5, 6 and 8 String 60mA LED Drivers with Integrated Boost Controller ______________ General Description The MSL3050/MSL3060/MSL3080 multi-channel LED drivers with integrated boost regulator controller offer a complete solution to drive parallel LED strings at up to 40V. The LED current sinks control up to 60mA each for up to 19W of LED power. The MSL3050 has five current sinks, the MSL3060 has six and the MSL3080 has eight. Parallel connect the current sinks for increased string current. A single resistor sets LED current, with string matching and accuracy within ±3%. The advanced integrated PWM circuitry allows up to 4095:1 dimming, and offers simple PWM dimming control. External PWM dimming is controlled by a signal at the PWM input, which sets both the PWM duty cycle and frequency of the dimming signals. The internal PWM dimming is controlled by registers accessible through the I2C serial interface. The MSL3050/60/80 feature integrated fault detection circuitry that detects and acts upon string open-circuit and LED short circuit faults, boost regulator over-voltage faults, and die overtemperature faults. A proprietary Efficiency Optimizer maintains Features: sufficient boost regulator output voltage to maintain LED current 2 regulation while minimizing power use. A 1MHz I C/SMBus serial allows optional dimmingat control, • Drives 8 parallelinterface 60mA LED strings up fault to inspection and control of driver configuration; for serial interface information see 40V LED string the voltage MSL3050/60/80/50/60/80/86/87/88 Programming Guide. • Integrated boost controller The MSL3050/60/80 are offered in the 24-pin VQFN lead-free, • Offers true 12-bit LED dimming at 120Hz halogen-free, RoHS compliant package and operate over -40°C to +85°C. • String open circuit and LED short circuit fault detection and automatic shut down _____________________ Applications • ±3% current accuracy and current balance Long Life, Efficient LED Backlighting for: Televisionsfor and all Desktop Monitors • Single resistor sets current LED strings Medical and Industrial Instrumentation • External PWM dimming Automotive Audio-Visual Displays Channel Signs • Internal PWM dimming control engine Architectural Lighting • Single PWM input sets dimming duty cycle and frequency _____________ Ordering Information • Internal PWM dimming (use optional) • Synchronizes PWM LCD panel refresh PKG rate PARTdimming to DESCRIPTION 5-CH LED driverdimming with integrated at boost • Frequency multiplier allows PWM multiples 24 pin controller and resistor based LED Short 4 x 4 x 0.75mm MSL3050 Circuit threshold setting, with single of LCD panel refresh frequency (see Programming Guide) VQFN PWM input. • 1MHz I²C/SMBus interface; use optional 6-CH LED driver with integrated boost 24 pin controller and resistor based LED Short MSL3060 4 x 4 x 0.75mm • Resistor programmable LED short circuit threshold Circuit threshold setting, with single VQFN PWM input.protection • Die over-temperature cut-off 8-CH LED driver with integrated boost 24 pin • -40°C to +85°C MSL3080 operating temperature range controller and resistor based LED Short 4 x 4 x 0.75mm Circuit threshold setting, with single VQFN • Lead free, halogen free, RoHS compliant package PWM input. I²C and SMBus are trademarks of their respective owners. MSL3050/60/80 preliminary datasheet revision 0.1 Description: © Atmel Inc., 2011. All rights reserved. ____________________ Key Features Drives 5/6/8 parallel 60mA LED strings at up to 40V LED string voltage Integrated boost controller Offers true 12-bit LED dimming at 200Hz String open circuit and LED short circuit fault detection and automatic shut down ±3% current accuracy and current balance Single resistor sets current for all LED strings External PWM dimming Internal PWM dimming control engine Single PWM input sets dimming duty cycle and frequency Internal PWM dimming (use optional) Synchronizes PWM dimming to LCD panel refresh rate Frequency multiplier allows PWM dimming at multiples of LCD panel refresh frequency (see Programming Guide) 1MHz I²C/SMBus interface; use optional Resistor programmable LED short circuit threshold Die over-temperature cut-off protection -40°C to +85°C operating temperature range Lead free, halogen free, RoHS compliant package Atmel MSL3080 8 String 60mA LED Drivers with Integrated Boost Controller FULL DATASHEET _______________ Application Circuit VPWR = 12V VIN = 5V 10 F 10 H 20 F 60V 3A VIN PVIN GATE CS ENABLE I 2C INTERFACE EN MSL3080 FDC 5612 25m FB 3.12k COMP SDA VLED 47.5k 2nF 22k SCL FAULT OUTPUT FLTB PWM INPUT PWM STR0 STR1 STR2 ILED STR3 STR4 91.3k STR5 FBI STR6 STR7 PGND GND EP APPLICATION CIRCUIT Page 1 of 24 The MSL3080 8-channel LED drivers with integrated boost regulator controller offers a complete solution to drive parallel LED strings at up to 40V. The LED current sinks control up to 60mA each for up to 19W of LED power. The MSL3080 has eight current sinks. Parallel connect the current sinks for increased string current. A single resistor sets LED current, with string matching and accuracy within ±3%. The advanced integrated PWM circuitry allows up to 4095:1 dimming, and offers simple PWM dimming control. External PWM dimming is controlled by a signal at the PWM input, which sets both the PWM duty cycle and frequency of the dimming signals. The internal PWM dimming is controlled by registers accessible through the I2C serial interface. The MSL3080 feature integrated fault detection circuitry that detects and acts upon string open-circuit and LED short circuit faults, boost regulator over-voltage faults, and die over-temperature faults. A proprietary Efficiency Optimizer maintains sufficient boost regulator output voltage to maintain LED current regulation while minimizing power use. A 1MHz I2C/SMBus serial interface allows optional dimming control, fault inspection and control of driver configuration; for serial interface information see the “MSL3040/50/60/80/86/87/88 Programming Guide”. The MSL3080 IS offered in the 24-pin VQFN lead-free, halogen-free, RoHS compliant package and operate over -40°C to +85°C. Atmel MSL3080 Datasheet 8 String 60mA LED Driver with Integrated Boost Controller 1 DBIE-20120814 Table of Contents 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 Packages and Pin Connections.................................................................. 3 Pin Descriptions........................................................................................... 4 Absolute Maximum Ratings........................................................................ 5 Electrical Characteristics............................................................................ 6 Typical Operating Characteristics.............................................................. 7 Block Diagram.............................................................................................. 9 Typical Application Circuits...................................................................... 10 Detailed Description.................................................................................. 13 8.1 LED Driver Comparison..................................................................................................13 8.2 Boost Regulator Overview..............................................................................................14 8.3 Error Amplifier.................................................................................................................14 8.4 Gate Driver.....................................................................................................................15 8.5Soft-Start........................................................................................................................15 8.6 Boost Fault Monitoring and Protection...........................................................................15 8.7 LED Current Regulators and PWM Dimming Modes.....................................................15 8.8 Efficiency Optimizer (EO)...............................................................................................15 8.9 Fault Monitoring and Auto-Handling...............................................................................15 8.10 Internal Supervisory and LDO........................................................................................16 8.11 Internal Oscillator............................................................................................................16 8.12 Over Temperature Shutdown..........................................................................................16 8.13 Power Saving Modes......................................................................................................16 8.14I2C Serial Interface and Driver Control...........................................................................16 9.0 Application Information............................................................................. 17 9.1 Bypassing VIN and PVIN................................................................................................17 9.2 Setting the LED Current.................................................................................................17 9.3 Fault Monitoring and Automatic Fault Handling..............................................................17 9.4 Setting the LED Short-Circuit Threshold.........................................................................17 9.5 Boost Regulator..............................................................................................................18 9.6 The Efficiency Optimizer (EO)........................................................................................19 9.7 Setting the Boost Regulator Output Voltage...................................................................20 9.8 Choosing the Input and output Capacitors.....................................................................20 9.9 Choosing the Inductor....................................................................................................20 9.10 Setting the External MOSFET Current Limit...................................................................21 9.11 Choosing the Switching MOSFET..................................................................................21 9.12 Choosing the Output Rectifier........................................................................................21 9.13 Loop Compensation.......................................................................................................21 10.0 LED Dimming Control................................................................................ 23 11.0 Ordering Information................................................................................. 23 Atmel MSL3080 Datasheet 8 String 60mA LED Driver with Integrated Boost Controller 2 PHASE SHIFTED LED DIMMING SIGNALS /MSL3060/MSL3080 1.0 Packages andDatasheet Pin Connections Preliminary By default, string PWM dimming is staggered in time to reduce t MSL3040/41 automatically determine the stagger times based o frequency. FB 1 VIN 2 COMP CS EN FLTB PVIN ● GND PHASE SHIFTED LED DIMMING SIGNALS 1.1 24 pin 4 x 4 x 0.75mm VQFN Package By default, string PWM dimming is staggered in time to reduce the transient current d Packagedetermine Information MSL3040/41 automatically the stagger times based on the number of enab frequency. 24 23 22 21 20 19 18 GATE Package Information 17 PGND 3 TED LEDSDADIMMING SIGNALS MSL3080 16 ILED 4 15 CGND ng PWM SCL dimming is staggered in time to reduce the transient current demand on the boost regulator. The (TOP VIEW) utomatically SCTH 5determine the stagger times 14 PWM based on the number of enabled strings and the PWM dimming 9 10 11 12 STR6 STR1 8 STR5 7 nformation MMING SIGNALS STR4 13 STR7 STR3 6 STR2 STR0 ming is staggered in time to reduce the transient current demand on the boost regulator. The determine the stagger times based on the number of enabled strings and the PWM dimming on Page 2 of 24 eserved. Page 22 of 22 Atmel MSL3080 Datasheet 8 String 60mA LED Driver with Integrated Boost Controller © Atmel Inc., 2011. All rights reserved. 3 Page 22 of 22 Page 22 of 2.0 Pin Descriptions Table 2.1 Pin Assignments Name MSL3080 Pin Description VLED Voltage Regulator Feedback Input: Connect a resistive voltage divider from the boost regulator output, VLED, to FB to set the unoptimized boost regulator output voltage. The feedback regulation voltage is 2.5V. FB 1 VIN 2 Power Supply Input: Power supply input. Apply 4.5V to 5.5V to VIN. Decouple VIN to GND a 1µF or greater capacitor placed close to VIN. SDA 3 I²C Serial Data I/O: SDA is the I²C serial interface data input/output. Connect SDA to VIN when unused. For interface information see the “MSL3040/50/60/80/86/87/88 Programming Guide”. SCL 4 I²C Serial Clock Input: SCL is the I²C serial interface clock input. Connect SCL to VIN when unused. For interface information see the “MSL3040/50/60/80/86/87/88 Programming Guide”. SCTH 5 String Short Circuit Threshold Level Setting Input: SCTH programs the LED string short-circuit detection threshold. Connect a resistor from SCTH to GND to set the short-circuit threshold level to 4.9V (1kΩ), 5.8V (27kΩ), 6.8V (68kΩ) or 7.6V (330kΩ). A short circuit is detected when the STRn voltage is above the threshold while STRn is on. See the section “Setting the LED Short-Circuit Threshold” on page 17 for information. STR0 6 LED String 0 Current Sink: Connect the cathode end of series LED String 0 to STR0. If not used, connect STR0 to GND. STR1 7 LED String 1 Current Sink: Connect the cathode end of series LED String 1 to STR1. If not used, connect STR1 to GND. STR2 8 LED String 2 Current Sink: Connect the cathode end of series LED String 2 to STR2. If not used, connect STR2 to GND. STR3 9 LED String 3 Current Sink: Connect the cathode end of series LED String 3 to STR3. If not used, connect STR3 to GND. STR4 10 LED String 4 Current Sink: Connect the cathode end of series LED String 4 to STR4. If not used, connect STR4 to GND. STR5 11 LED String 5 Current Sink: Connect the cathode end of series LED String 5 to STR5. If not used, connect STR5 to GND. STR6 12 LED String 6 Current Sink: Connect the cathode end of series LED String 6 to STR6. If not used, connect STR6 to GND. STR7 13 LED String 7 Current Sink: Connect the cathode end of series LED String 7 to STR7. If not used, connect STR7 to GND. CGND 15 Connect To Ground: Connect CGND to GND close to the driver. PWM 14 PWM Dimming and Synchronization Input: Drive PWM with a pulse-width modulated signal with duty cycle of 0% to 100% and frequency of 20Hz to 50kHz to control the duty cycle and the frequency of all LED strings. For serial interface controlled PWM dimming connect PWM to GND and refer to the register definitions section for registers 0x10 through 0x14 in the “MSL3040/50/60/80/86/87/88 Programming Guide”. ILED 16 Maximum LED Current Control Input: Connect a resistor from ILED to GND to set the full-scale LED current. See the section “Setting the LED Current” on page 17 for more information. PGND 17 Power Ground: Ground of the boost regulator gate driver. Connect PGND to GND, EP and CGND as close to the MSL3080 as possible. GATE 18 Gate Drive Output: Connect GATE to the gate of the boost regulator switching MOSFET PVIN 19 Boost Regulator Power Supply Input: PVIN is the power supply input for the external MOSFET gate driver. Apply 4.5V to 5.5V to PVIN. Decouple PVIN with two 1µF capacitors placed close to PVIN. FLTB 20 Fault Output: FLTB sinks current to GND when a fault is detected. Clear faults by toggling EN low and then high, by cycling input power off and on, or through the I2C serial interface; see the “MSL3040/50/60/80/86/87/88 Programming Guide” for information. EN 21 Enable Input: Drive EN high to turn on the device, drive it low to turn it off. For automatic startup connect EN to VIN. Toggle EN low then high to reset FLTB, or reset it through the I2C serial interface. CS 22 Boost Regulator Current Sense Input: Connect the current sense resistor from CS and the MOSFET source to GND to set the boost regulator current limit. The current limit threshold is 100mV. See the section “Setting the External MOSFET Current Limit” beginning on page 21 for more COMP 23 Boost Regulator Compensation Node: Connect the compensation network components from COMP to FB to compensate the boost regulator control loop, as shown in the Typical Applications Circuit on page 10. See the section “Loop Compensation” beginning on page 21 for more information. GND 24 Signal Ground: Connect GND to EP, PGND and CGND as close to the device as possible. EP Exposed Die-Attach Paddle: Connect EP to GND, CGND, PGND and to the system ground. EP is the return path for the LED current as well as the primary thermal path to remove heat generated in the MSL3080. Use a large circuit board trace to connect from EP to the boost supply output capacitor ground and to the input supply ground return. Connect EP to a large copper ground plane for best thermal and electrical performance. EP Atmel MSL3080 Datasheet 8 String 60mA LED Driver with Integrated Boost Controller 4 3.0 Absolute Maximum Ratings Voltage (with respect to GND) VIN, PVIN, EN, SDA, SCL, PWM, FLTB, SCTH, ILED, CS, COMP, FB, GATE................................................................ -0.3V to +5.5V STR0 to STR7.................................................................................................................................................................... -0.3V to +40V PVIN to VIN........................................................................................................................................................................................ ±1V PGND, CGND, EP............................................................................................................................................................ -50mV to 50mV Current (into pin) VIN .................................................................................................................................................................................................. 50mA GATE, PVIN................................................................................................................................................................................ ±1250mA STR0 to STR7, CGND...................................................................................................................................................................... 75mA EP, PGND, GND..........................................................................................................................................................................-1000mA All other pins......................................................................................................................................................................-20mA to 20mA Continuous Power Dissipation 24-Pin 4mm x 4mm VQFN (derate 25mW/°C above TA = +70°C)............................................................................................... 1850mW Ambient Operating Temperature Range TA = TMIN to TMAX........................................................................................................... -40°C to +85°C Junction to Ambient Thermal Resistance (θJA), 4-Layer (Note 8).............................................................................................................29°C/W Junction to Ambient Thermal Resistance (θJA), 2-Layer (Note 8).............................................................................................................38°C/W Junction to Case Thermal Resistance (θJC).............................................................................................................................................8.6°C/W Junction Temperature .............................................................................................................................................................................. +125°C Storage Temperature Range...................................................................................................................................................... -65°C to +125°C Lead Soldering Temperature, 10s............................................................................................................................................................. +300°C Atmel MSL3080 Datasheet 8 String 60mA LED Driver with Integrated Boost Controller 5 4.0 Electrical Characteristics VVIN = 5V, VEN = 5V, Default Register Settings of Table 1, TA = -40°C to 85°C, unless otherwise noted. Typical values are at TA = +25°C Parameter DC Electrical Characteristics VIN Operating Supply Voltage VIN Operating Supply Current VIN Shutdown Supply Current SDA, SCL, PWM, SYNC Input High Voltage SDA, SCL, PWM, SYNC Input Low Voltage Minimum PWM On-Time PWM, SYNC Input Frequency Range SDA, FLTB Output Low Voltage EN Threshold ILED Regulation Voltage STR0 to STR7 LED Regulation Current STR0 to STR7 LED Current Load Regulation STR0 to STR7 LED Current Matching STR0 to STR7 Minimum Headroom STR0 to STR7 Short Circuit Fault Threshold FB Feedback Output Current FB Feedback Output Current Step Size FBI Input Disable Threshold Thermal shutdown temperature Boost Regulator Electrical Characteristics Switching Frequency Gate Voltage Rise/Fall Time CS Current Limit Threshold Voltage Maximum Duty Cycle Minimum On Time Boost Regulator Leading-Edge Blanking Period FB Regulation Voltage I²C Switching Characteristics SCL Clock Frequency Bus Timeout Period STOP to START Condition Bus Free Time Repeated START condition Hold Time Repeated START condition Setup Time STOP Condition Setup Time SDA Data Hold Time SDA Data Valid Acknowledge Time SDA Data Valid Time SDA Data Set-Up Time SCL Clock Low Period SCL Clock High Period SDA, SCL Fall Time SDA, SCL Rise Time SDA, SCL Input Suppression Filter Period Note 1. Note 2. Note 3. Note 4. Note 5. Note 6. Note 7. Note 8. Note 9. Conditions and Notes Min Typ 4.5 All STRn outputs 100% duty EN = GND Max Unit 5.5 18 1 V mA µA V V ns Hz V V V mA %/V % V V µA µA mV °C 1.82 0.72 20 Sinking 6mA VEN rising Minimum RILED = 60kΩ RILED = 100kΩ, TA= 25°C VSTRn = 1V RILED = 100kΩ VSTRn = 1V to 5V String to average of all strings VSTRn = 60mA RSCTH = 1.0kΩ FBO DAC = 0xFF, VFB = 0 400 200 50,000 0.4 1.5 58.2 1.25 60.0 0.15 -3 3.98 224 61.8 3 0.5 4.96 350 1.1 50 Temperature Rising, 10°C Hysteresis 135 569 CGATE = 1nF 75 At factory set boost frequency fBOOST = 350kHz to 1MHz (contact factory for boost frequencies different from 625kHz) 2.4 1/tSCL ttimeout tBUF tHD:STA tSU:STA tSU:STOP tHD:DAT tVD:ACK tVD:DAT tSU:DAT tLOW tHIGH tf tr tSP Bus timeout disabled (Note 1) TA = 25°C (Note 7) (Note 7) (Note 7) (Note 7) (Note 7) (Note 7) (Note 2) (Note 7) (Note 3) (Note 7) (Note 7) (Note 7) (Note 7) (Note 4) (Note 5) (Note 7) (Note 7) (Note 6) (Note 7) 0 29 0.5 0.26 0.26 0.26 0 0.05 0.05 100 0.5 0.26 665 50 111 90.1 762 147 kHz ns mV % 241 300 ns 130 2.5 2.6 ns V 1000 30 0.55 0.55 120 120 50 kHz ms µs µs µs µs ns µs µs ns µs µs ns ns ns Minimum SCL clock frequency is limited by the bus timeout feature, which resets the serial bus interface if either SDA or SCL is held low for timeout. tVD:ACK = SCL LOW to SDA (out) LOW acknowledge time. tVD:DAT = minimum SDA output data-valid time following SCL LOW transition. A master device must internally provide an SDA hold time of at least 300ns to ensure an SCL low state. The maximum SDA and SCL rise times is 300ns. The maximum SDA fall time is 250ns. This allows series protection resistors to be connected between SDA and SCL inputs and the SDA/SCL bus lines without exceeding the maximum allowable rise time. MSL3080 include input filters on SDA and SCL that suppress input noise less than 50ns Parameter is guaranteed by design and not production tested. Per JEDEC specification JESD51-5 and JESD51-12. Tests performed at TA = 25°C, specifications over temperature guaranteed by design. Atmel MSL3080 Datasheet 8 String 60mA LED Driver with Integrated Boost Controller 6 MSL3050/MSL3060/MSL3080 Datasheet Preliminary 5.0 Typical Operating Characteristics Typical Operating Characteristics (Typical Operating Circuit, unless otherwise stated) (Typical Operating Circuit, unless otherwise stated, TA = +25°C, unless otherwise noted) BOOST REGULATOR EFFICIENCY vs. OUTPUT CURRENT 100 10000 1000000 90 10000 85 IIN(µA) (µA) IIN 80 75 70 10100 VPWR = 12V 60 0.1 fBOOST = 625kHz 50 0 200 400 600 800 10 EN = 1 sleep = slpPwrSv = 1 EN = 0EN = 0 1 VLED 37V 55 EN = 1 sleep = slpPwrSv = 0 BOOST NOT SWITCHING 100 1000 1 65 1,000 0.1 0.010.01 4.5 4.5 4.6 4.6 4.7 4.7 4.8 4.8 4.9 OUTPUT CURRENT (mA) STRn CURRENT (mA EN = 1 sleep = slpPwrSv = 0 BOOST NOT SWITCHING EN = 1 100000 sleep = slpPwrSv = 1 1000 95 EFFICIENCY (%) SUPPLY CURRENT SUPPLY CURRENT SUPPLY VOLTAGE vs.vs. SUPPLY VOLTAGE 10 100 RISET (k ) 5.5 START-UP WAVEFORMS STRn CURRENT vs. RISET 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5 0 5.0 5.1 4.9 5.0 5.2 5.1 5.3 5.2 5.4 5.3 5.5 5.4 VIN (V) VIN (V) 1000 MSL3050/MSL3060/MSL3080 Datasheet CH1 = V , CH2 = V , CH3 = V , CH4 = I EN © Atmel Inc., 2011. All rights reserved. CH1 = VEN, CH2 = VLED, CH3 = VSTRx, CH4 = IPWR AUTO CALIBRATION STRx PWR Preliminary BOOST WAVEFORMS 10% LED DUTY CYCLE START-UP WAVEFORMS (ZOOM) MSL3050/60/80 preliminary datasheet revision 0.1 LED Page 6 of 24 CH1 = VLED, CH2 = VGATE, CH3 = IINDUCTOR BOOST WAVEFORMS 100% LED DUTY CYCLE Atmel MSL3080 Datasheet 8 String 60mA LED Driver with Integrated Boost Controller 7 CH1 = V CH3 = VSTRx, CH4 = IPWR(continued) 5.0 Typical Operating EN, CH2 = VLED,Characteristics CH1 = VLED, CH2 = VGATE, CH3 = IINDUCTOR (Typical Operating Circuit, unless otherwise stated, TA = +25°C, unless otherwise noted) BOOST WAVEFORMS 100% LED DUTY CYCLE AUTO CALIBRATION CH2 = VLED, CH3 = VSTRx MSL3050/MSL3060/MSL3080 Datasheet CH1 = VLED, CH2 = VGATE, CH3 = IINDUCTOR BOOST REGULATOR WAVEFORMS 10% TO 99.5% LED DUTY CYCLE MSL3050/60/80 preliminary datasheet revision 0.1 © Atmel Inc., 2011. All rights reserved. Preliminary BOOST REGULATOR GATE DRIVE RISE/FALL WITH 3nF CAPACITIVE LOAD Page 7 of 24 CH1 = VLED, CH2 = VGATE, CH3 = VPWM, CH4 = IINDUCTOR DRIVER RISE TIME CH2 = VGATE DRIVER FALL TIME AUTOMATIC PHASE SHIFTED PWM DIMMING This scope image shows the voltage (VSTR0) and current (ISTR0) waveforms for string zero, and their turn-on rise times and delay from PWM rising. Also shown is the string power supply output CH1 = VSTR0 , CH2 VSTR2 , CH3 = V , CH4 VSTR6 STR4 (VLED), which shows=little disturbance. For this photo=string 0 is enabled with all other strings disabled. This scope image shows the voltage (VSTR0) and current (ISTR0) waveforms for string zero, and their turn-off fall times. Also shown is the string power supply output (VLED), which shows very little disturbance. For this photo string 0 is enabled with all other strings disabled, and a 220pF capacitor in series with a 11Ω resistor in series is placed from STR0 to GND at the device. Atmel MSL3080 Datasheet 8 String 60mA LED Driver with Integrated Boost Controller 8 MSL3050/MSL3060/MSL3080 Datasheet Preliminary 6.0 Block BlockDiagram Diagram Figure 6.1. Block Diagram MSL3080 Figure 1. MSL3050/MSL3060/MSL3080 Block Diagram MSL3050/60/80 preliminary datasheet revision 0.1 © Atmel Inc., 2011. All rights reserved. Page 9 of 24 Atmel MSL3080 Datasheet 8 String 60mA LED Driver with Integrated Boost Controller 9 MSL3050/MSL3060/MSL3080 Datasheet Preliminary 7.0 Typical Application Circuits Figure 7.1. Typical Operating Circuit for Eight 60mA Strings of 10 White LEDs each. Typical Application Circuits VPWR = 12V 10 F VIN = 5V 1 F 2 VIN ENABLE 21 3 I2C INTERFACE 4 PWM INPUT 14 FAULT OUTPUT 20 5 18 GATE 22 CS VLED 47.5k SDA MSL3080 FB 1 22k PWM 3.12k 2nF FLTB COMP 23 SCTH STR0 STR1 ILED STR2 STR3 93.1k STR4 STR5 15 FDC5612 25m EN SCL 2x 10 F B380 19 PVIN 82k 16 10 H 2x 1 F STR6 CGND PGND 17 EP STR7 GND 24 6 7 8 9 10 11 12 13 Figure 2. Typical Operating Circuit for Eight 60mA Strings of 10 White LEDs each. MSL3050/60/80 preliminary datasheet revision 0.1 © Atmel Inc., 2011. All rights reserved. Page 10 of 24 Atmel MSL3080 Datasheet 8 String 60mA LED Driver with Integrated Boost Controller 10 MSL3050/MSL3060/MSL3080 Datasheet Figure 7.2. Typical Operating Circuit for Four 120mA Strings of 10 White LEDs each. VPWR = 12V Preliminary 10 F VIN = 5V 1 F 2 VIN ENABLE 21 3 I2C INTERFACE 4 PWM INPUT 14 FAULT OUTPUT 20 5 18 GATE 22 CS VLED 47.5k SDA MSL3080 FB 1 22k PWM 3.12k 2nF FLTB COMP 23 SCTH STR0 STR1 ILED STR2 STR3 93.1k STR4 STR5 15 FDC5612 25m EN SCL 2x 10 F B380 19 PVIN 82k 16 10 H 2x 1 F STR6 CGND PGND 17 EP STR7 GND 24 6 7 8 9 10 11 12 13 Figure 3. Typical Operating Circuit for Four 120mA Strings of 10 White LEDs each. MSL3050/60/80 preliminary datasheet revision 0.1 © Atmel Inc., 2011. All rights reserved. Page 11 of 24 Atmel MSL3080 Datasheet 8 String 60mA LED Driver with Integrated Boost Controller 11 MSL3050/MSL3060/MSL3080 Datasheet Figure 7.3. Typical Operating Circuit for One 480mA String of 10 White LEDs. VPWR = 12V Preliminary 10 F VIN = 5V 1 F 2 VIN ENABLE 21 3 I2C INTERFACE 4 PWM INPUT 14 FAULT OUTPUT 20 5 18 GATE 22 CS VLED 47.5k SDA MSL3080 FB 1 22k PWM 3.12k 2nF FLTB COMP 23 SCTH STR0 STR1 ILED STR2 STR3 93.1k STR4 STR5 15 FDC5612 25m EN SCL 2x 10 F B380 19 PVIN 82k 16 10 H 2x 1 F STR6 CGND PGND 17 EP STR7 GND 24 6 7 8 9 10 11 12 13 Figure 4. Typical Operating Circuit for One 480mA String of 10 White LEDs. Detailed Description The MSL3050/MSL3060/MSL3080 are LED drivers with five, six and eight internal current regulators respectively, each capable of driving up to 60mA LED current They feature an integrated boost regulator controller with a proprietary Efficiency Optimizer voltage control algorithm that lowers power use to the minimum required to assure LED current regulation. The driver outputs allow parallel connection to increase string current, at the expense of the number of strings, and a single resistor sets the current for all strings. The drivers support 12-bit PWM LED dimming ratios. The driver synchronizes LED dimming and controls duty cycle with a single external digital signal at the PWM input. The MSL3050/60/80 include comprehensive fault monitoring and automatic fault handling. Automatic fault handling allows the drivers to operate without any microcontroller or FPGA, while optional control via I2C allows customized fault handling and driver control for more complex applications. All drivers also feature optional register-set PWM dimming, fault management and other controls via the I2C serial interface; for interface information see the MSL3050/60/80/50/60/80/86/87/88 Programming Guide. The small 4x4mm VQFN package allows a small overall LED driver solution, while maintaining high package power dissipation for high output power capability. MSL3050/60/80 preliminary datasheet revision 0.1 © Atmel Inc., 2011. All rights reserved. Page 12 of 24 Atmel MSL3080 Datasheet 8 String 60mA LED Driver with Integrated Boost Controller 12 8.0 Detailed Description The MSL3080 is an LED driver with eight internal current regulators, each capable of driving up to 60mA LED current. They feature an integrated boost regulator controller with a proprietary Efficiency Optimizer voltage control algorithm that lowers power use to the minimum required to assure LED current regulation. The driver outputs allow parallel connection to increase string current, at the expense of the number of strings, and a single resistor sets the current for all strings. The drivers support 12-bit PWM LED dimming ratios. The driver synchronizes LED dimming and controls duty cycle with a single external digital signal at the PWM input. The MSL3080 includes comprehensive fault monitoring and automatic fault handling. Automatic fault handling allows the drivers to operate without any microcontroller or FPGA, while optional control via I2C allows customized fault handling and driver control for more complex applications. All drivers also feature optional register-set PWM dimming, fault management and other controls via the I2C serial interface; for interface information see the “MSL3040/50/60/80/86/87/88 Programming Guide”. The small 4x4mm VQFN package allows a small overall LED driver solution, while maintaining high package power dissipation for high output power capability 8.1 LED Driver Comparison Table 8.1. LED Driver Comparison with Similar Parts PART NUMBER OF LED STRINGS MAX CURRENT PER STRING PHASE SHIFTED STRING DRIVERS INTERNAL BOOST CONTROLLER RESISTOR SET LED SHORT CIRCUIT THRESHOLD SEPARATE SYNC INPUT*** MSL3086 8 60mA YES YES YES NO MONITOR, INDUSTRIAL PANEL BEST FOR MSL3087* 8 60mA YES NO YES NO SMALL TV MSL3088 8 60mA YES YES NO YES SMALL TV 8 60mA NO YES YES NO MONITOR, INDUSTRIAL PANEL 4** 120mA NO YES YES NO MONITOR, INDUSTRIAL PANEL 2** 240mA NO YES YES NO MONITOR, INDUSTRIAL PANEL 1** 480mA NO YES YES NO MONITOR, INDUSTRIAL PANEL MSL3040* 4 120mA YES YES YES NO MONITOR, AUTOMOTIVE MSL3041* 4 120mA YES YES YES YES MONITOR, AUTOMOTIVE MSL3080 MSL3050* MSL3060* 5 60mA NO YES YES NO INDUSTRIAL PANEL 1** 300mA NO YES YES NO INDUSTRIAL PANEL 6 60mA NO YES YES NO MONITOR, INDUSTRIAL PANEL 3** 120mA NO YES YES NO MONITOR, INDUSTRIAL PANEL 2** 180mA NO YES YES NO MONITOR, INDUSTRIAL PANEL 1** 360mA NO YES YES NO MONITOR, INDUSTRIAL PANEL * Future product, contact factory for information. ** Drivers without phase shift allow parallel connection of string drive outputs for increased string current. *** Drivers with separate SYNC input expect two control signals, one for dimming duty cycle and one for dimming frequency. Atmel MSL3080 Datasheet 8 String 60mA LED Driver with Integrated Boost Controller 13 8.2 Boost Regulator Overview The MSL3080 boost regulator boosts the input voltage up to the regulated output voltage (for design details see the section “Boost Regulator” beginning on page 17, the following text presents an overview of the boost regulator controller). The boost regulator uses an external switching MOSFET, current sense resistor, inductor, rectifier, and input and output capacitors (Figure 8.1). External MOSFET and current sense resistor allow the boost regulator to operate over wide input and output voltage ranges, and LED currents. It includes a 2.5V reference voltage, fixed slope compensation and external voltage regulator compensation to optimize the control loop for each configuration. Because the boost regulator components are external it supports a number of converter topologies, such as SEPIC, flyback, and single-switch forward. The boost regulator includes soft-start, adjustable cycle-by-cycle current limiting, and output overvoltage fault detection. Preliminary Figure 8.1. Power Section of MSL3080 MSL3050/MSL3060/MSL3080 Datasheet 5V VPWR PVIN CIN L1 D1 GATE DRIVE GATE LIMIT 1.1V SLOPE COMP 0.4V CURRENT 0.1 V Q1 COUT RESR RCS GND A = 11 SENSE RTOP FB EFFICIENCY OPTIMIZER + 1.5V CS VLED RCOMP SOFT START CCOMP2 CCOMP1 RBOTTOM COMP COMPENSATION: CCOMP2 = POLE CCOMP1, RCOMP = ZERO REF DROPOUT DETECT MSL3080 MSL3050 MSL3060 MSL3080 STRn LED CURRENT SINK Figure 5. Power section of MSL3050/60/80 RROR AMPLIFIER 8.3 ErrorEAmplifier The internal error amplifier compares the external divided output voltage at FB to the internal 2.5V reference voltage to set Thethe internal error amplifier compares the. external divided output voltage at FB at to the internal 2.5V reference voltage use to set the regulated The error amplifier output voltage COMP is externally accessible; it to regulated output voltage, VLED errorregulator. amplifier output voltage at COMP is externally accessible; use itcomparator to compensate voltageif regulator. FB output voltage, VLED compensate the. The voltage FB also drives the integrated boost over-voltage thatthe detects the output alsovoltage drives the integrated over-voltage thata detects if the output exceeds the regulation voltage, generate a exceeds the boost regulation voltage,comparator to generate fault condition. Thevoltage error amplifier internally controls thetocurrent faultmode condition. error amplifier internally controls the current mode PWM regulator. PWMThe regulator. GATE DRIVER The gate driver drives the gate of the external boost regulator switching MOSFET. The drain of the switching MOSFET in turn drives the boost inductor and rectifier to boost the input voltage to the regulated output voltage. The gate driver sources and sinks up to 1A allowing fast switching speed and allows the use of MOSFETs with high gate capacitance. The gate driver power is separated from the internal circuitry power to reduce internal noise and to allow separate gate driver bypassing for optimal performance. SOFT-START The boost regulator includes a built in soft-start to prevent excessive input current overshoot at turn-on. The soft-start ramps the output regulation voltage from 0V at turn-on to the as-configured regulation output voltage over 1.6ms. Note that the boost regulator only controls output voltages greater than the input voltage; when the soft-start sets the regulation voltage below the input voltage, the actual output voltage remains at approximately theAtmel input MSL3080 voltage. Datasheet 8 String 60mA LED Driver with Integrated Boost Controller MSL3050/60/80 preliminary datasheet revision 0.1 © Atmel Inc., 2011. All rights reserved. Page 14 of 24 14 8.4 Gate Driver The gate driver drives the gate of the external boost regulator switching MOSFET. The drain of the switching MOSFET in turn drives the boost inductor and rectifier to boost the input voltage to the regulated output voltage. The gate driver sources and sinks up to 1A allowing fast switching speed and allows the use of MOSFETs with high gate capacitance. The gate driver power is separated from the internal circuitry power to reduce internal noise and to allow separate gate driver bypassing for optimal performance. 8.5 Soft-Start The boost regulator includes a built in soft-start to prevent excessive input current overshoot at turn-on. The soft-start ramps the output regulation voltage from 0V at turn-on to the as-configured regulation output voltage over 1.6ms. Note that the boost regulator only controls output voltages greater than the input voltage; when the soft-start sets the regulation voltage below the input voltage, the actual output voltage remains at approximately the input voltage. 8.6 Boost Fault Monitoring and Protection The boost regulator includes fault monitoring and protection circuits to indicate faults and prevent damage to the boost regulator or other circuitry. The boost regulator has cycle by cycle current limiting that prevents excessive current through the power MOSFET. The current limit is has a fixed threshold voltage across the current sense resistor, thus set the current limit by choosing the proper value current sense resistor. The boost regulator includes an output over-voltage fault monitor that indicates a fault when the voltage at FB exceeds the 2.8V overvoltage protection (OVP) threshold. When an over-voltage fault occurs FLTB sinks current to GND to indicate that a fault has occurred. OVP fault is non-latching, the fault clears when the over-voltage condition disappears. 8.7 LED Current Regulators and PWM Dimming Modes The MSL3080 includes eight open-drain LED current regulators that sink LED current up to 60mA per channel and sustain up to 40V, allowing them to drive up to 10 white LEDs each. The current regulators inform the Efficiency Optimizers, which in turn control the boost regulator output voltage to minimize LED voltage while maintaining sufficient headroom for the LED current regulators. Set the LED regulation current using a single resistor from ILED to GND. LED dimming is by PWM, and is by default controlled through an external signal, or optionally by internal registers accessed through the I2C compatible serial interface (for interface information see the “MSL3040/50/60/80/86/87/88 Programming Guide”). The drivers feature synchronized dimming, where all PWM dimming outputs sink current in unison. 8.8 Efficiency Optimizer (EO) The Efficiency Optimizer monitors the LED string drivers and controls the boost regulator output voltage to minimize LED current regulator overhead voltage while maintaining sufficient voltage for accurate current regulation. The Efficiency Optimizer injects a current into the boost regulator FB input node to reduce the boost regulator output voltage. The Efficiency Optimizer has two modes of operation, initial calibration and auto calibration. Initial calibration happens at turn-on and optimizes boost regulator output voltage. Auto calibration happens once per second to re-optimize the boost output voltage in response to changing LED forward voltage due to aging or temperature effects. 8.9 Fault Monitoring and Auto-handling The MSL3080 includes comprehensive fault monitoring and corrective action. The LED current regulators are monitored for LED string open circuit and LED short circuit faults. It also monitors the boost regulator for output over-voltage. Strings with LED Short Circuit or Open Circuit faults are turned off and ignored by the Efficiency Optimizer. FLTB sinks current to GND when a fault is detected. The Boost Over-Voltage Fault does not latch, the fault goes away when the fault condition no longer exists and FLTB is released; all other faults latch. Clear faults by toggling EN low and then high, or by cycling input power off and on. Additionally, fault control is available through the I2C compatible serial interface; see the “MSL3040/50/60/80/86/87/88 Programming Guide” for information. Atmel MSL3080 Datasheet 8 String 60mA LED Driver with Integrated Boost Controller 15 8.10 Internal Supervisory and LDO The MSL3080 has a Power-On-Reset circuit that monitors VIN and allows operation when VIN exceeds 4.25V. The MSL3080 has built-in LDOs that generate 2.5V to power the logic and oscillator sections. An integrated supervisor ensures that the LDO and internal oscillator are stable before enabling the boost controller. The boost controller goes through a soft-start before the LED drivers are enabled. 8.11 Internal Oscillator The MSL3080 includes a 20MHz internal oscillator that is divided down to drive the boost controller, and the LED PWM engine. The oscillator is factory trimmed. Contact the factory if required to change the 20MHz default oscillator frequency; available frequencies fall between 16MHz and 24MHz. 8.12 Over Temperature Shutdown The MSL3080 includes automatic over-temperature shutdown. When the die temperature exceeds 135°C, the driver turns off, as if EN is pulled low, and is held off until the die temperature drops below 120°C, at which time it turns back on. While MSL3080 is in overtemperature shutdown the onboard regulators are off, register values reset to their power-on default values, and the serial interface is disabled. 8.13 Power Saving Modes The MSL3080 has 3 primary power save modes available through the I2C compatible serial interface. See the “MSL3040/50/60/80/86/87/88 Programming Guide” for information. 8.14 I2C Serial Interface and Driver Control The I2C serial interface, whose use is optional, allows control of PWM dimming, fault monitoring, and various other control functions. For a detailed explanation of interface operation see the “MSL3040/50/60/80/86/87/88 Programming Guide”. Atmel MSL3080 Datasheet 8 String 60mA LED Driver with Integrated Boost Controller 16 9.0 Application Information 9.1 Bypassing VIN and PVIN Bypass VIN with a capacitor of at least 1µF. Bypass PVIN to PGND with at least 2µF. Place all bypass capacitors close to the MSL3080. 9.2 Setting the LED Current Set the on-current for all LED strings with a resistor from ILED to GND. Choose the resistor using: where ILED is the LED full-scale current in Amps. The maximum LED current per-string is 60mA. Driving all eight strings with 60mA at high duty cycles and elevated ambient temperatures requires proper thermal management to avoid over-temperature shutdown. Connect the exposed pad (EP) to a large copper ground plane for best thermal and electrical performance. 9.3 Fault Monitoring and Automatic Fault Handling The MSL3080 monitors the LED strings and boost regulator output voltage to detect LED short-circuit, LED string open-circuit and Boost Over-voltage faults. String faults latch the open drain fault output FLTB low. A boost over-voltage fault pulls FLTB low but does not latch. When shorted LEDs are detected in a string, the driver disables and the Efficiency Optimizer stops monitoring it. The MSL3080 flags these strings as faults in registers 0x05 through 0x08, pulls FLTB low and recalibrates the LED power supply voltage. Set the short circuit voltage threshold with a resistor between SCTH and GND, as explained in the section “Setting the LED Short-Circuit Threshold” beginning on page 17. For information about the fault registers and the I2C compatible serial interface see the “MSL3040/50/60/80/86/87/88 Programming Guide”. When an open circuit occurs, the Efficiency Optimizer detects a loss of current regulation which must persist for greater than 2 µs to be detected. The minimum on-time for the strings is 2 µs. In this case the Efficiency Optimizer increases the LED voltage (boost regulator output voltage), in an attempt to bring the LED current back in to regulation. This continues until the voltage is at the maximum level. The MSL3080 then determines that any LED strings that are not regulating current are open circuit. It disables those strings, flags them as faults in registers 0x05 through 0x08, pulls FLTB low and recalibrates the LED power supply voltage. When the boost regulator is at its maximum value fictitious LED short circuit faults can occur. Toggle EN low and then high to clear all faults and return the MSL3080 to controlling and monitoring all LED strings. Fault conditions that persist re-establish fault responses. For information about the fault registers and the I2C compatible serial interface see the “MSL3040/50/60/80/86/87/88 Programming Guide”. 9.4 Setting the LED Short-Circuit Threshold When a given string, STRn, is sinking LED string current, the fault detection circuit monitors the STRn voltage. Typical optimized STRn on-voltage is 0.5V. When one or more LED’s of a string are shorted, the STRn voltage increases above the nominal. When the voltage is above the Short-Circuit Threshold the fault circuit generates an LED short circuit fault. In most cases, two LEDs in a string must be shorted to cause a short circuit fault, but because LED VF differs for different LEDs, the number of shorted LEDs required to generate a fault varies.Set the LED short-circuit threshold with a resistor from SCTH to GND using: Table 9.1 Short Circuit Threshold Resistor RSCTH Threshold Voltage 1.0kΩ (or GND) 4.9V 27kΩ 5.8V 68kΩ 6.8V 330kΩ (or open) 7.6V RSCTH is measured only at power up, and when EN is taken high, to set the threshold level. Additionally, register 0x04 holds the Short Circuit Threshold level, changeable through the I2C compatible serial interface. For information about the Short Circuit Threshold register and the serial interface see the “MSL3040/50/60/80/86/87/88 Programming Guide”. Atmel MSL3080 Datasheet 8 String 60mA LED Driver with Integrated Boost Controller 17 Figure 9.1 Open-Circuit and Short-Circuit Detection Block Diagram 9.5 Boost Regulator The boost regulator boosts the input voltage to the regulated output voltage that drives the LED anodes. The MSL3080 boost regulator uses an external MOSFET switch and current sense resistor, allowing a wide variety of input/output voltage combinations and load currents. The boost regulator switching frequency is 625kHz. Switching frequencies of 350kHz, 500kHz, 750kHz, 875kHz and 1Mhz are also available; contact the factory for information. Atmel MSL3080 Datasheet 8 String 60mA LED Driver with Integrated Boost Controller 18 9.6 The Efficiency Optimizer (EO) MSL3050/MSL3060/MSL3080 Datashee Prelimi A voltage the boost regulator output voltage to FB sets the regulation voltage (RTOP 8.1 oninto page 14). BOTTOM in Figure power divider supplyfrom noise rejection, while minimizing power dissipation. It does thisand byRinjecting a current the FB The EO improves power efficiency by dynamically adjusting the power supply output voltage to the minimum required to power the LEDs. 256 steps (8-bit resolution). This ensures that there is sufficient voltage available for LED current regulation, and good power supply noise rejection, while minimizing power dissipation. It does this by injecting a current into the FB input over 256 steps (8-bit resolution). input ov When turned on, either by applying input voltage to VIN while EN is high, or by driving EN high with voltage applied to When on, either by applying voltage to cycle VIN while is high, or by high with voltage applied VIN, the EO regulators begins VIN,turned the EO begins an initialinput calibration by EN monitoring thedriving LED EN current regulators. If alltothe current anmaintain initial calibration cycle by monitoring thethe LED current regulators. current regulators maintain LED current regulation theAfter EO the 4ms LED current regulation EO output currentIf all is the increased to reduce the boost output voltage. output current is increased to reduce the boost output voltage. After the 4ms power supply settling time, it rechecks the regulators, and power supply settling time, it rechecks the regulators, and if they continue to maintain regulation the process repeats u if they continue to maintain regulation the process repeats until one or more current regulator loses regulation. This step requires that or more current regulation. This step requires thatdecreases the strings are turned for a minimum of 3 µs theone strings are turned on forregulator a minimumlooses of 2 µs to detect current regulation. The EO then the output currenton to increase boost detect current regulation. EOheadroom then decreases the outputwith current to power increase boost The output voltage, giving the regula output voltage, giving the regulatorThe enough to maintain regulation minimal dissipation. oscilloscope picture 1 second, and at any time increases the boost voltage Figure 9.2 shows this procedure. The EO automatically re-calibrates enough headroom to maintain regulation with minimal Vpower dissipation. The oscilloscope picture Figure 7 shows this OUT every when detects anThe LED EO stringautomatically with insufficient re-calibrates current. procedure. VOUT every 1 second, and at any time increases the boost voltage when detects an LED string with insufficient current. Figure 9.2 Efficiency Optimizer (EO) Figure 7. Efficiency Optimizer (EO) SETTING THE BOOST REGULATOR OUTPUT VOLTAGE Select the voltage divider resistors (RTOP and RBOTTOM in Figure 5 on page 14) to set the boost regulator output voltage first determining VOUT(MIN) and VOUT(MAX), the required minimum and maximum LED string anode power supply (boost regulator) voltage, using: MSL3050/60/80 preliminary datasheet revision 0.1 © Atmel Inc., 2011. All rights reserved. Page 19 of 24 Atmel MSL3080 Datasheet 8 String 60mA LED Driver with Integrated Boost Controller 19 OUT ( in MAX MAX total ) LEDs a) string,f (the minimum and maximum voltage drop across a string is 35V and 38V. Adding allowance of 0. for the current regulator headroom brings VOUT(MIN) to 35.5V and VOUT(MAX) to 38.5. Next determine RTOP using: where Vf(MIN) and Vf(MAX) are the LED’s minimum and maximum forward voltage drops at the full-scale current set by RI (page 14). For( MAX example, if the LED minimum forward voltage is Vf(MIN) = 3.5V and maximum is Vf(MAX) = 3.8V, using 10 VOUT ) VOUT ( MIN ) . RTOP in a string, the total LEDs 6 minimum and maximum voltage drop across a string is 35V and 38V. Adding allowance of 0 365 10 for the current regulator headroom VOUT(MIN) to 35.5V and VOUT(MAX) to 38.5. Next determine RTOP using: 9.7 Setting the Boost Regulator Outputbrings Voltage MSL3050/M MSL3050/MSL3060/MSL3080 Datash Pr Then the determine Select voltage divider resistors (RTOP and RBOTTOM in Figure 8.1 on page 14) to set the boost regulator output voltage by first BOTTOM VVOUT ( MAXRand VOUTusing: VOUT ( MIN V f ( MIN # ofLEDs 0.5 , and ) V ( MIN ) anode supply regulator)voltage, determining ) power ) (boost OUT(MIN) OUT(MAX), the required minimum and maximum LED string . R TOP 6 using: 365 10 2.5 V .0.5 , ( MAX ) RV f ( MAX ) # ofLEDs ROUT BOTTOM TOP 0.5 , and VOUT ( MIN) V OUT # ofLEDs 2 . 5 f ( MIN ) (MAX ) VOUT ( MAX ) V f ( MAX ) # ofLEDs 0.5 , and Then determine RBOTTOM using: where Vf(MIN) and Vf(MAX) are the LED’s minimum and maximum forward voltage drops at the full-scale current set by RI and Vf(MAX) are minimum and max V=f(MIN) 3.5V and maximum Vf(MAX) = 17). 3.8V, using 10 (pageVf(MIN) 14).and ForVf(MAX) example, the minimum voltage iswhere Vf(MIN)at where are theifLED’s and maximum voltage drops the full-scale current set the byis RLED’s (page ILED V LED #minimum ofLEDs 0forward .5 , forward OUT ( MAX ) V f ( MAX2) .5 (page 16). For example, if the LED minimum forward volt = 3.5V and maximum is V = 3.8V, using 10 LEDs in a string, the total For example, if the LED minimum forward voltage is V f(MIN) f(MAX) LEDs in a string, the total minimum and maximum voltage drop across a string is 35V and 38V. Adding allowance of 0 RTOP . R BOTTOM minimum and maximum voltage drop across a string V is 35V and to 38V. Addingand allowance ofa0.5V for the current regulator headroom brings LEDs in string, the total minimum and maximum voltag 2 . 5 V 35.5V V to 38.5. Next determine R using: for the current regulator headroom brings OUT(MIN) OUT(MAX) TOP OUT AND (MAX ) OUTPUT CAPACITORS COUT(MIN) HOOSING THE NPUT V to 35.5V andIV to 38.5. RTOP using:and maximum and Vf(MAX) areNext thedetermine LED’s minimum voltage drops at the brings full-scale currenttoset where Vf(MIN) OUT(MAX) 35.b for the forward current regulator headroom VOUT(MIN) 3.5Vregulator and maximum is Vf(MAX) 3.8V, using (page 16). For example, the LED forward voltage is V The input and output capacitorsif carry the minimum high frequency current due tof(MIN) the =boost switching. The =input capac VOUT VOUT ( MAX )frequency ) minimum a string, the( MIN total maximum dropvoltage across a string is 35V and 38V. Adding prevents current travelling back voltage to the input source, reducing conducted andallowance radiated VOUT ( MAX thisinhigh . from and RTOP LEDs ) VOUT ( MIN ) 6 to 35.5V and VOUT(MAX) to 38.5. Next determine Rprevents current regulator headroom VOUT(MIN) noise. for Thethe output prevents highbrings frequency current to R the load, in this case the LEDs, and also TOP using: , 10 365capacitor TOP 6 CHOOSINGand THE INPUTnoise. AND O UTPUT CAPACITORS 10boost conducted radiated The output capacitors also have a large effect365 on the regulator loop stability and -6 Where 350 xresponse, 10 isV the maximum EO output current. transient and so are critical to optimal boost regulator operation. V The and output capacitors carry the high frequency current due to the boost regulator switching. The input capac using: Theninput determine R BOTTOM OUT ( MAX ) OUT ( MIN ) -6 high frequency current , travelling back to theWhere RTOP is the reducing maximumconducted EO outputand current. 3.65x10source, prevents this from input voltage radiated 6 Then determine RBOTTOM 365 using: 10 noise. The output capacitor high frequency current to the load, in this case the LEDs, and also prevents 2.prevents 5 using: determine RBOTTOM and . CAPACITORS RHOOSING R conducted radiated output capacitors also haveThen a large effect on the boost regulator loop stability and C THE INPUT AND OThe UTPUT -6 noise. BOTTOM TOP is(MAX the maximum outputboost current. Where 3.65x10 2.5 toEO V transient response, and are optimal regulator operation. OUTso ) critical Use ceramic input and output capacitors that keep their rated capacitance values at the expected operating voltages. T .5 TypicalThen Application Circuit on page 10 shows recommended values for and LEDs and2120mA per using: determine RBOTTOM R10 ,string. Use a bulk R BOTTOM TOP electrolytic capacitor where power enters the circuit board. 2 . 5 V OUT (MAX ) 9.8 Choosing the Input and output Capacitors where 2.5V is the internal reference voltage. CHOOSING THE INPUT AND OUTPUT CAPACITORS 2.5 CHOOSING THE IR NPUT ANDthe Ohigh UTPUT Cthat APACITORS , keepdue capacitors carry Rand The input output frequency current to the boostcapacitance regulator switching. input prevents this highvoltages. T Use ceramic input and capacitors their rated values at thecapacitor expected operating BOTTOM TOP output where 2.5V is theThe internal reference voltage. 2 . 5 V frequency current from travelling back to the input voltage source, reducing conducted and radiated noise. The output capacitor prevents OUT (MAX ) Typical Application Circuit on page 10 shows recommended values for and 10 LEDs and 120mA per string. Use capac a bulk C HOOSING THE I NDUCTOR The input and output capacitors carry the high frequency current due to the boost regulator switching. The high input frequency current to the load, in this case the LEDs, and also prevents conducted and radiated noise. The output capacitors also have a large electrolytic capacitor where power enters the circuit board. prevents this high frequency current from travelling back to the input voltage source, reducing conducted and radiated The boost regulator inductor takes current from and thesoinput source and directs that current to the load. Using the prop effect on the boost regulator loop stability andthe transient response, are critical to optimal boost regulator operation. Regulator Components 2.5V to is the internal reference noise.where The output capacitor prevents high voltage. frequency toOther theinductor load,Boost inwith this sufficient case the LEDs, and also prevents inductor is critical proper boost regulator operation.current Choose an inductance to keep the induct Use the component values shown in the Typical Applicat conducted and radiated noise. The output capacitors also have a large effect on the boost regulator loop stability and Use ceramic input and output capacitors that keep their rated capacitance values at the expected operating voltages. The Typical ripple current within limits, and with sufficient current handling capability for steady-state and transient conditions. Application Circuit onIpage 10so shows values for and 10regulator LEDs and 60mA perrequired string. Useuse a bulk electrolytic capacitor where in the fol design is the guidelines presented transient response, and arerecommended critical to optimal boost operation. C HOOSING THE NDUCTOR Other Boost power enters the circuit board. Regulator Components The causes current inductor. The current rises during on-time The boost boost regulator regulator switching inductor takes theripple current from through the inputthe source and directs that current to thethe load. Usingand the falls prop Use the component values shown in the Typical Applications Circuits THE beginning page 10. When custom boost C HOOSING INPUTonAND OUTPUT Ckeep APACITORS during the off time.toThe slope of the inductoroperation. current is Choose a function of the voltage across the inductor, and so the total inductor is critical proper boost regulator an inductor with sufficient inductance to the induct 9.9 Choosing the Inductor design is required use the guidelines presented in the following sections. CHOOSING THE INPUT Owith UTPUT CAPACITORS the current slope multiplied the time in input that phase (on time, tON , ortransient off time, thigh InPrelimina steadychange in current, ∆Ilimits, ripple current within and sufficient current by handling capability for steady-state and L, is AND OFF). frequency The and output capacitors carry theconditions. state, where the load current, input voltage, and output voltage are all constant, the inductor current does not change The regulator inductor the current from the inputkeep source and directs current to the load. Using the expected proper inductor is critical prevents this high frequency current from travelling backoT Useboost ceramic input andtakes output capacitors that their rated that capacitance values at the operating voltages. C HOOSING THE I NPUT AND O UTPUT C APACITORS V V to proper boost regulator operation. Choose an inductor with sufficient inductance to keep the inductor ripple current within limits, and with one cycle, and so the amount the current rises during the on time is the same as the amount the current drops during The boost regulator switching causes ripple current through the inductor. The current rises during the on-time and noise.for The output capacitor prevents high frequency curr OUT IN Typical Application Circuit on page 10 shows recommended values and 10 LEDs and 120mA per string. Use a falls bulkt , the D time. sufficient current handling capability forof steady-state and transient conditions. off Calculate duty cycle (equal to the on-time divided by the switching period) using: The input and output capacitors carry the high frequency current due to the boost regulator switching. The input c during the off time. The slope the inductor current is a function of the voltage across the inductor, and so the total conducted and radiated noise. The output capacitors also electrolytic VINcapacitor where power enters the circuit board. prevents this∆I high frequency current from travelling back to the input voltage source, reducing conducted and radi , is the current slope multiplied by the time in that phase (on time, t , or off time, t ). In steady change in current, transient response, and so are critical to optimal boost re L causes ripple current through the inductor. The current rises during the on-time and falls ON during the off time. OFF The boost regulator switching noise. The output capacitor high frequency current toall the load, in the this case ΔI the LEDs, and state, where the load current, inputprevents voltage, and output voltage are constant, inductor current doesalso not prevents change o V V The slope of the inductor current is a function of the voltage across the inductor, and so the total change in current, L, is the current slope OUT IN output voltage and V the input voltage.also have a large effect on the boost regulator loop stability where VOUT is the,and IN isoutput D cycle, conducted radiated noise. The capacitors one and so the amount the current rises during the on time is the same as the amount the current drops during t , or off time, t ). In steady-state, where the load current, input voltage, and output voltage multiplied by the time in that phase (on time, t ON OFF CHOOSING THE INDUCTOR VIN the transient response, sonot are critical toone optimal boost regulator operation. are constant, inductor does change cycle, and so the amount current rises duringAND the onO time is the same as off all time. Calculate the current dutyand cycle (equal toover the on-time divided by the the switching period) using: C HOOSING THE I NPUT UTPUT C APACITORS Calculate the on-time induring seconds The boost regulator inductor takes theCalculate currentthe from and directs that the using: load. Using the prop the amount the current drops the offusing: time. dutythe cycleinput (equalsource to the on-time divided by the current switching to period) ceramicwith inputsufficient and output capacitors their r inductor is critical to proper boostand regulator operation. ChooseUse an inductor inductance to that keepkeep the induct is the output voltage V is the input voltage. where V OUT IN Vcurrent OUT Vwithin IN Typical Application Circuit on page 10 shows recommend ripple limits, and with sufficient current handling capability for steady-state and transient conditions. VININPUT AND OUTPUT CAPACITORS V , THE D fD HOOSING where theOUT boost regulator switching frequency. t ON C , SWVis electrolytic capacitor where power enters the circuit boar Calculate the IN on-time in seconds using: f V f Use ceramic input and output capacitors that keep theirthe rated capacitance valuesrises at the expected operating SW regulator IN SW The boost switching causes ripple current through inductor. The current during the on-time andvoltag falls where VOUT is the output voltage and VIN is the input voltage. Calculate the on-time in seconds using: Typical Application Circuit on page 10 shows recommended values for and 10 LEDs and 60mA per string. Use a Calculate the inductor ripple current using: during the off time. The slope of the inductor current is a function of the voltage across the inductor, and so the total thecapacitor output and VIN enters is the input voltage. whereelectrolytic VD V INvoltage OUT is V where power the circuit board. the OUT boost switching frequency. where fSW is the slope multiplied by the time in that phase time, tON, or off time, tOFF). In steady change iniscurrent, ∆IL,regulator CHOOSING THE(on INDUCTOR , current t ON V t V V V f V f state, where the load current, input voltage, and output voltage are all constant, the inductor current notfrom change IN ON IN OUT IN SW IN SW The boost regulator inductor takes the does current the ino Calculate the on-time in seconds using: , rises during the on time I L cycle,the Calculate inductor ripple current using: one and so the amount the current is the same as the amount the current drops during inductor is critical to proper boost regulator operation. Ch V INDUCTOR f SW frequency. L where fSW is theLboost regulator switching Calculate the inductor ripple current using: CHOOSING off time. Calculate THE the OUT duty cycle (equal to the on-time divided ripple by thecurrent switching period) using: within limits, and with sufficient current han Page 18 of 22 VD t ONVOUT VINVVINOUT The regulator inductor the current from the input source and directs that current to the load. Using the , VIN takes twhere IN boost ON © Inc., 2011. All rights reserved. IAtmel , Lf is the value inboost Henrys. Choose a value for L thatan produces awith ripple currentinductance in the range of 25%the to in 5 L V V critical Vf SWto inductor is regulator operation. Choose inductor sufficient keep Vinductance The boost regulator switching causes ripple to current throu SW L OUT IN IN DC proper f SW current. L ofDthe state steadycurrent state DC inductor current is equal to the input current. Estimate the INinductor steady , within ripple current limits, and withThe sufficient handling capability for steady-state and transient conditions. during the off time. The slope of the inductor current is a where L is the in Henrys. Choose a value for L that produces a ripple current in the range of 25% to 50% of the steady VINinductance steady-state DC inputvalue current using: is the current slope multiplied by t change in current, ∆I L,steady-state state DC inductor current. The steady state DC inductor current is equal to the current. Estimate the input current where L is the inductance value in Henrys. Choose a value Linput that a ripple current inDC the range ofon-time 25% toand 50 Pagefor 18 of 22theproduces inductor. theand state, where the The load current current,rises inputduring voltage, output v using: The boost regulator switching causes ripple current through © Atmel Inc., 2011. All rights reserved. of the steady state DC inductor current. The steady state DC inductor current is equal to the input current. Estimate the the output andofVthe the input voltage. whereduring VOUT isthe time. voltage The slope current is a one function of and the voltage across the current inductor,rises andduring so thethe to IN isinductor Voff cycle, so the amount OUT steady-state , ∆IL, isusing: in input I IN change I LOAD DC the current slope multiplied by the time in that phase time, tON(equal , or offtotime, tOFF). In st current, current off time. Calculate the(on duty cycle the on-time di V INtheinload Calculate thewhere on-time seconds using: state, current, input voltage, and output voltage are all constant, the inductor current does not cha where ILOAD is the sum of all strings steady-state LED currents with all LEDs on simultaneously, VOUT is the maximum (un-optimized) one cycle,Vand so the amount the current rises during the on time is the same as the amount the current drops du OUT boost regulator output voltage, and VIN is the minimum boost regulator input voltage. , the I IN off IILOAD time. Calculate duty cycle (equal to the divided byLEDs the switching period) is the sum all strings steady-state LEDon-time currents with all on simultaneously, VOUT0.1 is the maximumPa( where LOAD VOUT Vof D MSL3050/60/80 preliminary datasheetusing: revision IN Vregulator IN , t ON Atmel MSL3080 Datasheet boost regulator input voltage. optimized) boost output voltage, and VIN is the minimum © Atmel Inc., 2011. All rights reserved. 20 MSL3050/MSL3060/MSL3080 Datashee f SW V IN f SW 8 String 60mA LED Driver with Integrated Boost Controller is the sum of all steady-state LED currents with20all LEDs on simultaneously, VOUT is the where ILOAD Inductors have two types of strings maximum current RMS Page current and current. Make sure thatmaximum the peak (un MSL3050/60/80 preliminary datasheet revision 0.1 ratings, of 24 saturation minimum boost regulator input voltage, and n iswhich the boost regulator optimized) boost voltage, Vcurrent © Atmel Inc., 2011. All output rights reserved. inductor current isregulator less than the saturation Note that during load current transients, occur whenev IN is therating. Page 18 of 22 Inductors have two types of maximum current ratings, RMS current and saturation current. Make sure that the peak inductor current is less than the saturation current rating. Note that during load current transients, which occur whenever the LEDs are turned on or off (due to PWM dimming), the inductor current may overshoot its steady state value. How much it overshoots depends on the boost regulator loop dynamics. If unsure of the loop dynamics, a typical value to use for the overshoot is 50% of the steady-state current. Add half of the inductor ripple current to this value to determine the peak inductor current. With inductor ripple current in the 25% to 50% range, estimate the inductor RMS current as 115% of the DC steady state inductor current. 9.10 Setting the External MOSFET Current Limit The current sense resistor, connected from the switching MOSFET source to GND, sets the boost regulator current limit. The cycle-bycycle current limit turns-off the boost regulator switching MOSFET when the current sense input detects instantaneous current above the current limit threshold. This causes the current to drop until the end of the switching cycle. The current limit threshold is 100mV typical, and 75mV minimum. Choose the current sense resistor value to set the current limit using: where IL(MAX) is the maximum inductor current. When RCS is not equal to a standard 1% resistor value use the next lower value. 9.11 Choosing the Switching MOSFET The MSL3080 uses an external logic level MOSFET to drive the boost converter. Choose a MOSFET that can pass at least twice the peak inductor current, and that minimizes simultaneously both the MOSFET on-resistance, RDSon, and gate charge for fast switching speed. Make sure that the MOSFET drain-source voltage rating is above the maximum un-optimized boost output voltage, with some extra margin for voltage overshoot due to excess circuit board stray inductance and output rectifier recovery artefacts. Assure that the MOSFET is heat sunk to withstand the worst-case power dissipation while maintaining die temperature within the MOSFET ratings. 9.12 Choosing Outputand Rectifier Place the the MOSFET rectifier close together and as close to the output capacitor(s) as possible to reduce circuit boa radiated emissions. The output passesand the inductor the outputand capacitor and load during the switching off-time.as Duepossible to the hightoboost Place therectifier MOSFET rectifiercurrent closetotogether as close to the output capacitor(s) reduce circuit boa regulator switching frequency use a Schottky rectifier. Use a Schottky diode that has a current rating sufficient to supply the load radiated emissions. Place the and rectifier close together as close the output capacitor(s) possible to reduce circuit boa current, aMOSFET voltage rating higher than the maximum boostand regulator outputto voltage. Schottky rectifiers haveas very low on voltage L OOPand COMPENSATION radiated emissions. and fast switching speed, however at high voltage and temperatures Schottky leakage current can be significant. Make sure that the Use a power RC network from COMPspecifications. to FB to compensate the MSL3040/41 regulation loop 3 on page 12). Th rectifier dissipation is within the rectifier Place the MOSFET and rectifier close together and as (Figure close to the output LOOPseries COMPENSATION regulationas loop dynamics are sensitive to output capacitor and inductor values. To begin, determine the right-half-plan capacitor(s) possible to reduce circuit board radiated emissions. L OOP COMPENSATION Use a series RC network from COMP to FB to compensate the MSL3040/41 regulation loop (Figure 3 on page 12). Th zero frequency: regulation loop are sensitive output capacitor and values. To begin, determine Use Compensation a series RCdynamics network from COMP totoFB to compensate theinductor MSL3040/41 regulation loop (Figure 3the onright-half-plan page 12). Th 9.13 Loop zero frequency: 2 regulation loop dynamics are sensitive to output capacitor and inductor values. To begin, determine the right-half-plan V INnetwork fromRCOMP Use RC LOAD to FB to compensate the MSL3080 regulation loop (Figure 8.1 on page 14). The regulation loop zero frequency: , f a series RHPZ are sensitive2to output capacitor and inductor values. To begin, determine the right-half-plane zero frequency: dynamics L VVOUT R2LOAD IN 2 , f RHPZ R2LOAD IN L , VVOUT f x RHPZ R is the minimum equivalent load resistor, or where =LOAD 2L VOUT is the minimum equivalent load resistor, or where R equivalent load resistor, or where . R LOAD RLOAD is the minimum LOAD where RLOAD is V the minimum equivalent load resistor, or OUT I OUT V (MAX ) R LOAD VOUT . OUT (MAX ) . I OUT R LOAD The output capacitance and type of capacitor affect the regulation loop and method of compensation. In the case of I OUT (MAX )the zero caused by the equivalent series resistance (ESR) is at such a high frequency that it is not ceramic capacitors The output capacitance and type of capacitor affect the regulation loop and method of compensation. In the case of ceramic capacitors The output capacitance and type of capacitor affect thearegulation method ofso compensation. In the case the zero caused byIn the equivalent resistance is at such high frequency thatand it issignificant, not of consequence. In be the considered case of consequence. the case ofseries electrolytic or(ESR) tantalum capacitors the loop ESR is must whenof electrolytic or tantalum capacitors the ESR is significant, so must be considered when compensating the regulation loop. Determine the ceramic capacitors the zero caused by the equivalent series resistance (ESR) is at such a high frequency that it isofnot The output capacitance and type capacitor the affect thezero regulation loopby and of compensation. In the case compensating the regulation loop.ofDetermine ESR frequency themethod equation: ESR zero frequency the equation: consequence. Inbythe case ofcaused electrolytic or tantalum capacitors the ESR(ESR) is significant, so amust considered ceramic capacitors the zero by the equivalent series resistance is at such highbe frequency thatwhen it is not compensating In thethe loop. Determine the ESR zero frequency byisthe equation:so must be considered when consequence. case of electrolytic or tantalum capacitors the ESR significant, 1regulation f ESRZ compensating the regulation loop. Determine the ESR zero frequency by the equation: 2 ESR 1 C OUT f ESRZ 1 ofthe 2isthevalue ESR C OUT where output capacitor, and ESR is the Equivalent Series Resistance of the output capacitor. Assure that the loop f ESRZCOUT OUT is the value of the output capacitor, and ESR is the Equivalent Series Resistance of the output capacitor. where C crossover frequency is at least 1/5th of the ESR zero frequency. 2 ESR C OUT Assure that the loop crossover frequency is at least 1/5th of the ESR zero frequency. where COUT is the value of the output capacitor, and ESR is the Equivalent Series Resistance of the output capacitor. th th of the ESR zero Assure loop crossover frequency is at least 1/5 is the value of the output capacitor, and ESR isthe thelower Equivalent Series Resistance the output capacitor. where Cthat OUT the of of thefrequency. ESR zero fESRZ, theofright-half-plane zero fRH Next determine the desired crossover frequency as 1/5 th of the ESR zero frequency. Assure that the loop crossover frequency is at least 1/5 or the switching frequency fSW. The crossover frequencyth equation is: Next determine the desired crossover frequency as 1/5 of the lower of the ESR zero fESRZ, the right-half-plane zero fR . The crossover frequency is: of the ESR zero fESRZ, the right-half-plane zero fR or thedetermine switching the frequency of the lower Next desiredfSW crossover frequency as 1/5th equation equation R R 1 COMP LOAD . The crossover frequency is: or the switching frequency f Atmel MSL3080 Datasheet SW fC , 21 8 String 60mA LED Driver with Integrated Boost Controller RCS 2 RLOAD RLOAD TOP 11 RRCOMP 1 C OUT f C R RLOAD , 1 C RCOMP 11 RCS 2 RLOAD TOP OUT , voltage divider resistor (from the output voltage to FB), RCOMP f C fC is the crossover RTOP is the top side frequency, where crossover is: zero frequency. or the switching frequency fSW. The of the ESR Assure that the loop crossover frequency is at frequency least 1/5thth equation of the lower of the ESR zero fESRZ, theof right-half-plane zero fRH Next determine the desired crossover frequency as 1/5 Series Resistance the output capacitor. where COUT is the value of the output capacitor, and ESR is the Equivalent th . The crossover frequency equation is: orAssure the switching frequency f SW thelower ESR of zero the 1/5 Rthat loop Rcrossover frequency th ofofthe thefrequency. ESR zero fESRZ, the right-half-plane zero fRH Next determine frequency as 1/5 1is at least COMP the desired LOAD crossover , f . The crossover frequency thequation is: orCthe switching frequency fSW RCS crossover TOP LOAD RRCOMP 11R 2 Rfrequency of the lower of the ESR zero fESRZ, the right-half-plane zero fR the Next determine desired as 1/5 1 C OUT LOAD f Next determine the desired as 1/5th offrequency the lower the ESR zero C the switching crossover , of equation . The crossover is:fESRZ, the right-half-plane zero fRHPZ or the or frequency fSWfrequency Rfrequency fSW.11 LOAD Cis:OUT RCOMP RCS frequency 2 RLOAD R 1 switching The crossover equation TOP is the crossover frequency, R is the top side voltage divider resistor (from the output voltage to FB), RCOMP where f C TOP fC , the resistor of the series RC compensation network. Rearranging the factors of this equation yields the solution for RCO R 11 R 2 R C CS LOAD OUT RTOP RLOAD 1 the crossover frequency, RTOP is the top side, voltage divider resistor (from the output voltage to FB), RCOMP where as: f C fC isCOMP the resistor network. the factors of this equation yields the solution for RCO C OUTRearranging R of the RCS compensation RLOAD series 11 RC 2RTOP voltage divider the crossover frequency, is the top side resistor (from the output voltage to FB), RCOMP where fC is TOP as: RCOMP R ofcrossover 11 frequency, RCSRC 2compensation RTOP isf Cthe top C OUT . voltage divider the resistor the series network. Rearranging the the factors this equation yields solution for RCO side resistor (from outputof voltage to FB), RCOMP is thethe resistor of where fC is theTOP iscompensation the crossover frequency, RTOP the top side voltage divider resistor the output voltage to FB), RCOMP where as: the seriesfC RC network. Rearranging theisfactors of this equation yields the solution for R(from COMP as: Rthe RTOP 11 accurate RCS RC 2compensation f C OUT network. . resistor of the series Rearranging of this equation yields the solution for RC COMP These equations are if theCcompensation zero (formed bythe thefactors compensation resistor R COMP and the as: at a. lower frequency than crossover. Therefore the next step is to choose the compensation RCOMP RTOP capacitor 11 RCSCCOMP 2) happens f C C OUT These equations are accurate if the compensation zero (formed resistoror: RCOMP and the of the the compensation crossover frequency, compensation capacitor such that the compensation zero is 1/5thby ) happens at a lower frequency than crossover. Therefore the next step is to choose the compensation capacitor C R R 11 R 2 f C . COMP These equations are accurate if the compensation zero by the(formed compensation resistor RCOMP and the compensation COMP TOP CS C OUT(formedzero and the These equations are accurate if the compensation resistor RCOMPcapacitor thby the compensation of the crossover frequency, or: compensation capacitor such that the compensation zero is 1/5 CCOMP) happens at a lower frequency than crossover. Therefore the next step is to choose the compensation capacitor such that the f C capacitor CCOMP 1 ) happens at a lower frequency than crossover. Therefore the next step is to choose the compensation compensation zero is 1/5th of the crossover frequency, or: fThese . COMPZ equations are accurate if the bythe thecrossover compensation resistor frequency, or:RCOMP and the compensation capacitor such that thecompensation compensationzero zero(formed is 1/5th of 5 2 R C COMP f C capacitorCOMP 1 ) happens at a lower frequency than crossover. Therefore the next step is to choose th compensation CCOMP fcompensation . COMPZ = =capacitor such that the compensation zero is 1/5th of the crossover frequency, or: 5 2 R C f x x 1 COMP COMP Solving for CCCOMP: fExample: . COMPZ Solving for CCOMP 5 : 2 RCOMP C COMP 1 C :5 Solving for CfCOMP f COMPZ . As an example, set the maximum (un-optimized) output voltage to 39V, using voltage divider as follows: Example: C . 5 2 R C = COMP COMP COMP Example: 49.9k RTOP =for : Solving C COMP x x 2 RCOMP fC 5 = 3.40kset RBOTTOM Example: C . As an example, the maximum (un-optimized) output voltage to 39V, using voltage divider as follows: COMP As an example, (un-optimized) output voltage to 39V, using voltage divider as follows: :5 the maximum Solving for 2CCOMP Rset fC RTOP = 49.9k COMP Example: = 49.9k R C . TOP Let theexample, load current be 800mA maximum, use 10uH inductor, output a 12V as input voltage, a 12m R an set the maximum (un-optimized) output voltage to 39V, usingcapacitor, voltage divider follows: COMP Page 20 ofa2220F RAs BOTTOM =23.40k 2011. R Allfrequency = 3.40k R C(un-optimized) BOTTOM © Atmel 5rightsfreserved. and the switching is 625kHz. =Inc., 49.9k R TOPexample, As an set theCOMP maximum output voltage to 39V, using voltage divider as follows: CBOTTOM . COMP = 3.40k Page 20 of 22 R Let the load2current be 800mA maximum, use 10uH inductor, a 20F output capacitor, a 12V input voltage, a 12m R R f COMP C =the 49.9k RLet © Atmel Inc., 2011. All rights reserved. load current be 800mA maximum, use 10uH inductor, a 20F output capacitor, a 12V input voltage, a 12m R TOP V V 39 and the switching frequency is 625kHz. Page 20 of 22 OUT = 3.40k Rand BOTTOM the switching frequency is 625kHz. R 48 . 75 Let the load current be 800mA maximum, use 10uH inductor, a 20F output capacitor, a 12V input voltage, a 12m R LOADInc., 2011. All rights reserved. © Atmel I LOAD frequency 0.8 A and the switching is 625kHz. Let the load current be 800mA maximum, use 10uH inductor, a 20µF Page output20 capacitor, of 22 a 12V input voltage, a 12mΩ RCS, and the V 39V RLOAD 2 LOAD IIVLOAD AA 48.75 2 039 ..88V OUT 0 V 48.75 12 LOAD IN Rf LOAD RLOAD 48.75 73kHz RHPZ I LOAD 0.8 A 6 39 V 2 L 2 10 10 2 2 OUT V 2 R 48 12 2 48..75 75 6 73kHz ffRHPZ VININ 2 RLOAD LOAD 12 th 2 39 1/5 RHPZ frequency 73kHz LL to fRHPZ : 2 10. Set the crossover R22LOAD 12 OUT VVV IN 39 10 75 10 10 6 73kHz 2 48 f RHPZ OUT 6 2L to 1/5th39f : 2 10 10 VOUT frequency f RHPZ Set the crossover th RHPZ fRHPZ: Set crossover 1/5 . fto f Cthethe 14frequency .6kHz Set crossover frequency to 1/5th : RHPZ 5 Set the crossover frequency to 1/5th fRHPZ: ffRHPZ ffC calculate RHPZ 14.6kHz . Next resistor value to achieve the 15kHz crossover frequency, or 14.6compensation kHz . C 55 the f RHPZ fC 14.6kHz . Next calculate compensation value the 15kHz crossover frequency, RCOMP 5Rthe 11 RCSresistor 2 f C to achieve Cvalue .9k 11the .025 2crossover or15k frequency, 20 F 25or.9k Next calculate the compensation resistor to49 achieve 15kHz TOP OUT VOUT V reserved. switching frequency is625kHz. © Inc., 2011. All39 rights R Atmel 48.75 OUT Next calculate the compensation resistor value to achieve the 15kHz crossover frequency, or Next calculate the compensation resistor value to achieve the 15kHz crossover frequency, or the compensation zero of.9the crossover frequency, o Then compensation R RRTOP the 11 RRCS 22 ffcapacitor, C 49 ..9,9kto set 11 ..025 22 15 kk 20 to FF1/5 th25 COMP COMPcalculate C OUT C R 11 C 49 k 11 025 15 20 25 . 9kk COMP TOP CS C OUT 3kHz RCOMP Rthe 11 RCS capacitor, 2 fCCCOMP C 49 .9k 11 zero .025to1/5th 2 of 15 20 Ffrequency, th 25.9or k3kHz Then calculate , toOUT set the compensation the kcrossover TOPcompensation Then calculate the compensation capacitor, CCOMP, to set the compensation zero to 1/5 th of the crossover frequency, o Then calculate the compensation capacitor, 1 1 CCOMP, to set the compensation zero to 1/5 th of the crossover frequency, o 3kHz C COMPcalculate .1nF 3kHz the. compensation zero to 1/5 of the crossover frequency, o Then the compensationcapacitor, CCOMP,to2set 2 R f 2 25 k 3 k COMP COMPZ 3kHz 1 11 resistors and compensation resistor/capacitors as close to the MSL3040/41 When laying out the circuit1board, place the voltage divider C 22..11nF . COMP 2 to25 asCpossible trace COMP and FB. nF . COMP and 22minimize RRCOMP lengths ffCOMPZconnected k 3 k 1 1 2 the 25kvoltage 3k divider COMP C COMPlaying out the 2.1nF resistors . When circuitCOMPZ board,place and compensation resistor/capacitors as close to 2 as Rpossible 2 trace 25k lengths 3k connected to COMP and FB. MSL3040/41 minimize COMP fand COMPZ When laying out the circuit board, place the voltage divider resistors and compensation resistor/capacitors as close to When laying out the circuit board, place the voltage divider resistors and compensation resistor/capacitors as close to MSL3040/41 as possible and minimize trace lengths connected to COMP and FB. LED Dimming Control MSL3040/41 as possible and minimize lengthsdivider connected to COMP and FB. When laying out the circuit board, placetrace the voltage resistors and compensation resistor/capacitors as close to MSL3040/41 as possible and minimize trace lengths connected to COMP and FB. 2 LED Dimming EXTERNAL AND Control IControl C CONTROL OF LED BRIGHTNESS LED Dimming Control MSL3040 LED brightness using Pulse Width Modulation (PWM) with a PWM signal applied to the external PW LED Dimming Atmel MSL3080 Datasheet 2Control input. The PWM signalsOF (outputs) take the frequency and8duty cycle the signal but are staggered in t 22 E XTERNAL AND dimming I LED BRIGHTNESS 2C CONTROL String 60mA LEDof Driver withinput Integrated Boost Controller E XTERNAL AND I C CONTROL OF LED BRIGHTNESS so that they start at evenly spaced intervals relative to the PWM input signal. When one or more strings are disabled 2 Control MSL3040 LED brightness using Pulse Width Modulation (PWM) with a PWM signal applied to the external PWb E XTERNAL AND CC ONTROL LED BRIGHTNESS Control MSL3040 brightness using Pulse Width Modulation (PWM) with a enabled PWM signal applied to the external PW fault response, theILED stagger delaysOF automatically re-calculate for the remaining strings. input. The PWM dimming signals (outputs) take the frequency and duty cycle of the input signal but are staggered in ti input. The PWM dimming signals (outputs) takeWidth the frequency and duty cycle the input signal but are staggered t Control MSL3040 LED brightness using Pulse Modulation (PWM) with aofPWM signal applied to the external in PW 10.0 LED Dimming Control 10.1 External and I2C Control of LED Brightness Control LED brightness using Pulse Width Modulation (PWM) with a PWM signal applied to the external PWM input. The LED PWM dimming occurs at the same frequency and duty cycle as the input signal. For all drivers, use PWM input frequency between 20Hz and 50kHz and duty cycle between 0% and 100%. Additionally, internal registers, accessed using the I2C compatible serial interface, allow control of the PWM dimming frequency and duty cycle. For programming details see the “MSL3040/50/60/80/86/87/88 Programming Guide”. 11.0 Ordering Information Table 11.1 Ordering Information PART MSL3080-IU Atmel Corporation 2325 Orchard Parkway San Jose, CA 95131 USA Tel: (+1)(408) 441-0311 Fax: (+1)(408) 487-2600 www.atmel.com DESCRIPTION PKG 8-CH LED driver with integrated boost controller and resistor based LED Short Circuit threshold setting, with single PWM input. Atmel Asia Limited Unit 01-5 & 16, 19F BEA Tower, Millennium City 5 418 Kwun Tong Road Kwun Tong, Kowloon HONG KONG Tel: (+852) 2245-6100 Fax: (+852) 2722-1369 Atmel Munich GmbH Business Campus Parkring 4 D-85748 Garching b. Munich GERMANY Tel: (+49) 89-31970-0 Fax: (+49) 89-3194621 24 pin 4 x 4 x 0.75mm VQFN Atmel Japan 9F, Tonetsu Shinkawa Bldg. 1-24-8 Shinkawa Chuo-ku, Tokyo 104-0033 JAPAN Tel: (+81)(3) 3523-3551 Fax: (+81)(3) 3523-7581 © 2012 Atmel Corporation. All rights reserved. / Rev.: MSL3080 Datasheet DBIE-20120814 Atmel®, logo and combinations thereof, and others are registered trademarks or trademarks of Atmel Corporation or its subsidiaries. Other terms and product names may be trademarks of others. Disclaimer: The information in this document is provided in connection with Atmel products. No license, express or implied, by estoppel or otherwise, to any intellectual property right is granted by this document or in connection with the sale of Atmel products. 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Atmel does not make any commitment to update the information contained herein. Unless specifically provided otherwise, Atmel products are not suitable for, and shall not be used in, automotive applications. Atmel products are not intended, authorized, or warranted for use as components in applications intended to support or sustain life. Atmel MSL3080 Datasheet 8 String 60mA LED Driver with Integrated Boost Controller 23