LTC3429/LTC3429B 600mA, 500kHz Micropower Synchronous Boost Converter with Output Disconnect U FEATURES DESCRIPTIO ■ The LTC®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. ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Up to 96% Efficiency True Output Load Disconnect Inrush Current Limiting and Internal Soft-Start Low Voltage Start-Up: 0.85V Automatic Burst Mode® Operation with IQ ~ 20µA 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: <1µA Antiringing Control Minimizes EMI Tiny External Components Low Profile (1mm) SOT-23 Package U APPLICATIO S ■ ■ ■ ■ ■ The devices also feature low shutdown current of under 1µA. 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. MP3 Players Digital Cameras LCD Bias Supplies Handheld Instruments Wireless Handsets GPS Receivers , 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. U ■ 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. TYPICAL APPLICATIO 2-Cell to 3.3V Efficiency 100 100 VIN = 3V 4.7µH 4.7µF SW VIN VOUT LTC3429 OFF ON SHDN GND 1.02M VOUT 3.3V 250mA 10µF FB 80 70 60 10 EFFICIENCY VIN = 2.4V 1 0.1 VIN = 2.4V VIN = 3V 0.01 POWER LOSS (W) 2-CELL AA 90 EFFICIENCY (%) + 604k POWER LOSS 50 0.001 3429 F01a Figure 1. 2-Cell to 3.3V Synchronous Boost Converter 40 0.1 1 10 100 OUTPUT CURRENT (mA) 0.0001 1000 3429 F01b 3429fa 1 LTC3429/LTC3429B W W W AXI U U ABSOLUTE RATI GS U U W PACKAGE/ORDER I FOR ATIO (Note 1) 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) .. – 40°C to 85°C Storage Temperature Range ................... – 65°C to 150° Lead Temperature (Soldering, 10 sec).................. 300°C ORDER PART NUMBER TOP VIEW SW 1 GND 2 FB 3 6 VIN LTC3429ES6 LTC3429BES6 5 VOUT 4 SHDN S6 PART MARKING S6 PACKAGE 6-LEAD PLASTIC TSOT-23 LTH5 LTBMS TJMAX = 125°C, θJC = 102°C/W Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 1.2V, VOUT = 3.3V, unless otherwise specified. PARAMETER CONDITIONS MIN TYP Minimum Start-Up Voltage ILOAD = 1mA, VOUT = 0V 0.85 1 V Minimum Operating Voltage SHDN = VIN (Note 3) 0.5 0.65 V Output Voltage Adjust Range (Note 5) 5 V 1.230 1.268 V 2.5 ● Feedback Voltage 1.192 MAX UNITS Feedback Input Current VFB = 1.25V 1 50 nA Quiescent Current (Burst Mode Operation) VFB = 1.4V (Note 4) 20 30 µA Quiescent Current (Shutdown) VSHDN = 0V, Not Including Switch Leakage, VOUT = 0V 0.01 1 µA Quiescent Current (Active) Measured on VOUT, Nonswitching 380 550 µA NMOS Switch Leakage VSW = 5V 0.1 5 µA PMOS Switch Leakage VSW = 5V, VOUT = 0V 0.1 5 µA NMOS Switch On Resistance 0.35 PMOS Switch On Resistance 0.45 Ω 850 mA 1.25 mA 40 ns NMOS Current Limit Burst Mode Operation Current Threshold 600 L = 4.7µH (LTC3429 Only) Current Limit Delay to Output Max Duty Cycle VFB = 1.15V Switching Frequency SHDN Input High ● 80 90 ● 380 500 Soft-Start Time % 620 kHz 1 V SHDN Input Low SHDN Input Current Ω 0.35 VSHDN = 5.5V SHDN to 90% of VOUT 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 0°C to 70°C. Specifications over the –40°C to 85°C operating temperature range are assured by design, characterization and correlation with statistical process controls. 0.01 2.5 1 V µA ms 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. 3429fa 2 LTC3429/LTC3429B U W TYPICAL PERFOR A CE CHARACTERISTICS (TA = 25°C unless otherwise specified) Single-Cell to 3.3V Efficiency (LTC3429 Only) 2-Cell to 3.3V Efficiency (LTC3429 Only) 100 Efficiency vs Input Voltage 100 100 100 100 10 90 VOUT = 3.3V IOUT = 50mA VIN = 1.2V 70 0.1 VIN = 1.2V 0.01 60 VIN = 2.4V 80 EFFICIENCY (%) 1 EFFICIENCY 70 1 0.1 VIN = 2.4V VIN = 3V 60 0.01 POWER LOSS (W) EFFICIENCY 80 90 10 VIN = 1.5V POWER LOSS (W) EFFICIENCY (%) 90 EFFICIENCY (%) VIN = 3V 80 70 60 VIN = 1.5V POWER LOSS POWER LOSS 50 40 0.1 40 0.1 0.0001 1000 1 10 100 OUTPUT CURRENT (mA) 40 0.0001 1000 1 10 100 OUTPUT CURRENT (mA) VIN > VOUT PMOS LDO MODE 50 0.001 50 0.001 0.5 3429 G05 Burst Mode Output Current Threshold vs Input Voltage (LTC3429 Only) Li-Ion to 5V Efficiency (LTC3429 Only) 2-Cell to 5V Efficiency (LTC3429 Only) 100 100 100 35 10 30 L = 4.7µH VIN = 3V 90 10 1 VIN = 2.4V 70 0.1 VIN = 3V 0.01 60 EFFICIENCY (%) VIN = 2.4V 80 1 70 0.1 VIN = 3.6V VIN = 4.2V 60 POWER LOSS POWER LOSS 0.001 40 0.1 0.0001 1000 1 10 100 OUTPUT CURRENT (mA) 600 100 VOUT = 3.3V 3429 G07 3.4 1.9 2.4 2.9 INPUT VOLTAGE (V) 4.4 1.9 L = 4.7µH CURRENT SINK LOAD 1.7 400 VOUT = 3.3V 300 VOUT = 5V 200 0 0.5 3.9 Minimum Start-Up Input Voltage vs Load Current 1.5 RESISTOR LOAD 1.3 1.1 0.9 100 4.4 1.4 3429 G06 INPUT VOLTAGE (V) OUTPUT CURRENT (mA) INPUT CURRENT (µA) VOUT = 5V 3.9 VOUT = 5V 10 0 0.9 500 1.9 2.4 2.9 3.4 INPUT VOLTAGE (V) VOUT = 3.3V 15 Maximum Load Current Capability at Output 4% Below Regulation Point L = 4.7µH 1.4 20 3429 G04 No Load Input Current vs Input Voltage (LTC3429 Only) 10 0.9 25 5 0.0001 1000 1 10 100 OUTPUT CURRENT (mA) 3429 G03 1000 0.01 50 0.001 50 40 0.1 VIN = 3.6V POWER LOSS (W) EFFICIENCY 80 POWER LOSS (W) EFFICIENCY (%) EFFICIENCY OUTPUT CURRENT (mA) VIN = 4.2V 90 4.5 3429 G02 3429 G01 100 1.5 2.5 3.5 INPUT VOLTAGE (V) 1 3 3.5 1.5 2 2.5 INPUT VOLTAGE (V) 0.7 4 4.5 3429 G08 0 50 100 OUTPUT CURRENT (mA) 150 3429 G09 3429fa 3 LTC3429/LTC3429B U W TYPICAL PERFOR A CE CHARACTERISTICS (TA = 25°C unless otherwise specified) Normalized Oscillator Frequency vs Temperature Output Voltage vs Temperature 3.44 3.40 Burst Mode Quiescent Current vs Temperature (LTC3429 Only) 1.02 VIN = 1.5V IOUT = 30mA 40 35 VOUT (V) 3.36 3.32 3.28 3.24 QUIESCENT CURRENT (µA) NORMALIZED FREQUECY 1.00 0.98 0.96 0.94 3.20 VOUT = 5V 30 25 VOUT = 3.3V 20 15 10 5 3.16 20 40 60 –60 –40 –29 0 TEMPERATURE (°C) 80 100 0.92 –60 –40 –20 0 20 40 60 TEMPERATURE (°C) 3429 G10 80 0 20 40 60 –60 –40 –20 0 TEMPERATURE (°C) 100 3429 G11 Fixed Frequency and Burst Mode Operation (LTC3429 Only) VOUT 100mV/DIV AC-COUPLED VSW 1V/DIV VSW 1V/DIV 100 3429 G12 SW Pin Discontinuous Mode Antiringing Operation SW Pin Fixed Frequency Continuous Mode Operation 80 50mA IOUT 120µA VIN = 1.5V VOUT = 3.3V IOUT = 50mA L = 10µH COUT = 10µF CPL = 150pF 200ns/DIV 3429 G13 VIN = 1.5V VOUT = 3.3V IOUT = 20mA L = 10µH COUT = 10µF CPL = 150pF 200ns/DIV 3429 G14 Inrush Current Control and Soft-Start Output Voltage Transient Response VOUT 2V/DIV VOUT 100mV/DIV AC-COUPLED INDUCTOR CURRENT 100mA/DIV 90mA 40mA VIN = 1.5V 100µs/DIV VOUT = 3.3V IOUT = 40mA TO 90mA STEP L = 10µH COUT = 10µF CPL = 150pF 3429 G16 3429 G15 Inrush Current Control and Soft-Start VOUT 1V/DIV IOUT VIN = 1.5V 5ms/DIV VOUT = 3.3V IOUT = 120µA TO 50mA STEP L = 10µH COUT = 10µF CPL = 150pF INDUCTOR CURRENT 200mA/DIV VIN = 1.5V VOUT = 3.3V IOUT = 10mA L = 4.7µH COUT = 10µF CPL = 100pF 500µs/DIV 3429 G17 VIN = 2.5V VOUT = 5V IOUT = 50mA L = 4.7µH COUT = 10µF CPL = 100pF 2ms/DIV 3429 G18 3429fa 4 LTC3429/LTC3429B U U U PI FU CTIO S SHDN = Low: Shutdown, quiescent current < 1µA. Output capacitor can be completely discharged through the load or feedback resistors. A 150Ω resistor is internally connected between SW and VIN. 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 150Ω antiringing switch is connected from SW to VIN to minimize EMI. 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. 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: 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. VOUT = 1.23V • [1 + (R1/R2)] SHDN (Pin 4): Logic Controlled Shutdown Input. SHDN = High: Normal free running operation, 500kHz typical operating frequency. W BLOCK DIAGRA L1 + 1V TO 4.4V 6 VIN 1 SW CIN + VOUT GOOD – START-UP OSC A A/B MUX WELL SWITCH 0.45Ω B VOUT 2.5V TO 5V 5 SYNC DRIVE CONTROL PWM CONTROL RAMP GEN 500kHz VIN 2.3V CPL (OPTIONAL) CURRENT SENSE Σ SLOPE COMP 0.35Ω R1 PWM COMPARATOR – – + FB Burst Mode OPERATION CONTROL CC 150pF SHDN 4 SHUTDOWN CONTROL SHUTDOWN + SLEEP – RC 80k 3 1.23V REF gm ERROR AMP CP2 2.5pF COUT R2 2 GND 3429 BD 3429fa 5 LTC3429/LTC3429B U 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. 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 150Ω 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. 3429fa 6 LTC3429/LTC3429B U OPERATIO Thermal Shutdown An internal temperature monitor will start to reduce the peak current limit if the die temperature exceeds 125°C. If the die temperature continues to rise and reaches 160°C, 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 15°C. 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 20µA 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 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 125°C. If the die temperature still reaches 160°C, 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 3429fa 7 LTC3429/LTC3429B U 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 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. U W U U 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. inductor ripple current. Increasing the inductance above 10µH 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) = η • ⎜IP – IN ⎟ • (1 – D) ⎝ f • L • 2⎠ where: VIN 1 SW VIN 6 2 GND VOUT 5 3 FB SHDN 4 SHDN VOUT η = 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 3429 F02 200 RECOMMENDED COMPONENT PLACEMENT. TRACES CARRYING HIGH CURRENT ARE DIRECT. TRACE AREA AT FB PIN IS SMALL. LEAD LENGTH TO BATTERY IS SHORT COMPONENT SELECTION Inductor Selection The LTC3429/LTC3429B can utilize small surface mount and chip inductors due to its fast 500kHz switching frequency. Typically, a 4.7µH inductor is recommended for most applications. Larger values of inductance will allow greater output current capability by reducing the 160 OUTPUT CURRENT (mA) Figure 2. Recommended Component Placement for Single Layer Board VIN = 1.2V 180 VOUT = 3.3V 140 120 100 VOUT = 5V 80 60 40 20 0 3 5 7 9 11 13 15 17 19 21 23 INDUCTANCE (µH) 3429 F03 Figure 3. Maximum Output Current vs Inductance Based on 90% Efficiency 3429fa 8 LTC3429/LTC3429B U W U U 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. Output and Input Capacitor Selection Table 1. Recommended Inductors 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 10µF 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. PART L (µH) MAX DCR mΩ HEIGHT (mm) 2.0 2.0 1.8 1.8 3.5 3.5 0.8 0.8 Sumida www.sumida.com 2.9 2.9 2.9 Coilcraft www.coilcraft.com CDRH5D18-4R1 CDRH5D18-100 CDRH3D16-4R7 CDRH3D16-6R8 CR43-4R7 CR43-100 CMD4D06-4R7MC CMD4D06-3R3MC 4.1 10 4.7 4.7 10 4.7 3.3 57 124 105 170 109 182 216 174 DS1608-472 DS1608-103 DO1608C-472 4.7 10 4.7 60 75 90 VENDOR D52LC-4R7M D52LC-100M 4.7 10 84 137 2.0 2.0 Toko www.tokoam.com LQH32CN4R7M24 4.7 195 2.2 Murata www.murata.com 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 4.7µF to 15µF output capacitor is sufficient for most applications. Larger values up to 22µF 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 10µF to maintain acceptable phase margin. X5R and X7R dielectric materials are preferred for their ability to maintain capacitance over wide voltage and temperature ranges. Table 2. Capacitor Vendor Information SUPPLIER WEBSITE AVX www.avxcorp.com Murata www.murata.com Taiyo Yuden www.t-yuden.com 3429fa 9 LTC3429/LTC3429B U TYPICAL APPLICATIO S Applications Where VOUT > 4.3V 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. 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 Application Circuit for VOUT > 4.3V Where Inrush Current Limiting and Output Disconnect are Required Li-Ion to 5V Efficiency D1* 100 + Li-Ion C1 4.7µF 1 6 MP1 SW VIN VOUT OFF ON SHDN FB 3 R2 604k GND 2 C2 10µF 3429 TA04 VIN = 4.2V 90 10 EFFICIENCY *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 VIN = 3.6V 80 1 70 0.1 VIN = 3.6V VIN = 4.2V 60 0.01 POWER LOSS (W) R1 1.82M LTC3429 4 VOUT 5V 250mA 5 100 C3* 0.22µF EFFICIENCY (%) VIN 2.7V TO 4.2V L1 4.7µH POWER LOSS 50 40 0.1 0.001 0.0001 1000 1 10 100 OUTPUT CURRENT (mA) 3429 TA04b Application Circuit for VOUT > 4.3V Where Inrush Current Limiting and Output Disconnect are Not Required L1 4.7µH + 100 2 AA CELL C1 4.7µF 6 SW VIN VOUT 5 4 SHDN FB 3 GND 2 R1 1.82M R2 604k VOUT 5V 150mA C2 10µF 3429 TA05 *LOCATE COMPONENTS CLOSE TO THE PIN C1: TAIYO YUDEN X5R JMK212BJ475MM C2: TAIYO YUDEN X5R JMK212BJ106MM D1: MOTOROLA MBR0520L L1: COILCRAFT D0160C-472 VIN = 3V 90 80 70 EFFICIENCY 10 VIN = 2.4V 1 VIN = 2.4V 0.1 VIN = 3V 0.01 60 POWER LOSS (W) LTC3429 OFF ON 100 1 EFFICIENCY (%) VIN 2-Cell to 5V Efficiency D1* POWER LOSS 50 40 0.1 0.001 1 10 100 OUTPUT CURRENT (mA) 0.0001 1000 3429 TA05b 3429fa 10 LTC3429/LTC3429B U PACKAGE DESCRIPTIO S6 Package 6-Lead Plastic TSOT-23 (Reference LTC DWG # 05-08-1636) 0.62 MAX 2.90 BSC (NOTE 4) 0.95 REF 1.22 REF 3.85 MAX 2.62 REF 1.4 MIN 2.80 BSC 1.50 – 1.75 (NOTE 4) PIN ONE ID RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR 0.30 – 0.45 6 PLCS (NOTE 3) 0.95 BSC 0.80 – 0.90 0.20 BSC 0.01 – 0.10 1.00 MAX DATUM ‘A’ 0.30 – 0.50 REF 0.09 – 0.20 (NOTE 3) 1.90 BSC S6 TSOT-23 0302 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 U TYPICAL APPLICATIO Single AA Cell to 2.5V Synchronous Boost Converter Single AA Cell to 3.3V L1 4.7µH L1 4.7µH + SINGLE AA CELL C1 4.7µF 1 6 SW VIN VOUT 5 R1 1.02M LTC3429 OFF ON 4 SHDN FB VOUT 2.5V 130mA 3 R2 1.02M GND 2 SINGLE AA CELL + C1 4.7µF 1 6 SW VIN VOUT LTC3429 C2 10µF OFF ON 4 SHDN FB 3 R1 1.02M R2 604k GND 2 3429 TA03 C1: TAIYO YUDEN X5R JMK212BJ475MM C2: TAIYO YUDEN X5R JMK212BJ106MM L1: COILCRAFT D0160C-472 VOUT 3.3V 100mA 5 C2 10µF 3429 TA06 C1: TAIYO YUDEN X5R JMK212BJ475MM C2: TAIYO YUDEN X5R JMK212BJ106MM L1: COILCRAFT D0160C-472 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1613 550mA (ISW), 1.4MHz High Efficiency Step-Up DC/DC Converter 90% Efficiency, VIN: 0.9V to 10V, VOUT(MAX) = 34V, IQ = 3mA, ISD < 1µA, ThinSOT LT1615/LT1615-1 300mA/80mA (ISW), High Efficiency Step-Up DC/DC Converters VIN: 1V to 15V, VOUT(MAX) = 34V, IQ = 20µA, ISD < 1µA, ThinSOT LT1618 1.5A (ISW), 1.25MHz High Efficiency Step-Up DC/DC Converter 90% Efficiency, VIN: 1.6V to 18V, VOUT(MAX) = 35V, IQ = 1.8mA, ISD < 1µA LTC1700 No RSENSETM, 530kHz, Synchronous Step-Up DC/DC Controller 95% Efficiency, VIN: 0.9V to 5V, IQ = 200µA, ISD < 10µA, MS10 LT1930/LT1930A 1A (ISW), 1.2MHz/2.2MHz, High Efficiency Step-Up DC/DC Converters High Efficiency, VIN: 2.6V to 16V, VOUT(MAX) = 34V, IQ = 4.2mA/5.5mA, ISD < 1µA, ThinSOT LT1946/LT1946A 1.5A (ISW), 1.2MHz/2.7MHz, High Efficiency Step-Up DC/DC Converters High Efficiency, VIN: 2.45V to 16V, VOUT(MAX) = 34V, IQ = 32mA, ISD < 1µA, MS8 LT1961 1.5A (ISW), 1.25MHz High Efficiency Step-Up DC/DC Converter 90% Efficiency, VIN: 3V to 25V, VOUT(MAX) = 35V, IQ = 0.9mA, ISD < 6µA, MS8E LTC3400/LTC3400B 600mA (ISW), 1.2MHz, Synchronous Step-Up DC/DC Converters 92% Efficiency, VIN: 0.85V to 5V, VOUT(MAX) = 5V, IQ = 19µA/300µA, ISD < 1µA, ThinSOT LTC3401/LTC3402 1A/2A (ISW), 3MHz, Synchronous Step-Up DC/DC Converters 97% Efficiency, VIN: 0.5V to 5V, VOUT(MAX) = 5.5V, IQ = 38µA, ISD < 1µA, MS10 LTC3421 3A (ISW), 3MHz, Synchronous Step-Up DC/DC Converter with Output Disconnect 95% Efficiency, VIN: 0.5V to 4.5V, VOUT(MAX) = 5.25V, IQ = 12µA, ISD < 1µA, QFN24 LTC3425 5A (ISW), 8MHz, 4-Phase Synchronous Step-Up DC/DC Converter with Output Disconnect 95% Efficiency, VIN: 0.5V to 4.5V, VOUT(MAX) = 5.25V, IQ = 12µA, ISD < 1µA, QFN32 LT3464 85mA (ISW), High Efficiency Step-Up DC/DC Converter with Integrated Schottky and PNP Disconnect VIN: 2.3V to 10V, VOUT(MAX) = 34V, IQ = 25µA, ISD < 1µA, ThinSOT No RSENSE is a trademark of Linear Technology Corporation. 3429fa 12 Linear Technology Corporation LT/TP 1104 1K REV A • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2004