LT3599IUH

FeaTures n n n n n n n n n n n n n n n LT3599 4-Channel 120mA LED Driver with ±1.5% Current Matching DescripTion The LT®3599 is a fixed frequency 2A step-up DC/DC converter designed to drive four strings of 120mA LEDs up to a 44V output voltage. The switching frequency is programmable from 200kHz to 2.1MHz through an external resistor. LED dimming can be achieved with analog dimming on the CTRL pin, and with pulse width modulation dimming on the PWM pin. The LT3599 accurately regulates LED current even when the input voltage is higher than the LED output voltage. Additional features include programmable LED current derating, switching frequency synchronization to an external clock, LED string disable control, OPENLED alert pin, SHORTLED alert pins and programmable maximum output voltage when all LED strings are disconnected. The LT3599 is available in the thermally enhanced 32-pin (5mm × 5mm) QFN and 28-pin TSSOP packages. L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. True Color PWM is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents, including 7199560. True Color PWMTM Dimming Ratio Up to 3000:1 Drives Four Strings of LEDs at Up to 120mA ±1.5% Accurate LED Current Matching Wide Input Voltage Range: 3.1V to 30V Output Voltage Up to 44V Regulates LED Current Even When VIN > VOUT Disconnects LEDs in Shutdown Programmable Maximum VOUT (Regulated) Open/Short LED Protection and Fault Flags Programmable LED Current Derating Adjustable Frequency: 200kHz to 2.1MHz Synchronizable to an External Clock Analog Dimming Up to 20:1 Programmable Input UVLO with Hysteresis Thermally Enhanced 32-Pin (5mm × 5mm) QFN and 28-Pin TSSOP Packages applicaTions n n Automotive Navigation TFT LCD Displays Desktop and Notebook TFT LCD Displays Typical applicaTion 90% Efficient 12W LED Driver PVIN 8V TO 24V 3.3µF VIN 200k 100k VIN VIN 3.1V TO 5.5V 100k 1µF VIN SW VO_SW 1M FB VOUT 10µH 4.7µF 2 LED Current Matching 1.5 1.0 0.5 0 –0.5 –1.0 ALL FOUR LED STRINGS 31.6k 33.2k 53.6k 53.6k TSET 80.6k DISABLE4 ISET SS 16.5k LED1 LED2 LED3 LED4 GND VC 47nF 10k 2.2nF MATCHING (%) 3599 TA01a PWM SHORTLED OPENLED SHDN/UVLO PWM SYNC LT3599 CTRL RT VREF 31.6k 80mA PER STRING –1.5 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 3599 TA01b 100pF 3599fd  LT3599 absoluTe MaxiMuM raTings (Note 1) VIN, SHDN/UVLO, OPENLED, SHORTLED .................. 30V SHDN/UVLO Pin Above VIN......................................... 3V SW ............................................................................45V VOUT, VO_SW..............................................................45V LED1, LED2, LED3, LED4 ..........................................45V PWM, SYNC, CTRL, FB, TSET, DISABLE4 .................... 6V VC, SS ......................................................................... 3V VREF, RT, ISET.............................................................. 2V Operating Junction Temperature Range (Note 2) LT3599E/LT3599I .............................. –40°C to 125°C LT3599H ............................................ –40°C to 150°C Maximum Junction Temperature LT3599E/LT3599I ............................................. 125°C LT3599H ........................................................... 150°C Storage Temperature Range .................. –65°C to 150°C Lead Temperature (Soldering, sec) (Note 5) ......... 300°C pin conFiguraTion SW VOUT VO_SW LED1 LED2 LED3 LED4 DISABLE4 SHORTLED 1 2 3 4 5 6 7 8 9 29 28 VIN VIN SW NC NC NC 27 SHDN/UVLO 26 NC 25 GND 24 VREF 23 SS 22 RT 21 PWM 20 NC 19 SYNC 18 NC 17 TSET 16 FB 15 VC VOUT 1 VO_SW 2 LED1 3 LED2 4 LED3 5 LED4 6 DISABLE4 7 SHORTLED 8 9 10 11 12 13 14 15 16 OPENLED ISET VC FB CTRL TSET NC NC 33 SHDN/UVLO TOP VIEW TOP VIEW NC 32 31 30 29 28 27 26 25 24 NC 23 NC 22 GND 21 VREF 20 SS 19 RT 18 PWM 17 SYNC NC 10 OPENLED 11 NC 12 ISET 13 CTRL 14 FE PACKAGE 28-LEAD PLASTIC TSSOP TJMAX = 125°C, θJA = 28°C/W , θJC = 10°C/W EXPOSED PAD (PIN 29) IS GND, MUST BE SOLDERED TO PCB UH PACKAGE 32-LEAD (5mm 5mm) PLASTIC QFN TJMAX = 125°C, θJA = 34°C/W EXPOSED PAD (PIN 33) IS GND, MUST BE SOLDERED TO PCB orDer inForMaTion LEAD FREE FINISH LT3599EFE#PBF LT3599IFE#PBF LT3599HFE#PBF LT3599EUH#PBF LT3599IUH#PBF TAPE AND REEL LT3599EFE#TRPBF LT3599IFE#TRPBF LT3599HFE#TRPBF LT3599EUH#TRPBF LT3599IUH#TRPBF PART MARKING* LT3599FE LT3599FE LT3599FE 3599 3599 PACKAGE DESCRIPTION 28-Lead Plastic TSSOP 28-Lead Plastic TSSOP 28-Lead Plastic TSSOP 32-Lead (5mm × 5mm) Plastic QFN 32-Lead (5mm × 5mm) Plastic QFN TEMPERATURE RANGE –40°C to 125°C –40°C to 125°C –40°C to 150°C –40°C to 125°C –40°C to 125°C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. Consult LTC Marketing for information on non-standard lead based finish parts. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ 3599fd  NC LT3599 elecTrical characTerisTics PARAMETER Minimum Operating Voltage Maximum Operating Voltage Reference Voltage VREF Reference Voltage Line Regulation Maximum VREF Pin Current VREF Load Regulation Feedback Voltage FB Pin Bias Current FB Error Amp Transconductance FB Error Amp Voltage Gain Current Loop Amp Transconductance Current Loop Amp Voltage Gain VC Source Current (Out of Pin) VC Sink Current (OVP Mode) Quiescent Current Quiescent Current in Shutdown LED Current LED String Current Matching LED Open Detection Threshold (VLED–GND) LED Short Detection Threshold (VOUT –VLED) LED Regulation Voltage LED1-4 Leakage Current CTRL Pin Bias Current Switching Frequency VLED1-4 = 45V VCTRL = 0.8V (Note 3) RT = 324k RT = 53.6k RT = 20k RT = 324k RT = 53.6k RT = 20k (Note 4) ISW = 0.5A VSW = 45V, FB = 1.3V Shutdown Rising SHDN = VSD_UVLO – 50mV SHDN = VSD_UVLO + 50mV SS = 1V (Note 3) 0.4 0.3 1.28 2.5 176 0.9 1.82 97 85 70 2 LED1-4 = 0.4V, FB = 1V, VC = 1.5V LED1-4 = 0.4V, FB = 1.5V, VC = 1.5V VSHDN = 5V, PWM = 0V, Not Switching, VC = 0.7V VSHDN = 0V RISET = 13.3k 100mA LED Current FB > 1.25V 0.8 l The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 5V, VSHDN = 5V, unless otherwise noted. (Note 2) CONDITIONS l l MIN TYP 2.7 MAX 3.1 30 1.24 1.25 0.03 100 UNITS V V V V %/V µA mV V nA µmhos V/V µmhos V/V µA µA I(VREF ) = 0µA l 1.21 1.20 1.227 0.01 1 I(VREF ) = 0µA, 3.1V < VIN < 30V (Note 3) 0 < I(VREF) ≤ 100µA (Max) l 1.196 1.223 100 200 210 50 50 8 15 3 0 1.250 250 (Note 3) ∆I = 5µA 4.8 1 102 ±1.5 0.4 2.2 1 200 220 1.1 2.3 mA µA mA % V V V µA nA kHz MHz MHz mV % % % 96 99 ±0.25 0.3 1.5 0.77 0.1 100 198 1 2.06 595 98 90 80 2.5 0.10 0.2 0.7 1.36 4 0 11 TSET Voltage Maximum Switch Duty Cycle l Switch Current Limit Switch VCESAT Switch Leakage Current SHDN/UVLO Pin Threshold (VSD_SHDN) SHDN/UVLO Pin Threshold (VSD_ UVLO) SHDN/UVLO Pin Hysteresis Current Soft-Start Current PWM Input High Threshold PWM Input Low Threshold 3 5 0.95 1.44 5.5 A V µA V V µA µA µA V V 3599fd 1  LT3599 The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 5V, VSHDN = 5V, unless otherwise noted. (Note 2) PARAMETER PWM Pin Bias Current SYNC Input High Threshold SYNC Input Low Threshold SYNC Pin Bias Current VO_SW Switch Resistance OPENLED Pull-Down Current SHORTLED Pull-Down Current DISABLE4 Input High Threshold DISABLE4 Input Low Threshold Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: The LT3599E is guaranteed to meet performance specifications from 0°C to 125°C junction temperature. Specifications over the –40°C to 125°C operating junction temperature range are assured by design, characterization and correlation with statistical process controls. The LT3599I is guaranteed over the full –40°C to 125°C operating junction temperature range. 0.4 PWM = 5V; LEDx < 0.2V, OPENLED = 0.3V PWM = 5V, SHORTLED = 0.3V 1 1 1.15 SYNC = 0V (Note 3) SYNC = 3.3V 0.8 25 0.1 50 1 1000 CONDITIONS PWM = 3.3V MIN TYP 0.1 MAX 2 1.7 UNITS µA V V µA µA Ω mA mA V V elecTrical characTerisTics Note 3: Current flows out of pin. Note 4: Current limit guaranteed by design and/or correlation to static test. Current limit is independent of duty cycle and is guaranteed by design. Note 5: TSSOP package only. 3599fd  LT3599 Typical perForMance characTerisTics TA = 25°C unless otherwise specified 1.45 SHDN/UVLO Pin Turn-On Threshold (VSD_UVLO) SHDN / UVLO PIN CURRENT (µA) SHDN/UVLO Pin (Hysteresis) Current 6 5 4 3 2 1 0 –50 –25 AFTER PART TURN-OFF 0 25 50 75 100 125 150 3599 G02 500 450 VIN Current (Shutdown) 1.40 SHDN / UVLO (V) VIN CURRENT (nA) JUST BEFORE PART TURN-ON 400 350 300 250 200 150 100 50 0 –50 –25 0 25 50 75 100 125 150 3599 G03 1.35 VIN = 30V VIN = 3V 1.30 1.25 –50 –25 0 25 50 75 100 125 150 3599 G01 JUNCTION TEMPERATURE (°C) JUNCTION TEMPERATURE (°C) JUNCTION TEMPERATURE (°C) VREF 1250 SWITCHING FREQUENCY (MHz) Switching Frequency 3.0 2.5 2.1MHz 2.0 1.5 1.0 0.5 0 –50 –25 1MHz 10000 Switching Frequency vs RT 1240 VREF (mV) VIN = 30V VIN = 3V 1230 SWITCHING FREQUENCY (kHz) 1000 1220 0.2MHz 25 50 75 100 125 150 0 JUNCTION TEMPERATURE (°C) 3599 G05 1210 –50 –25 0 25 50 75 100 125 150 3599 G04 100 10 JUNCTION TEMPERATURE (°C) 100 RT (k) 1000 3599 G06 LED Current vs CTRL Pin 120 100 80 60 40 20 0 ISS (µA) (OUT OF PIN) LED CURRENT (mA) ISET = 13.3k 13 12 11 10 9 8 Soft-Start Pin Current 900 850 VTSET THRESHOLD (mV) 0 25 50 75 100 125 150 3599 G08 TSET Pin Threshold vs Junction Temperature 800 750 700 650 600 550 500 0 25 50 75 100 125 JUNCTION TEMPERATURE (°C) 150 3599 G09 0 0.2 0.4 0.8 1.0 0.6 CTRL PIN VOLTAGE (V) 1.2 3599 G07 7 –50 –25 JUNCTION TEMPERATURE (°C) 3599fd  LT3599 Typical perForMance characTerisTics TA = 25°C unless otherwise specified 2500 VC Pin Active and Clamp Voltages 100 VC HIGH LED Current vs PWM Duty Cycle 0.40 0.35 10 LED CURRENT (mA) VCESAT (V) 0.30 0.25 0.20 0.15 0.10 0.05 Switch Saturation Voltage 2000 1500 VC (V) 1000 500 VC ACTIVE 1 0.1 0 –50 –25 0 25 50 75 100 125 150 3599 G10 0.01 0.01 JUNCTION TEMPERATURE (°C) 0.1 1 10 PWM DUTY CYCLE (%) 100 3599 G11 0 0 0.5 1 1.5 ISW (A) 2 2.5 3599 G12 Switch Current Limit 2.8 2.4 SWITCH CURRENT (A) 2.0 1.6 1.2 0.8 0.4 –50 –25 1250 1245 FEEDBACK PIN VOLTAGE (mV) 1240 Feedback Pin Voltage 101 LED Current vs Temperature 1230 1225 1220 1215 1210 1205 LED CURRENT (mA) 1235 100 99 98 0 25 50 75 100 125 150 3599 G13 JUNCTION TEMPERATURE (°C) 1200 25 50 75 100 125 150 –50 –25 0 JUNCTION TEMPERATURE (°C) 3599 G14 97 –50 –25 0 25 50 75 100 125 150 3599 G15 JUNCTION TEMPERATURE (°C) LED Current Waveforms (0.1% PWM) (10ms Period) PWM 5V/DIV PWM 5V/DIV LED Current Waveforms (90% PWM) (10ms Period) SW 20V/DIV SW 20V/DIV ILED1 50mA/DIV ILED1 50mA/DIV 2µs/DIV 3599 G16 100µs/DIV 3599 G17 3599fd  LT3599 pin FuncTions CTRL: LED Current Control. If the CTRL pin is not used, tie this pin to VREF. DISABLE4: Allows Disabling Channel 4. Connect to VREF to disable channel 4. If channel 4 is disabled, the LED4 pin should be connected to the LED3 pin. Connect DISABLE4 to ground to allow operation of channel 4. Exposed Pad: Ground. The ground for the IC should be soldered to a continuous copper ground plane under the LT3599 die. FB: Feedback Pin for Overvoltage Protection. Reference voltage is 1.223V. Connect the resistive divider tap here. Minimize trace area at FB. Set VOUT according to VOUT = 1.223(1 + R2/R1) when overvoltage protection occurs. GND: Analog Ground. Tie directly to local ground plane. Connect RT, ISET and TSET resistors between this local ground plane and their respective pins. ISET: Programs Led Current for Each String. A resistor to ground programs LED currents between 30mA and 120mA. LED1-4: LED String Output. Connect the bottom cathode of each LED string to these pins. OPENLED: Open LED Flag. An open-collector output when any LED string opens. NC: No Connect Pins. Can be left open or connected to any ground plane. PWM: Input Pin for PWM Dimming Control. Above 1V allows converter switching, and below 0.4V disables switching with VC pin level maintained. A PWM signal driving the PWM pin provides accurate dimming control. The PWM signal can be driven from 0V to 5V. If unused, the pin should be connected to VREF. RT: A Resistor to Ground Which Programs Switching Frequency Between 200kHz and 2.1MHz. For SYNC function, choose the resistor to program a frequency 20% slower than the SYNC pulse frequency. Do not leave this pin open. SHDN/UVLO: The SHDN/UVLO pin has an accurate 1.36V threshold and can be used to program an undervoltage lockout (UVLO) threshold for system input supply using a resistor divider from supply to ground. A 4µA pin current hysteresis allows programming of undervoltage lockout (UVLO) hysteresis. 1.36V turns the part on and removes a 4µA sink current from the pin. SHDN/UVLO = 0V reduces VIN current < 0.1µA. SHDN/UVLO can be directly connected to VIN. Do not leave this pin open. SHORTLED: Indicates a high side short (LED pin shorted to VOUT). This is an open-collector output. SS: Soft-Start Pin. Place a soft-start capacitor here. Upon start-up, a 11µA current charges the capacitor. Use a larger capacitor for a slower start-up. SW: Switch Pin. This is the collector of the internal NPN power switch. Minimize the metal trace area connected to this pin to minimize EMI. SYNC: Frequency Synchronization Pin. This input allows for synchronizing the operating frequency to an external clock. The RT resistor should be chosen to program a switching frequency 20% slower than SYNC pulse frequency. This pin should be grounded if this feature is not used. TSET: Programs LT3599 junction temperature breakpoint, beyond which LED currents will begin to decrease. An internal VPTAT threshold (see Block Diagram) increases with junction temperature. When VPTAT exceeds TSET pin voltage, LED currents are decreased. If the function is not required, connect TSET pin to VREF pin. If the TSET pin is not used, tie this pin to VREF. VC: Error Amplifier Output Pin. Tie the external compensation network to this pin. VIN : Input Supply Pin. Must be locally bypassed with a capacitor to ground. VO_SW: Drain of an Internal PMOS. The internal PMOS disconnects the feedback resistors from the VOUT pin during shutdown and when the PWM pin is low. VOUT: Output Pin. This pin provides power to all LEDs. VREF : Bandgap Voltage Reference. Internally set to 1.227V. This pin can supply up to 100µA. Can be used to program the CTRL pin voltage using resistor dividers to ground. 3599fd  LT3599 block DiagraM SHDN/UVLO VIN RT SYNC SW 1.4V – + 1.227 VREF SLOPE SOFT-START LOGIC OSCILLATOR S A2 R SS A3 PWM PWM DIMMING LOGIC PMOS VO_SW VREF FB R1 R2 VREF CTRL TSET ISET GND  + VPTAT + 1V A1 Figure 1. Block Diagram – + OVP gm VC + Q Q1 + –– VOUT – + LED gm 0.7V – SHORTLED OPENLED, SHORTLED DETECTION OPENLED LED1 LED DRIVE CIRCUITRY LED2 LED3 LED4 DISABLE4 – – LED4 DISABLE 3599 F01 3599fd LT3599 operaTion The LT3599 uses a constant-frequency, peak current mode control scheme to provide excellent line and load regulation. Operation can be best understood by referring to the Block Diagram in Figure 1. To turn on the LT3599, the VIN pin must exceed 3.1V and the SHDN/UVLO pin must exceed 1.4V. The SHDN/UVLO pin threshold allows programming of an undervoltage lockout (UVLO) threshold for the system input supply using a simple resistor divider. A 4µA current flows into the SHDN/UVLO pin before the part turns on and is removed after the part turns on. This current hysteresis allows the programming of hysteresis for the UVLO threshold. See “Shutdown Pin and Programming Undervoltage Lockout” in the Applications Information section. For part switching, the PWM pin must exceed 1V (typical). For micropower shutdown, the SHDN/UVLO pin at 0V reduces VIN supply current to approximately ~0µA. LT3599 has a built-in boost converter which converts the input voltage to a higher output voltage for driving LEDs. The LED strings are connected to current sources where the current level is set with an external resistor on the ISET pin. The LED1 to LED4 voltages are monitored for output voltage regulation. During normal operation, when all LEDs are used, the lowest LED pin voltage (LED1 to LED4) is used to regulate the output voltage to ensure all LED strings have enough voltage to run the programmed current. If the user prefers only three strings, then LED string 4 can be disabled through the DISABLE4 pin and by connecting LED4 to any other LED pin. If the user prefers only two strings, then two pins are connected in parallel (i.e., LED1,2 and LED3,4 can be connected together in operation). The basic loop uses a pulse from an internal oscillator to set the SR latch and turn on the internal power NPN switch Q1. The signal at the noninverting input of the PWM comparator (A2) is proportional to the sum of the switch current and oscillator ramp. When this signal exceeds the VC voltage, the PWM comparator resets the latch. The switch is then turned off, causing the inductor current to lift the SW pin and turn on an external Schottky diode connected to the output. Inductor current flows via the Schottky diode charging the output capacitor. The switch is turned on again at the next reset cycle of the internal oscillator. During normal operation, the VC voltage controls the peak switch current limit and, hence, the inductor current available to the output LEDs. Dimming of the LEDs is accomplished by either PWM dimming or analog dimming. PWM dimming is achieved by pulsing the LED current using the PWM pin. For constant color LED dimming, the LT3599 provides up to a 3000:1 wide PWM dimming range by allowing the duty cycle of the PWM pin to be reduced from 100% to as low as 0.033%. When the PWM pin is low, switching is disabled and the error amplifier is turned off so that it does not drive the VC pin. Also, all internal loads on the VC pin are disabled so that the state of the VC pin is maintained on the external compensation capacitor. This feature reduces transient recovery time. When the PWM input again transitions high, the peak switch current returns to the correct value. In applications where the user can sacrifice OPENLED, SHORTLED fault flag diagnostics, the dimming ratios can be as high as 3000:1. Analog dimming of LED currents is accomplished by varying the level of CTRL pin voltage. This method, however, changes LED color since dimming is achieved by changing LED current. For CTRL pin voltage less than 1V, LED current is defined as:  1330  ILED = VCTRL •  ( Amps)  RISET   The LT3599 uses the FB pin to provide overvoltage protection when all LED strings are open. There is an internal PMOS switch between VOUT and VO_SW that is controlled by the PWM signal. During the PWM off-period, this PMOS is turned off, allowing for higher dimming range and lower current during shutdown. A resistor divider is connected between the VO_SW pin and ground, which sets the overvoltage protection voltage. If the LED1-4 pin voltage is below 0.3V, the string is treated as an open LED string. As a result, an OPENLED flag is set. If a LED string is opened during regular operation, the output voltage will regulate to the optimum voltage for the remaining connected strings. If a short occurs between VOUT and any LED pin during operation, the LT3599 immediately turns off the shorted channel and sets a SHORTLED flag. Disabling the channel protects the LT3599 from high power thermal dissipation and ensures reliable operation. 3599fd  LT3599 operaTion SHORTLED and OPENLED detection are disabled during the start-up phase to avoid false flag generation. If an LED string is open during normal operation, it will no longer be used to regulate the output voltage. The output voltage will regulate itself to find the LED string with the lowest LED pin voltage. Fault detection (SHORTLED, OPENLED) is updated when the PWM pin is high and latched when the PWM pin is low. During start-up, 11µA of current charges the external soft-start capacitor. The SS pin directly limits the rate of voltage rise on the VC pin, which in turn, limits the peak switch current. Soft-start also enables switching frequency foldback to provide a clean start-up for the LT3599. Switch current limit protects the power switch and external components. applicaTions inForMaTion Inductor Selection Table 1 lists several inductors that work well with the LT3599, however, there are many other manufacturers and devices that can be used. Consult each manufacturer for detailed information on their entire range of parts. Ferrite core inductors should be used to obtain the best efficiency. Choose an inductor that can handle the necessary peak current without saturating. Also, ensure that the inductor has a low DCR (copper wire resistance) to minimize I2R power losses. Values between 4.7µH and 22µH will suffice for most applications. Inductor manufacturers specify the maximum current rating as the current where inductance falls by a given percentage of its nominal value. An inductor can pass a current greater than its rated value without damaging it. Consult each manufacturer to determine how the maximum inductor current is measured and how much more current the inductor can reliably conduct. Table 1. Recommended Inductors PART B1015AS-100M 817FY-4R7M 744065100 74454068 74454010 CDH115-100 CDH74NP-120L CDH74NP-150L IHLP2020-BZ IHLP2525-BD L (µH) 10 4.7 10 6.8 10 10 12 15 10 10 MAX DCR CURRENT (Ω) RATING (A) 0.07 0.06 0.04 0.055 0.065 0.028 0.065 0.083 0.184 0.116 2.2 2.26 3 2.2 2 3 2.45 2.10 2.3 2.5 VENDOR TOKO www.toko.com Würth Electronics www.we-online.com Sumida www.sumida.com Vishay www.vishay.com Capacitor Selection Low ESR (equivalent series resistance) ceramic capacitors should be used at the output to minimize the output ripple voltage. Use only X5R or X7R dielectrics, as these materials retain their capacitance over wider voltage and temperature ranges than other dielectrics. A 4.7µF to 10µF output capacitor is sufficient for most high output current designs. Table 2 lists some suggested manufacturers. Consult the manufacturers for detailed information on their entire selection of ceramic parts. Table 2. Recommended Ceramic Capacitor Manufacturers Taiyo Yuden AVX Murata Kemet (408) 573-4150 www.t-yuden.com (843) 448-9411 www.avxcorp.com (770) 436-1300 www.murata.com (408) 986-0424 www.kemet.com Diode Selection Schottky diodes, with their low forward voltage drop and fast switching speed, should be used for all LT3599 applications. Table 3 lists several Schottky diodes that work well. The diode’s average current rating must exceed the application’s average output current. The diode’s maximum reverse voltage must exceed the application’s output voltage. A 2A diode is sufficient for most designs. For PWM dimming applications, be aware of the reverse leakage current of the diode. Lower leakage current will drain the output capacitor less, allowing for higher dimming range. 3599fd 0 LT3599 applicaTions inForMaTion The companies below offer Schottky diodes with high voltage and current ratings. Standard silicon diodes (PN junction diodes) should not be used. Table 3. Suggested Diodes PART B250A DFLS240 B240A B350A B340A HSM150G HSM150J HSM350G MAX CURRENT (A) 2 2 2 3 3 1 1 3 MAX REVERSE VOLTAGE (V) 50 40 40 50 40 50 50 50 MANUFACTURER Diodes, Inc. www.diodes.com The output voltage should be set 10% higher than the normal LED string operating voltage. Under normal operation, LED1 to LED4 pin voltages are monitored and provide feedback information to the converter for output voltage regulation given the programmed LED current. The output voltage regulation loop is activated only when all LEDs are open. Programming Maximum LED Current Maximum LED current can be programmed by placing a resistor between the ISET pin and ground (RISET). The ISET pin resistor can be selected from 11k to 44.2k. The LED current can be programmed according to the following equation: ILED ≈ 1330 ( Amps) (CTRL > 1V) RISET Microsemi www.microsemi.com Overvoltage Protection The LT3599 uses the FB pin to provide overvoltage protection. A resistor divider is connected between the VO_SW pin and ground (Figure 2). There is an internal PMOS switch between VOUT and VO_SW, which is controlled by the PWM signal. The PMOS switch addition prevents the feedback resistor divider from draining the output capacitor during PWM off-period, allowing for a higher dimming range without falsely tripping the OPENLED flag. It also reduces the system current in shutdown. This PMOS has about 1k resistance, so select FB resistor values taking this resistance into account. To set the maximum output voltage, select the values of R1 and R2 (see Figure 2) according to the following equation:  R2  VOUT(M AX ) = 1.223V  1+   R1 See Table 4 and Figure 3 for resistor values and corresponding programmed LED current. LED current can also be adjusted by programming the CTRL pin voltage. Table 4. RISET Value Selection for LED Current LED CURRENT (mA) 30mA 50mA 99mA 120mA RESISTOR ON ISET PIN (k) 44.2 26.7 13.3 11 120 100 80 LT3599 VOUT VO_SW R2 FB R1 3599 F02 ILED (mA) 60 40 20 0 0 20 40 60 80 100 120 140 160 RISET (k) 3599 F03 Figure 2. Overvoltage Protection Voltage Feedback Connections Figure 3. RISET Value Selection for LED Current 3599fd  LT3599 applicaTions inForMaTion LED Current Dimming Two different types of dimming control can be used with the LT3599. The LED brightness can be set either by analog dimming (CTRL pin voltage adjustment between 0V and 1V) or PWM dimming (PWM pin duty cycle adjustment). For some applications, the preferred method of brightness control is to use a variable DC input voltage. The CTRL pin voltage can be adjusted to set the dimming of the LED string (see Figures 4 and 5). As the voltage on the CTRL pin increases from 0V to 1V, the LED current increases from 0 to the programmed LED current level. Once the CTRL pin voltage increases beyond 1V, it has no effect on the LED current. For True Color PWM dimming, the LT3599 provides up to a 3000:1 PWM dimming range by allowing the duty cycle of the PWM pin to be reduced from 100% to as 120 100 LED CURRENT (mA) 80 60 40 20 R1 0 0 0.2 0.4 0.8 1.0 0.6 CTRL PIN VOLTAGE (V) 1.2 3599 F04 3599 F05 low as 0.033% at a PWM frequency of 100Hz (Figure 6). Dimming by PWM duty cycle, allows for constant LED color to be maintained over the entire dimming range. For LT3599 PWM dimming control during startup and normal operation, observe the following guidelines: (1) STARTUP LT3599 VOUT start-up requires the SHDN/UVLO pin to be asserted from off to on and the PWM on-time to be above a minimum value. The lowest PWM on-time allowed for fault detection is ≈20µs. The lowest PWM on-time allowed for reaching VOUT regulation is typically 20µs but might be greater depending on external circuit parameters. Once LED current is in regulation, PWM on-time can be reduced as low as 3µs depending on external component selection. (2) VOUT Collapse If during normal operation VOUT collapses due to a fault or because PWM on-time is too low, a re-start is required (see STARTUP in item (1)). ISET = 13.3k VREF R2 LT3599 CTRL Figure 4. LED Current vs CTRL Voltage TPWM TONPWM PWM Figure 5. LED Current vs CTRL (= 1/fPWM) INDUCTOR CURRENT LED CURRENT MAX ILED 3599 F06 Figure 6. LED Current Using PWM Dimming 3599fd  LT3599 applicaTions inForMaTion PROGRAMMING LED CURRENT DERATING vs TEMPERATURE Programming LED Current Derating Using the CTRL Pin A useful feature of the LT3599 is its ability to program a derating curve for maximum LED current versus temperature. LED data sheets provide curves of maximumallowable LED current versus temperature to warn against exceeding this current limit and damaging the LED. The LT3599 allows the output LEDs to be programmed for maximum allowable current while still protecting the LEDs from excessive currents at high temperature. This is achieved by programming a voltage at the CTRL pin with a negative temperature coefficient using a resistor divider with temperature dependent resistance (Figure 7). As the temperature increases, the CTRL voltage will fall below the internal 1V voltage reference, causing LED currents to be controlled by the CTRL pin voltage. The LED current curve breakpoint and slope versus temperature is defined by the choice of resistor ratios and use of temperature-dependent resistance in the divider for the CTRL pin. A variety of resistor networks and NTC resistors with different temperature coefficients can be used for programming CTRL to achieve the desired CTRL curve vs temperature. Table 5 shows a list of manufacturers/distributors of NTC resistors. There are several other manufacturers available and the chosen supplier should be contacted for more detailed information. If an NTC resistor is used to indicate LED temperature, it is effective only if the resistor is connected as closely as possible to the LED strings. LED derating curves shown by manufacturers are listed for ambient temperature. The NTC resistor should have the same ambient temperature as the LEDs. Since the temperature dependency of an NTC resistor can be nonlinear over a wide range of temperatures, it is important to obtain a resistor’s exact values over temperature from the manufacturer. Hand calculations of CTRL voltage can then be performed at each given temperature, resulting in the CTRL versus temperature plotted curve. Several iterations of resistor value calculations may be required to achieve the desired breakpoint and slope of the LED current derating curve. Table 5. NTC Resistor Manufacturers/Distributors Murata Electronics North America TDK Corporation Digi-Key (770) 436-1300 www.murata.com (516) 535-2600 www.tdk.com (800) 344-4539 www.digikey.com If calculating the CTRL voltage at various temperatures gives a downward slope that is too strong, alternative resistor networks can be chosen (B, C, D in Figure 7) which use temperature-independent resistance to reduce the effects of the NTC resistor overtemperature. Murata Electronics provides a selection of NTC resistors with complete data over a wide range of temperatures. In addition, a software tool is available which allows the user to select from different resistor networks and NTC resistor values, and then simulate the exact output voltage curve (CTRL behavior) over temperature. Referred to as the “Murata Chip NTC Thermistor Output Voltage Simulator,” users can log onto www.murata.com/designlib and download the software followed by instructions for creating an output voltage VOUT (CTRL) from a specified VCC supply (VREF). At any time during the selection of circuit parameters, the user can access data on the chosen NTC resistor by clicking on a link to the Murata catalog. RY RY VREF R2 LT3599 CTRL R1 (OPTION A TO D) RNTC RNTC RX RNTC RNTC RX A B C D 3599 F07 Figure 7 . LED Current Derating vs Temperature Using NTC Resistor 3599fd  LT3599 applicaTions inForMaTion Using the TSET Pin for Thermal Protection The LT3599 contains a special programmable thermal regulation loop that limits the internal junction temperature of the part. Since the LT3599 topology consists of a single boost converter with four linear current sources, any LED string voltage mismatch will cause additional power to be dissipated in the package. This topology provides excellent current matching between LED strings and allows a single power stage to drive a large number of LEDs, but at the price of additional power dissipation inside the part (which means a higher junction temperature). Being able to limit the maximum junction temperature allows the benefits of this topology to be fully realized. This thermal regulation feature provides important protection at high ambient temperatures, and allows a given application to be optimized for typical, not worst case, ambient temperatures with the assurance that the LT3599 will automatically protect itself and the LED strings under worst-case conditions. The operation of the thermal loop is simple. As the ambient temperature increases, so does the internal junction temperature of the part. Once the programmed maximum junction temperature is reached, the LT3599 begins to linearly reduce the LED current, as needed, to try and maintain this temperature. This can only be achieved when the ambient temperature stays below the desired maximum junction temperature. If the ambient temperature continues to rise past the programmed maximum junction temperature, the LEDs’ current will be reduced to approximately 5% of the full LED current. While this feature is intended to directly protect the LT3599, it can also be used to derate the LED current at high temperatures. Since there is a direct relationship between the LED temperature and LT3599 junction temperature, the TSET function also provides some LED current derating at high temperatures. VREF R2 LT3599 TSET R1 3599 F08 Two external resistors program the maximum IC junction temperature using a resistor divider from the VREF pin, as shown in Figure 8. Choose the ratio of R1 and R2 for the desired junction temperature. Table 6 shows commonly used values for R1 and R2 (see TSET graph). Table 6. Resistor Values to Program Maximum IC Junction Temperature TJ (°C) 100 105 110 115 120 135 145 R1 (k) 80.6 82.5 82.5 84.5 84.5 84.5 90.9 R2 (k) 53.6 53.6 51.1 51.1 49.9 44.2 44.2 Programming Switching Frequency The switching frequency of the LT3599 is set between 200kHz and 2.1MHz by an external resistor connected between the RT pin and ground (see Table 7). Do not leave this pin open. Selecting the optimum switching frequency depends on several factors. Inductor size is reduced with higher frequency, but efficiency drops due to higher switching losses. In addition, some applications require very high duty cycles to drive a large number of LEDs from a low supply. Low switching frequency allows a greater operational duty cycle and, hence, a greater number of LEDs to be driven. In each case, the switching frequency can be tailored to provide the optimum solution. When programming the switching frequency, the total power losses within the IC should be considered. Table 7. Switching Frequency SWITCHING FREQUENCY (MHz) 2.1 2.0 1.5 1.0 0.5 0.4 0.3 0.2 RT (k) 20 21.5 31.6 53.6 121 154 210 324 3599fd Figure 8. Programming the TSET Pin  LT3599 applicaTions inForMaTion Switching Frequency Synchronization The nominal operating frequency of the LT3599 is programmed using a resistor from the RT pin to ground and can be controlled over a 200kHz to 2.1MHz range. In addition, the internal oscillator can be synchronized to an external clock applied to the SYNC pin. The synchronizing clock signal input to the LT3599 must have a frequency between 240kHz and 1.5MHz, a pulse on-time of at least 150ns, a pulse off-time of at least 300ns, a low state below 0.8V and a high state above 1.7V. Synchronization signals outside of these parameters will cause erratic switching behavior. For proper operation, an RT resistor should be chosen to program a switching frequency 20% slower than the SYNC pulse frequency. Synchronization occurs at a fixed delay after the rising edge of SYNC. The SYNC pin should be grounded if the clock synchronization feature is not used. When the SYNC pin is grounded, the internal oscillator generates switching frequency to the converter. Shutdown and Programming Undervoltage Lockout The LT3599 has an accurate 1.4V shutdown threshold at the SHDN/UVLO pin. This threshold can be used in conjunction with a resistor divider from the system input supply to define an accurate undervoltage lockout (UVLO) threshold for the system (Figure 10). A pin current hysteresis allows programming of the hysteresis voltage for this UVLO threshold. Just before the part turns on, 4µA 10000 flows into the SHDN/UVLO pin. After the part turns on, 0µA flows from the SHDN/UVLO pin. Calculation of the on/off thresholds for a system input supply using the LT3599 SHDN/UVLO pin can be made as follows :  R1 VS(OFF ) = 1.4  1+   R2  VS(ON) = VS(OFF ) + (4µA • R1) A simple open drain transistor can be added to the resistor divider network at the SHDN/UVLO pin to independently control the turn off of the LT3599. With the SHDN/UVLO pin connected directly to the VIN pin, an internal undervoltage lockout threshold of approximately 2.7V exists for the VIN pin. This prevents the converter from operating in an erratic mode when supply voltage is too low. The LT3599 provides a soft-start function when recovering from such faults as SHDN < 1.4V and/or VIN < 2.7V. See “Soft-Start” in the Applications Information section for details. Soft-Start and Switching Frequency Foldback To limit inrush current and output voltage overshoot during start-up/recovery from a fault condition, the LT3599 provides a soft-start pin, SS. The SS pin is used to program switch current ramp-up timing using a capacitor to ground. The LT3599 monitors system parameters for the following faults: VIN < 2.7V or SHDN < 1.4. On detection of any of these faults, the LT3599 stops switching immediately and VS LT3599 R1 11 SHDN/UVLO SWITCHING FREQUENCY (kHz) – 1.4V 1000 OFF ON R2 4µA + 100 10 100 RT (k) 1000 3599 F10 3599 F11 Figure 9. Switching Frequency Figure 10. Programming Undervoltage Lockout (UVLO) with Hysteresis 3599fd  LT3599 applicaTions inForMaTion a soft-start latch is set causing the SS pin to be discharged (see the Soft-Start Pin Timing Diagram in Figure 11). All faults are detected internally and do not require external components. When all faults no longer exist and the SS pin has been discharged to at least 0.25V, the soft-start latch is reset and an internal 11µA supply charges the SS pin. During start-up or recovery from a fault, the SS pin ramp up controls the ramp up of switch current limit. Soft-start ramp rate is given by: ∆VSS ISS = (ISS = 11µA typ) ∆T CS S A 10nF capacitor from the SS pin to ground will therefore provide a 1V/ms ramp rate on the SS pin. In addition, during soft-start, switching frequency is reduced to protect the inductor from high currents. SW but continues to ramp upwards. If the soft-start ramp voltage was held every time PWM goes low, this would cause very slow start-up of LED displays for applications using very high PWM dimming ratios. OPENLED FLAG The OPENLED pin is an open-collector output and needs an external resistor tied to a supply (see Figure 12). If any LED string is open during normal operation, the OPENLED pin will be pulled down. The open LED detection is enabled only when the PWM signal is enabled. There is a delay for OPENLED flag generation when the PWM signal is enabled to avoid generating a spurious flag signal. During start-up (see the Operation section), the open LED detection is disabled. SHORTLED FLAG The SHORTLED pin is an open-collector output, and needs an external resistor tied to a supply (see Figure 12). If any LED pin is shorted to VOUT during normal operation, the SHORTLED pin will be pulled down. In addition, the shorted LED string (channel) is immediately disabled, thereby protecting the LT3599. The short LED detection is enabled only when the PWM signal is enabled. There is a delay for SHORTLED flag generation when the PWM signal is enabled to avoid spurious signal being generated. During start-up, the SHORTLED flag is disabled (see the Operation section). LT3599 R1 OPENLED SHORTLED 3599 F13 SS FAULTS TRIGGERING SOFT-START LATCH WITH SW TURNED OFF IMMEDIATELY: VIN < 2.7V OR SHDN < 1.4V 0.3V (ACTIVE THRESHOLD) 0.25V (RESET THRESHOLD) 0.15V SOFT-START LATCH SET SOFT-START LATCH RESET: SS < 0.25V AND VIN > 2.7V AND SHDN > 1.4V AND PWM > 1V (FOR >200ns) 3599 F12 Figure 11. Soft-Start Pin Timing Diagram A useful feature of the LT3599 is that it waits for the first PWM pin active high (minimum 200ns pulse width) before it allows the soft-start of VC pin to begin. This feature ensures that during start-up of the LT3599 the soft-start ramp has not timed out before PWM is asserted high. Without this ‘wait for PWM high’ feature, systems which apply PWM after VIN and SHDN are valid, can potentially turn on without soft-start and experience high inductor currents during wake up of the converter’s output voltage. It is important to note that when PWM subsequently goes low, the soft-start ramp is not held at its present voltage R2 Figure 12. OPENLED and SHORTLED Connection 3599fd  LT3599 applicaTions inForMaTion Loop Compensation The LT3599 has an internal transconductance error amplifier for LED current regulation whose VC output compensates the control loop. During overvoltage, the VC node also compensates the control loop. The external inductor, output capacitor, and the compensation resistor and capacitor determine the loop stability. The inductor and output capacitor are chosen based on performance, size and cost. The compensation resistor and capacitor at VC are selected to optimize control loop stability. For typical LED applications, a 10nF compensation capacitor in series with a 2k resistor at VC is adequate. Thermal Consideration The LT3599 provides four channels for LED strings with internal NPN devices serving as constant-current sources. When LED strings are regulated, the lowest LED pin voltage is 0.7V. The higher the programmed LED current, the more power dissipation in the LT3599. For 100mA LED programming current with a 100% PWM dimming ratio, at least 280mW is dissipated within the IC due to current sources. Thermal calculations shall include the power dissipation on current sources in addition to conventional switch DC loss, switch AC loss and input quiescent loss. For best efficiency, it is recommended that all channels have the same number of LEDs, and each string has a similar voltage drop across the LEDs. Board Layout Considerations As with all switching regulators, careful attention must be paid to the PCB board layout and component placement. To prevent electromagnetic interference (EMI) problems, proper layout of high frequency switching paths is essential. Minimize the length and area of all traces connected to the switching node pin (SW). Always use a ground plane under the switching regulator to minimize interplane coupling. Good grounding is essential in LED fault detection. Recommended component placement is shown in Figure 13. POWER VIN BYPASS CAPACITOR GROUND INDUCTOR LT3599 SOLDER EXPOSED PAD (PIN 29) TO THE ENTIRE COPPER GROUND PLANE UNDERNEATH THE DEVICE. CONNECT MULTIPLE GROUND PLANES THROUGH VIAS UNDERNEATH THE IC SCHOTTKY DIODE SW VOUT 1 2 3 POWER GROUND 28 27 26 25 24 23 VIN SHDN/UVLO NC GND VREF SS RT PWM NC SYNC NC TSET FB VC Cf CVIN COUT VO_SW LED1 LED2 LED3 LED4 DISABLE4 4 5 6 7 8 9 10 11 12 13 14 EXPOSED PAD (PIN 29) LED + (VOUT) CVREF CSS RT 22 21 20 19 18 17 16 15 R SHORTLED NC R OPENLED NC R ISET CTRL R RC R CC 3599 F13 Figure 13. Recommended Component Placement 3599fd  LT3599 Typical applicaTions 12W LED Driver 1MHz Boost, 80mA per String, 10 LEDs per String PVIN 8V TO 24V C1 3.3µF 25V VIN R1 200k R2 31.6k R3 33.2k R4 100k VIN 3.1V TO 5.5V R5 100k C3 1µF 6.3V VIN SW VOUT VO_SW FB R11 31.6k L1 10µH D1 C2 4.7µF 50V 2 R10 1M VIN PWM R6 53.6k R7 53.6k R8 80.6k SHORTLED OPENLED SHDN/UVLO PWM SYNC LT3599 CTRL RT VREF TSET DISABLE4 ISET SS R9 16.5k LED1 LED2 LED3 LED4 GND VC C4 47nF RC 10k CC 2.2nF 80mA PER STRING C1: MURATA GRM21BR71E335K C2: MURATA GRM31CR71H475K D1: DIODES INC. DFLS240 L1: VISHAY IHLP2020BZER100M01 100pF 3599 TA02a Efficiency 100 95 90 EFFICIENCY (%) 85 80 75 70 65 60 ILED TOTAL 200mA/DIV PVIN = 12V PVIN = 24V PWM 5V/DIV PWM Dimming Range 1000:1 (10ms Period) 10µs/DIV 40 80 120 160 200 240 280 TOTAL LED CURRENT (mA) 320 3599 TA02c 3599 TA02b 3599fd  LT3599 Typical applicaTions 12W LED Driver 400kHz Boost, Two LED Strings, 200mA per String, 8 LEDs per String L1 22µH C1 3.3µF 25V VIN R3 464k CTRL R12 64.9k R1 200k R2 64.9k R4 100k VIN 3.1V TO 5.5V R5 100k C3 1µF 6.3V VIN SW VOUT VO_SW FB R11 39.2k D1 C2 4.7µF 50V 3 R10 1M PVIN 9V TO 16V VIN PWM R6 154k R7 53.6k R8 80.6k SHORTLED OPENLED SHDN/UVLO PWM SYNC LT3599 CTRL RT VREF TSET DISABLE4 ISET SS 8 LEDs/ STRING LED1 LED2 LED3 LED4 GND VC C4 47nF RC 3.01k CC 10nF 200mA PER STRING C1: MURATA GRM21BR71E335K C2: MURATA GRM31CR71H475K D1: DIODES INC. DFLS240 L1: VISHAY IHLP2525CZER220M11 R9 13.3k 100pF 3599 TA03a 3599fd  LT3599 Typical applicaTions 7W LED Driver SEPIC (Survives Output Short to Ground) 300kHz, Three Strings, 100mA per String, 6 LEDs per String C7 4.7µF 25V D1 C6 1µF 25V VIN SW SHORTLED OPENLED SHDN/UVLO PWM SYNC LT3599 CTRL RT VREF DISABLE4 TSET ISET R9 13.3k SS L2 22µH PVIN 8V TO 16V C1 3.3µF 25V L1 22µH 10 C2 4.7µF 50V 2 VIN R1 200k R2 31.6k R3 33.2k R4 100k VIN VIN 3.1V TO 5.5V R5 100k C3 1µF 6.3V VOUT VO_SW FB R10 1M R11 49.9k 6 LEDs/ STRING PWM R6 210k R7 53.6k R8 80.6k LED1 LED2 LED3 LED4 100mA PER STRING GND VC C4 47nF RC 10k CC 2.2nF 100pF 3599 TA04a C1: MURATA GRM21BR71E335K C2: MURATA GRM31CR71H475K D1: DIODES INC. B360A L1, L2: VISHAY IHLP2525CZER220M11 3599fd 0 LT3599 Typical applicaTions 8W LED Driver 2MHz Boost, Three Strings, 100mA per String, 7 LEDs per String PVIN 8V TO 16V C1 3.3µF 25V VIN R1 200k R2 31.6k R4 100k VIN 3.1V TO 5.5V R5 100k C3 1µF 6.3V L1 4.7µH D1 C2 4.7µF 50V 2 R10 1M R11 43.2k VIN VIN SW VOUT VO_SW FB PWM SHORTLED OPENLED SHDN/UVLO PWM SYNC LT3599 CTRL RT VREF DISABLE4 TSET ISET SS GND VC C4 47nF 7 LEDs/ STRING R3 33.2k R6 21.5k R7 53.6k R8 80.6k LED1 LED2 LED3 LED4 100mA PER STRING C1: MURATA GRM21BR71E335K C2: MURATA GRM31CR71H475K D1: DIODES INC. DFLS240 L1: SUMIDA CDRH4D22HPNP-4R7N R9 13.3k RC 10k CC 2.2nF 100pF 3599 TA05a 3599fd  LT3599 Typical applicaTions 2.1 MHz Boost, Four Strings, 80mA per String, 7 LEDs per String PVIN 9V TO 16V C1 3.3µF 25V VIN R1 200k R2 32.4k R3 32.4k R6 20k R4 100k VIN 3.1V TO 5.5V R5 100k C3 1µF 6.3V VIN SW VOUT VO_SW FB R11 43.2k L1 4.7µH D1 VIN C2 4.7µF 50V 2 R10 1M 7 LEDs/ STRING PWM R7 53.6k R8 80.6k SHORTLED OPENLED SHDN/UVLO PWM SYNC LT3599 CTRL RT VREF TSET DISABLE4 ISET SS R9 16.5k LED1 LED2 LED3 LED4 VC GND 80mA PER STRING RC 10k CC 2.2nF 100pF C1: MURATA GRM21BR71E335K C2: MURATA GRM31CR71H475K D1: DIODES INC. DFLS240 L1: SUMIDA CDRH4D22HPNP-4R7N C4 47nF 3599 TA06a PWM Dimming 3000:1 (10ms Period) PWM 5V/DIV ILED TOTAL 200mA/DIV 10µs/DIV 3599 TA07 3599fd  LT3599 package DescripTion FE Package 28-Lead Plastic TSSOP (4.4mm) (Reference LTC DWG # 05-08-1663) Exposed Pad Variation EB 4.75 (.187) 9.60 – 9.80* (.378 – .386) 4.75 (.187) 28 2726 25 24 23 22 21 20 19 18 1716 15 6.60 ± 0.10 4.50 ± 0.10 SEE NOTE 4 2.74 (.108) 0.45 ± 0.05 EXPOSED PAD HEAT SINK ON BOTTOM OF PACKAGE 6.40 2.74 (.252) (.108) BSC 1.05 ± 0.10 0.65 BSC RECOMMENDED SOLDER PAD LAYOUT 1 2 3 4 5 6 7 8 9 10 11 12 13 14 0.25 REF 4.30 – 4.50* (.169 – .177) 1.20 (.047) MAX 0° – 8 ° 0.09 – 0.20 (.0035 – .0079) 0.50 – 0.75 (.020 – .030) 0.65 (.0256) BSC NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS 2. DIMENSIONS ARE IN MILLIMETERS (INCHES) 3. DRAWING NOT TO SCALE 0.195 – 0.30 (.0077 – .0118) TYP 0.05 – 0.15 (.002 – .006) FE28 (EB) TSSOP 0204 4. RECOMMENDED MINIMUM PCB METAL SIZE FOR EXPOSED PAD ATTACHMENT *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.150mm (.006") PER SIDE 3599fd  LT3599 package DescripTion (Reference LTC DWG # 05-08-1693 Rev D) UH Package 32-Lead Plastic QFN (5mm × 5mm) 0.70 0.05 5.50 0.05 4.10 0.05 3.50 REF (4 SIDES) 3.45 0.05 3.45 0.05 PACKAGE OUTLINE 0.25 0.05 0.50 BSC RECOMMENDED SOLDER PAD LAYOUT APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 5.00 0.10 (4 SIDES) PIN 1 TOP MARK (NOTE 6) 0.75 0.05 R = 0.05 TYP 0.00 – 0.05 BOTTOM VIEW—EXPOSED PAD R = 0.115 TYP PIN 1 NOTCH R = 0.30 TYP OR 0.35 45° CHAMFER 31 32 0.40 1 2 3.45 0.10 0.10 3.50 REF (4-SIDES) 3.45 0.10 (UH32) QFN 0406 REV D 0.200 REF NOTE: 1. DRAWING PROPOSED TO BE A JEDEC PACKAGE OUTLINE M0-220 VARIATION WHHD-(X) (TO BE APPROVED) 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.20mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE 0.25 0.05 0.50 BSC 3599fd  Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. LT3599 revision hisTory REV D DATE 01/10 DESCRIPTION Updated Typical Applications Added H-Grade to Abs Max Ratings and Order Information Updated Typical Performance Characteristics Revised Pin Functions Updated Table 6 and Deleted Text in Programming Switching Frequency Section Added to Related Parts Table (Revision history begins at Rev D) PAGE NUMBER 1, 18, 19, 20, 21, 22 2 5, 6 7 14 26 3599fd Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.  LT3599 relaTeD parTs PART NUMBER DESCRIPTION LT3463/ LT3463A LT3466/ LT3466-1 LT3474 LT3475 LT3476 LT3477 LT3478/ LT3478-1 LT3486 LT3496 LT3497 LT3498 LT3518/ LT3517 LT3590 LT3591 Dual Output, Boost/Inverter, 250mA ISW, Constant Off-Time, High Efficiency Step-Up DC/DC Converter with Integrated Schottkys Dual Constant Current, 2MHz, High Efficiency White LED Boost Regulator with Integrated Schottky Diode 36V, 1A (ILED), 2MHz, Step-Down LED Driver Dual 1.5A (ILED), 36V, 2MHz, Step-Down LED Driver Quad Output 1.5A, 2MHz High Current LED Driver with 1000:1 Dimming 3A, 42V, 3MHz Boost, Buck-Boost, Buck LED Driver High Current LED Driver Dual 1.3A, 2MHz High Current LED Driver 45V, 2.1MHz 3-Channel (ILED = 1A) Full Featured LED Driver Dual 2.3MHz, Full Function LED Driver with Integrated Schottkys and 250:1 True Color PWM Dimming 2.3MHz, 20mA LED Driver and OLED Driver with Integrated Schottkys COMMENTS VIN: 2.3V to 15V, VOUT(MAX) = ±40V, IQ = 40µA, ISD < 1µA, 3mm × 3mm DFN-10 Package VIN: 2.7V to 24V, VOUT(MAX) = 40V, IQ = 5µA, ISD < 16µA, 3mm × 3mm DFN-10 Package VIN: 4V to 36V, VOUT(MAX) = 13.5V, True Color PWM Dimming = 400:1, ISD < 1µA, TSSOP-16E Package VIN: 4V to 36V, VOUT(MAX) = 13.5V, True Color PWM Dimming = 3000:1, ISD < 1µA, TSSOP-20E Package VIN: 2.8V to 16V, VOUT(MAX) = 36V, True Color PWM Dimming = 1000:1, ISD < 3µA, 5mm × 7mm QFN-10 Package VIN: 2.5V to 25V, VOUT(MAX) = 40V, Dimming = Analog/PWM, ISD < 1µA, QFN and TSSOP-20E Packages VIN: 2.8V to 36V, VOUT(MAX) = 42V, True Color PWM Dimming = 3000:1, ISD < 10µA, TSSOP-16E Package VIN: 2.5V to 24V, VOUT(MAX) = 36V, True Color PWM Dimming = 1000:1, ISD < 1µA, 5mm × 3mm DFN and TSSOP-16E Packages VIN: 3V to 30V (40VMAX), VOUT(MAX) = 45V, True Color PWM Dimming = 3000:1, ISD < 1µA, 4mm × 5mm QFN-28 Package VIN: 2.5V to 10V, VOUT(MAX) = 32V, IQ = 6mA, ISD < 12µA, 2mm × 3mm DFN-10 Package VIN: 2.5V to 12V, VOUT(MAX) = 32V, IQ = 1.65mA, ISD < 9µA, 2mm × 3mm DFN-12 Package 2.3A/1.3A 45V, 2.5MHz Full Featured LED Driver with True VIN: 3V to 30V (40VMAX), VOUT(MAX) = 42V, True Color PWM Dimming = Color PWM Dimming 3000:1, ISD < 5µA, 4mm × 4mm QFN-16 Package 48V Buck Mode LED Driver VIN: 4.5V to 55V, VOUT(MAX) = 5V, IQ = 700µA, ISD < 15µA, 2mm × 2mm DFN-6 and SC70 Packages Constant Current, 1MHz, High Efficiency White LED Boost VIN: 2.5V to 12V, VOUT(MAX) = 40V, IQ = 4mA, ISD < 9µA, 2mm × 3mm Regulator with Integrated Schottky Diode and 80:1 True DFN-8 Package Color PWM Dimming 45V, 2.5MHz 16-Channel Full Featured LED Driver 44V, 1.5A, 2.5MHz Boost 6-Channel LED Driver 16-Channel × 50mA LED Driver 8-Channel × 100mA LED Driver VIN: 4.5V to 45V, VOUT(MAX) = 45V, True Color PWM Dimming = 5000:1, ISD < 1µA, 5mm × 9mm QFN-56 Package VIN: 3V to 30V, VOUT(MAX) = 44V, True Color PWM Dimming = 3000:1, ISD < 1µA, 4mm × 4mm QFN-24 Package VIN: 6V to 40V, VOUT(MAX) = 60V, 3,000:1 True Color PWM Dimming, ISD < 2µA, 5mm × 5mm QFN-32 Package VIN: 6V to 40V, VOUT(MAX) = 60V, 3,000:1 True Color PWM Dimming, ISD < 2µA, TSSOP-28E Package LT3595 LT3598 LT3754 LT3760 3599fd  Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● LT 0110 REV D • PRINTED IN USA www.linear.com  LINEAR TECHNOLOGY CORPORATION 2009