View LTC3539-2_4419013.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

LTC3539/LTC3539-2 2A, 1MHz/2MHz Synchronous Step-Up DC/DC Converters FEATURES
n n n n n n n n n n n n n
DESCRIPTION
The LTC(R)3539/LTC3539-2 are synchronous, 2A step-up DC/DC converters with output disconnect. Synchronous rectification enables high efficiency in the low profile 2mm x 3mm DFN package. Battery life is extended with a 700mV start-up voltage and operation down to 500mV once started. A switching frequency of 1MHz (LTC3539) or 2MHz (LTC3539-2) minimizes solution footprint by allowing the use of tiny, low profile inductors and ceramic capacitors. The current mode PWM design is internally compensated, reducing external parts count. The LTC3539/LTC3539-2 feature a pin-enabled automatic Burst Mode operation at light load conditions. Anti-ring circuitry reduces EMI by damping the inductor in discontinuous mode. Additional features include a low shutdown current of under 1A and thermal overload protection. The LTC3539/LTC3539-2 are offered in a 2mm x 3mm x 0.75mm DFN package.
L, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
Delivers 3.3V at 900mA From 2 Alkaline/NiMH Cells Delivers 5V at 900mA From a Lithium-Polymer Battery VIN Start-Up Voltage: 700mV 1.5V to 5.25V VOUT Range Up to 94% Efficiency VIN > VOUT Operation 1MHz (LTC3539) or 2MHz (LTC3539-2) Fixed Frequency Operation Output Disconnect Selectable Burst Mode(R) or PWM Operation 10A Quiescent Current Logic Controlled Shutdown: <1A Requires Only 6 External Components Low Profile (2mm x 3mm x 0.75mm) DFN Package
APPLICATIONS
n n n n n
Medical Instruments Portable Bar Code Scanners Noise Canceling Headphones Portable GPS Navigation Handheld PCs
TYPICAL APPLICATION
Wide VIN, High Power 3.3V Regulator
4.7H VIN 1.8V TO 3.6V 100 2.2F VIN LTC3539 PWM BURST MODE VOUT 1M OFF ON SHDN GND FB PGND 562k
3539 TA01a
Efficiency and Power Loss vs Load Current
1000 90
SW VOUT 3.3V 600mA 22F EFFICIENCY (%)
80 70 60 V = 2.4V 50 VIN = 3.3V OUT 40 30 20 10 0 0.1 1
EFFICIENCY 100 POWER LOSS (mW)
22pF
10 POWER LOSS 1 FREQUENCY = 1MHz FREQUENCY = 2MHz
10 100 ILOAD AVERAGE (mA)
0.1 1000
3539 TA01b
3539f
1
LTC3539/LTC3539-2 ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW SW 1 PGND 2 GND 3 VIN 4 9 8 VOUT 7 MODE 6 FB 5 SHDN
VIN Voltage ................................................... -0.3V to 6V SW Voltage DC............................................................ -0.3V to 6V Pulsed <100ns ......................................... -0.3V to 7V SHDN, FB, MODE Voltage ............................ -0.3V to 6V VOUT ............................................................. -0.3V to 6V Operating Temperature (Notes 2, 5) ......... -40C to 85C Storage Temperature Range................... -65C to 125C
DCB PACKAGE 8-LEAD (2mm 3mm) PLASTIC DFN TJMAX = 125C, JA = 60C/W TO 85C/W (NOTE 6) EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH LTC3539EDCB#PBF LTC3539EDCB-2#PBF TAPE AND REEL LTC3539EDCB#TRPBF LTC3539EDCB-2#TRPBF PART MARKING LDCS LDPH PACKAGE DESCRIPTION 8-Lead (2mm x 3mm) Plastic DFN 8-Lead (2mm x 3mm) Plastic DFN TEMPERATURE RANGE -40C to 85C -40C to 85C
Consult LTC Marketing for parts specified with wider operating temperature ranges. 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/
ELECTRICAL CHARACTERISTICS
PARAMETER Input Voltage Range Minimum Start-Up Voltage Output Voltage Adjust Range Feedback Voltage Feedback Input Current Quiescent Current - Shutdown Quiescent Current - Active Quiescent Current - Burst N-Channel MOSFET Switch Leakage Current P-Channel MOSFET Switch Leakage Current N-Channel MOSFET Switch On Resistance P-Channel MOSFET Switch On Resistance N-Channel MOSFET Current Limit VFB = 1.2V CONDITIONS After Start-Up
The l denotes the specifications which apply over the specified temperature range of -40C to 85C, otherwise specifications are at TA = 25C. VIN = 1.2V, VOUT = 3.3V, unless otherwise noted.
MIN 0.5 0.7
l l
TYP
MAX 5 0.88 5.25 1.230 50 1 500 18 10 20
UNITS V V V V nA A A A A A A
ILOAD = 1mA, VOUT = 0V 1.5 1.170
1.200 1 0.01 300 10 0.1 0.1 0.09 0.125
VSHDN = 0V, Not Including Switch Leakage, VOUT = 0V Measured on VOUT, Non-Switching Measured on VOUT, FB >1.230V VSW = 5V VSW = 5V, VOUT = 0V VOUT = 3.3V VOUT = 3.3V
l
2
2.6
3539f
2
LTC3539/LTC3539-2 ELECTRICAL CHARACTERISTICS
PARAMETER Maximum Duty Cycle Minimum Duty Cycle Switching Frequency MODE Input High Voltage MODE Input Low Voltage MODE Input Current SHDN Input High Voltage SHDN Input Low Voltage SHDN Input Current VSHDN = 1.2V VSHDN = 3.3V 0.3 1 VMODE = 1.2V 0.88 0.3 1 2 0.3 CONDITIONS VFB = 1.15V VFB = 1.3V LTC3539 LTC3539-2
l l l l
The l denotes the specifications which apply over the specified temperature range of -40C to 85C, otherwise specifications are at TA = 25C. VIN = 1.2V, VOUT = 3.3V, unless otherwise noted.
MIN 87 0.7 1.8 0.88 0.3 1 TYP 90 0 1 2 1.3 2.4 MAX UNITS % % MHz MHz V V A V V A A
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 LTC3539E/LTC3539E-2 is guaranteed to meet performance specifications from 0C to 85C. Specifications over -40C to 85C operating temperature range are assured by design, characterization and correlation with statistical process controls. Note 3: Specification is guaranteed by design and not 100% tested in production.
Note 4: Current measurements are made when the output is not switching. Note 5: This IC includes overtemperature protection that is intended to protect the device during momentary overload conditions. Junction temperature will exceed 125C when overtemperature protection is active. Continuous operation above the specified maximum operating junction temperature may result in device degradation or failure. Note 6: Failure to solder the exposed backside of the package to the PC board ground plane will result in a thermal resistance much higher than 60C/W.
3539f
3
LTC3539/LTC3539-2 TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Load Current and VIN, VOUT = 1.8V
100 90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0 0.1 1 VIN = 1V VIN = 1.2V VIN = 1.5V 10 100 LOAD CURRENT (mA) 0.1 POWER LOSS 1 EFFICIENCY 10 100 POWER LOSS (mW) EFFICIENCY (%) 1000 100 90 80 70 60 50 40 30 20 10 0 0.1 1 VIN = 1.2V VIN = 1.8V VIN = 3V 10 100 LOAD CURRENT (mA) POWER LOSS 1 10 100 POWER LOSS (mW) EFFICIENCY
(TA = 25C unless otherwise noted)
Efficiency vs Load Current and VIN, VOUT = 3.3V
1000
0.01 1000
0.1 1000
3539 G01
3539 G02
Efficiency vs Load Current and VIN, VOUT = 5V
100 90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0 0.1 1 VIN = 2.4V VIN = 3.6V VIN = 4.2V 10 100 LOAD CURRENT (mA) POWER LOSS 1 10 EFFICIENCY 100 POWER LOSS (mW) 1000 100 90 80 70
No Load Input Current vs VIN
VOUT = 1.8V VOUT = 2.5V VOUT = 3.3V VOUT = 5V IOUT (mA) 2000 1800 1600 1400 1200 1000 800 600 400 200 1.0 1.5 2.0 2.5 3.0 VIN (V) 3.5 4.0 4.5
3539 G04
Maximum Output Current vs VIN
IIN (A)
60 50 40 30 20 10 0 0.5
0.1 1000
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 VIN (V)
3539 G05
VOUT = 1.8V VOUT = 2.5V VOUT = 3.3V VOUT = 5V
3539 G03
Minimum Load Resistance During Start-Up vs VIN
10000 VOUT = 3.3V 60 50 OUTPUT CURRENT (mA) LOAD RESISTANCE () 1000 40 30 20 10 0.1 0.65 0 0.75 0.85 0.95 VIN (V) 1.05 1.15
3539 G06
Burst Mode Threshold Current vs VIN and VOUT
1.10 NORMALIZED CURRENT LIMIT (A) 1.05 1.00 0.95 0.90 0.85
Normalized Current Limit vs VOUT
100
10
VOUT = 1.8V VOUT = 2.5V VOUT = 3.3V VOUT = 5V 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 INPUT VOLTAGE (V)
3539 G11
0.80 1.0
1.5
2.0
2.5 3.0 3.5 VOUT (V)
4.0
4.5
5.0
3539 G16
3539f
4
LTC3539/LTC3539-2 TYPICAL PERFORMANCE CHARACTERISTICS
RDS(ON) vs VOUT
0.30 0.25 NORMALIZED RDS(ON) () 0.20 RDS(ON) () 0.15 0.10 NMOS 0.05 0 1.5 1.3 1.2 1.1 1.0 0.9 0.8 0.7 -50 CHANGE IN VFB (%)
RDS(ON) Change vs Temperature
0.50 0.25 0 -0.25 -0.50 -0.75
VFB vs Temperature
PMOS
2.0
2.5
3.0 3.5 4.0 VOUT (V)
4.5
5.0
5.5
3539 G07
-30
-10 10 30 50 TEMPERATURE (C)
70
90
3539 G08
-1.00 -60 -40 -20 0 20 40 60 TEMPERATURE (C)
80
100
3539 G09
Start-Up Voltage vs Temperature
0.80 0.75 1mA LOAD 0.70 VIN (V) 0.65 NO LOAD 0.60 0.55 0.50 -50 SW PIN 2V/DIV VOUT 20mV/DIV AC-COUPLED INDUCTOR CURRENT 500mA/DIV
Fixed Frequency SW and IL(AC)
SW PIN 5V/DIV VOUT 20mV/DIV AC-COUPLED INDUCTOR CURRENT 200mA/DIV
Burst Mode SW and IL(AC)
500ns/DIV VIN = 2.4V VOUT = 3.3V AT 400mA COUT = 22F
3539 G12
5s/DIV VIN = 3.3V VOUT = 5V COUT = 22F
3539 G13
-25
0 25 50 TEMPERATURE (C)
75
100
3539 G10
Load Step, Fixed Frequency
Load Step, Burst Mode Operation
VOUT 50mV/DIV AC-COUPLED LOAD CURRENT 200mA/DIV 500s/DIV VIN = 2.4V VOUT = 3.3V COUT = 22F ILOAD = 100mA TO 250mA STEP
3539 G14
VOUT 50mV/DIV AC-COUPLED LOAD CURRENT 200mA/DIV 500s/DIV VIN = 2.4V VOUT = 3.3V COUT = 22F ILOAD = 20mA TO 170mA
3539 G15
3539f
5
LTC3539/LTC3539-2 PIN FUNCTIONS
SW (Pin 1): Switch Pin. Connect inductor between SW and VIN. Keep PCB trace lengths as short and wide as possible to reduce EMI. If the inductor current falls to zero, or SHDN is low, an internal anti-ring resistor is connected from SW to VIN to minimize EMI. PGND (Pin 2), GND (Pin 3): Signal and Power Ground. Provide a short direct PCB path between PGND, GND and the (-) side of the input and output capacitors. VIN (Pin 4): Battery Input Voltage. Connect a minimum of 2.2F ceramic decoupling capacitor from this pin to ground. SHDN (Pin 5): Logic Controlled Shutdown Input. There is an internal 4M pull-down on this pin. SHDN = High: Normal operation. SHDN = Low: Shutdown, quiescent current <1A. FB (Pin 6): Feedback Input to the gm Error Amplifier. Connect resistor divider tap to this pin. The output voltage can be adjusted from 1.5V to 5.25V by: VOUT = 1.20V * [1 + (R2/R1)] MODE (Pin 7): Burst Mode Pin. A logic controlled input to select either automatic Burst Mode operation or forced fixed frequency operation. MODE = High: Burst Mode operation at light loads MODE = Low: Fixed frequency PWM Mode VOUT (Pin 8): Output Voltage Sense and Drain of the Internal Synchronous Rectifier. PCB trace length from VOUT to the output filter capacitor should be as short and wide as possible. Exposed Pad (Pin 9): The exposed pad must be soldered to the PCB ground plane. It serves as another ground connection, and as a means of conducting heat away from the die.
BLOCK DIAGRAM
VIN 1 VOUT VSEL VBEST VB WELL SWITCH 8 VOUT GATE DRIVERS AND ANTI-CROSS CONDUCTION IPK COMPARATOR VREF UVLO VREF UVLO IPK SLOPE COMPARATOR R2 VOUT SW 4 VIN
-
+
IZERO COMPARATOR FB
6 R1
OFF ON
5 SHDN
SHUTDOWN
SHUTDOWN
START-UP 1MHz/2MHz OSC PWM BURST 7 MODE THERMAL SHUTDOWN TSD CLK LOGIC AND BURST MODE CONTROL
IZERO ERROR AMPLIFIER/SLEEP COMPARATOR BURST WAKE SOFT-START 2 PGND 3 GND
3539 BD
CLAMP
9
EXPOSED PAD
6
+ -
- +
VREF FB
3539f
LTC3539/LTC3539-2 OPERATION
DETAILED DESCRIPTION The LTC3539 is a high power synchronous boost converter in an 8-lead 2mm x 3mm DFN package. With the ability to start up and operate from inputs of 700mV, the device features fixed frequency, current mode PWM control for exceptional line and load regulation. The current mode architecture with adaptive slope compensation provides excellent transient load response, requiring minimal output filtering. Internal soft-start and internal loop compensation simplifies the design process while minimizing the number of external components. The switching frequency of the LTC3539 is nominally 1MHz, while the LTC3539-2 switches at 2MHz. Operation of the LTC3539 and LTC3539-2 is identical in all other respects. With its low RDS(ON) and low gate charge internal N-channel MOSFET switch and P-channel MOSFET synchronous rectifier, the LTC3539 achieves high efficiency over a wide range of load current. Burst Mode operation maintains high efficiency at very light loads, reducing the quiescent current to just 10A. Converter operation can be best understood by referring to the Block Diagram. Low Voltage Start-Up The LTC3539 includes an independent start-up oscillator designed to start up at an input voltage of 0.7V (typical). Soft-start and inrush current limiting are provided during start-up, as well as normal mode. When either VIN or VOUT exceeds 1.4V typical, the IC enters normal operating mode. Once the output voltage exceeds the input by 0.24V, the IC powers itself from VOUT instead of VIN. At this point the internal circuitry has no dependency on the VIN input voltage, eliminating the requirement for a large input capacitor. The input voltage can drop as low as 0.5V. The limiting factor for the application becomes the ability of the power source to supply sufficient energy to the output at the low voltages, and the maximum duty cycle, which is clamped at 90% typical. Note that at low input voltages, small voltage drops due to series resistance become critical, and greatly limit the power delivery capability of the converter. Low Noise Fixed Frequency Operation Soft-Start: The LTC3539/LTC3539-2 contains internal circuitry to provide soft-start operation. The internal soft-start circuitry ramps the peak inductor current from zero to its peak value of 2.6A (typical) in approximately 0.5ms, allowing start-up into heavy loads. The soft-start circuitry is reset in the event of a thermal shutdown or shutdown command. Oscillator: An internal oscillator sets the switching frequency to 1MHz for the LTC3539, and 2MHz for the LTC3539-2. Shutdown: The part is shutdown by pulling the SHDN pin below 0.3V, and activated by pulling the SHDN pin above 0.88V. Note that SHDN can be driven above VIN or VOUT, as long as it is limited to less than the absolute maximum rating. Error Amplifier: The error amplifier is a transconductance type. The non-inverting input is internally connected to the 1.2V reference and the inverting input is connected to FB. Clamps limit the minimum and maximum error amp output voltage for improved large signal transient response. Power converter control loop compensation is provided internally. A voltage divider from VOUT to ground programs the output voltage via FB from 1.5V to 5.25V. VOUT = 1.2V * [1 + (R2/R1)]. Current Sensing: Lossless current sensing converts the peak current signal of the N-channel MOSFET switch into a voltage which is summed with the internal slope compensation. The summed signal is compared to the error amplifier output to provide a peak current control command for the PWM. Current Limit: The current limit comparator shuts off the N-channel MOSFET switch once its threshold is reached. Peak switch current is limited to approximately 2.6A, independent of input or output voltage, unless VOUT falls below 0.7V, in which case the current limit is cut in half.
3539f
7
LTC3539/LTC3539-2 OPERATION
Zero Current Comparator: The zero current comparator monitors the inductor current to the output and shuts off the synchronous rectifier once this current reduces to approximately 40mA. This prevents the inductor current from reversing in polarity, improving efficiency at light loads. Synchronous Rectifier: The P-channel MOSFET synchronous rectifier is disabled when VOUT is much less than VIN. This is to control inrush current and to prevent inductor current from running away Anti-ringing Control: The anti-ringing control connects a resistor across the inductor to prevent high frequency ringing on the SW pin during discontinuous current mode operation. The ringing of the resonant circuit formed by L and CSW (capacitance on SW pin) is low energy, but can cause EMI radiation. Output Disconnect: The LTC3539 is designed to allow true output disconnect by eliminating body diode conduction of the internal P-channel MOSFET rectifier. This allows VOUT to go to zero volts during shutdown, drawing no current from the input source. It also provides inrush current limiting at turn-on, minimizing surge currents seen by the input supply. Note that to obtain the advantages of output disconnect, there must not be an external Schottky diode connected between the SW pin and VOUT. The output disconnect feature also allows VOUT to be pulled high, without any reverse current into a battery on VIN. Thermal Shutdown: If the die temperature exceeds 160C, the device will go into thermal shutdown. All switches will be turned off and the internal soft-start capacitor will be discharged. The device will be enabled again when the die temperature drops by about 15C. Burst Mode Operation When Burst Mode operation is enabled by bringing the MODE pin above 0.88V, the LTC3539 will automatically enter Burst Mode operation at light load current, then return to fixed frequency PWM mode when the load increases. Refer to the typical performance characteristics to see the output load Burst Mode threshold vs VIN. The load current at which Burst Mode operation is entered can be changed by adjusting the inductor value. Raising the inductor value will lower the load current at which Burst Mode operation is entered. In Burst Mode operation, the LTC3539 still switches at a fixed frequency, using the same error amplifier and loop compensation for peak current mode control. This control method eliminates any output transient when switching between modes. In Burst Mode operation, energy is delivered to the output until it reaches the nominal regulation value, then the LTC3539 transitions to Sleep mode where the outputs are off and the LTC3539 consumes only 10A of quiescent current from VOUT. When the output voltage droops slightly, switching resumes. This maximizes efficiency at very light loads by minimizing switching and quiescent current losses. Burst Mode output voltage ripple, which is typically 1% peak to peak, can be reduced by using more output capacitance (47F or greater). As the load increases, the LTC3539 will automatically leave Burst Mode operation. Once the LTC3539 has left Burst Mode operation and returned to normal operation, it will remain there until the output load is reduced below the burst threshold. Burst Mode operation is inhibited during start-up until soft-start is complete and VOUT is at least 0.24V greater than VIN. When the MODE pin is below 0.3V, the LTC3539 features continuous PWM operation. In this mode, at very light loads, the LTC3539 will exhibit pulse-skip operation. If the MODE pin voltage exceeds the greater of VIN or VOUT by 0.5V, the MODE pin will sink additional current.
3539f
8
LTC3539/LTC3539-2 APPLICATIONS INFORMATION
VIN > VOUT Operation The LTC3539 will maintain output voltage regulation even when the input voltage is above the desired output. Note that the efficiency and the maximum output current capability are reduced. Refer to Typical Performance Characteristics. Short-Circuit Protection The LTC3539 output disconnect feature allows an output short circuit while maintaining a maximum internally set current limit. To reduce power dissipation under shortcircuit conditions, the peak switch current limit is reduced to 1.4A (typical). Schottky Diode Although it is not required, adding a Schottky diode from SW to VOUT will improve efficiency by about 2%. Note that this defeats the output disconnect, VIN > VOUT operation and short circuit protection features. PCB LAYOUT GUIDELINES The high speed operation of the LTC3539 demands careful attention to board layout. A careless layout will result in reduced performance. Figure 1 shows the recommended component placement. A large ground pin copper area will help to lower the die temperature. A multilayer board with a separate ground plane is ideal. L> Where: f = 1 for the LTC3539 or 2.2 for the LTC3539-2 Ripple = allowable inductor current ripple (Amps peak-to-peak) VIN(MIN) = minimum input voltage VOUT(MAX) = maximum output voltage The inductor current ripple is typically set for 20% to 40% of the maximum inductor current. High frequency ferrite core inductor materials improve efficiency by reducing frequency dependent power losses compared to cheaper powdered iron types. The inductor should have low ESR (series resistance of the windings) to reduce the I2R power losses, and must accomodate the peak inductor current without saturating. Molded chokes and some chip inductors usually do not have enough core area to support the peak inductor current of 2.6A seen on the LTC3539. To minimize radiated noise, use a shielded inductor. See Table 1 for suggested suppliers and representative components.
*Single cell applications (VIN < 1.6V) should use a 2.2H inductor for the LTC3539 MULTIPLE VIAS TO GROUND PLANE
3539 F01
COMPONENT SELECTION Inductor Selection The LTC3539 can utilize small surface mount and chip inductors due to the high switching frequency. Inductor values between 3.3H and 4.7H for the LTC3539 and between 1.5H and 2.5H for the LTC3539-2 are suitable for most applications*. Larger values of inductance will allow slightly greater output current capability (and lower the Burst Mode threshold) by reducing the inductor ripple current. However, increasing the inductance above 10H will increase size while providing little improvement in output current capability. The minimum inductance value is given by: VIN(MIN) * ( VOUT(MAX ) - VIN(MIN) ) Ripple * VOUT(MAX ) * f
LTC3539 SW 1 PGND 2 GND 3 VIN 4 8 VOUT 7 MODE 6 FB 5 SHDN MINIMIZE TRACE ON FB AND SW
+
VIN
Figure 1. Recommended Component Placement for Single Layer Board
3539f
9
LTC3539/LTC3539-2 APPLICATIONS INFORMATION
Table 1. Representative Inductors
VENDOR Coilcraft (847) 639-6400 www.coilcraft.com Murata www.murata.com Sumida (847) 956-0666 www.sumida.com TDK (847) 803-6100 www.component.tdk.com Toko (408) 432-8282 www.tokoam.com Wurth (201) 785-8800 www.we-online.com PART/STYLE MSS5131 LPS4018-222 MSS6132 MOS6020 LQH55D LQH66S CDRH4D22 CDRH4D28C CDRH5D28 CDR6D23 VLF5014ST
An output capacitor of up to 100F is required at lower output voltages. Even with VOUT greater than 3V, larger values up to 100F may be used to obtain extremely low output voltage ripple and improve transient response. X5R and X7R dielectric materials are preferred for their ability to maintain capacitance over wide voltage and temperature ranges. Y5V types should not be used. A small ceramic capacitor in parallel with a larger tantalum capacitor may be used in demanding applications which have large load transients. A feedforward capacitor across the top resistor of the feedback divider (from VOUT to FB) is usually required to improve transient response. A typical value of 22pF will generally suffice. Low ESR input capacitors reduce input switching noise and reduce the peak current drawn from the battery. It follows that ceramic capacitors are also a good choice for input decoupling and should be located as close as possible to the device. A 2.2F input capacitor is sufficient for most applications. Larger values may be used without limitations. Table 2 shows a list of several ceramic capacitor manufacturers. Consult the manufacturers directly for detailed information on their selection of ceramic parts.
Table 2. Capacitor Vendor Information
SUPPLIER AVX Murata Taiyo-Yuden TDK PHONE (803) 448-9411 (714) 852-2001 (408) 573-4150 (847) 803-6100 WEBSITE www.avxcorp.com www.murata.com www.t-yuden.com www.component.tdk.com
D53LC D63LCB WE-TPC Type LH, X WE-PD Type XS
Output and Input Capacitor Selection The internal loop compensation of the LTC3539 is designed to be stable with output capacitor values of 10F or greater. Although ceramic capacitors are recommended, low ESR (equivalent series resistance) tantalum capacitors may be used as well. Low ESR capacitors should be used to minimize the output voltage ripple. Multilayer ceramic capacitors are an excellent choice as they have extremely low ESR and are available in small footprints. A 22F to 47F output capacitor is sufficient for output voltages of 3V or greater.
TYPICAL APPLICATIONS
1 Cell to 1.8V
2.2H VIN 1V TO 1.6V 2.2F VIN SW VOUT 1.8V 500mA 22F* x5 VIN 0.9V TO 1.6V 2.2F VIN SW VOUT 3.3V 350mA 22F x2
1 Cell to 3.3V
2.2H VIN 3V TO 4.5V 2.2F
Li-Ion Cell to 5V
2.2H
VIN
SW VOUT 5V 750mA 22F 309k
3539 TA04
LTC3539 PWM BURST MODE VOUT 1M OFF ON SHDN FB 1.91M
3539 TA02
LTC3539 PWM BURST MODE VOUT 1M OFF ON SHDN FB 562k
3539 TA03
LTC3539-2 PWM BURST MODE VOUT 1M OFF ON SHDN FB 22pF
22pF
22pF
GND PGND *AT HIGH LOAD CURRENTS, A TANTALUM CAPACITOR WILL IMPROVE PERFORMANCE.
GND PGND
GND PGND
3539f
10
LTC3539/LTC3539-2 PACKAGE DESCRIPTION
DCB Package 8-Lead Plastic DFN (2mm x 3mm)
(Reference LTC DWG # 05-08-1718 Rev A)
0.70 0.05 1.35 0.05 1.65 0.05
3.50 0.05 2.10 0.05
PACKAGE OUTLINE
0.25 0.05 0.45 BSC 1.35 REF RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 2.00 0.10 (2 SIDES) R = 0.115 TYP R = 0.05 5 TYP 0.40 0.10 8
1.35 0.10 3.00 0.10 (2 SIDES) PIN 1 BAR TOP MARK (SEE NOTE 6) 4 0.200 REF 0.75 0.05 1.35 REF BOTTOM VIEW--EXPOSED PAD 0.00 - 0.05 NOTE: 1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE 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 0.15mm 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 1 1.65 0.10 PIN 1 NOTCH R = 0.20 OR 0.25 x 45 CHAMFER
(DCB8) DFN 0106 REV A
0.23 0.05 0.45 BSC
3539f
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.
11
LTC3539/LTC3539-2 RELATED PARTS
PART NUMBER DESCRIPTION LTC3400/ LTC3400B LTC3401 LTC3402 LTC3421 LTC3422 LTC3423/ LTC3424 LTC3426 LTC3428 LTC3429 LTC3458 LTC3458L 600mA ISW, 1.2MHz, Synchronous Step-Up DC/DC Converters COMMENTS 92% Efficiency VIN: 0.85V to 5V, VOUT(MAX) = 5V, IQ = 19A/300A, ISD <1A, ThinSOTTM Package
1A ISW, 3MHz, Synchronous Step-Up DC/DC Converter 97% Efficiency VIN: 0.5V to 5V, VOUT(MAX) = 6V, IQ = 38A, ISD <1A, 10-Lead MS Package 2A ISW, 3MHz, Synchronous Step-Up DC/DC Converter 97% Efficiency VIN: 0.5V to 5V, VOUT(MAX) = 6V, IQ = 38A, ISD <1A, 10-Lead MS Package 3A ISW, 3MHz, Synchronous Step-Up DC/DC Converter 95% Efficiency VIN: 0.5V to 4.5V, VOUT(MAX) = 5.25V, IQ = 12A, ISD <1A, with Output Disconnect QFN24 Package 1.5A ISW, 3MHz Synchronous Step-Up DC/DC Converter with Output Disconnect 1A/2A ISW, 3MHz, Synchronous Step-Up DC/DC Converter 2A ISW, 1.2MHz, Step-Up DC/DC Converter 500mA ISW, 1.25MHz/2.5MHz, Synchronous Step-Up DC/DC Converters with Output Disconnect 600mA ISW, 500kHz, Synchronous Step-Up DC/DC Converter with Output Disconnect and Soft-Start 1.4A ISW, 1.5MHz, Synchronous Step-Up DC/DC Converter/Output Disconnect/Burst Mode Operation 1.7A ISW, 1.5MHz, Synchronous Step-Up DC/DC Converter with Output Disconnect, Automatic Burst Mode Operation 70mA ISW, 10V Micropower Synchronous Boost Converter/Output Disconnect/Burst Mode Operation 400mA Micropower Synchronous Step-Up DC/DC Converter with Output Disconnect 400mA Micropower Synchronous Step-Up DC/DC Converter with Output Disconnect 95% Efficiency VIN: 0.5V to 4.5V, VOUT(MAX) = 5.25V, IQ = 25A, ISD <1A, 3mm x 3mm DFN Package 95% Efficiency VIN: 0.5V to 5.5V, VOUT(MAX) = 5.5V, IQ = 38A, ISD <1A, 10-Lead MS Package 92% Efficiency VIN: 1.6V to 4.3V, VOUT(MAX) = 5V, ISD <1A, SOT-23 Package 92% Efficiency VIN: 1.8V to 5V, VOUT(MAX) = 5.25V, ISD <1A, 3mm x 3mm DFN Package 96% Efficiency VIN: 0.5V to 4.4V, VOUT(MAX) = 5V, IQ = 20A/300A, 93% Efficiency VIN: 1.5V to 6V, VOUT(MAX) = 7.5V, IQ = 15A, ISD <1A, DFN12 Package 94% Efficiency VOUT(MAX) = 6V, IQ = 12A, DFN12 Package
LTC3459 LTC3525-3/ LTC3525-3.3/ LTC3525-5 LTC3525L-3 LTC3526/ LTC3526B LTC3526L LTC3527/ LTC3527-1 LTC3528/ LTC3528B
VIN: 1.5V to 5.5V, VOUT(MAX) = 10V, IQ = 10A, ISD <1A, ThinSOT Package 95% Efficiency VIN: 1V to 4.5V, VOUT(MAX) = 3.3V or 5V, IQ = 7A, ISD <1A, SC-70 Package 95% Efficiency VIN: 0.88V to 4.5V, VOUT(MAX) = 3V, IQ = 7A, ISD <1A, SC-70 Package
500mA, 1MHz Synchronous Step-Up DC/DC Converter 94% Efficiency VIN: 0.85V to 5V, VOUT(MAX) = 5.25V, IQ = 9A, ISD <1A, 2mm x 2mm DFN-6 Package with Output Disconnect 550mA, 1MHz Synchronous Step-Up DC/DC Converter 94% Efficiency VIN: 0.68V to 5V, VOUT(MAX) = 5.25V, IQ = 9A, ISD <1A, with Output Disconnect 2mm x 2mm DFN-6 Package Dual 800mA/400mA, 1.2MHz/2.2MHz Synchronous Step-Up DC/DC Converter with Output Disconnect 94% Efficiency VIN: 0.68V to 5V, VOUT(MAX) = 5.25V, IQ = 12A, ISD <1A, 3mm x 3mm QFN-16 Package
1A, 1MHz Synchronous Step-Up DC/DC Converter with 94% Efficiency VIN: 0.68V to 5V, VOUT(MAX) = 5.25V, IQ = 12A, ISD <1A, 2mm x 3mm DFN-8 Package Output Disconnect
ThinSOT is a trademark of Linear Technology Corporation.
3539f
12 Linear Technology Corporation
(408) 432-1900 FAX: (408) 434-0507
LT 0408 * PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2008

▲Up To Search▲

Price & Availability of LTC3539-2

	To Download LTC3539-2 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .