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FEATURES
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LTC3526/LTC3526B 500mA 1MHz Synchronous Step-Up DC/DC Converters in 2mm x 2mm DFN DESCRIPTION
The LTC(R)3526/LTC3526B are synchronous, fixed frequency step-up DC/DC converters with output disconnect. Synchronous rectification enables high efficiency in the low profile 2mm x 2mm DFN package. Battery life in single AA/AAA powered products is extended further with an 850mV start-up voltage and operation down to 500mV once started. A switching frequency of 1MHz 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 LTC3526 features automatic Burst Mode operation at light load conditions, while the LTC3526B features continuous switching at light loads. Anti-ringing control circuitry also reduces EMI concerns by damping the inductor in discontinuous mode. Additional features include a low shutdown current of under 1A and thermal shutdown. The LTC3526/LTC3526B are housed in a 2mm x 2mm x 0.75mm DFN package.
, 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 100mA from a Single Alkaline/ NiMH Cell or 3.3V at 200mA from Two Cells VIN Start-Up Voltage: 850mV 1.6V to 5.25V VOUT Range Up to 94% Efficiency Output Disconnect 1MHz Fixed Frequency Operation VIN > VOUT Operation Integrated Soft-Start Current Mode Control with Internal Compensation Automatic Burst Mode(R) Operation with 9A Quiescent Current (LTC3526) Low Noise PWM Operation (LTC3526B) Internal Synchronous Rectifier Logic Controlled Shutdown (IQ < 1A) Anti-Ringing Control Low Profile (2mm x 2mm x 0.75mm) DFN Package
APPLICATIONS
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Medical Instruments Flash-Based MP3 Players Noise Canceling Headphones Wireless Mice Bluetooth Headsets
TYPICAL APPLICATION
4.7H
LTC3526 Efficiency and Power Loss vs Load Current
100 90 80 VIN = 2.4V EFFICIENCY 100 POWER LOSS (mW) 1000
VIN 1.6V TO 3.2V 1F OFF ON
VIN
VOUT 1.78M FB 1M
VOUT 3.3V 200mA 4.7F
EFFICIENCY (%)
SW
70 60 50 40 30 POWER LOSS 1 10
LTC3526 SHDN GND
3526 TA01a
20 10 0 0.01 0.1 1 10 100
0.1
0.01 1000
3526 TA01b
LOAD CURRENT (mA)
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1
LTC3526/LTC3526B ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW SW 1 GND 2 VIN 3 7 6 VOUT 5 FB 4 SHDN
VIN Voltage ................................................... -0.3V to 6V SW Voltage DC............................................................ -0.3V to 6V Pulsed <100ns ......................................... -0.3V to 7V SHDN, FB Voltage ........................................ -0.3V to 6V VOUT ............................................................. -0.3V to 6V Operating Temperature Range (Note 2).... -40C to 85C Storage Temperature Range................... -65C to 150C
DC PACKAGE 6-LEAD (2mm x 2mm) PLASTIC DFN TJMAX = 125C, JA = 60C/W (NOTE 6) EXPOSED PAD (PIN 7) IS GND, MUST BE SOLDERED TO PC BOARD
ORDER INFORMATION
LEAD FREE FINISH LTC3526EDC#PBF LTC3526BEDC#PBF TAPE AND REEL LTC3526EDC#TRPBF LTC3526BEDC#TRPBF PART MARKING LCHW LCNN PACKAGE DESCRIPTION 6-Lead (2mm x 2mm) Plastic DFN 6-Lead (2mm x 2mm) 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 Minimum Start-Up Input Voltage Output Voltage Adjust Range 0C to 85C Feedback Pin Voltage Feedback Pin 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 Current Limit Delay to Output Maximum Duty Cycle Minimum Duty Cycle Switching Frequency SHDN Pin Input High Voltage SHDN Pin Input Low Voltage SHDN Pin Input Current (Note 3) VFB = 1.15V VFB = 1.3V VFB = 1.30V
The l denotes the specifications which apply over the specified operating temperature range of -40C to 85C, otherwise specifications are at TA = 25C. VIN = 1.2V, VOUT = 3.3V unless otherwise noted.
CONDITIONS ILOAD = 1mA
l l
MIN 1.7 1.6 1.165
TYP 0.85
MAX 1 5.25 5.25
UNITS V V V V nA A A A A A mA ns %
1.195 1 0.01 250 9 0.1 0.1 0.4 0.6
1.225 50 1 500 18 5 10
VSHDN = 0V, Not Including Switch Leakage, VOUT = 0V Measured on VOUT, Nonswitching, LTC3526 Only Measured on VOUT, FB > 1.230V VSW = 5V VSW = 5V, VOUT = 0V VOUT = 3.3V VOUT = 3.3V
l l l l
500 85 0.7 0.9
700 60 90 0 1 1.3 0.3
% MHz V V A A
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VSHDN = 1.2V VSHDN = 3.3V
0.3 1
1 2
2
LTC3526/LTC3526B ELECTRICAL CHARACTERISTICS
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 LTC3526E 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.
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Load Current and VIN for VOUT = 1.8V (LTC3526)
100 90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0 0.01 0.1 PLOSS AT VIN = 1.0V PLOSS AT VIN = 1.2V PLOSS AT VIN = 1.5V 1 10 100 LOAD CURRENT (mA) 0.1 1 VIN = 1.0V VIN = 1.2V VIN = 1.5V 100 POWER LOSS (mW) EFFICIENCY (%) 1000 100 90 80 70 60 50 40 30 20 10 0 0.01 VIN = 1.2V VIN = 1.8V VIN = 2.4V VIN = 3.0V 100 POWER LOSS (mW) IIN (A)
Efficiency vs Load Current and VIN for VOUT = 3.3V (LTC3526)
1000
100 90 80 70 60 50 40 30 20 10 0.5
No-Load Input Current vs VIN
VOUT = 5V VOUT = 3.3V VOUT = 2.5V VOUT = 1.8V
10
10
1
0.01 1000
PLOSS AT VIN = 1.2V 0.1 PLOSS AT VIN = 1.8V PLOSS AT VIN = 2.4V PLOSS AT VIN = 3.0V 0.01 0.1 1 10 100 1000 LOAD CURRENT (mA)
3526 G02
1.0
1.5
2.0
2.5 VIN (V)
3.0
3.5
4.0
4.5
3526 G04
3526 G01
Efficiency vs Load Current and VIN for VOUT = 5V (LTC3526)
100 90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0 0.01 10 VIN = 1.2V VIN = 2.4V VIN = 3.6V 1 VIN = 4.2V 100 POWER LOSS (mW) IOUT (mA) 1000
400 350 300 250 200
Maximum Output Current vs VIN
VOUT = 3.3V VOUT = 2.5V VOUT = 1.8V
1000
Minimum Load Resistance During Start-Up vs VIN
LOAD () 4.0 4.5
100
VOUT = 5V 150 100 50 0 0.5 L = 4.7H 1.0 1.5 2.0 2.5 VIN (V)
3526 G05
PLOSS AT VIN = 1.2V 0.1 PLOSS AT VIN = 2.4V PLOSS AT VIN = 3.6V PLOSS AT VIN = 4.2V 0.01 0.1 1 10 100 1000 LOAD CURRENT (mA)
3526 G03
3.0
3.5
10 0.85
0.95
1.05 VIN (V)
1.15
1.25
3526 G06
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LTC3526/LTC3526B TYPICAL PERFORMANCE CHARACTERISTICS
Start-Up Delay Time vs VIN
100 90 80 LOAD CURRENT (mA) 70 DELAY (s) 60 50 40 30 20 10 0 1.0 1.5 2.0 0 2.5 3.0 VIN (V) 3.5 4.0 4.5 1 1.25 VIN (V) 1.5
3526 G08a
Burst Mode Threshold Current vs VIN
30 VOUT = 1.8V COUT = 10F 25 L = 4.7H 20 LEAVE BURST 15 ENTER BURST 10 5 LOAD CURRENT (mA) 40
Burst Mode Threshold Current vs VIN
VOUT = 2.5V 35 COUT = 10F L = 4.7H 30 25 LEAVE BURST 20 15 ENTER BURST 10 5 0 1 1.25 VIN (V)
3526 G08b
1.5
1.75
3526 G07
Burst Mode Threshold Current vs VIN
50 VOUT = 3.3V 45 COUT = 10F L = 4.7H 40 LOAD CURRENT (mA) 35 30 25 20 15 10 5 0 1.0 1.5 2.0 VIN (V) 2.5 3.0
3526 G08c
Burst Mode Threshold Current vs VIN
60 50 LOAD CURRENT (mA) 40 LEAVE BURST 30 20 ENTER BURST 10 0 1.0 VOUT = 5V COUT = 10F L = 4.7H FREQUENCY CHANGE (%) 2 1 0 -1 -2 -3 -4 -5 1.5 2.0 2.5 3.0 VIN (V) 3.5 4.0 4.5
Oscillator Frequency Change vs VOUT
NORMALIZED TO 3.3V
LEAVE BURST
ENTER BURST
-6 1.5
2.0
2.5
3.0 3.3 VOUT (V)
4.0
4.5
5.0
3526 G08d
3526 G09
RDS(ON) vs VOUT
0.90 0.85 0.80 0.75 0.70 RDS(ON) () 0.65 0.60 0.55 0.50 0.45 0.40 0.35 0.30 1.5 2.0 2.5 3.0 3.5 VOUT (V) 4.0 4.5 5.0 NMOS PMOS FREQUENCY CHANGE (%) 10 8 6 4 2 0 -2 -4 -6 -8
Oscillator Frequency Change vs Temperature
1.3 NORMALIZED TO 25C 1.2 NORMALIZED RDS(ON) 1.1 1.0 0.9 0.8
RDS(ON) Change vs Temperature
NORMALIZED TO 25C
-10 -50
-30
-10 10 30 50 TEMPERATURE (C)
70
90
0.7 -50
-30
-10 10 30 50 TEMPERATURE (C)
70
90
3526 G10
3526 G11
3526 G12
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LTC3526/LTC3526B TYPICAL PERFORMANCE CHARACTERISTICS
VFB vs Temperature
0.50 0.25 CHANGE IN VFB (%) 0 VIN (V) -0.25 -0.50 -0.75 -1.00 20 40 60 -60 -40 -20 0 TEMPERATURE (C) 1.00 NORMALIZED TO 25C 0.95 0.90 IQ (A) 0.85 0.80 0.75 0.70 -50
Start-Up Voltage vs Temperature
LOAD = 1mA 10.0 9.5 9.0 8.5 8.0 7.5 7.0 1.5
Burst Mode Current vs VOUT
80
100
-30
-10 10 30 -50 TEMPERATURE (C)
70
90
2.0
2.5
3.0 3.5 VOUT (V)
4.0
4.5
5.0
3526 G13
3526 G14
3526 G15
Fixed Frequency Switching Waveform and VOUT Ripple
SW PIN 2V/DIV VOUT 10mV/DIV AC COUPLED VIN = 1.2V 500ns/DIV VOUT = 3.3V AT 100mA COUT = 10F
3526 G16
Burst Mode Waveforms
SW PIN 2V/DIV VOUT 20mV/DIV AC COUPLED INDUCTOR CURRENT 0.2A/DIV VIN = 1.2V VOUT = 3.3V COUT = 10F 10s/DIV
3526 G17
VOUT and IIN During Soft-Start
VOUT 1V/DIV INPUT CURRENT 0.2A/DIV SHDN PIN 1V/DIV VOUT = 3.3V COUT = 10F 200s/DIV
3526 G18
Load Step Response (from Burst Mode Operation)
VOUT 100mV/DIV AC COUPLED LOAD CURRENT 50mA/DIV VIN = 3.6V 100s/DIV VOUT = 5V 20mA TO 170mA STEP COUT = 10F
3526 G19
Load Step Response (Fixed Frequency)
VOUT 100mV/DIV AC COUPLED LOAD CURRENT 50mA/DIV VIN = 3.6V 100s/DIV VOUT = 5V 50mA TO 150mA STEP COUT = 10F
3526 G20
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LTC3526/LTC3526B TYPICAL PERFORMANCE CHARACTERISTICS
Load Step Response (Fixed Frequency)
VOUT 100mV/DIV AC COUPLED LOAD CURRENT 50mA/DIV VIN = 1.2V 100s/DIV VOUT = 3.3V 50mA TO 100mA STEP COUT = 10F
3526 G21
Load Step Response (from Burst Mode Operation)
VOUT 100mV/DIV AC COUPLED LOAD CURRENT 50mA/DIV VIN = 1.2V 50s/DIV VOUT = 3.3V 5mA TO 100mA STEP COUT = 10F
3526 G22
ELECTRICAL CHARACTERISTICS
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-ringing switch is connected from SW to VIN to minimize EMI. GND (Pin 2): Signal and Power Ground. Provide a short direct PCB path between GND and the (-) side of the input and output capacitors. VIN (Pin 3): Input Supply Pin. Connect a minimum of 1F ceramic decoupling capacitor from this pin to ground using short direct PCB traces. SHDN (Pin 4): 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 5): Feedback Input to the gm Error Amplifier. Connect resistor divider tap to this pin. The top of the divider connects to the output capacitor, the bottom of the divider connects to GND. Referring to the Block Diagram, the output voltage can be adjusted from 1.6V to 5.25V by: VOUT = 1.195V * 1+ R2 R1
VOUT (Pin 6): Output voltage sense and drain of the internal synchronous rectifier. PCB trace from VOUT to the output filter capacitor (4.7F minimum) should be as short and wide as possible. Exposed Pad (Pin 7): The Exposed Pad must be soldered to the PCB ground plane. It serves as an additional ground connection and as a means of conducting heat away from the package.
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LTC3526/LTC3526B BLOCK DIAGRAM
VIN 0.85V TO 5V L1 4.7H CIN 2.2F VOUT 3 VIN VSEL VBEST VB VOUT ANTI-RING GATE DRIVERS AND ANTI-CROSS CONDUCTION 6 VOUT 1.6V TO 5.25V R2 1 SW
WELL SWITCH
4
SHDN 4M
SHUTDOWN
SHUTDOWN
-+
IPK IZERO IPK COMP SLOPE COMP
FB IZERO COMP
5 R1
COUT 4.7F
UVLO
START-UP LOGIC 1MHz OSC CLK MODE CONTROL CLAMP THERMAL SHUTDOWN TSD WAKE CSS EXPOSED PAD 7 GND 2
+ -
VREF
VREF
ERROR AMP SLEEP COMP
+ -
VREF
3526 BD
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LTC3526/LTC3526B OPERATION
(Refer to Block Diagram)
The LTC3526/LTC3526B are 1MHz synchronous boost converters housed in a 6-lead 2mm x 2mm DFN package. With the ability to start up and operate from inputs less than 1V, these devices feature 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. With its low RDS(ON) and low gate charge internal N-channel MOSFET switch and P-channel MOSFET synchronous rectifier, the LTC3526 achieves high efficiency over a wide range of load currents. Automatic Burst Mode operation maintains high efficiency at very light loads, reducing the quiescent current to just 9A. Operation can be best understood by referring to the Block Diagram. LOW VOLTAGE START-UP The LTC3526/LTC3526B include an independent start-up oscillator designed to start up at an input voltage of 0.85V (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. When 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 availability of the power source to supply sufficient energy to the output at low voltages, and 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 LTC3526/LTC3526B contain internal circuitry to provide soft-start operation. The soft-start circuitry slowly ramps
the peak inductor current from zero to its peak value of 700mA (typical) in approximately 0.5ms, allowing startup into heavy loads. The soft-start circuitry is reset in the event of a shutdown command or a thermal shutdown. Oscillator An internal oscillator sets the switching frequency to 1MHz. Shutdown Shutdown is accomplished by pulling the SHDN pin below 0.3V and enabled by pulling the SHDN pin above 0.8V typical. 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 positive input of the transconductance error amplifier is internally connected to the 1.195V reference and the negative 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. An external resistive voltage divider from VOUT to ground programs the output voltage via FB from 1.6V to 5.25V. VOUT = 1.195V * 1+ Current Sensing Lossless current sensing converts the peak current signal of the N-channel MOSFET switch into a voltage that 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. The current limit comparator delay to output is typically 60ns. Peak switch current is limited to approximately 700mA, independent of input or output voltage, unless VOUT falls below 0.7V, in which case the current limit is cut in half.
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R2 R1
8
LTC3526/LTC3526B OPERATION
(Refer to Block Diagram)
Zero Current Comparator The zero current comparator monitors the inductor current to the output and shuts off the synchronous rectifier when this current reduces to approximately 30mA. This prevents the inductor current from reversing in polarity, improving efficiency at light loads. Synchronous Rectifier To control inrush current and to prevent the inductor current from running away when VOUT is close to VIN, the P-channel MOSFET synchronous rectifier is only enabled when VOUT > (VIN + 0.24V). 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. Although the ringing of the resonant circuit formed by L and CSW (capacitance on SW pin) is low energy, it can cause EMI radiation. Output Disconnect The LTC3526/LTC3526B are designed to allow true output disconnect by eliminating body diode conduction of the internal P-channel MOSFET rectifier. This allows for VOUT to go to zero volts during shutdown, drawing no current from the input source. It also allows for 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 connected to VIN. Thermal Shutdown If the die temperature exceeds 160C, the LTC3526/ LTC3526B will go into thermal shutdown. All switches will be off and the soft-start capacitor will be discharged. The device will be enabled again when the die temperature drops by about 15C.
Burst Mode OPERATION The LTC3526 will automatically enter Burst Mode operation at light load and return to fixed frequency PWM mode when the load increases. Refer to the Typical Performance Characteristics to see the output load Burst Mode threshold current 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 LTC3526 still switches at a fixed frequency of 1MHz, 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 LTC3526 transitions to sleep mode where the outputs are off and the LTC3526 consumes only 9A 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 losses. Burst Mode output voltage ripple, which is typically 1% peak-to-peak, can be reduced by using more output capacitance (10F or greater), or with a small capacitor (10pF to 50pF) connected between VOUT and FB. As the load current increases, the LTC3526 will automatically leave Burst Mode operation. Note that larger output capacitor values may cause this transition to occur at lighter loads. Once the LTC3526 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 and softstart and until VOUT is at least 0.24V greater than VIN. The LTC3526B features continuous PWM operation at 1MHz. At very light loads, the LTC3526B will exhibit pulse-skip operation.
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LTC3526/LTC3526B APPLICATIONS INFORMATION
VIN > VOUT OPERATION The LTC3526/LTC3526B will maintain voltage regulation even when the input voltage is above the desired output voltage. Note that the efficiency is much lower in this mode, and the maximum output current capability will be less. Refer to the Typical Performance Characteristics. SHORT-CIRCUIT PROTECTION The LTC3526/LTC3526B output disconnect feature allows output short circuit while maintaining a maximum internally set current limit. To reduce power dissipation under short-circuit conditions, the peak switch current limit is reduced to 400mA (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 and short-circuit protection features. PCB LAYOUT GUIDELINES The high speed operation of the LTC3526/LTC3526B 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, but not absolutely necessary. COMPONENT SELECTION Inductor Selection The LTC3526/LTC3526B can utilize small surface mount chip inductors due to their fast 1MHz switching frequency. Inductor values between 3.3H and 6.8H 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. Increasing the inductance above 10H will increase size while providing little improvement in output current capability. The minimum inductance value is given by: L> where: Ripple = Allowable inductor current ripple (amps peakpeak) 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 reduce frequency dependent power losses compared to cheaper powdered iron types, improving efficiency. The inductor should have low ESR (series resistance of the windings) to reduce the I2R power losses, and must be able to support the peak VIN(MIN) * VOUT(MAX) - VIN(MIN) Ripple * VOUT(MAX)
(
)
LTC3526 SW 1 6 VOUT
GND 2
5 FB
MINIMIZE TRACE ON FB AND SW
+
VIN
VIN 3
4 SHDN MULTIPLE VIAS TO GROUND PLANE
3526 F01
Figure 1. Recommended Component Placement for Single Layer Board
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LTC3526/LTC3526B APPLICATIONS INFORMATION
inductor current without saturating. Molded chokes and some chip inductors usually do not have enough core area to support the peak inductor currents of 700mA seen on the LTC3526/LTC3526B. To minimize radiated noise, use a shielded inductor. See Table 1 for suggested components and suppliers.
Table 1. Recommended Inductors
VENDOR Coilcraft (847) 639-6400 www.coilcraft.com PART/STYLE LPO4815 LPS4012, LPS4018 MSS5131 MSS4020 MOS6020 ME3220 DS1605, DO1608 SD10, SD12, SD14, SD18, SD20, SD52, SD3114, SD3118 MIP3226D4R7M, MIP3226D3R3M MIPF2520D4R7 MIPWT3226D3R0 LQH43C LQH32C (-53 series) 301015 CDRH5D18 CDRH2D14 CDRH3D16 CDRH3D11 CR43 CMD4D06-4R7MC CMD4D06-3R3MC NP03SB NR3015T NR3012T VLP VLF VLCF , D412C D518LC D52LC D62LCB WE-TPC type S, M
Output and Input Capacitor Selection Low ESR (equivalent series resistance) 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 4.7F to 10F output capacitor is sufficient for most applications. Larger values up to 22F 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. The internal loop compensation of the LTC3526 is designed to be stable with output capacitor values of 4.7F or greater (without the need for any external series resistor). Although ceramic capacitors are recommended, low ESR tantalum capacitors may be used as well. A small ceramic capacitor in parallel with a larger tantalum capacitor may be used in demanding applications that have large load transients. Another method of improving the transient response is to add a small feed-forward capacitor across the top resistor of the feedback divider (from VOUT to FB). 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, although 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 capacitors.
Table 2. Capacitor Vendor Information
SUPPLIER AVX Murata Taiyo-Yuden TDK Samsung PHONE (803) 448-9411 (714) 852-2001 (408) 573-4150 (847) 803-6100 (408) 544-5200 WEBSITE www.avxcorp.com www.murata.com www.t-yuden.com www.component.tdk.com www.sem.samsung.com
Coiltronics www.cooperet.com FDK (408) 432-8331 www.fdk.com Murata (714) 852-2001 www.murata.com Sumida (847) 956-0666 www.sumida.com
Taiyo-Yuden www.t-yuden.com TDK (847) 803-6100 www.component.tdk.com Toko (408) 432-8282 www.tokoam.com Wurth (201) 785-8800 www.we-online.com
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LTC3526/LTC3526B TYPICAL APPLICATIONS
1-Cell to 1.8V Converter with <1mm Maximum Height
100 4.7H 90 80 SW VIN 1.6V TO 3.2V 1F OFF ON VIN VOUT 1.78M FB 1M
3526 TA01a
VOUT = 1.8V
EFFICIENCY (%)
VOUT 3.3V 200mA 4.7F
70 60 50 40 30 20 10 0 0.01 0.1 VIN = 1.5V VIN = 1.2V VIN = 0.9V 1 10 100 LOAD CURRENT (mA) 1000
3526 TA02b
LTC3526 SHDN GND
1-Cell to 2.85V Converter
100 4.7H* 90 80 VIN 1V TO 1.6V 1F OFF ON EFFICIENCY (%) SW VIN VOUT 1.4M FB 1M
3526 TA03a
VOUT = 2.85V
LTC3526 SHDN GND
VOUT 2.85V 100mA 10F
70 60 50 40 30 20 10 VIN = 1.5V VIN = 1.2V VIN = 0.9V 0.1 1 10 100 LOAD CURRENT (mA) 1000
3526 TA03b
*SUMIDA CDRH3D16-4R7
0 0.01
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12
LTC3526/LTC3526B TYPICAL APPLICATIONS
1-Cell to 3.3V
100 4.7H* 90 80 VIN 1V TO 1.6V 1F OFF ON EFFICIENCY (%) SW VIN VOUT 1.78M FB 1M
3526 TA04a
VOUT = 3.3V
LTC3526 SHDN GND
22pF
VOUT 3.3V 75mA 10F
70 60 50 40 30 20 10 VIN = 1.5V VIN = 1.2V VIN = 0.9V 0.1 1 10 100 LOAD CURRENT (mA) 1000
3526 TA04b
*TAIYO-YUDEN NP03SB4R7M
0 0.01
2-Cell to 3.3V
100 4.7H* 90 80 VIN 2V TO 3.2V 1F OFF ON EFFICIENCY (%) SW VIN VOUT 1.78M FB 1M
3526 TA05a
VOUT = 3.3V
LTC3526 SHDN GND
VOUT 3.3V 200mA 4.7F
70 60 50 40 30 20 10 0 0.01 0.1 VIN = 3.0V VIN = 2.4V VIN = 1.8V 1 10 100 LOAD CURRENT (mA) 1000
3526 TA05b
*TAIYO-YUDEN NP03SB4R7M
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13
LTC3526/LTC3526B TYPICAL APPLICATIONS
2-Cell to 5V
100 6.8H* 90 80 VOUT 5V 150mA 10F 1.02M
3526 TA06a
VOUT = 5V
VIN 2V TO 3.2V 1F OFF ON
EFFICIENCY (%)
SW VIN VOUT 3.24M FB 22pF
70 60 50 40 30 20 10 VIN = 3.0V VIN = 2.4V VIN = 1.8V 0.1 1 10 100 LOAD CURRENT (mA) 1000
3526 TA06b
LTC3526 SHDN GND
*TAIYO-YUDEN NP03SB6R8M
0 0.01
3.3V Converter with Output OR'd with 5V USB Input
MBR120ESFT 5V USB 4.7H VOUT 3.3V/5V USB 1.78M DC/DC FB 1M
3526 TA07a
LDO
SW VBATT 1.8V TO 3.2V 1F OFF ON VIN VOUT
LTC3526 SHDN GND
10F
Li-Ion to 5V
100 6.8H* 90 80 VIN 2.7V TO 4.3V 1F OFF ON VIN VOUT 3.24M FB 1.02M
3526 TA08a
VOUT = 5V
EFFICIENCY (%)
SW 22pF
LTC3526 SHDN GND
VOUT 5V 200mA 10F
70 60 50 40 30 20 10 0 0.01 0.1 VIN = 4.2V VIN = 3.6V VIN = 3.0V 1 10 100 LOAD CURRENT (mA) 1000
3526 TA08b
*TAIYO-YUDEN NP03SB6R8M
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14
LTC3526/LTC3526B PACKAGE DESCRIPTION
DC Package 6-Lead Plastic DFN (2mm x 2mm)
(Reference LTC DWG # 05-08-1703)
0.675 0.05 2.50 0.05 1.15 0.05 0.61 0.05 (2 SIDES) PACKAGE OUTLINE 2.00 0.10 (4 SIDES)
R = 0.115 TYP 0.56 0.05 (2 SIDES)
0.38 0.05 4 6
PIN 1 BAR TOP MARK (SEE NOTE 6)
PIN 1 CHAMFER OF EXPOSED PAD 3 1
(DC6) DFN 1103
0.25 0.05 0.50 BSC 1.42 0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
0.200 REF
0.75 0.05
0.25 0.05 0.50 BSC 1.37 0.05 (2 SIDES)
0.00 - 0.05
BOTTOM VIEW--EXPOSED PAD
NOTE: 1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WCCD-2) 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
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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.
15
LTC3526/LTC3526B RELATED PARTS
PART NUMBER LT 1613 LT1615 LT1618 LT1930/LT1930A LTC3400/LTC3400B LTC3401 LTC3402 LTC3421 LTC3422 LTC3423/LTC3424 LTC3426 LTC3428 LTC3429 LTC3458 LTC3458L
(R)
DESCRIPTION 800mA ISW, 1.4MHz, Step-Up DC/DC Converter 350mA ISW, Micropower, Step-Up DC/DC Converter 1.5A ISW, 1.4MHz, Constant Current/Constant Voltage Step-Up DC/DC Converter 1A ISW, 1.2MHz/2.2MHz, Step-Up DC/DC Converters 600mA ISW, 1.2MHz, Synchronous Step-Up DC/DC Converters 1A ISW, 3MHz, Synchronous Step-Up DC/DC Converter 2A ISW, 3MHz, Synchronous Step-Up DC/DC Converter 3A ISW, 3MHz, Synchronous Step-Up DC/DC Converter with Output Disconnect 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
COMMENTS VIN: 1.1V to 10V, VOUT(MAX) = 34V, IQ = 3mA, ISD < 1A, 5-Lead SOT-23 Package VIN: 1.2V to 15V, VOUT(MAX) = 34V, IQ = 20A, ISD < 1A, ThinSOTTM Package VIN: 1.6V to 18V, VOUT(MAX) = 35V, IQ = 1.8mA, ISD < 1A, DFN, MSOP Packages VIN: 2.6V to 16V, VOUT(MAX) = 34V, IQ = 4.2mA/5.5mA, ISD < 1A, ThinSOT Package 92% Efficiency VIN: 0.85V to 5V, VOUT(MAX) = 5V, IQ = 19A/300A, ISD < 1A, ThinSOT Package 97% Efficiency VIN: 0.5V to 5V, VOUT(MAX) = 6V, IQ = 38A, ISD < 1A, 10-Lead MS Package 97% Efficiency VIN: 0.5V to 5V, VOUT(MAX) = 6V, IQ = 38A, ISD < 1A, 10-Lead MS Package 95% Efficiency VIN: 0.5V to 4.5V, VOUT(MAX) = 5.25V, IQ = 12A, ISD < 1A, QFN24 Package 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, 2mm x 2mm DFN Package 96% Efficiency VIN: 0.5V to 4.4V, VOUT(MAX) = 5V, IQ = 20A/300A, ISD < 1A, ThinSOT Package 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
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
ThinSOT is a trademark of Linear Technology Corporation.
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16 Linear Technology Corporation
(408) 432-1900 FAX: (408) 434-0507
LT 0807 REV B * PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2006

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