LTC3486 dual step-up DC/DC converter specifically designed drive White

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LTC3486 dual step-up DC/DC converter specifically designed drive White

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LT3486 Dual 1.3A White Step-Up Converters with Wide Dimming DESCRIPTION
LTC3486 dual step-up DC/DC converter specifically designed drive White LEDs series converter) constant current from single Li-Ion cell. Series connection LEDs provides identical currents resulting uniform brightness. independent converters capable driving asymmetric strings. dimming strings controlled independently respective CTRL pins. internal dimming system allows dimming range extended 1000:1 feeding signal respective pins. LT3486 operating frequency with external resistor over 200kHz 2.5MHz range. 200mV feedback voltage (±3% accuracy) minimizes power loss current setting resistor better efficiency. Additional features include output voltage limiting when LEDs disconnected overtemperature protection. LT3486 available space saving 16-pin (5mm 0.75mm) 16-pin thermally enhanced TSSOP packages.
Lare registered trademarks Linear Technology Corporation. other trademarks property their respective owners.
Wide (1000:1) Dimming Range with ColorShift Independent Dimming Shutdown Control Drivers Drives White LEDs 25mA Driver) from Single Li-Ion Cell Drives White LEDs 100mA Driver) from Supply Current Programming Accuracy Open Protection: Clamp Voltage Fixed Frequency Operation: 2.5MHz Wide Input Voltage Range: 2.5V Shutdown Current: Overtemperature Protection Available (5mm 0.75mm) 16-Pin 16-Pin Thermally Enhanced TSSOP Packages
APPLICATIONS
Notebook Display Camera Light Cell Phones Dashboard Lighting Avionics Displays
TYPICAL APPLICATION
Li-Ion Powered Driver Camera Flash Backlighting
4.2V
Efficiency
2.2F LED1 AOT3218 DIMMING OVP1 CTRL1 SHDN PWM1 RFB1 0.62 0.1F 100k 63.4k LT3486 OVP2 CTRL2 PWM2 2.8k 4.7nF RFB2 8.06
3486 TA01a
2.2F LEDs EFFICIENCY MOVIE MODE ILED1 175mA FLASH MODE ILED1 320mA
DIMMING
25mA
0.1F LEDS/25mA
3486 TA01b
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LT3486 ABSOLUTE MAXIMUM RATINGS
(Note
Input Voltage (VIN). SHDN Voltage SW1, Voltages OVP1, OVP2 Voltages CTRL1, CTRL2 Voltages PWM1, PWM2 Voltages FB1, Voltages
Operating Junction Temperature Range (Note LT3486E .-40°C 85°C LT3486I .-40°C 125°C Storage Temperature Range .-65°C 125°C TSSOP .-65°C 150°C Maximum Junction Temperature. 125°C Lead Temperature (Soldering, sec, TSSOP) 300°C
CONFIGURATION
VIEW OVP1 CTRL1 PWM1 OVP2 SHDN CTRL2 PWM2 OVP1 CTRL1 PWM1 VIEW OVP2 SHDN CTRL2 PWM2
PACKAGE 16-LEAD (5mm 3mm) PLASTIC EXPOSED (PIN MUST SOLDERED TJMAX 125°C, 43°C/W, 4°C/W
PACKAGE 16-LEAD PLASTIC TSSOP EXPOSED (PIN MUST SOLDERED TJMAX 125°C, 38°C/W, 10°C/W
ORDER INFORMATION
LEAD FREE FINISH LTC3486EDHC#PBF LTC3486EFE#PBF LTC3486IFE#PBF LEAD BASED FINISH LTC3486EDHC LTC3486EFE LTC3486IFE TAPE REEL LTC3486EDHC#TRPBF LTC3486EFE#TRPBF LTC3486IFE#TRPBF TAPE REEL LTC3486EDHC#TR LTC3486EFE#TR LTC3486IFE#TR PART MARKING 3486 3486EFE 3486IFE PART MARKING 3486 3486EFE 3486IFE PACKAGE DESCRIPTION 16-Lead (5mm 3mm) Plastic 16-Lead Plastic TSSOP 16-Lead Plastic TSSOP PACKAGE DESCRIPTION 16-Lead (5mm 3mm) Plastic 16-Lead Plastic TSSOP 16-Lead Plastic TSSOP TEMPERATURE RANGE -40°C 85°C -40°C 85°C -40°C 125°C TEMPERATURE RANGE -40°C 85°C -40°C 85°C -40°C 125°C
Consult Marketing parts specified with wider operating temperature ranges. more information lead free part marking, http://www.linear.com/leadfree/ more information tape reel specifications,
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LT3486 ELECTRICAL CHARACTERISTICS
PARAMETER Minimum Operating Voltage Maximum Operating Voltage Feedback Voltage (FB1, FB2) Offset between Feedback Bias Current (FB1, FB2) Quiescent Current Switching Frequency Oscillator Frequency Range (Typical Value) Nominal Voltage Maximum Duty Cycle |FB1-FB2| VFB1 VFB2 0.2V (Note VFB1 VFB2 SHDN CTRL1 CTRL2 53.6k 20.5k (Note 53.6k 53.6k 20.5k 309k ISW1 ISW2 0.75A VSW1 VSW2
denotes specifications which apply over full operating temperature range, otherwise specifications 25°C. VCTRL1 VCTRL2 VPWM1 VPWM2 VSHDN unless otherwise noted.
CONDITIONS 0.75 0.54 0.85 VFB1 VFB2 VFB1 VFB2 VPWM1 VPWM2
UNITS
1.25 2500
Switch Current Limit (SW1, SW2) Switch VCESAT Switch Leakage Current Error Amplifier Transconductance Error Amplifier Voltage Gain VC1, Switching Threshold VC1, Clamp Voltage VC1, Source Current VC1, Sink Current VC1, Leakage Current OVP1, OVP2 Overvoltage Threshold Voltage CTRL1, CTRL2 Voltages Turn LED1, Currents CTRL1, CTRL2 Voltages Turn LED1, Currents CTRL1, CTRL2 Voltages Full LED1, Currents CTRL1, CTRL2 Bias Current PWM1, PWM2 Voltage High PWM1, PWM2 Voltage PWM1, PWM2 Bias Current SHDN Voltage High SHDN Voltage SHDN Bias Current Voltage Source Current Note Stresses beyond those listed under Absolute Maximum Ratings cause permanent damage device. Exposure Absolute Maximum Rating condition extended periods affect device reliability lifetime. Note LT3486E guaranteed meet specified performance from 85°C designed, characterized expected meet VSHDN IREF
VCTRL1 VCTRL2
VPWM1 VPWM2
1.25
these extended temperature limits, tested -40°C 85°C. LT3486I specifications guaranteed over -40°C 125°C temperature range. Note Current flows pin. Note Guaranteed design test correlation, production tested.
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LT3486 TYPICAL PERFORMANCE CHARACTERISTICS
Switching Waveforms
VSW2 50V/DIV 500mA/DIV VSW1 10V/DIV 1A/DIV 0.5s/DIV 3.6V LEDs/25mA LEDs/320mA CIRCUIT FRONT PAGE APPLICATION
3486
25°C unless otherwise specified.
Dimming Wavforms
ILED 200mA/DIV 500mA/DIV 5V/DIV 0.2ms/DIV LEDs FREQ 1kHz
3486
Current Duty Cycle Wide Dimming Range (1000:1)
LEDs FREQ 100Hz FEEDBACK VOLTAGE (mV)
VCTRL
3.6V 25°C FEEDBACK VOLTAGE (mV)
VCTRL (Temperature Variation)
85°C
ILED (mA)
-50°C
25°C
0.01 0.01
DUTY CYCLE
3486
CONTROL VOLTAGE
3486
CONTROL VOLTAGE
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SHDN Bias Current (CTRL1 CTRL2
3.6V SHDN BIAS CURRENT 50°C OUTPUT CLAMP VOLTAGE 25°C 100°C
Open-Circuit Output Clamp Voltage Temperature
3.6V 63.4k OUTPUT CLAMP VOLTAGE VOUT2 VOUT1
Open-Circuit Output Clamp Voltage
3.6V 63.4k
VOUT1 VOUT2
SHDN VOLTAGE
3486
TEMPERATURE (°C)
3486
3486
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LT3486 TYPICAL PERFORMANCE CHARACTERISTICS
Input Current with Output Output Open Circuit
1000 OSCILLATOR FREQUENCY (kHz) 25°C 63.4k
25°C unless otherwise specified.
Oscillator Frequency
1100
Oscillator Frequency
53.6k
INPUT CURRENT (mA)
1050
1000
3486
1000 1500 2000 OSCILLATOR FREQUENCY (kHz)
2500
3486
3486
Oscillator Frequency Temperature
10000 OSCILLATOR FREQUENCY (kHz) QUIESCENT CURRENT (mA) 22.1k 53.6k TEMPERATURE (°C)
Quiescent Current
Input Bias Current
3.6V
UVLO
CURRENT
1000
309k
-0.5
SHDN CTRL1 CTRL2
3486
-1.0
VOLTAGE
3486
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Switch Current Limit Duty Cycle
1400 1300 CURRENT LIMIT (mA) VOLTAGE 1200 1100 1000
Voltage Temperature
1.30 1.30
Voltage Load Regulation
1.25 1.20 VOLTAGE 85°C 1.15 1.10 1.05 1.00 25°C -50°C
3.6V
3.6V
1.28
1.26
1.24
1.22 0.95 DUTY CYCLE 1.20 0.90 TEMPERATURE (°C) LOAD CURRENT 3468
3.6V 25°C
3486
3486
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LT3486 FUNCTIONS
SW1, (Pins 16): Pins Collectors Internal Power Transistors. Connect inductors Schottky diodes these pins. Minimize trace area these pins minimize EMI. (Pin Input Supply Pin. Must locally bypassed with type ceramic capacitor. OVP1, OVP2 (Pins 14): Output Overvoltage Protection Pins. Connect these pins output capacitors. on-chip voltage detectors monitor voltages these pins limit (typ) turning respective switcher pulling low. (Pin Timing Resistor Program Switching Frequency. switching frequency programmed from 200kHz 2.5MHz. VC1, (Pins 12): Pins Outputs Internal Error Amplifier. voltages these pins control peak switch currents. Connect resistor capacitor compensation network from these ground. FB1, (Pins 11): LT3486 regulates voltage each feedback 200mV. Connect cathode lowest string feedback resistor (RFB) respective feedback pin. current each string programmed ILED 200mV/RFB, when VCTRL 1.8V ILED VCTRL/(5RFB), when VCTRL CTRL1, CTRL2 (Pins 10): CTRL pins used provide dimming shutdown control individual switching converters. Connecting these ground shuts down respective converter. voltages these pins ramped from 1.8V, current each converter ramps from ILED (200mV/RFB). voltage above 1.8V does affect current. PWM1, PWM2 (Pins control pins used extend dimming range individual switching converter. current each string controlled down levels feeding signal these pins. When voltage taken below 0.4V, respective converter turned disconnected from internal circuitry. Taking higher than 0.9V resumes normal operation. Connect these pins 0.9V supply higher, use. SHDN (Pin 13): Shutdown Device. Connect 1.6V higher enable device; 0.4V less disable device. (Pin 15): internal bandgap reference (1.25V) available this pin. Bypass with 0.1F ceramic capacitor. Draw more than from this pin. Exposed (Pin 17): Ground. exposed package provides electrical contact ground good thermal connection printed circuit board (PCB). Solder exposed system ground.
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LT3486 BLOCK DIAGRAM
OVP1 OVERVOLT DETECTION OVERVOLT DETECTION DRIVER LOGIC RAMP LOGIC OVP2
CONVERTER1
CONVERTER2
RSNS1
RSNS2
COMP
COMP
CONVERTER1 CONTROL
1.25V
SHDN START-UP CONTROL
CONVERTER CONTROL
3486
SHDN
PWM1 CTRL1
CTRL2 PWM2
Figure LT3486 Block Diagram
EXPOSED
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0.2V 0.2V
LT3486 OPERATION
Main Control Loop LT3486 uses constant frequency, current mode control scheme provide excellent line load regulation. incorporates identical, fully independent converters. Operation best understood referring block diagram Figure oscillator, start-up bias bandgap reference shared between converters. control circuitry, power switch, dimming control etc., identical both converters. power-up, output capacitors both converters charged (input supply voltage) their respective inductor Schottky diode. SHDN taken above 1.6V, bandgap reference, start-up bias oscillator turned Grounding SHDN shuts down part. CTRL1 CTRL2 pins perform independent dimming shutdown control converters. Taking CTRL pins high, enables respective converters. Connecting these pins ground, shuts down each converter pulling their respective low. Working main control loop understood following operation converter start each oscillator cycle, power switch turned voltage proportional switch current added stabilizing ramp resulting into positive terminal comparator When this voltage exceeds level negative input logic turns power switch. level negative input error amplifier simply amplified version difference between feedback voltage 200mV reference voltage. this manner, error amplifier regulates feedback voltage 200mV reference voltage. output error amplifier sets correct peak current level inductor keep output regulation. CTRL1 voltage used adjust reference voltage. PWM1, control pins used extend dimming range individual converter. current each string controlled down levels feeding signal these pins. Refer Applications Information section more detail. only converters turned other converter will stay output will remain charged (input supply voltage). Minimum Output Current LT3486 drive 8-LED string current without pulse skipping. current further reduced, device begin skipping pulses. This will result some frequency ripple, although current remains regulated average basis down zero. photo Figure shows circuit operation with white LEDs current driven from 3.6V supply. Peak inductor current less than 200mA regulator operates discontinuous mode implying that inductor current reached zero during discharge phase. After inductor current reaches zero, switch exhibits ringing tank circuit formed inductor combination with switch diode capacitance. This ringing harmful; less spectral energy contained ringing than switch transitions. ringing damped application resistor across inductors, although this will degrade efficiency.
VOUT2 10mV/DIV VSW2 20V/DIV
200mA/DIV 3.6V 0.5s/DIV ILED2 LEDs) CIRCUIT FRONT PAGE APPLICATION
3486
Figure Switching Waveforms
Open-Circuit Protection LT3486 internal open-circuit protection both converters. Connect overvoltage protection pins (OVP1, OVP2) output respective converter. When LEDs disconnected from circuit fail open, on-chip voltage detectors monitor voltages OVP1 OVP2 pins limits these voltages (typ) turning respective switcher. converter will then switch very frequency minimize input current. Output voltage input current during
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LT3486 OPERATION
output open circuit shown Typical Performance Characteristics graphs. Figure shows transient response switcher with LEDs disconnected from output. When LED1 string disconnected from output, voltage feedback (FB1) drops result, error amplifier charges node clamp voltage level 1.5V (typ). converter starts switching peak current limit ramps output voltage. When output voltage reaches clamp voltage level (typ), LT3486 shuts converter pulling node ground. converter then regulates output voltage (typ) switching very frequency. event converters output opencircuit, output voltage will clamped (typ). However, other converter will continue functioning properly. photo Figure shows circuit operation with converter output open-circuit converter driving eight LEDs 25mA. Converter starts switching very frequency, reducing input current. Soft-Start LT3486 separate internal soft-start circuitry each converter. Soft-start helps limit inrush current during start-up. Soft-start achieved clamping output error amplifier during soft-start period. This limits peak inductor current ramps output voltage controlled manner. converter enters into soft-start mode whenever respective CTRL pulled from high. Figure shows start-up waveforms with converter driving eight LEDs 25mA. filtered input current, shown Figure well controlled. soft-start circuit more effective when driving smaller number LEDs. Undervoltage Lockout LT3486 undervoltage lockout circuit which shuts down both converters when input voltage drops below 2.1V (typ). This prevents converter operate erratic mode when powered from supply voltages. Overtemperature Protection maximum allowable junction temperature LT3486 125°C. normal operation, IC's junction temperature should kept below 125°C ambient temperature 85°C less. junction temperature exceeds 150°C, internal thermal shutdown circuitry kicks turns-off both converters. converters will remain until temperature falls below 150°C.
1A/DIV VOUT1 20V/DIV
2V/DIV 3.6V CIRCUIT FRONT PAGE APPLICATION 100s/DIV LED1 DISCONNECTED THIS INSTANT
3486
Figure Transient Response Switcher with LED1 Disconnected from Output
1A/DIV VOUT1 1V/DIV COUPLED 500mA/DIV 3.6V 2ms/DIV CIRCUIT FRONT PAGE APPLICATION LED1 DISCONNECTED
3486
200mA/DIV VOUT2 10V/DIV VFB2 200mV/DIV CTRL2 5V/DIV 3.6V 0.5ms/DIV LEDs, 25mA CIRCUIT FRONT PAGE APPLICATION
3486
Figure Switching Waveforms with Output Open Circuit
Figure Start-Up Waveforms
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LT3486 APPLICATIONS INFORMATION
Duty Cycle duty cycle step-up converter given where: VOUT Output voltage Schottky forward voltage drop VCESAT Saturation voltage switch Input battery voltage maximum duty cycle achievable LT3486 (typ) when running 1MHz switching frequency. increases (typ) when 200kHz drops (typ) 2MHz. Always ensure that converter duty-cycle limited when powering LEDs given switching frequency. Setting Switching Frequency LT3486 uses constant frequency architecture that programmed over 200kHz 2.5MHz range with single external timing resistor from ground. nominal voltage 0.54V, current that flows into timing resistor used charge discharge internal oscillator capacitor. graph selecting value given operating frequency shown Figure
1000
25mA OVP1 CTRL1 SHDN PWM1 2.8k LT3486 OVP2 25mA CTRL2 PWM2 2.8k 4.7nF 8.06
3486 F06a
Operating Frequency Selection choice operating frequency determined several factors. There tradeoff between efficiency component size. Higher switching frequency allows smaller inductors albeit cost increased switching losses decreased efficiency. Another consideration maximum duty cycle achievable. certain applications converter needs operate maximum duty cycle order light maximum number LEDs. LT3486 fixed oscillator off-time variable on-time. result, maximum duty cycle increases switching frequency decreased. circuit Figure operated with different values timing resistor (RT). chosen converters 800kHz 63.4k), 1.25MHz 39.1k) 2MHz 21.5k). CTRL pins used provide dimming respective strings. efficiency comparison different values shown Figure
VOUT VOUT VCESAT
COUT1 2.2F
COUT2 2.2F
1.25V CREF 0.1F
8.06
4.7nF CIN: 10V, COUT1, COUT2: 35V, ZETEX ZHCS400 TOKO D53LC TYPE
Figure White LEDs
1000 1500 2000 OSCILLATOR FREQUENCY (kHz) 2500
3486
Figure Timing Resistor (RT) Value
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LT3486 APPLICATIONS INFORMATION
63.4k EFFICIENCY 21.5k CURRENT (mA)
3486 F06b
LEDs
Several inductors that work well with LT3486 listed Table Consult each manufacturer more detailed information their entire selection related parts.
Table Recommended Inductors
0.150 0.190 0.045 0.068 0.090 0.098 0.149 0.048 0.145 CURRENT RATING 1.40 1.20 2.49 2.01 1.77 1.22 0.94 1.30 0.97
39.1k
PART LQH55DN150M LQH55DN220M A915AY-4R7M A915AY-6R8M A915AY-100M A918CY-100M A918CY-150M CDRH4D28-100 CDRH5D18-150
VENDOR Murata (814) 237-1431 www.murata.com Toko (847) 297-0070 www.toko.com
Figure Efficiency Comparison Different Resistors
Inductor Selection choice inductor will depend selection switching frequency LT3486. switching frequency programmed from 200kHz 2.5MHz. Higher switching frequency allows smaller inductors albeit cost increased switching losses. inductor current ripple (IL), neglecting drop across Schottky diode switch, given VIN(MIN) (VOUT (MAX) VIN(MIN) VOUT (MAX)
Sumida (847) 956-0666 www.sumida.com
Capacitor Selection small size ceramic capacitors make them ideal LT3486 applications. only types because they retain their capacitance over wider voltage temperature ranges than other types such Z5U. 4.7F larger input capacitor sufficient most applications. Always capacitor with sufficient voltage rating. Table shows list several ceramic capacitor manufacturers. Consult manufacturers detailed information their entire selection ceramic parts.
Table Ceramic Capacitor Manufacturers
Taiyo Yuden Murata (408) 573-4150 www.t-yuden.com (803) 448-9411 www.avxcorp.com (714) 852-2001 www.murata.com
where:
Inductor Operating frequency VIN(MIN) Minimum input voltage VOUT(MAX) Maximum output voltage typically maximum inductor current. inductor should have saturation current rating greater than peak inductor current required application. Also, ensure that inductor (copper wire resistance) minimize power losses. Recommended inductor values range from 4.7H 22H.
Diode Selection Schottky diodes with their forward voltage drop fast reverse recovery, ideal choices LT3486 applications. diode conducts current only during switch time. peak reverse voltage that diode must withstand equal regulator output voltage.
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LT3486 APPLICATIONS INFORMATION
average forward current normal operation equal output current, peak current equal peak inductor current. Schottky diode rated sufficient most LT3486 applications. Some recommended Schottky diodes listed Table
Table Recommended Schottky Diodes
PART NUMBER MBR0530 MBRM120E ZLLS400 ZLLS1000 ZHCS400 ZHCS1000 IAVG MANUFACTURER Semiconductor www.onsemi.com Zetex www.zetex.com
200mV ILED1 200mV RFB2 ILED2 RFB1
Table Value Selection
ILED (mA) 40.2 20.0 13.3 10.0 8.06
When LT3486 dimming operation, choose Schottky diode with reverse leakage current. During dimming operation, output capacitor required hold charge "off" period. reverse leakage Schottky helps that mode operation. Zetex ZLLS400 ZLLS1000 available small surface mount package good this application. MOSFET Selection power MOSFET used LT3486 applications with wide dimming range requirements should chosen based maximum drain-source voltage. maximum drain current ID(MAX) gate-to-source voltages should also considered when choosing FET. Choose MOSFET with maximum (drain source) voltage greater than output clamp voltage i.e., (typ). Fairchild Semiconductor's FDN5630 (60V, 1.7A N-channel FET) good most LT3486 applications. dimming current LEDs (~25mA), Fairchild 2N7002 good alternative. Programming Current current each string independently choice resistors RFB1 RFB2 respectively (see front page application). feedback reference 200mV. order have accurate current, precision resistors preferred recommended).
Most power white LEDs driven maximum currents 15mA 25mA. LT3486 used power high power LEDs well. Refer Typical Applications more detail. Dimming Control dimming strings controlled independently modulating respective CTRL pins. There ways control intensity LEDs. Adjusting Current Value Controlling current flowing through LEDs controls intensity LEDs.This easiest control intensity LEDs. forward current controlled modulating voltage respective CRTL pin. pins when appying this scheme. They must connected 0.9V supply higher. voltage CTRL modulated ways. Using Voltage Source some applications, preferred method brightness control variable voltage CTRL pins. CTRL1, CTRL2 voltage modulated dimming respective string. voltage CTRL1, CTRL2 increases from 1.8V, current increases from ILED. CTRL1, CTRL2 voltage increases beyond 1.8V, effect current.
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LT3486 APPLICATIONS INFORMATION
current ILED (200mV/RFB), when VCTRL 1.8V ILED (VCTRL/5 RFB), when VCTRL Feedback voltage variation versus control voltage given Typical Performance Characteristics graphs. Using Filtered Signal variable duty cycle used control brightness string. signal filtered (Figure network CTRL1, CTRL2 pins. corner frequency should much lower than frequency signal. needs much smaller than internal impedance CTRL pins, which 100k.
10kHz LT3486 CTRL1,2
3486
Pulse-Width Modulation (PWM) Adjusting forward current flowing LEDs changes intensity LEDs, explained previous section. However, change forward current also changes color LEDs. chromaticity LEDs changes with change forward current. Many applications cannot tolerate shift color LEDs. Controlling intensity LEDs applying signal allows dimming LEDs without changing color. Dimming LEDs signal essentially involves turning LEDs frequency. human limit frames second. increasing frequency say, 80Hz, deceived into believing that pulsed light source continously Additionally modulating duty cycle (amount "on-time"), intensity LEDs controlled. color LEDs remains unchanged this scheme since current value either zero constant value. Figure 8(a) shows white driver. dimming control method requires external NMOS tied cathode lowest string, shown
Figure Dimming Control Using Filtered Signal
(TYP) COUT1 2.2F
COUT2 2.2F
LUXEON LEDs LXCL-PWF1 OVP1 100mA PWM1
DIMMING INPUT
OVP2 CTRL2 CREF 0.1F LUXEON LEDs LXCL-PWF1
ILED 200mA/DIV 500mA/DIV 5V/DIV
CTRL1 SHDN LT3486
PWM2
100mA
22pF 3.65k
DIMMING INPUT FREQ 1kHz 100k
3.65k 21.5k 2.2nF
0.2ms/DIV LEDs FREQ 1kHz
3486
FREQ 1kHz 100k
2.2nF
Figure Dimming Waveforms
RFB1 COUT1, COUT2: 35V, CIN: 25V, 10V, CREF: 6.3V,
ZETEX ZLLS1000 TOKO D53LC (TYPE FAIRCHILD FDN5630
RFB2
3486 TA10a
Figure White LEDs
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LT3486 APPLICATIONS INFORMATION
figure. logic input applied gate NMOS LT3486. When input taken high, LEDs connected resistor current ILED 200mV/RFB flows through LEDs. When input taken low, LEDs disconnected turn off. input applied LT3486 ensures that respective converter turns goes high impedance. This ensures that capacitor connected retains voltage which turn allows LEDs turn faster, shown Figure 8(b). CTRL used modulate current scheme. connected supply voltage greater than 1.8V. dimming control pins (PWM1, PWM2) used extend dimming range individual switching converters. current controlled down levels feeding signal with frequencies range 80Hz 50kHz. current controlled frequencies above 50kHz controllable current decreases with increasing frequency. Pulling pins below 0.4V disables respective switcher. Taking higher than 0.9V resumes normal operation. Connect these pins 0.9V higher use. Figure shows current variation duty cycle. current controlled applying frequency 100Hz, 1kHz 25kHz circuit Figure seen curves, string able wide (1000:1) dimming range with frequency 100Hz. dimming range decreases frequency goes Board Layout Consideration with switching regulators, careful attention must paid board layout component placement. prevent electromagnetic interference (EMI) problems, proper layout high frequency switching paths essential. Minimize length area traces connected switching node pins (SW1 SW2). Keep feedback pins (FB1 FB2) away from switching nodes. packages both have exposed paddle that must connected system ground. ground connection feedback resistors should tied directly ground plane shared with other component, except resistor, ensuring clean, noise-free connection. Recommended component placement package shown Figure
VIAs PLANE VOUT1 OVP1 VOUT2 OVP2 SHDN
CURRENT (mA)
FREQ 100Hz FREQ 1kHz FREQ 25kHz DUTY CYCLE
3486
LED1
CTRL1
CTRL2
LED2
0.01 0.01
PWM1 VIAs PLANE
PWM2 VIAs GROUND PLANE
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Figure Current Variation Duty Cycle
Figure Recommended Layout LT3486
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LT3486 TYPICAL APPLICATIONS
Li-Ion Cell Powered Driver Camera Flash Backlighting
COUT1 2.2F OVP1 320mA DIMMING CTRL1 SHDN PWM1 100k RFB1 0.62 0.1F 63.4k LT3486 OVP2 25mA CTRL2 PWM2 2.8k 4.7nF RFB2 8.06
3486 TA02a
COUT2 2.2F
LED1 AOT3218
DIMMING CREF 0.1F
CIN: 6.3V, DIELECTRIC COUT1, COUT2: 35V, ZETEX ZHCS1000 ZETEX ZHCS400
TOKO D53LC (TYPE FAIRCHILD FDN5630
Efficiency
MOVIE MODE ILED1 175mA EFFICIENCY FLASH MODE ILED1 320mA
LEDS/25mA
3486 TA01b
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LT3486 TYPICAL APPLICATIONS
Li-Ion Cell White LEDs
COUT1 2.2F LEDs 25mA PWM1 2.8k PWM1 100Hz 4.7nF 63.4k OVP1 CTRL1 SHDN LT3486 OVP2 CTRL2 PWM2 2.8k 4.7nF PWM2 100Hz 8.06 100k CREF 0.1F 25mA LEDs
COUT2 2.2F
100k
8.06
COUT1, COUT2: 35V, CIN: 10V,
ZETEX ZLLS400 TOKO D53LC (TYPE FAIRCHILD 2N7002
3486 TA05A
Current Efficiency Duty Cycle
EFFICIENCY EFFICIENCY CURRENT DUTY CYCLE
3486 TA05b
Wide (250:1) Dimming Range (LED Current 0.1mA 25mA)
3.6V LEDs FREQ 100Hz CURRENT (mA)
3.6V LEDs
CURRENT (mA)
0.10
0.01 DUTY CYCLE
3486 TA05d
Dimming Waveforms
CURRENT 20mA/DIV
200mA/DIV 5V/DIV 3.6V CTRL1 3.6V LEDs/25mA FREQ 100Hz 2ms/DIV
3486 TA05c
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LT3486 TYPICAL APPLICATIONS
16/16 White LEDs
LEDs 0.1F 0.1F LEDs
COUT1 2.2F
OVP1 OVP2 CTRL2 LT3486 PWM2 63.4k 4.02k
COUT2 2.2F
25mA
CTRL1 SHDN PWM1 4.02k
CREF 0.1F
25mA
22pF
FREQ 200Hz 100k
4.7nF
4.7nF
100k
FREQ 200Hz
8.06 CIN: 6.3V, COUT1, COUT2: 35V, C1-C4: 50V, CREF: 6.3V,
8.06 ZETEX ZLLS400 D3-D6: PHILIPS BAV99W TOKO D53LC (TYPE FAIRCHILD 2N7002
3486 TA08a
Current Efficiency Duty Cycle
EFFICIENCY EFFICIENCY CURRENT DUTY CYCLE
3486 TA08b
Dimming Waveforms
ILED 50mA/DIV
16/16 LEDs
CURRENT (mA)
500mA/DIV
5V/DIV FREQ 200Hz 1ms/DIV
3486 TA08c
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LT3486 PACKAGE DESCRIPTION
Package 16-Lead Plastic (5mm 3mm)
(Reference 05-08-1706)
0.65 ±0.05
3.50 ±0.05
1.65 ±0.05 2.20 ±0.05 SIDES) PACKAGE OUTLINE 0.25 0.05 0.50 4.40 ±0.05 SIDES) RECOMMENDED SOLDER PITCH DIMENSIONS 0.115 0.20 0.40 0.10
5.00 ±0.10 SIDES)
3.00 ±0.10 SIDES) MARK (SEE NOTE
1.65 0.10 SIDES) NOTCH
(DHC16) 1103
0.200 0.75 ±0.05 4.40 ±0.10 SIDES)
0.25 0.05 0.50
0.00 0.05 NOTE: DRAWING PROPOSED MADE VARIATION VERSION (WJED-1) JEDEC PACKAGE OUTLINE MO-229 DRAWING SCALE DIMENSIONS MILLIMETERS DIMENSIONS EXPOSED BOTTOM PACKAGE INCLUDE MOLD FLASH. MOLD FLASH, PRESENT, SHALL EXCEED 0.15mm SIDE EXPOSED SHALL SOLDER PLATED SHADED AREA ONLY REFERENCE LOCATION BOTTOM PACKAGE
BOTTOM VIEW-EXPOSED
3486fc
Information furnished Linear Technology Corporation believed accurate reliable. However, responsibility assumed use. Linear Technology Corporation makes representation that interconnection circuits described herein will infringe existing patent rights.
LT3486 PACKAGE DESCRIPTION
Package 16-Lead Plastic TSSOP (4.4mm)
(Reference 05-08-1663)
Exposed Variation
3.58 (.141)
4.90 5.10* (.193 .201) 3.58 (.141) 1514 1110
6.60 ±0.10 4.50 ±0.10
NOTE
2.94 (.116) 0.45 ±0.05 1.05 ±0.10 0.65 2.94 6.40 (.116) (.252)
RECOMMENDED SOLDER LAYOUT
1.10 (.0433)
4.30 4.50* (.169 .177)
0.25
0.09 0.20 (.0035 .0079)
0.50 0.75 (.020 .030)
0.65 (.0256)
NOTE: CONTROLLING DIMENSION: MILLIMETERS MILLIMETERS DIMENSIONS (INCHES) DRAWING SCALE
0.195 0.30 (.0077 .0118)
0.05 0.15 (.002 .006)
FE16 (BB) TSSOP 0204
RECOMMENDED MINIMUM METAL SIZE EXPOSED ATTACHMENT *DIMENSIONS INCLUDE MOLD FLASH. MOLD FLASH SHALL EXCEED 0.150mm (.006") SIDE
3486fc
Information furnished Linear Technology Corporation believed accurate reliable. However, responsibility assumed use. Linear Technology Corporation makes representation that interconnection circuits described herein will infringe existing patent rights.
LT3486 TYPICAL APPLICATION
White LEDs
(TYP) COUT1 2.2F
COUT2 2.2F
Current Efficiency Duty Cycle
EFFICIENCY CURRENT (mA) CURRENT LEDs
DIMMING INPUT FREQ 1kHz 100k
LUXEON LEDs LXCL-PWF1 OVP1 100mA PWM1
DIMMING INPUT
OVP2 CTRL2 LT3486 PWM2 22pF CREF 0.1F
CTRL1 SHDN
LUXEON LEDs LXCL-PWF1
EFFICIENCY
3486 TA10b
100mA
DUTY CYCLE
3.65k 21.5k 2.2nF
3.65k 2.2nF
FREQ 1kHz 100k
RFB1 COUT1, COUT2: 35V, CIN: 25V, 10V, CREF: 6.3V,
ZETEX ZLLS1000 TOKO D53LC (TYPE FAIRCHILD FDN5630
RFB2
3486 TA10a
RELATED PARTS
PART NUMBER LT1618 LT1932 LT1937 LTC3200 LTC3200-5 LTC3201 LTC3202 LTC3205 LT3465/LT3465A LT3466 DESCRIPTION Constant Current, Constant Voltage 1.24MHz, High Efficiency Boost Regulator Constant Current, 1.2MHz, High Efficiency White Boost Regulator Constant Current, 1.2MHz, High Efficiency White Boost Regulator Noise, 2MHz, Regulated Charge Pump White Driver Package Noise, 2MHz, Regulated Charge Pump White Driver ThinSOT Package Noise, 1.7MHz, Regulated Charge Pump White Driver Package Noise, 1.5MHz, Regulated Charge Pump White Driver Package High Efficiency, Multidisplay Controller Constant Current, 1.2MHz/2.7MHz, High Efficiency White Boost Regulator with Integrated Schottky Diode Dual Full Function White Boost Regulator with Integrated Schottky Diode COMMENTS White LEDs, VIN: 1.6V 18V, VOUT(MAX) 34V, 1.8mA, Package White LEDs, VIN: 10V, VOUT(MAX) 34V, 1.2mA, ThinSOTPackage White LEDs, VIN: 2.5V 10V, VOUT(MAX) 34V, 1.9mA, ThinSOT, SC70 Packages White LEDs, VIN: 2.7V 4.5V, 8mA, White LEDs, VIN: 2.7V 4.5V, 8mA, White LEDs, VIN: 2.7V 4.5V, 6.5mA, White LEDs, VIN: 2.7V 4.5V, 5mA, (Main), (Sub) RGB, VIN: 2.8V 4.5V, 50A, QFN-24 Package White LEDs, VIN: 2.7V 16V, VOUT(MAX) 34V, 1.9mA, ThinSOT Package Drives LEDs, VIN: 2.7V 24V, VOUT(MAX) 40V, 5mA, 16A, Package
3486fc
Linear Technology Corporation
(408) 432-1900 FAX: (408) 434-0507
0408 PRINTED
1630 McCarthy Blvd., Milpitas, 95035-7417
www.linear.com
LINEAR TECHNOLOGY CORPORATION 2008

LTC3486 dual step-up DC/DC converter specifically designed drive White

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