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LTC3429/LTC3429B 600mA, 500kHz Micropower Synchronous Boost Converter with Output Disconnect
FEATURES

DESCRIPTIO
Up to 96% Efficiency True Output Load Disconnect Inrush Current Limiting and Internal Soft-Start Low Voltage Start-Up: 0.85V Automatic Burst Mode(R) Operation with IQ ~ 20A Continuous Switching at Light Loads (LTC3429B) Internal Synchronous Rectifier Current Mode Control with Internal Compensation Short-Circuit Protection 500kHz Fixed Frequency Switching Input Range: 0.5V to 4.4V Output Range: 2.5V to 4.3V (Up to 5V with Schottky) Shutdown Current: <1A Antiringing Control Minimizes EMI Tiny External Components Low Profile (1mm) SOT-23 Package
The LTC(R)3429/LTC3429B are high efficiency synchronous, fixed frequency, step-up DC/DC converters with true output load disconnect, inrush current limiting and softstart in a low profile 6-lead ThinSOTTM package. These devices are capable of supplying 100mA from a single AA cell input or 250mA from a 2-cell AA with a 3.3V output. A switching frequency of 500kHz minimizes overall solution footprint by allowing the use of tiny, low profile inductors and ceramic capacitors. Current mode PWM control with internal compensation reduces external parts count thereby saving critical board real estate. The LTC3429 shifts automatically to power saving Burst Mode operation at light loads while the LTC3429B features continuous switching at light loads. Antiringing control circuitry reduces EMI concerns by damping the inductor in discontinuous mode. The devices also feature low shutdown current of under 1A. The true output disconnect feature allows the output to be completely discharged in shutdown. It also limits the inrush of current during start-up, minimizing surge currents seen by the input supply.
, LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Burst Mode is a registered trademark of Linear Technology Corporation. ThinSOT is a trademark of Linear Technology Corporation.
APPLICATIO S

MP3 Players Digital Cameras LCD Bias Supplies Handheld Instruments Wireless Handsets GPS Receivers
TYPICAL APPLICATIO
4.7H
100 VIN = 3V 90
VOUT 3.3V 250mA 10F 604k
EFFICIENCY (%)
+
EFFICIENCY VIN = 2.4V
2-CELL AA
4.7F VIN
SW VOUT 1.02M
80 70 60 50
LTC3429 OFF ON SHDN GND FB
3429 F01a
Figure 1. 2-Cell to 3.3V Synchronous Boost Converter
40 0.1
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2-Cell to 3.3V Efficiency
100 10
POWER LOSS (W)
U
U
1 0.1 VIN = 3V 0.01
VIN = 2.4V
POWER LOSS 0.001 0.0001 1000
3429 F01b
1 10 100 OUTPUT CURRENT (mA)
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LTC3429/LTC3429B
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW SW 1 GND 2 FB 3 6 VIN 5 VOUT 4 SHDN
VIN Voltage .............................................. - 0.3V to 4.4V SW Voltage ................................................. - 0.3V to 6V 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 150 Lead Temperature (Soldering, 10 sec).................. 300C
ORDER PART NUMBER LTC3429ES6 LTC3429BES6 S6 PART MARKING LTH5 LTBMS
S6 PACKAGE 6-LEAD PLASTIC TSOT-23
TJMAX = 125C, JC = 102C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
PARAMETER Minimum Start-Up Voltage Minimum Operating Voltage Output Voltage Adjust Range Feedback Voltage Feedback Input Current Quiescent Current (Burst Mode Operation) Quiescent Current (Shutdown) Quiescent Current (Active) NMOS Switch Leakage PMOS Switch Leakage NMOS Switch On Resistance PMOS Switch On Resistance NMOS Current Limit Burst Mode Operation Current Threshold Current Limit Delay to Output Max Duty Cycle Switching Frequency SHDN Input High SHDN Input Low SHDN Input Current Soft-Start Time
The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VIN = 1.2V, VOUT = 3.3V, unless otherwise specified.
CONDITIONS ILOAD = 1mA, VOUT = 0V SHDN = VIN (Note 3) (Note 5)
MIN
TYP 0.85 0.5
MAX 1 0.65 5 1.268 50 30 1 550 5 5
UNITS V V V V nA A A A A A mA mA ns %
2.5 1.192 1.230 1 20 0.01 380 0.1 0.1 0.35 0.45 600 850 1.25 40

VFB = 1.25V VFB = 1.4V (Note 4) VSHDN = 0V, Not Including Switch Leakage, VOUT = 0V Measured on VOUT, Nonswitching VSW = 5V VSW = 5V, VOUT = 0V
L = 4.7H (LTC3429 Only) VFB = 1.15V 80 380 1
90 500 620 0.35
VSHDN = 5.5V SHDN to 90% of VOUT
0.01 2.5
1
Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LTC3429ES6/LTC3429BES6 are guaranteed to meet performance specifications from 0C to 70C. Specifications over the -40C to 85C operating temperature range are assured by design, characterization and correlation with statistical process controls.
Note 3: Minimum VIN operation after start-up is only limited by the battery's ability to provide the necessary power as it enters a deeply discharged state. Note 4: Burst Mode operation IQ is measured at VOUT. Multiply this value by VOUT/VIN to get the equivalent input (battery) current. Note 5: For applications where VOUT > 4.3V, an external Schottky diode is required. See the Applications Information.
2
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kHz V V A ms
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LTC3429/LTC3429B TYPICAL PERFOR A CE CHARACTERISTICS (TA = 25C unless otherwise specified)
Single-Cell to 3.3V Efficiency (LTC3429 Only)
100 90 100 10 100 VIN = 3V VIN = 1.5V EFFICIENCY VIN = 1.2V 70 60 VIN = 1.5V POWER LOSS 50 40 0.1 POWER LOSS 0.001 0.0001 1000
3429 G01
EFFICIENCY (%)
EFFICIENCY (%)
EFFICIENCY (%)
80
VIN = 1.2V
1 10 100 OUTPUT CURRENT (mA)
2-Cell to 5V Efficiency (LTC3429 Only)
100 90 VIN = 3V EFFICIENCY VIN = 2.4V VIN = 2.4V VIN = 3V 60 POWER LOSS 50 40 0.1 0.001 0.0001 1000
3429 G03
VIN = 3.6V
OUTPUT CURRENT (mA)
EFFICIENCY (%)
EFFICIENCY (%)
80 70
1 10 100 OUTPUT CURRENT (mA)
No Load Input Current vs Input Voltage (LTC3429 Only)
1000 L = 4.7H
OUTPUT CURRENT (mA)
INPUT CURRENT (A)
400 VOUT = 3.3V 300 VOUT = 5V 200 100
INPUT VOLTAGE (V)
VOUT = 5V 100
VOUT = 3.3V
10 0.9
1.4
1.9 2.4 2.9 3.4 INPUT VOLTAGE (V)
UW
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2-Cell to 3.3V Efficiency (LTC3429 Only)
100 EFFICIENCY VIN = 2.4V 10 100 90
Efficiency vs Input Voltage
VOUT = 3.3V IOUT = 50mA
90
POWER LOSS (W)
POWER LOSS (W)
80 70 60 50 40 0.1
1 0.1 VIN = 3V 0.01
80 70 60 50 40 0.5 1.5 2.5 3.5 INPUT VOLTAGE (V) 4.5
3429 G05
0.1 0.01
VIN = 2.4V
0.001 0.0001 1000
3429 G02
VIN > VOUT PMOS LDO MODE
1 10 100 OUTPUT CURRENT (mA)
Li-Ion to 5V Efficiency (LTC3429 Only)
100 10 100 VIN = 4.2V 90 EFFICIENCY 10 100
Burst Mode Output Current Threshold vs Input Voltage (LTC3429 Only)
35 30 25 20 VOUT = 3.3V 15 VOUT = 5V 10 5 0 0.9 L = 4.7H
POWER LOSS (W)
POWER LOSS (W)
1 0.1 0.01
80 70 60 50 40 0.1
1 0.1 VIN = 4.2V POWER LOSS 0.01
VIN = 3.6V
0.001 0.0001 1000
3429 G04
1 10 100 OUTPUT CURRENT (mA)
1.4
3.4 1.9 2.4 2.9 INPUT VOLTAGE (V)
3.9
4.4
3429 G06
Maximum Load Current Capability at Output 4% Below Regulation Point
600 500 L = 4.7H
1.9 1.7 1.5 1.3 1.1 0.9 0.7
Minimum Start-Up Input Voltage vs Load Current
CURRENT SINK LOAD
RESISTOR LOAD
3.9
4.4
0 0.5
1
3 3.5 1.5 2 2.5 INPUT VOLTAGE (V)
4
4.5
0
50 100 OUTPUT CURRENT (mA)
150
3429 G09
3429 G07
3429 G08
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LTC3429/LTC3429B TYPICAL PERFOR A CE CHARACTERISTICS (TA = 25C unless otherwise specified)
Output Voltage vs Temperature
3.44 3.40 3.36 VIN = 1.5V IOUT = 30mA
NORMALIZED FREQUECY
QUIESCENT CURRENT (A)
VOUT (V)
3.32 3.28 3.24 3.20 3.16 20 40 60 -60 -40 -29 0 TEMPERATURE (C)
SW Pin Fixed Frequency Continuous Mode Operation
VSW 1V/DIV
VIN = 1.5V VOUT = 3.3V IOUT = 50mA L = 10H COUT = 10F CPL = 150pF
200ns/DIV
Output Voltage Transient Response
VOUT 100mV/DIV AC-COUPLED 90mA IOUT 40mA VIN = 1.5V 100s/DIV VOUT = 3.3V IOUT = 40mA TO 90mA STEP L = 10H COUT = 10F CPL = 150pF
3429 G16
4
UW
80
3429 G10
Normalized Oscillator Frequency vs Temperature
1.02
40 35
Burst Mode Quiescent Current vs Temperature (LTC3429 Only)
1.00
VOUT = 5V 30 25 20 15 10 5 VOUT = 3.3V
0.98
0.96
0.94
100
0.92 -60 -40 -20 0 20 40 60 TEMPERATURE (C)
80
100
0 20 40 60 -60 -40 -20 0 TEMPERATURE (C)
80
100
3429 G11
3429 G12
SW Pin Discontinuous Mode Antiringing Operation
Fixed Frequency and Burst Mode Operation (LTC3429 Only)
VSW 1V/DIV
VOUT 100mV/DIV AC-COUPLED 50mA IOUT 120A
3429 G13
VIN = 1.5V VOUT = 3.3V IOUT = 20mA L = 10H COUT = 10F CPL = 150pF
200ns/DIV
3429 G14
VIN = 1.5V 5ms/DIV VOUT = 3.3V IOUT = 120A TO 50mA STEP L = 10H COUT = 10F CPL = 150pF
3429 G15
Inrush Current Control and Soft-Start
Inrush Current Control and Soft-Start
VOUT 1V/DIV
VOUT 2V/DIV
INDUCTOR CURRENT 100mA/DIV
INDUCTOR CURRENT 200mA/DIV VIN = 1.5V VOUT = 3.3V IOUT = 10mA L = 4.7H COUT = 10F CPL = 100pF 500s/DIV
3429 G17
VIN = 2.5V VOUT = 5V IOUT = 50mA L = 4.7H COUT = 10F CPL = 100pF
2ms/DIV
3429 G18
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LTC3429/LTC3429B
PI FU CTIO S
SW (Pin 1): Switch Pin. Connect inductor between SW and VIN. Keep these PCB trace lengths as short and wide as possible to reduce EMI and voltage overshoot. If the inductor current falls to zero, or SHDN is low, an internal 150 antiringing 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 output capacitor(s). FB (Pin 3): Feedback Input to the gm Error Amplifier. Connect resistor divider tap to this pin. The output voltage can be adjusted from 2.5V to 5V by: VOUT = 1.23V * [1 + (R1/R2)] SHDN (Pin 4): Logic Controlled Shutdown Input. SHDN = High: Normal free running operation, 500kHz typical operating frequency. SHDN = Low: Shutdown, quiescent current < 1A. Output capacitor can be completely discharged through the load or feedback resistors. A 150 resistor is internally connected between SW and VIN. VOUT (Pin 5): Output Voltage Sense Input and Drain of the Internal Synchronous Rectifier MOSFET. Bias is derived from VOUT. PCB trace length from VOUT to the output filter capacitor(s) should be as short and wide as possible. VOUT is completely disconnected from VIN when SHDN is low due to the output disconnect feature. VIN (Pin 6): Battery Input Voltage. The device gets its start-up bias from VIN. Once VOUT exceeds VIN, bias comes from VOUT. Thus, once started, operation is completely independent from VIN. Operation is only limited by the output power level and the battery's internal series resistance.
BLOCK DIAGRA
+
1V TO 4.4V 6 VIN
VOUT GOOD START-UP OSC A B A/B MUX
PWM CONTROL RAMP GEN 500kHz PWM COMPARATOR
SYNC DRIVE CONTROL
SLOPE COMP
SLEEP
Burst Mode OPERATION CONTROL
CC 150pF
CP2 2.5pF
SHDN 4 SHUTDOWN CONTROL SHUTDOWN
2 GND
3429 BD
+
RC 80k
gm ERROR AMP
-
-
+
- - +
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L1 CIN 1 SW
VIN 2.3V 0.45 WELL SWITCH
VOUT 5
2.5V TO 5V
0.35 CPL (OPTIONAL) R1
CURRENT SENSE
FB 3 1.23V REF R2 COUT
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LTC3429/LTC3429B
OPERATIO
The LTC3429/LTC3429B are 500kHz, synchronous boost converters housed in a 6-lead SOT-23 package. Able to operate from an input voltage below 1V, the device features fixed frequency, current mode PWM control for exceptional line and load regulation. Low RDS(ON) internal MOSFET switches enable the device to maintain high efficiency over a wide range of load current. Detailed descriptions of the different operating modes follow. Operation can be best understood by referring to the Block Diagram. LOW VOLTAGE START-UP The LTC3429/LTC3429B include an independent start-up oscillator designed to start up at input voltages of 0.85V typically. The frequency and duty cycle of the start-up oscillator are internally set to 150kHz and 67% respectively. In this mode, the IC operates completely open-loop and the current limit is also set internally to 850mA. Once the output voltage exceeds 2.3V, the start-up circuitry is disabled and normal close-loop PWM operation is initiated. In normal mode, the LTC3429/LTC3429B power themselves from VOUT instead of VIN. This allows the battery voltage to drop to as low as 0.5V without affecting the circuit operation. The only limiting factor in the application becomes the ability of the battery to supply sufficient energy to the output. Soft-start and inrush current limiting are provided during start-up as well as normal mode operation. Soft-Start The LTC3429/LTC3429B provide soft-start by charging an internal capacitor with a very weak current source. The voltage on this capacitor, in turn, slowly ramps the peak inductor current from zero to a maximum value of 850mA. The soft-start time is typically 2.5ms, the time it takes to charge the capacitor from zero to 1.35V. However, this time varies greatly with load current, output voltage and input voltage (see Typical Performance Characteristics, Inrush Current Control and Soft-Start). The soft-start capacitor is discharged completely in the event of a commanded shutdown or a thermal shutdown. It is discharged only partially in case of a short circuit at the output.
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LOW NOISE FIXED FREQUENCY OPERATION Oscillator The frequency of operation is internally set to 500kHz. Error Amp The error amplifier is an internally compensated transconductance type (current output) with a transconductance (gm) = 33 microsiemens. The internal 1.23V reference voltage is compared to the voltage at the FB pin to generate an error signal at the output of the error amplifier. A voltage divider from VOUT to ground programs the output voltage via FB from 2.5V to 5V using the equation: VOUT = 1.23V * [1 + (R1/R2)] Current Sensing Lossless current sensing converts the NMOS switch current signal to a voltage to be 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. Peak switch current is limited to approximately 850mA independent of input or output voltage. The switch current signal is blanked for 60ns to enhance noise rejection. 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 27mA. This prevents the inductor current from reversing in polarity thereby improving efficiency at light loads. Antiringing Control The antiringing control circuitry prevents high frequency ringing of the SW pin as the inductor current goes to zero in discontinuous mode. The damping of the resonant circuit formed by L and CSW (capacitance on SW pin) is achieved by placing a 150 resistor across the inductor. Synchronous Rectifier To prevent the inductor current from running away, the PMOS synchronous rectifier is only enabled when VOUT > (VIN + 0.1V) and the FB pin is >0.8V.
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LTC3429/LTC3429B
OPERATIO
Thermal Shutdown An internal temperature monitor will start to reduce the peak current limit if the die temperature exceeds 125C. If the die temperature continues to rise and reaches 160C, the part will go into thermal shutdown, all switches will be turned off and the soft-start capacitor will be reset. The part will be enabled again when the die temperature drops by about 15C. Burst Mode OPERATION (LTC3429 Only) Portable devices frequently spend extended time in low power or standby mode, only switching to high power consumption when specific functions are enabled. To improve battery life in these types of products, it is important to maintain a high power conversion efficiency over a wide output power range. The LTC3429 provides automatic Burst Mode operation to increase efficiency of the power converter at light loads. Burst Mode operation is initiated if the output load current falls below an internally programmed threshold. This threshold has an inverse dependence on the duty cycle of the converter and also the value of the external inductor (See Typical Performance Characteristics, Output Current Burst Mode Threshold vs VIN). Once Burst Mode operation is initiated, only the circuitry required to monitor the output is kept alive and the rest of the device is turned off. This is referred to as the sleep state in which the IC consumes only 20A from the output capacitor. When the output voltage droops by about 1% from its nominal value, the part wakes up and commences normal PWM operation. The output capacitor recharges and causes the part to re-enter the sleep state if the output load remains less than the Burst Mode threshold. The frequency of this intermittent PWM or burst operation depends on the load current; that is, as the load current drops further below the burst threshold, the LTC3429 turns on less frequently. When the load current increases above the burst threshold, the LTC3429 seamlessly resumes continuous PWM operation. Thus, Burst Mode operation maximizes the efficiency at very light loads by minimizing switching and quiescent losses. However, the output ripple typically increases to about 2% peak-to-peak. Burst Mode ripple can be reduced, in some circumstances, by placing a small phase-lead capacitor (CPL) between VOUT and FB pins (refer to the Block
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Diagram). However, this may adversely affect the efficiency and the quiescent current requirement at light loads. Typical values of CPL range from 15pF to 220pF. OUTPUT DISCONNECT AND INRUSH LIMITING The LTC3429/LTC3429B are designed to allow true output disconnect by eliminating body diode conduction of the internal PMOS rectifier. This allows VOUT to go to zero volts during shutdown, drawing zero current from the input source. It also allows for inrush current limiting at start-up, minimizing surge currents seen by the input supply. Note that to obtain the advantage of output disconnect, there must not be an external Schottky diode connected between the SWITCH pin and VOUT. Board layout is extremely critical to minimize voltage overshoot on the SWITCH pin due to stray inductance. Keep the output filter capacitor as close as possible to the VOUT pin and use very low ESR/ESL ceramic capacitors tied to a good ground plane. For applications with VOUT over 4.3V, a Schottky diode is required to limit the peak SWITCH voltage to less than 6V unless some form of external snubbing is employed. This diode must also be placed very close to the pins to minimize stray inductance. See the Applications Information. SHORT CIRCUIT PROTECTION Unlike most boost converters, the LTC3429/LTC3429B allow their output to be short circuited due to the output disconnect feature. The devices incorporate internal features such as current limit foldback, thermal regulation and thermal shutdown for protection from an excessive overload or short circuit. In the event of a short circuit, the internal soft-start capacitor gets partially discharged. This, in turn, causes the maximum current limit to foldback to a smaller value. In addition to this, a thermal regulation circuit starts to dial back the current limit farther if the die temperature rises above 125C. If the die temperature still reaches 160C, the device shuts off entirely. VIN > VOUT OPERATION The LTC3429/LTC3429B will maintain voltage regulation even if the input voltage is above the output voltage. This
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LTC3429/LTC3429B
OPERATIO
is achieved by terminating the switching of the synchronous PMOS and applying VIN statically on its gate. This ensures that the slope of the inductor current will reverse during the time current is flowing to the output. Since the PMOS no longer acts as a low impedance switch in this
APPLICATIO S I FOR ATIO
PCB LAYOUT GUIDELINES
The high speed operation of the LTC3429/LTC3429B demands careful attention to board layout. You will not get advertised performance with careless layout. Figure 2 shows the recommended component placement. A large ground pin copper area will help to lower the chip temperature. A multilayer board with a separate ground plane is ideal, but not absolutely necessary.
VIN
1 2 3
SW
VIN 6
GND VOUT 5 FB SHDN 4 SHDN
VOUT
3429 F02
RECOMMENDED COMPONENT PLACEMENT. TRACES CARRYING HIGH CURRENT ARE DIRECT. TRACE AREA AT FB PIN IS SMALL. LEAD LENGTH TO BATTERY IS SHORT OUTPUT CURRENT (mA)
Figure 2. Recommended Component Placement for Single Layer Board
COMPONENT SELECTION Inductor Selection The LTC3429/LTC3429B can utilize small surface mount and chip inductors due to its fast 500kHz switching frequency. Typically, a 4.7H inductor is recommended for most applications. Larger values of inductance will allow greater output current capability by reducing the
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mode, there will be more power dissipation within the IC. This will cause a sharp drop in the efficiency (see Typical Performance Characteristics, Efficiency vs VIN). The maximum output current should be limited in order to maintain an acceptable junction temperature. inductor ripple current. Increasing the inductance above 10H will increase size while providing little improvement in output current capability. The approximate output current capability of the LTC3429 versus inductance value is given in the equation below and illustrated graphically in Figure 3. V *D IOUT(MAX) = * IP - IN * (1 - D) f * L * 2 where: = estimated efficiency IP = peak current limit value (0.6A) VIN = input (battery) voltage D = steady-state duty ratio = (VOUT - VIN)/VOUT f = switching frequency (500kHz typical) L = inductance value
200 180 160 140 120 100 80 60 40 20 0 3 5 7 9 11 13 15 17 19 21 23 INDUCTANCE (H)
3429 F03
VIN = 1.2V
VOUT = 3.3V
VOUT = 5V
Figure 3. Maximum Output Current vs Inductance Based on 90% Efficiency
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LTC3429/LTC3429B
APPLICATIO S I FOR ATIO
The inductor current ripple is typically set for 20% to 40% of the maximum inductor current (IP). 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 handle the peak inductor current without saturating. Molded chokes and some chip inductors usually do not have enough core to support the peak inductor currents of 850mA seen on the LTC3429/LTC3429B. To minimize radiated noise, use a toroid, pot core or shielded bobbin inductor. See Table 1 for some suggested components and suppliers.
Table 1. Recommended Inductors
L (H) 4.1 10 4.7 4.7 10 4.7 3.3 4.7 10 4.7 4.7 10 4.7 MAX DCR m 57 124 105 170 109 182 216 174 60 75 90 84 137 195 HEIGHT (mm) 2.0 2.0 1.8 1.8 3.5 3.5 0.8 0.8 2.9 2.9 2.9 2.0 2.0 2.2
PART CDRH5D18-4R1 CDRH5D18-100 CDRH3D16-4R7 CDRH3D16-6R8 CR43-4R7 CR43-100 CMD4D06-4R7MC CMD4D06-3R3MC DS1608-472 DS1608-103 DO1608C-472 D52LC-4R7M D52LC-100M LQH32CN4R7M24
VENDOR Sumida www.sumida.com
Coilcraft www.coilcraft.com Toko www.tokoam.com Murata www.murata.com
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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 15F 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. An additional phase lead capacitor may be required with output capacitors larger than 10F to maintain acceptable phase margin. X5R and X7R dielectric materials are preferred for their ability to maintain capacitance over wide voltage and temperature ranges. 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 10F input capacitor is sufficient for virtually any application. 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 entire selection of ceramic capacitors.
Table 2. Capacitor Vendor Information
SUPPLIER AVX Murata Taiyo Yuden WEBSITE www.avxcorp.com www.murata.com www.t-yuden.com
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LTC3429/LTC3429B
TYPICAL APPLICATIO S
Applications Where VOUT > 4.3V When the output voltage is programmed above 4.3V, it is necessary to add a Schottky diode either from SW to VOUT, or to add a snubber network in order to maintain an acceptable peak voltage on the SW pin. The Schottky diode between SW and VOUT will provide a peak efficiency improvement but will negate the output disconnect feature. If output disconnect is required, an active snubber network is suggested as shown below. Examples of Schottky diodes are: MBR0520L, PMEG2010EA, 1N5817 or equivalent.
Application Circuit for VOUT > 4.3V Where Inrush Current Limiting and Output Disconnect are Required
L1 4.7H D1*
100
VIN 2.7V TO 4.2V
+
Li-Ion
C1 4.7F
6
VIN
OFF ON
4
SHDN GND 2
FB
3
R2 604k
C2 10F
EFFICIENCY (%)
LTC3429
*LOCATE COMPONENTS CLOSE TO THE PIN C1: TAIYO YUDEN X5R JMK212BJ475MM C2: TAIYO YUDEN X5R JMK212BJ106MM D1: MOTOROLA MBR0520L L1: COILCRAFT D0160C-472 MP1: ZETEX ZXM61P02F
Application Circuit for VOUT > 4.3V Where Inrush Current Limiting and Output Disconnect are Not Required
L1 4.7H VIN D1*
+
2 AA CELL
C1 4.7F
6
VIN
OFF ON
4
SHDN GND 2
FB
3
R2 604k
C2 10F
EFFICIENCY (%)
LTC3429
*LOCATE COMPONENTS CLOSE TO THE PIN C1: TAIYO YUDEN X5R JMK212BJ475MM C2: TAIYO YUDEN X5R JMK212BJ106MM D1: MOTOROLA MBR0520L L1: COILCRAFT D0160C-472
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Li-Ion to 5V Efficiency
100 VIN = 4.2V 90 EFFICIENCY 80 70 60 50 40 0.1 VIN = 3.6V 10
1 SW VOUT MP1 5 R1 1.82M VOUT 5V 250mA
C3* 0.22F
POWER LOSS (W)
1 0.1 VIN = 4.2V POWER LOSS 0.01
VIN = 3.6V
3429 TA04
0.001 0.0001 1000
3429 TA04b
1 10 100 OUTPUT CURRENT (mA)
2-Cell to 5V Efficiency
100 100 VIN = 3V EFFICIENCY VIN = 2.4V VIN = 2.4V VIN = 3V 60 POWER LOSS 50 40 0.1 0.001 0.0001 1000
3429 TA05b
1 SW VOUT 5 R1 1.82M VOUT 5V 150mA
90 80 70
10
POWER LOSS (W)
1 0.1 0.01
3429 TA05
1 10 100 OUTPUT CURRENT (mA)
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LTC3429/LTC3429B
PACKAGE DESCRIPTIO U
S6 Package 6-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1636)
2.90 BSC (NOTE 4) 1.22 REF 1.4 MIN 2.80 BSC 1.50 - 1.75 (NOTE 4) PIN ONE ID 0.95 BSC 0.30 - 0.45 6 PLCS (NOTE 3) 0.80 - 0.90 0.20 BSC 1.00 MAX DATUM `A' 0.01 - 0.10 0.09 - 0.20 (NOTE 3) 1.90 BSC
S6 TSOT-23 0302
0.62 MAX
0.95 REF
3.85 MAX 2.62 REF
RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR
0.30 - 0.50 REF
NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DRAWING NOT TO SCALE 3. DIMENSIONS ARE INCLUSIVE OF PLATING 4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR 5. MOLD FLASH SHALL NOT EXCEED 0.254mm 6. JEDEC PACKAGE REFERENCE IS MO-193
3429fa
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
LTC3429/LTC3429B
TYPICAL APPLICATIO
L1 4.7H
Single AA Cell to 2.5V Synchronous Boost Converter
+
SINGLE AA CELL
C1 4.7F
1 6 SW VIN VOUT 5 R1 1.02M R2 1.02M VOUT 2.5V 130mA C2 10F
LTC3429 OFF ON 4 SHDN GND 2 C1: TAIYO YUDEN X5R JMK212BJ475MM C2: TAIYO YUDEN X5R JMK212BJ106MM L1: COILCRAFT D0160C-472 FB 3
RELATED PARTS
PART NUMBER LT1613 LT1615/LT1615-1 LT1618 LTC1700 LT1930/LT1930A LT1946/LT1946A LT1961 LTC3400/LTC3400B LTC3401/LTC3402 LTC3421 LTC3425 LT3464 DESCRIPTION 550mA (ISW), 1.4MHz High Efficiency Step-Up DC/DC Converter 300mA/80mA (ISW), High Efficiency Step-Up DC/DC Converters 1.5A (ISW), 1.25MHz High Efficiency Step-Up DC/DC Converter No RSENSETM, 530kHz, Synchronous Step-Up DC/DC Controller 1A (ISW), 1.2MHz/2.2MHz, High Efficiency Step-Up DC/DC Converters 1.5A (ISW), 1.2MHz/2.7MHz, High Efficiency Step-Up DC/DC Converters 1.5A (ISW), 1.25MHz High Efficiency Step-Up DC/DC Converter 600mA (ISW), 1.2MHz, Synchronous Step-Up DC/DC Converters 1A/2A (ISW), 3MHz, Synchronous Step-Up DC/DC Converters 3A (ISW), 3MHz, Synchronous Step-Up DC/DC Converter with Output Disconnect 5A (ISW), 8MHz, 4-Phase Synchronous Step-Up DC/DC Converter with Output Disconnect 85mA (ISW), High Efficiency Step-Up DC/DC Converter with Integrated Schottky and PNP Disconnect COMMENTS 90% Efficiency, VIN: 0.9V to 10V, VOUT(MAX) = 34V, IQ = 3mA, ISD < 1A, ThinSOT VIN: 1V to 15V, VOUT(MAX) = 34V, IQ = 20A, ISD < 1A, ThinSOT 90% Efficiency, VIN: 1.6V to 18V, VOUT(MAX) = 35V, IQ = 1.8mA, ISD < 1A 95% Efficiency, VIN: 0.9V to 5V, IQ = 200A, ISD < 10A, MS10 High Efficiency, VIN: 2.6V to 16V, VOUT(MAX) = 34V, IQ = 4.2mA/5.5mA, ISD < 1A, ThinSOT High Efficiency, VIN: 2.45V to 16V, VOUT(MAX) = 34V, IQ = 32mA, ISD < 1A, MS8 90% Efficiency, VIN: 3V to 25V, VOUT(MAX) = 35V, IQ = 0.9mA, ISD < 6A, MS8E 92% Efficiency, VIN: 0.85V to 5V, VOUT(MAX) = 5V, IQ = 19A/300A, ISD < 1A, ThinSOT 97% Efficiency, VIN: 0.5V to 5V, VOUT(MAX) = 5.5V, IQ = 38A, ISD < 1A, MS10 95% Efficiency, VIN: 0.5V to 4.5V, VOUT(MAX) = 5.25V, IQ = 12A, ISD < 1A, QFN24 95% Efficiency, VIN: 0.5V to 4.5V, VOUT(MAX) = 5.25V, IQ = 12A, ISD < 1A, QFN32 VIN: 2.3V to 10V, VOUT(MAX) = 34V, IQ = 25A, ISD < 1A, ThinSOT
No RSENSE is a trademark of Linear Technology Corporation.
12
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 FAX: (408) 434-0507
U
Single AA Cell to 3.3V
L1 4.7H SINGLE AA CELL
+
C1 4.7F
1 6 SW VIN VOUT 5 R1 1.02M R2 604k VOUT 3.3V 100mA C2 10F
LTC3429 OFF ON 4 SHDN GND 2 FB 3
3429 TA03
3429 TA06
C1: TAIYO YUDEN X5R JMK212BJ475MM C2: TAIYO YUDEN X5R JMK212BJ106MM L1: COILCRAFT D0160C-472
3429fa LT/TP 1104 1K REV A * PRINTED IN USA
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2004

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