DESCRIPTIO High Efficiency: Over Entire Li-Ion Battery Range Wide

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DESCRIPTIO High Efficiency: Over Entire Li-Ion Battery Range Wide

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LTC3452 Synchronous Buck-Boost MAIN/CAMERA White Driver
DESCRIPTIO
High Efficiency: Over Entire Li-Ion Battery Range Wide Range: 2.7V 5.5V Independent MAIN/CAMERA Current Control 425mA Continuous Output Current Internal Soft-Start Open/Shorted Protection Brightness Control Current Matching Typically <2.5% Constant Frequency 1MHz Operation Shutdown Current: 6.5µA Overtemperature Protection Small Thermally Enhanced 20-Lead (4mm 4mm) Package
LTC3452 synchronous buck-boost DC/DC converter optimized driving banks white LEDs from single Li-Ion battery input. Five parallel LEDs driven 25mA each power bank, while LEDs driven 150mA each single 300mA) high power bank. regulator operates either synchronous buck, synchronous boost buck-boost mode, depending input voltage maximum forward voltage. Optimum efficiency achieved sensing which requires largest forward voltage drop programmed current, regulating common output rail lowest dropout. Efficiency achieved over entire usable range Li-Ion battery (2.7V 4.2V). Maximum current each display programmable with single external resistor. Dual enable pins allow brightness control power bank independent on/off control high current bank (optimal camera flash). shutdown, supply current only 6.5µA. high constant operating frequency 1MHz allows small external inductor. LTC3452 offered profile (0.75mm) thermally enhanced 20-lead (4mm 4mm) package.
APPLICATIO
Cell Phones Digital Cameras PDAs Portable Devices
registered trademarks Linear Technology Corporation. other trademarks property their respective owners.
TYPICAL APPLICATIO
4.7µH SINGLE Li-Ion CELL 2.7V 4.2V
20mA White Display 200mA Camera Light Driver
ISETH 6.19k LEDL1 0.1µF ISETL 10.2k PGND EXPOSED MAIN DISPLAY BACKLIGHT 2015 NICHIA NSCW100 COILCRAFT DO3314-472 LTC3452 1MHz BUCK/BOOST LEDL2 LEDL3 LEDL4 LEDL5
2.2µF PVIN VOUT
LEDH1 LEDH2 20mA 20mA 20mA 20mA 20mA 200mA
4.7µF
EFFICIENCY
3452 TA01a
Torch Flash Mode Efficiency
FLASH MODE 200mA 25°C VLEDx) ILEDx EFFICIENCY TORCH MODE 100mA
3452 TA01b
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LTC3452
ABSOLUTE
(Note
RATI
PACKAGE/ORDER ATIO
VIEW
PACKAGE 20-LEAD (4mm 4mm) PLASTIC TJMAX 125°C, 40°C/W EXPOSED (PIN GND, MUST SOLDERED
ORDER PART NUMBER LTC3452EUF
PART MARKING 3452
Order Options Tape Reel: Lead Free: #PBF Lead Free Tape Reel: #TRPBF Lead Free Part Marking: http://www.linear.com/leadfree/ Consult Marketing parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
denotes specifications which apply over full operating temperature range, otherwise specifications 25°C. PVIN VOUT 3.6V unless otherwise specified. (Note
PARAMETER Input Supply Voltage (VIN) Input Supply Current Normal Operation Shutdown UVLO Undervoltage Lockout Threshold ENL,H Threshold Normal Operation (VIH) ENL,H Threshold Shutdown (ILEDx (VIL) ENL,H Input Current (IIH, IIL) Frequency ISETL,H Servo Voltage LEDHx Output Current Ratio (ILEDHx/ISETH) LEDHx Output Current Matching LEDHx Voltage 2.7V 5.5V, RISETL RISETH 51.1k, ILEDx (Note 2.7V 5.5V, VENL VENH UVLO Threshold Rising Falling 2.7V 5.5V, VENL,H Rising 2.7V 5.5V, VENL,H Falling 2.7V 5.5V 2.7V 5.5V (Note RISETL RISETH
CONDITIONS
LEDH1
LEDL3
LEDL4
LEDL5
VIN, PVIN, SW1, SW2, VOUT Voltage 0.3V LEDL1 LEDL5 Voltage 0.3V (VOUT 0.3V) LEDH1, LEDH2 Voltage 0.3V (VOUT 0.3V) ENL, ENH, ISETL, ISETH Voltage 0.3V (VIN 0.3V) LEDL1 LEDL5 Current 50mA LEDH1, LEDH2 Current 250mA Operating Temperature Range (Note 40°C 85°C Junction Temperature (Note 125°C Storage Temperature Range 65°C 125°C
PGND
ISETL LEDL1 LEDL2 ISETH LEDH2
VOUT
PVIN
UNITS
1.87 0.54 0.52
ILEDHx 100mA, VLEDHx 300mV
mA/mA mA/mA
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(Max Min)/[(Max Min)/2] 100%, ILEDHx 100mA, VLEDHx 300mV, 2.7V 5.5V ILEDHx 100mA
LTC3452
ELECTRICAL CHARACTERISTICS
denotes specifications which apply over full operating temperature range, otherwise specifications 25°C. PVIN VOUT 3.6V unless otherwise specified. (Note
PARAMETER LEDLx Output Current Ratio (ILEDLx/ISETL) (Note CONDITIONS ILEDLx|MAX 20mA, VLEDLx 300mV Duty Cycle
1.75 3.66 3.56 7.32 7.12 14.72 14.32 29.44 28.64 58.88 57.92 117.12 114.56 234.24 229.12
2.16 2.21 4.28 4.38 8.56 8.76 17.04 17.44 33.92 34.56 67.2 68.16 134.4 137.6 268.8 272.64
UNITS mA/mA mA/mA mA/mA mA/mA mA/mA mA/mA mA/mA mA/mA mA/mA mA/mA mA/mA mA/mA mA/mA mA/mA mA/mA mA/mA
Duty Cycle
Duty Cycle
Duty Cycle
Duty Cycle
Duty Cycle
Duty Cycle
Duty Cycle
LEDLx Output Current Matching LEDLx Voltage Regulated Maximum VOUT PMOS Switch NMOS Switch Forward Current Limit Reverse Current Limit PMOS Switch Leakage NMOS Switch Leakage Oscillator Frequency Soft-Start Time
(Max Min)/[(Max Min)/2] 100%, ILEDLx 20mA, VLEDLx 300mV ILEDLx 20mA VLEDLx VLEDHy Switches 100mA Switches 100mA Switch Switch Switches Switches 1000
4.35
1600
4.75
2400
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 LTC3452E guaranteed meet specifications from 70°C. Specifications over -40°C 85°C operating temperature range assured design, characterization correlation with statistical process controls.
Note calculated from ambient temperature power dissipation according following formula: JA°C/W). Note Dynamic supply current higher gate charge being delivered switching frequency. Note exceed 50kHz frequency application. Note This parameter tested setup which forces conditions equivalent those programmed indicated duty cycle.
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LTC3452 TYPICAL PERFOR CHARACTERISTICS
Shutdown Current Temperature
SHUTDOWN CURRENT (µA)
SHUTDOWN CURRENT (µA)
2.7V
3.6V
5.5V 4.2V
UVLO THRESHOLD
TEMPERATURE (°C)
3452
Enable Thresholds Temperature
1200 1100 3.6V 1000
ENABLE THRESHOLDS (mV)
ENABLE THRESHOLDS (mV)
1000 TEMPERATURE (°C)
3452
VISETL,H (mV)
ISETL,H Servo Voltage
25°C
4.60 4.58 4.56 4.54
VISETL,H (mV)
VOUT
Shutdown Current
25°C
Undervoltage Lockout Threshold Temperature
RISING
FALLING
TEMPERATURE (°C)
3452
3452
Enable Thresholds
25°C
ISETL,H Servo Voltage Temperature
TEMPERATURE (°C)
3452
3.6V RISETL 10.2k RISETH 4.99k
3452
Maximum Regulated VOUT Temperature
3.6V
4.52 4.50 4.48 4.46 4.44 4.42 4.40 TEMPERATURE (°C)
3452
3452
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LTC3452 TYPICAL PERFOR CHARACTERISTICS
PMOS RDS(ON) Temperature
2.7V TEMPERATURE (°C)
3452
5.5V 4.2V
FREQUENCY (kHz)
RDS(ON)
RDS(ON)
3.6V
Output Voltage Ripple (Front Page Application)
VOUT 3.1V ILED 100mA
NMOS RDS(ON) Temperature
Oscillator Frequency Temperature
1050 1040 1030 VOUT
2.7V 3.6V
1020 1010 1000 4.2V
5.5V
3.6V
5.5V 4.2V
2.7V
TEMPERATURE (°C)
3452
TEMPERATURE (°C)
3452
Start-Up Transient
CH1, VOUT 1V/DIV CH2, ILED 300mA FINAL VALUE CH3, 1V/DIV
3452
3.6V ILEDH 300mA
3452
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LTC3452
CTIO
(Pin Signal Voltage Input Supply (2.7V 5.5V). Recommended bypass capacitor 2.2µF ceramic larger. Connect PVIN (Pin 20). (Pin Enable Input Brightness Control Power Bank. Active high. constant IMAXL operation, connect voltage >1.2V). voltage <0.2V, power bank current source outputs Hi-Z both <0.2V, part shutdown input supply current drops ~6µA). brightness control between zero current IMAXL, drive with waveform frequency 10kHz. power bank currents will equal percentage IMAXL given Table high impedance should floated. ISETL (Pin Power Bank Current Programming Pin. resistor ground programs each power bank current source output maximum ILEDLx|MAX (0.8V/RISETL). Enabled (Pin brightness control also ENL. LEDL1 LEDL5 (Pins Individual Dropout Current Source Outputs Power Bank Current Biasing. Connect each power between VOUT individual LEDLx pin. Unused LEDLx outputs should connected VOUT. (Pins 11): Signal Ground Pins. Connect together PGND (Pin Exposed ground (Pin 21). LEDH1, LEDH2 (Pins 12): Individual Dropout Current Source Outputs High Power Bank Current Biasing. Connect each high power between VOUT individual LEDHx pin. Unused LEDHx outputs should connected VOUT. ISETH (Pin 13): High Power Bank Current Programming Pin. resistor ground programs each high power bank current source output ILEDHx 768(0.8V/RISETH). Enabled (Pin 14). (Pin 14): Enable Input High Power Bank. Active high. high impedance should floated. (Pin 15): Compensation Point Internal Error Amplifier Output. Recommended compensation capacitor 0.1µF ceramic larger. VOUT (Pin 16): Buck-Boost Output Pin. Recommended bypass capacitor 4.7µF ceramic. (Pin 17): Switching Node Pin. Connected internal power switches External inductor connects between SW2. Recommended value 4.7µH. PGND (Pin 18): Power Ground Pin. Connect (Pins 11). (Pin 19): Switching Node Pin. Connected internal power switches External inductor connects between SW2. Recommended value 4.7µH. PVIN (Pin 20): Power Voltage Input Supply Pin. Connect (Pin Exposed (Pin 21): Heat Sink Ground. Connect (Pins solder ground electrical contact rated thermal performance.
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LTC3452
BLOCK DIAGRA
2.7V 5.5V
UNDERVOLTAGE LOCKOUT
OVERTEMPERATURE PROTECTION
BANDGAP REFERENCE
VBIAS
800mV ISETL RISETL
POWER CURRENT SETTING
800mV ISETH
HIGH POWER CURRENT SETTING IMAXH
RISETH
VOUT PVIN SWITCH SWITCH GATE DRIVERS ANTI-CROSSFORWARD CONDUCTION CURRENT LIMIT SWITCH SWITCH DETECT REVERSE CURRENT LIMIT DETECT LEDL2 POWER BANK LEDL1 VOUT 1.23V
1600mA
200mA
DETECT
LEDL3
COMPARATOR LOGIC COMPARATOR
1MHz OSCILLATOR
DETECT DETECT
LEDL4
LEDL5
MAIN ERROR
SAFETY ERROR
1.23V
VOUT 327k 123k
1.23V
SOFT-START CLAMP
IMAXL
EXPONENTIAL BRIGHTNESS CONTROL
LEVELS DETECT SHUTDOWN DETECT LEDH2 LEDH1 HIGH POWER BANK
SHUTDOWN CIRCUIT
PGND
EXPOSED
3452
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LTC3452
OPERATIO
Buck-Boost DC-DC Converter LTC3452 employs proprietary buck-boost DC/DC converter generate output voltage required drive LEDs. This architecture permits high-efficiency, noise operation input voltages above, below equal output voltage properly phasing four internal power switches. error output voltage determines duty cycle switches. Since filtered signal, provides rejection frequencies well below factory trimmed switching frequency 1MHz. RDS(ON), gate charge synchronous switches provide high frequency pulse width modulation control high efficiency. Schottky diodes across synchronous rectifier switch synchronous rectifier switch required, used, provide lower voltage drop during break-before-make time (typically 20ns), which improves peak efficiency typically higher loads. Figure shows simplified diagram four internal power switches connected inductor, PVIN, VOUT GND. Figure shows regions operation buck-boost function control voltage output switches properly phased transitions between regions operation continuous, filtered transparent user. When approaches VOUT, buck-boost region reached where conduction time four switch region typically 150ns. Referring Figures various regions operation encountered increases will described.
PVIN PMOS NMOS
Figure Simplified Diagram Internal Power Switches
Buck Mode (VIN VOUT) buck mode, switch always switch always off. Referring Figure when control voltage above voltage switch begins turn each cycle. During time switch synchronous rectifier switch turns remainder cycle. Switches will alternate conducting similar typical synchronous buck regulator. control voltage increases, duty cycle switch increases until maximum duty cycle converter buck mode reaches DCBUCK|max given DCBUCK|max 100% DC4SW where DC4SW equals duty cycle "four switch" range. DC4SW (150ns 100% where operating frequency Beyond this point "four switch" buck-boost region reached. Buck-Boost Four-Switch Mode (VIN VOUT) Referring Figure when control voltage above voltage switch pair continue operate duty cycle DCBUCK|max, switch pair begins phase switch pair phases switch pair phases accordingly. When voltage reaches edge buck-boost range voltage switch pair completely phases switch pair boost region begins
DMAX BOOST
VOUT PMOS
(2.1V) BOOST REGION SWITCHES
DMIN BOOST DMAX BUCK FOUR SWITCH BUCK/BOOST REGION
(1.65V) (1.55V) SWITCHES BUCK REGION
NMOS
DUTY CYCLE
(0.9V) CONTROL VOLTAGE,
3452
3452
Figure Switch Control Control Voltage,
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LTC3452
OPERATIO
duty cycle DC4SW. input voltage where four switch region begins given
VOUT (150ns
input voltage where four switch region ends given
VOUT (150ns
Boost Mode (VIN VOUT)
boost mode, switch always switch always off. Referring Figure when control voltage above voltage switches will alternate conducting similar typical synchronous boost regulator. maximum duty cycle converter limited typical reached when above Forward Current Limit current delivered from through PMOS switch exceeds 1600mA (typical), switch shut immediately. Switches turned remainder cycle order safely discharge forward inductor current maximum rate possible. Reverse Current Limit current delivered from VOUT backwards through PMOS switch exceeds 200mA (typical), switch shut immediately. Switches turned remainder cycle order safely discharge reverse inductor current maximum rate possible. Undervoltage Lockout prevent operation power switches high RDS(ON), undervoltage lockout incorporated LTC3452. When input supply voltage drops below approximately 1.9V, four power switches control circuitry turned except undervoltage block, which draws only microamperes.
Overtemperature Protection junction temperature LTC3452 exceeds 130°C reason, four switches shut immediately. overtemperature protection circuit typical hysteresis 11°C. Soft-Start LTC3452 includes internally fixed soft-start which active when powering coming shutdown. soft-start works clamping voltage node gradually releasing such that requires 650µs linearly slew from 0.9V 2.1V. This effect limiting rate duty cycle change transitions from buck region through buck-boost region into boost region. Once soft-start times out, only reset entering shutdown, undervoltage overtemperature condition. Main Error main error amplifier transconductance amplifier with source sink capability. output main error amplifier drives capacitor pin. This capacitor sets dominant pole regulation loop. (See Applications Information section selecting capacitor value.) error gets feedback signal from proprietary circuit which monitors current sources determine which close regulation loop Safety Error safety error amplifier transconductance amplifier with sink only capability. normal operation, effect loop regulation. However, pins open-circuits, output voltage will keep rising, safety error will eventually take over control regulation loop prevent VOUT runaway. VOUT threshold which this occurs approximately 4.5V.
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LTC3452
OPERATIO
Current Setting Amps maximum forward current LEDs given bank programmed single external resistor ground corresponding ISETL,H according following formulas:
IMAXL IMAXH RISETH RISETL
operation currents below IMAXL power bank, refer Exponential Brightness Control section also external circuit options given Applications Section. operation currents below IMAXH high power bank, refer only external circuit options given Applications Section. Shutdown Circuit shutdown circuit monitors voltages ENL,H pins. Logic high either/both inputs enables part logic both puts part shutdown. Since doubles input brightness control, output filter shutdown circuit employed prevent part from toggling shutdown normal PWMing input when low. low, LTC3452 enabled immediately after rising edge pin, waits 200µs (typical) after falling edge enter shutdown. Consequently, minimum frequency required smooth brightness control currents below IMAXL. recommended frequency 10kHz 50kHz. Exponential Brightness Control (Low Power Bank Only) LTC3452 implements exponential brightness control function power bank only which LEDLx current function duty cycle pin. current will equal fraction IMAXL given Table duty cycle (that waveform logic high) increases linearly, current will increase exponentially from 1/128th IMAXL 128/128ths IMAXL seven binary steps. function
implemented results "smoother" brightness dimming control perceived human eye, which logarithmic nature.
Table Power Bank Brightness Control
DUTY CYCLE LOGIC HIGH) (Logic Low) Duty Cycle 12.5% 12.5% Duty Cycle Duty Cycle 37.5% 37.5% Duty Cycle Duty Cycle 62.5% 62.5% Duty Cycle Duty Cycle 87.5% 87.5% Duty Cycle 100% LEDLx CURRENT (Shutdown) 1/128 IMAXL 1/64 IMAXL 1/32 IMAXL 1/16 IMAXL IMAXL IMAXL IMAXL IMAXL
Current Sources Each driven current source specifically designed dropout. LTC3452 employs proprietary architecture that determines which seven LEDs requires largest forward voltage drop programmed current, then generates feedback voltage based this closing buck-boost regulation loop. This results lowest output voltage required regulating LEDs thus highest power efficiency. voltage present "controlling LED" will typically 130mV 20mA (low power bank) 250mA 100mA (high power bank) current. Detect Circuit fewer than five outputs power bank and/ fewer than outputs high power bank required, unused outputs should connected VOUT. Each internal detect circuit that disables output current source save power output needed. small current employed detect presence startup. This current typically 10µA power bank 30µA high power bank.
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LTC3452
APPLICATIO ATIO
COMPONENT SELECTION Inductor Selection
high frequency operation LTC3452 allows small surface mount inductors. inductor current ripple typically maximum average inductor current. given ripple inductance term boost mode VIN(MIN)2
VOUT VIN(MIN) 100%
IOUT(MAX %Ripple VOUT
buck mode
where:
VOUT VIN(MAX VOUT 100% IOUT(MAX %Ripple VIN(MAX
operating frequency, %Ripple allowable inductor current ripple, VIN(MIN) minimum input voltage, VIN(MAX) maximum input voltage, VOUT output voltage, IOUT(MAX) maximum output load current high efficiency, choose inductor with high frequency core material, such ferrite, reduce core loses. inductor should have (equivalent series resistance) reduce losses, must able handle peak inductor current without saturating. Molded chokes chip inductors usually have enough core support peak inductor currents >1A. minimize radiated noise, toroid, core shielded bobbin inductor. white application, 4.7µH inductor value recommended. Table list component suppliers.
Table Inductor Vendor Information
SUPPLIER Coilcraft Cooper/Coiltronics Murata Sumida Vishay-Dale SITE www.coilcraft.com www.cooperet.com www.murata.com www.japanlink.com/sumida www.vishay.com
Input Capacitor Selection Since supply voltage recommended place least 2.2µF, bypass capacitor ground. Table list component suppliers.
Table Capacitor Vendor Information
SUPPLIER Sanyo Taiyo Yuden SITE www.avxcorp.com www.sanyovideo.com www.t-yuden.com www.component.tdk.com
Output Capacitor Selection bulk value capacitor reduce ripple charge into capacitor each cycle. steady state ripple charge given
IOUT(MAX VOUT VIN(MIN) COUT VOUT
%Ripple Boost
%Ripple Buck
VIN(MAX COUT
VIN(MAX) VOUT
where COUT output filter capacitor, output capacitance usually many times larger order handle transient response converter. rule thumb, ratio operating frequency unity-gain bandwidth converter amount output capacitance will have increase from above calculations order maintain desired transient response. other component ripple (equivalent series resistance) output capacitor. capacitors should used minimize output voltage ripple. surface mount applications, Taiyo Yuden, TDK, ceramic capacitors, series tantalum capacitors Sanyo POSCAP recommended. white application, 4.7µF capacitor value recommended. Table list component suppliers.
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LTC3452
APPLICATIO ATIO
Optional Schottky Diodes
Schottky diodes across synchronous switches required, provide lower drop during break-before-make time (typically 20ns) NMOS PMOS transition, improving efficiency. Schottky diode such MBRM120T3 equivalent. ordinary rectifier diodes, since slow recovery times will compromise efficiency. Closing Feedback Loop LTC3452 incorporates voltage mode control. control output gain varies with operation region (Buck, Boost, Buck/Boost), usually greater than output filter exhibits double pole response given
fFILTER POLE COUT
where COUT output filter capacitor. output filter zero given
fFILTER ZERO RESR COUT
where RESR capacitor equivalent series resistance. troublesome feature Boost mode right-half plane zero (RHP), given
fRHPZ
IOUT VOUT
loop gain typically rolled before zero frequency. simple Type compensation network incorporated stabilize loop cost reduced bandwidth slower transient response. ensure proper phase margin, loop required crossed over decade before double pole.
unity-gain frequency error amplifier with Type compensation given
where error transconductance (typically 1/5.2k) external capacitor pin. white application, 0.1µF greater capacitor value recommended. Paralleling Outputs Higher Current more output pins connected together parallel achieve higher output current fewer than LEDs. very high power such LumiLED, outputs connected parallel maximum total output current, shown back page application this data sheet. Maximum Current described Operation section, maximum output currents equal
IMAXL RISETL IMAXH RISETH
Since maximum current power bank 25mA, this sets minimum limit RISETL
RMINL 8192 25mA
Similarly, high power bank:
4096 RMINH 150mA
addition, since maximum continuous output current buck-boost limited 425mA, this impose higher resistor value minimums outputs used.
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LTC3452
APPLICATIO ATIO
Although LTC3452 safely provide this current continuously, external LED(s) rated this high level continuous current. Higher current levels single generally reserved pulsed applications, such camera flash. This accomplished programming high current with both RISET resistors pulsing appropriate enable pins shown back page application.
VOUT
ISETL RSET RMINL VOLTAGE VDAC
LEDL1 LTC3452 LEDL5 0.8V VDAC ILED RSET CURRENT
(3a)
VOUT
ISETL RMINL RPOT
LEDL1 LTC3452 LEDL5 0.8V ILED RMINL RPOT RSET
(3c)
Figure Additional Brightness Control Methods: (3a) Using Voltage DAC, (3b) Using Current DAC, (3c) Using Potentiometer, (3d) Using Input
Varying Brightness Linearly Continuously variable brightness control achieved interfacing directly both ISET pins. Figure shows four such methods employing voltage DAC, current DAC, simple potentiometer input applied ISETL controlling power bank currents. These four techniques similarly applied ISETH controlling high power bank currents.
VOUT ISETL IDAC 0.8V RMINL LEDL1 LTC3452 LEDL5 ILED IDAC
(3b)
VOUT
ISETL RSET RMINL VPWM
LEDL1 LTC3452 LEDL5 ILED DVCC fPWM 10kHz 0.8V VPWM RSET 0.8V (DC% VDVCC) RSET
(3d)
3452
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LTC3452
APPLICATIO ATIO
Unused Outputs
fewer than pins used, unused LEDx pins should connected VOUT. LTC3452 senses which current source outputs being used shuts corresponding output currents save power. small trickle current (10µA: power bank, 30µA: high power bank) still applied unused outputs detect white later switched also distinguish unused outputs from used outputs during start-up. Failure Modes individual fails short circuit, current source biasing shut save power. This same operation described previously output were
initially designated unused power-up connecting LEDx VOUT). Efficiency materially affected. individual fails open circuit, control loop will initially attempt regulate current source feedback signal, since will appear requiring largest forward voltage drop programmed current. This will drive VOUT higher. open circuited will never accept programmed current, VOUT must voltage-limited means secondary control loop. LTC3452 limits VOUT 4.5V this failure mode. other LEDs will still remain biased correct programmed current overall circuit efficiency will decrease.
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LTC3452
PACKAGE DESCRIPTIO
4.50 0.05 3.10 0.05 2.45 0.05 SIDES)
RECOMMENDED SOLDER PITCH DIMENSIONS BOTTOM VIEW-EXPOSED 4.00 0.10 SIDES) MARK (NOTE 2.45 0.10 (4-SIDES) 0.75 0.05 0.115 0.38 0.10 NOTCH 0.30
NOTE: DRAWING PROPOSED MADE JEDEC PACKAGE OUTLINE MO-220 VARIATION (WGGD-1)-TO APPROVED 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
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.
Package 20-Lead Plastic (4mm 4mm)
(Reference 05-08-1710)
0.70 ±0.05 PACKAGE OUTLINE 0.25 ±0.05 0.50
(UF20) 10-04
0.200 0.00 0.05
0.25 0.05 0.50
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LTC3452
TYPICAL APPLICATIO
5.5V 2.2µF ISETH 4.02k LEDH2 LEDL1, 20mA 0.1µF ISETL 10.2k PGND EXPOSED
3452 TA02a
20mA White Display 150mA Camera Light Driver
4.7µH 150mA PVIN VOUT 150mA 4.7µF
RELATED PARTS
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3452f 0406 PRINTED
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, 95035-7417
(408) 432-1900 FAX: (408) 434-0507
LEDH1 2015 D3-D6: NICHIA NSCW100 COILCRAFT D03314-472 POWER BANK 1MHz BUCK/BOOST LEDL2, 20mA LEDL3, 20mA LTC3452 LEDL4, 20mA LEDL5, UNUSED
www.linear.com
LINEAR TECHNOLOGY CORPORATION 2006

DESCRIPTIO High Efficiency: Over Entire Li-Ion Battery Range Wide

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