CVDD; use 300Ω for RVDD with input voltages ≥ 8V, use 50Ω for RVDD with input voltages < 8V. For the VP pin, connect a 10µF ceramic bypass capacitor to ground (CVP). If the EN pin is not used, connect a 100kΩ resistor to the positive power supply (REN). Do not allow the EN pin to float. Data Sheet December 20, 2011 © 2011 Zentrum Mikroelektronik Dresden AG — Rev. 1.00 All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. The information furnished in this publication is subject to changes without notice. 17 of 22 ZLED7015 1.0MHz Boost Converter with Internal 35V Switch 4 Operating Conditions 4.1 Under-Voltage Lockout The under-voltage lockout (UVLO) monitors the ZLED7015’s internal regulator output voltage, VP, to ensure correct operation of the internal circuitry. When the VP voltage is lower than the UVLO threshold VUVLO, the ZLED7015 disables the internal power switch. If the VP voltage reaches a level higher than the UVLO threshold plus UVLO hysteresis (VUVLO+VUVLO_HYS) the UVLO turns off and the internal power switch is re-enabled. See parameters 1.3.14 and 1.3.15 in section 1.3 for the UVLO threshold and hysteresis. 4.2 Over-Voltage Threshold and Open-Circuit Protection If the LED string becomes open or the FB pin is shorted to ground, the ZLED7015 would normally continually boost the output voltage to potentially damaging levels. To prevent this, the ZLED7015 includes an integrated over-voltage protection (OVP) mechanism. If the output voltage reaches the ZLED7015’s OVP threshold VOVP, the protection circuitry is triggered and the device automatically turns off the internal switch, stopping the boost function and protecting the device. Once the output voltage falls below the OVP threshold minus OVP threshold hysteresis (VOVP_TH-VOVP_TH_HYS), the device will enter soft-start mode. The OVP threshold VOVP for the ZLED7015 is selectable via the R1 and R2 resistor values determined by equation (5): VOVP VOVP _ TH ( R1 R2 ) R2 (5) Where VOVP = Over-voltage protection threshold VOVP_TH = Internal over-voltage threshold reference voltage (see Table 1.3, parameter 1.3.16) Important: Care must be taken to select proper R1 and R2 values to ensure proper functioning of the ZLED7015. See specification 1.3.16 in Table 1.3 for the over-voltage protection threshold voltage. Set VOVP 3V higher than the normal operation output voltage. Important: When setting VOVP, care must be taken to ensure VOUT cannot exceed 35V. Minimize noise coupling on the OVP pin, which could interfere with proper protection, by connecting a 10nF ceramic capacitor to GND from OVP (COVP). 4.3 Over-Temperature Protection The ZLED7015 features on-chip over-temperature protection. If its internal temperature exceeds the overtemperature protection (OTP) threshold, TOTP, due to high power dissipation and improper heat sinking, the internal power switch is disabled. Once the internal temperature has fallen below the OTP threshold minus the OTP threshold hysteresis (TOTP - TOTP_HYS), the ZLED7015 enters the soft-start mode (see section 2.1). Refer to Table 1.1 for the maximum package power dissipation specifications for the ZLED7015’s MSOP-10 package. Data Sheet December 20, 2011 © 2011 Zentrum Mikroelektronik Dresden AG — Rev. 1.00 All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. The information furnished in this publication is subject to changes without notice. 18 of 22 ZLED7015 1.0MHz Boost Converter with Internal 35V Switch 5 ESD/Latch-Up-Protection All high voltage pins (1, 4, 5, 9, and 10) have an ESD protection of >± 2500V according to the Human Body Model (HBM). The ESD test follows the Human Body Model based on MIL 883-H, Method 3015.8 All low voltage pins (2, 3, 6, 7, and 8) have an ESD protection of >± 4000V according to the Human Body Model (HBM). The ESD test follows the Human Body Model based on MIL 883-H, Method 3015.8 All pins pass the latch-up test based on the JEDEC Standard No. 78B, December 2008. 6 Pin Configuration and Package The ZLED7015 package is an MSOP-10, which has a thermal resistance (junction to ambient) of RθJA = 60°C/W. Figure 6.1 ZLED7015 Pin Configuration—MSOP-10 Package PGND LX VP VDD AGND NC EN FB AGND OVP Table 6.1 Pin Description MSOP-10 Pin Name No. PGND 1 Power ground VP 2 Internal 5V linear regulator output. VP is the power supply for the internal switch gate driver and the internal control circuitry. Use a 10µF ceramic bypass capacitor between VP and ground. AGND 3 Analog (signal) ground. EN 4 Enable control input. Important: Do not allow this pin to float. AGND 5 Analog (signal) ground. OVP 6 Over-voltage protection control input. FB 7 Feedback voltage input. The nominal average output current is set by the value of RS connected from FB to GND – see section 2.2.1 for details. Important: Do not allow the FB pin to float. n.c. 8 No connection VDD 9 Supply voltage (6V to 30V)—see section 7 for layout considerations. LX 10 Drain of the internal switch. Connect the power inductor between LX and the power supply. Connect the output rectifier D1 between LX and the output circuit. See section1.1 for output range specifications. Thermal Pad Data Sheet December 20, 2011 Description Connect to ground. © 2011 Zentrum Mikroelektronik Dresden AG — Rev. 1.00 All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. The information furnished in this publication is subject to changes without notice. 19 of 22 ZLED7015 1.0MHz Boost Converter with Internal 35V Switch Figure 6.2 MSOP-10 Package Dimensions for the ZLED7015 c D L D1 Thermal Pad (bottom) E1 E E2 A2 A θ b A1 e Symbol Dimension (mm, except θ) Symbol Dimension (mm) Min Max Min Max A 0.82 1.10 D 2.90 3.10 A1 0.02 0.15 D1 1.70 A2 0.75 0.95 e b 0.18 0.28 E 2.90 3.10 c 0.09 0.23 E1 4.75 5.05 E2 1.45 1.65 L 0.40 0.80 θ Data Sheet December 20, 2011 0° 6° 1.90 0.50 BSC © 2011 Zentrum Mikroelektronik Dresden AG — Rev. 1.00 All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. The information furnished in this publication is subject to changes without notice. 20 of 22 ZLED7015 1.0MHz Boost Converter with Internal 35V Switch 7 Layout Requirements Follow these layout guidelines to avoid circuit instability and EMI vulnerability, especially with high current or high switching frequency applications. Important: Route traces connecting the feedback network to the FB and OVP pin away from the L 1 inductor, the D1 Schottky diode, and the LX pin. These traces should be as short as possible. Shield the FB pin and feedback network with a ground plane or trace to prevent noise coupling. 7.1 General Considerations and Ground Traces Make the ground traces as wide and short as possible. To prevent a signal ground shift, keep traces for the signal ground (pin 5) separate from traces for the power ground (pin 1). Connect the signal and power ground traces together at either the large ground plane or the negative terminal of C IN. Connect the grounds for other components to the signal ground. Use wide traces for connection of the high current loop. 7.2 Layout Considerations for C1, CIN, C2 and COUT Place C1, C2 and COUT as close as possible to the ZLED7015 to minimize ripple. The CIN input decoupling capacitor must be placed as close as possible to the VDD pin to minimize power supply noise, which can reduce efficiency. 7.3 Layout Considerations for the EN Pin Important: Do not allow the EN pin to float. It must be terminated if it is not used. 7.4 Layout Considerations for the LX Pin, L1 External Coil, and D1 Diode Minimize the length of circuit board traces connected to the LX pin because it is a fast switching output. Place L1 and D1 as close as possible to the LX pin using traces that are as short and wide as possible. Avoid routing other traces crossing or in parallel with this node to minimize the noise coupling into this circuit. 7.5 Layout Considerations for the External Current Sense Resistor (RS) Any trace resistance in series with RS must be taken into consideration when selecting its value. For the most accurate LED current control, use a trace that is as wide and short as possible for the RS connection to ground. Connect it to the signal ground (pin 5), not the power ground (pin 1). 7.6 Layout Considerations for CVP and CVDD For good filtering, connect CVP as close as possible to the VP pin and place CVDD as close as possible to the VDD pin. 7.7 Layout Considerations for the Thermal Pad To optimize heat dissipation, solder the thermal pad on the back of the MSOP-10 package to the large ground plan. Data Sheet December 20, 2011 © 2011 Zentrum Mikroelektronik Dresden AG — Rev. 1.00 All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. The information furnished in this publication is subject to changes without notice. 21 of 22 ZLED7015 1.0MHz Boost Converter with Internal 35V Switch 8 Glossary of Terms Term 9 Definition LDO Low Dropout Regulator OTP Over-Temperature Protection OVP Over-Voltage Protection UVL Under-Voltage Lockout Ordering Information Product Sales Code Description Package ZLED7015-ZI1R ZLED7015 – 1MHz Boost Converter with Internal 35V Switch MSOP-10 (Tape & Reel) ZLED7015KIT-E1 ZLED7015-E1 Evaluation Board, 1 ZLED-PCB10, and 5 ZLED7015 ICs Kit 10 Document Revision History Revision Date 1.00 December 20, 2011 Description First Issue. Sales and Further Information www.zmdi.com [email protected] Zentrum Mikroelektronik Dresden AG Grenzstrasse 28 01109 Dresden Germany ZMD America, Inc. 275 South 5th Avenue Pocatello, ID 83201 USA Zentrum Mikroelektronik Dresden AG, Japan Office 2nd Floor, Shinbashi Tokyu Bldg. 4-21-3, Shinbashi, Minato-ku Tokyo, 105-0004 Japan ZMD FAR EAST, Ltd. 3F, No. 51, Sec. 2, Keelung Road 11052 Taipei Taiwan Zentrum Mikroelektronik Dresden AG, Korean Office POSCO Centre Building West Tower, 11th Floor 892 Daechi, 4-Dong, Kangnam-Gu Seoul, 135-777 Korea Phone +49.351.8822.7.533 Fax +49.351.8822.8.7533 Phone +1.208.478.7200 Fax +1.208.478.7200 Phone +81.3.6895.7410 Fax +81.3.6895.7301 Phone +886.2.2377.8189 Fax +886.2.2377.8199 Phone +82.2.559.0660 Fax +82.2.559.0700 DISCLAIMER: This information applies to a product under development. Its characteristics and specifications are subject to change without notice. Zentrum Mikroelektronik Dresden AG (ZMD AG) assumes no obligation regarding future manufacture unless otherwise agreed to in writing. The information furnished hereby is believed to be true and accurate. However, under no circumstances shall ZMD AG be liable to any customer, licensee, or any other third party for any special, indirect, incidental, or consequential damages of any kind or nature whatsoever arising out of or in any way related to the furnishing, performance, or use of this technical data. ZMD AG hereby expressly disclaims any liability of ZMD AG to any customer, licensee or any other third party, and any such customer, licensee and any other third party hereby waives any liability of ZMD AG for any damages in connection with or arising out of the furnishing, performance or use of this technical data, whether based on contract, warranty, tort (including negligence), strict liability, or otherwise. Data Sheet December 20, 2011 © 2011 Zentrum Mikroelektronik Dresden AG — Rev. 1.00 All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. The information furnished in this publication is subject to changes without notice. 22 of 22