LTC3528EDDB-2#TRMPBF

LTC3528-2 1A, 2MHz Synchronous Step-Up DC/DC Converter in 2mm × 3mm DFN FEATURES DESCRIPTION Delivers 3.3V at 200mA from a Single Alkaline/ NiMH Cell or 3.3V at 400mA from Two Cells n V Start-Up Voltage: 700mV IN n 0.50V to 5.5V Input Range n 1.6V to 5.25V V OUT Range n Up to 94% Efficiency n Output Disconnect n 2MHz Fixed Frequency Operation n V > V IN OUT Operation n Integrated Soft-Start n Current Mode Control with Internal Compensation n Burst Mode® Operation with 12µA Quiescent Current n Internal Synchronous Rectifier n Logic Controlled Shutdown: 1.230V 12 20 µA 0.1 10 µA 0.1 10 µA N-Channel MOSFET Switch Leakage Current VSW = 5V P-Channel MOSFET Switch Leakage Current VSW = 5V, VOUT = 0V N-Channel MOSFET Switch On Resistance 0.175 Ω P-Channel MOSFET Switch On Resistance 0.250 Ω 1.5 A 60 ns 92 % N-Channel MOSFET Current Limit l Current Limit Delay Time to Output (Note 3) Maximum Duty Cycle VFB = 1.15V l 1.0 87 35282fb 2 LTC3528-2 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the specified operating junction temperature range, otherwise specifications are at TA = 25°C (Note 2). VIN = 1.2V, VOUT = 3.3V, unless otherwise noted. PARAMETER CONDITIONS Minimum Duty Cycle VFB = 1.3V MIN TYP MAX 0 l Frequency l SHDN Input High Voltage 1.8 2.0 2.4 0.88 SHDN Input Current VSHDN = 1.2V Referenced to Feedback Voltage Falling PGOOD Low Voltage PGOOD Leakage Current 1 µA % IPGOOD = 1mA VOUT = 1.6V, IPGOOD = 1mA 0.05 0.05 0.1 0.2 V V VPGOOD = 5.5V 0.01 1 µA 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 125°C 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 76°C/W. Note 7: The IC is tested in a feedback loop to make the measurement. 90 80 40 1 30 VIN = 1V VIN = 1.2V VIN = 1.5V 0 0.01 0.1 10 100 1 LOAD CURRENT (mA) 0.1 0.01 1000 35282 G01 EFFICIENCY (%) 10 POWER LOSS 100 70 60 10 POWER LOSS 50 40 1 30 20 VIN = 1V VIN = 1.5V VIN = 2.4V 10 0 0.01 0.1 10 100 1 LOAD CURRENT (mA) POWER LOSS (mW) 70 1000 EFFICIENCY 80 100 POWER LOSS (mW) EFFICIENCY (%) 100 1000 EFFICIENCY 10 (TA = 25°C unless otherwise noted) Efficiency vs Load Current and VIN for VOUT = 3V 100 20 V –13 Efficiency vs Load Current and VIN for VOUT = 1.8V 50 0.25 0.3 –7 TYPICAL PERFORMANCE CHARACTERISTICS 60 MHz –10 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 LTC3528-2 is tested under pulsed load conditions such that TJ ≈ TA. The LTC3528E-2 is guaranteed to meet specifications from 0°C to 85°C junction temperature. Specifications over –40°C to 125°C operating junction temperature range are assured by design, characterization and correlation with statistical process controls. Note that the maximum ambient temperature consistent with these specifications is determined by specific operating conditions in conjunction with board layout, the rated package thermal impedance and other environmental factors. The junction temperature (TJ, in °C) is calculated from the ambient temperature (TA, in °C) and power dissipation (PD, in Watts) according to the formula: TJ = TA + (PD • qJA) where qJA = 76°C/W is the package thermal impedance. 90 % V SHDN Input Low Voltage PGOOD Threshold Percentage UNITS 0.1 0.01 1000 35282 G26 35282fb 3 LTC3528-2 TYPICAL PERFORMANCE CHARACTERISTICS Efficiency vs Load Current and VIN for VOUT = 5V 1000 100 50 VIN = 1.2V VIN = 1.8V VIN = 2.4V VIN = 3V 40 30 0.01 0.1 1 10 80 EFFICIENCY (%) 1 70 10 POWER LOSS 60 50 0.1 30 0.01 1 VIN = 1.2V VIN = 2.4V VIN = 3.6V VIN = 4.2V 40 0.01 1000 100 110 100 0.1 LOAD CURRENT (mA) 1 10 POWER LOSS (mW) POWER LOSS 60 POWER LOSS (mW) 10 70 EFFICIENCY 90 100 80 EFFICIENCY (%) 100 EFFICIENCY 90 No-Load Input Current vs VIN 130 1000 90 IIN (µA) Efficiency vs Load Current and VIN for VOUT = 3.3V (TA = 25°C unless otherwise noted) 10 5 Start-Up Delay Time vs VIN 130 10000 120 700 110 600 500 DELAY (µs) 1000 RLOAD (Ω) IOUT (mA) 4 35282 G04 Minimum Load Resistance During Start-Up vs VIN 800 400 300 100 100 90 80 70 200 VOUT = 1.8V VOUT = 3.3V VOUT = 5V 100 1 1.5 2 3 2.5 VIN (V) 3.5 4 60 10 4.5 0.7 0.8 Burst Mode Threshold Current vs VIN 80 IOUT (mA) ENTER BURST 20 1.3 1.2 VIN (V) 1.4 1.5 80 VOUT = 3V 4 4.5 VOUT = 3.3V EXIT BURST 40 ENTER BURST ENTER BURST 20 1 1.5 2 2.5 0 1 1.5 2 2.5 3 VIN (V) VIN (V) 35282 G08 3.5 60 40 0 3 2.5 VIN (V) Burst Mode Threshold Current vs VIN 20 1.1 2 EXIT BURST 40 1 1.5 35282 G07 60 EXIT BURST 1 35282 G06 Burst Mode Threshold Current vs VIN VOUT = 1.8V 60 50 1 IOUT (mA) 80 0.9 VIN (V) 35282 G05 IOUT (mA) 3 VIN (V) 35282 G03 Maximum Output Current vs VIN 0 2 1 LOAD CURRENT (mA) 35282 G02 0 VOUT = 1.8V VOUT = 3V VOUT = 3.3V VOUT = 5V 50 30 0.1 1000 100 70 35282 G09 35282 G10 35282fb 4 LTC3528-2 TYPICAL PERFORMANCE CHARACTERISTICS Oscillator Frequency Change vs VOUT Burst Mode Threshold Current vs VIN 80 (TA = 25°C unless otherwise noted) RDS(ON) vs VOUT 0.50 VOUT = 5V 450 0.25 400 0 EXIT BURST 40 ENTER BURST 20 –0.25 350 –0.50 RDS(ON) (mΩ) FREQUENCY CHANGE (%) IOUT (mA) 60 –0.75 –1.00 –1.25 1.5 2 2.5 VIN (V) 3 3.5 4 –2.25 1.5 2.5 2 3.5 3 VOUT (V) 4 35242 G11 100 1.5 5 2 2.5 3.5 3 VOUT (V) 4 40 1 30 0 20 4.5 5 35282 G13 VFB vs Temperature RDS(ON) Change vs Temperature 2 1.200 –1 –2 VFB (V) 1.199 CHANGE (%) FREQUENCY CHANGE (%) 4.5 35282 G12 Oscillator Frequency Change vs Temperature 1.198 10 0 1.197 –3 –10 –4 –50 –25 50 25 75 0 TEMPERATURE (˚C) 100 –20 –50 –25 125 50 25 75 0 TEMPERATURE (˚C) 35282 G14 0.20 VIN = 3.6V CHANGE IN OUTPUT VOLTAGE (%) 0.10 0.05 0 –0.05 –0.10 –0.15 0 200 400 1.196 –50 600 LOAD CURRENT (mA) 75 0 25 50 TEMPERATURE (°C) 100 125 Start-Up Voltage vs Temperature 850 VIN = 1.2V 0.15 0.10 0.05 0 –0.05 –0.10 800 750 700 650 –0.15 –0.20 0 50 100 150 200 LOAD CURRENT (mA) 3528-2 G27 –25 35282 G16 Output Voltage vs Load Current for VOUT = 3.3V 0.15 –0.20 125 START-UP VOLTAGE (mV) 0.20 100 35282 G15 Output Voltage vs Load Current for VOUT = 5V CHANGE IN OUTPUT VOLTAGE (%) NMOS 150 –2.00 1 PMOS 250 200 –1.50 –1.75 0 300 35282 G28 600 –50 –25 50 0 75 25 TEMPERATURE (°C) 100 125 35282 G17 35282fb 5 LTC3528-2 TYPICAL PERFORMANCE CHARACTERISTICS Fixed Frequency VOUT Ripple and Inductor Current Waveforms (TA = 25°C unless otherwise noted) Burst Mode Waveforms VOUT and IIN During Soft-Start VOUT 50mV/DIV VOUT 20mV/DIV VOUT 1V/DIV IIN 200mA/DIV INDUCTOR CURRENT 100mA/DIV IL 200mA/DIV VIN = 1.2V VOUT = 3.3V COUT = 10µF CFF = 33pF IOUT = 100mA L = 2.2µH 500ns/DIV 35282 G19 SHDN PIN VIN = 3.6V VOUT = 5V COUT = 10µF CFF = 33pF ILOAD = 30mA 35282 G20 5µs/DIV Load Step Response (Fixed Frequency, 3.6V to 5V) VIN = 1.2V VOUT = 3.3V COUT = 10µF L = 2.2µH 200µs/DIV 35282 G21 Load Step Response (Burst Mode Operation, 3.6V to 5V) VOUT 100mV/DIV VOUT 100mV/DIV LOAD CURRENT 200mA/DIV LOAD CURRENT 200mA/DIV VIN = 3.6V 20µs/DIV VOUT = 5V COUT = 10µF L = 2.2µH LOAD CURRENT = 100mA TO 550mA 35282 G22 VIN = 3.6V 20µs/DIV VOUT = 5V COUT = 10µF L = 2.2µH LOAD CURRENT = 20mA TO 550mA Load Step Response (Fixed Frequency, 1.2V to 3.3V) Load Step Response (Burst Mode Operation, 1.2V to 3.3V) VOUT 100mV/DIV VOUT 100mV/DIV LOAD CURRENT 100mA/DIV LOAD CURRENT 100mA/DIV 20µs/DIV VIN = 1.2V VOUT = 3.3V COUT = 10µF L = 2.2µH LOAD CURRENT = 20mA TO 170mA 35282 G23 35282 G24 VIN = 1.2V 20µs/DIV VOUT = 3.3V COUT = 10µF L = 2.2µH LOAD CURRENT = 10mA TO 160mA 35282 G25 35282fb 6 LTC3528-2 PIN FUNCTIONS SHDN (Pin 1): Logic Controlled Shutdown Input. There is an internal 4M pull-down resistor on this pin. • SHDN = High: Normal operation • SHDN = Low: Shutdown, quiescent current < 1µA FB (Pin 2): Feedback Input. Connect resistor divider tap to this pin. The output voltage can be adjusted from 1.6V to 5.25V by:  R2 VOUT = 1.20V • 1+   R1 PGOOD (Pin 3): Power Good Comparator Output. This open-drain output is low when VFB < 10% from its regulation voltage. VOUT (Pin 4): Output Voltage Sense and Drain Connection of the Internal Synchronous Rectifier. PCB trace length from VOUT to the output filter capacitor (4.7µF minimum) should be as short and wide as possible. SW (Pin 5): 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. PGND (Pin 6): Power Ground. Provide a short direct PCB path between PGND and the (–) side of the input and output capacitors. SGND (Pin 7): Signal Ground. Provide a short direct PCB path between SGND and the (–) side of the input and output capacitors. VIN (Pin 8): Battery Input Voltage. Connect a minimum of 1µF ceramic decoupling capacitor from this pin to ground. GND (Exposed Pad Pin 9): The exposed pad must be soldered to the PCB ground plane. It serves as another ground connection and as a means of conducting heat away from the die. 35282fb 7 LTC3528-2 BLOCK DIAGRAM VIN 0.7V TO 5V L1 2.2µH CIN 4.7µF 8 5 VIN SW ANTI-RING VOUT VSEL VBEST 1 SHDN SHUTDOWN SHUTDOWN WELL SWITCH VB VOUT GATE DRIVERS AND ANTI-CROSS CONDUCTION – + 4M Σ VREF UVLO PK COMP PK UVLO IZERO IZERO COMP 2MHz OSC 3 CLK BURST + – R1 + – MODE CONTROL PGOOD COUT 10µF ERROR AMP SLEEP COMP START-UP LOGIC R2 2 SLOPE COMP + – VREF FB VOUT 1.6V TO 5.25V 4 VREF FB CLAMP VREF – 10% FB THERMAL SHUTDOWN SOFT-START TSD WAKE PGND SGND EXPOSED PAD 6 7 9 35282 BD 35282fb 8 LTC3528-2 OPERATION (Refer to Block Diagram) The LTC3528-2 is a 2MHz synchronous boost converter housed in an 8-lead 3mm × 2mm DFN package. With the ability to start up and operate from inputs less than 0.88V, the device features fixed frequency, current mode PWM control for exceptional line and load regulation. The current mode architecture with adaptive slope compensation provides excellent transient load response and requires 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 LTC3528-2 achieves high efficiency over a wide range of load current. The LTC3528-2 features continuous 2MHz PWM operation over a wide range of load current. At very light loads, the LTC3528‑2 will enter Burst Mode operation to maintain high efficiency. Operation can be best understood by referring to the Block Diagram. LOW VOLTAGE START-UP The LTC3528-2 includes an independent start-up oscillator designed to operate at an input voltage of 0.70V (typical). Soft-start and inrush current limiting are provided during start-up, as well as normal operating mode. When either VIN or VOUT exceeds 1.6V typical, the IC enters normal operating mode. Once the output voltage exceeds the input by 0.24V, the IC powers itself from VOUT instead of VIN. At this point the internal circuitry has no dependency on the VIN input voltage, eliminating the requirement for a large input capacitor. The input voltage can drop as low as 0.5V. The limiting factor for the application becomes the availability of the power source to supply sufficient power to the output at the low voltages, and the maximum duty cycle, which is clamped at 92% 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 LTC3528-2 contains internal circuitry to provide softstart operation. The internal soft-start circuitry slowly ramps the peak inductor current from zero to its peak value of 1.5A (typical), allowing start-up into heavy loads. The soft-start time is approximately 0.5ms. The soft-start circuitry is reset in the event of a commanded shutdown or a thermal shutdown. Oscillator An internal oscillator sets the frequency of operation to 2MHz. Shutdown The converter is shut down by pulling the SHDN pin below 0.25V, and activated by pulling SHDN above 0.88V. Although SHDN can be driven above VIN or VOUT (up to the absolute maximum rating) without damage, the LTC35282 has a proprietary test mode that may be engaged if SHDN is held in the range of 0.5V to 1V higher than the greater of VIN or VOUT. If the test mode is engaged, normal PWM switching action is interrupted, which can cause undesirable operation in some applications. Therefore, in applications where SHDN may be driven above VIN, a resistor divider or other means must be employed to keep the SHDN voltage below (VIN + 0.4V) to prevent the possibility of the test mode being engaged. Please refer to Figure 1 for two possible implementations LTC3528-2 4M ±30% VCNTRL LTC3528-2 VIN 4M ±30% SHDN SHDN 3528 F01 R 1M R > (VCNTRL/(VIN + 0.4) – 1) MΩ ZETEX ZC2811E VCNTRL 1M Figure 1. Recommended Shutdown Circuits when Driving SHDN Above VIN 35282fb 9 LTC3528-2 OPERATION (Refer to Block Diagram) Error Amplifier Anti-Ringing Control The error amplifier is a transconductance type. The noninverting input is internally connected to the 1.20V reference and the inverting input is connected to FB. Clamps limit the minimum and maximum error amp output voltage for improved large-signal transient response. Power converter control loop compensation is provided internally. A voltage divider from VOUT to ground programs the output voltage via FB from 1.6V to 5.25V. The anti-ringing control connects a resistor across the inductor to prevent high frequency ringing on the SW pin during discontinuous current mode operation. The ringing of the resonant circuit formed by L and CSW (capacitance on SW pin) is low energy, but can cause EMI radiation. Output Disconnect Lossless current sensing converts the peak current signal of the N-channel MOSFET switch into a voltage which is summed with the internal slope compensation. The summed signal is compared to the error amplifier output to provide a peak current control command for the PWM. The LTC3528-2 is 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 enables inrush current limiting at turnon, minimizing surge currents seen by the input supply. Note that to obtain the advantages of output disconnect, a Schottky diode cannot be connected between SW and VOUT. The output disconnect feature also allows VOUT to be forced above the programmed regulation voltage, without any reverse current into the input power source. Current Limit Thermal Shutdown 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 1.5A, independent of input or output voltage, unless VOUT falls below 0.7V, in which case the current limit is cut in half. If the die temperature exceeds 160°C, the LTC3528-2 enters thermal shutdown. All switches will be turned off and the soft-start capacitor will be discharged. The device will be enabled again when the die temperature drops by approximately 15°C.  R2 VOUT = 1.20V • 1+   R1 Current Sensing Zero Current Comparator Burst Mode OPERATION Synchronous Rectifier The LTC3528-2 will automatically enter Burst Mode operation at light load current 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 vs VIN. The load 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. 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). In Burst Mode operation, the LTC3528-2 continues switching at a fixed frequency of 2MHz, using the same error amplifier and loop compensation for peak current mode control. This control method minimizes output transients The zero current comparator monitors the inductor current to the output and shuts off the synchronous rectifier when this current reduces to approximately 20mA. This prevents the inductor current from reversing in polarity, improving efficiency at light loads. 35282fb 10 LTC3528-2 OPERATION (Refer to Block Diagram) when switching between modes. In Burst Mode operation, energy is delivered to the output until it reaches the nominal regulated value, then the LTC3528-2 transitions to sleep mode where the outputs are off and the LTC3528–2 consumes only 12µA of quiescent current from VOUT. Once the output voltage has drooped slightly, switching resumes again. This maximizes efficiency at very light loads by minimizing switching and quiescent current losses. Burst Mode output ripple, which is typically 1% peak-to-peak, can be reduced by using more output capacitance (10µF or greater). As the load current increases, the LTC3528-2 automatically leaves Burst Mode operation. Note that larger output capacitor values may cause this transition to occur at lighter loads. The regulator will also leave Burst Mode operation if a load transient occurs which causes the inductor current to repeatedly reach current limit. Once the LTC3528-2 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 until soft-start is done and VOUT is at least 0.24V greater than VIN. Single Cell to 5V Step-Up Applications Due to the high inductor current slew rate in applications boosting to 5V from a single cell (alkaline, NiCd or NiMH), the LTC3528-2 may not enter Burst Mode operation at input voltages below 1.5V. For single cell to 5V applications requiring Burst Mode operation, the 1MHz LTC3528 is recommended. Refer to the Typical Performance Characteristics for the Burst Mode thresholds for different input and output voltages. 35282fb 11 LTC3528-2 APPLICATIONS INFORMATION VIN > VOUT OPERATION The LTC3528-2 maintains 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 LTC3528-2 output disconnect feature allows an output short circuit while maintaining a maximum internally set current limit. To reduce power dissipation under shortcircuit conditions, the peak switch current limit is reduced to 750mA (typical). SCHOTTKY DIODE Although 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. The high speed operation of the LTC3528-2 demands careful attention to board layout. A careless layout will not produce the advertised performance. Figure 2 shows VIN The LTC3528-2 can utilize small surface mount chip inductors due to its fast 2MHz switching frequency. Inductor values between 1.5µH and 3.3µH are suitable for most applications. Larger values of inductance will allow slightly greater output current capability by reducing the inductor ripple current. Increasing the inductance above 10µH will increase size while providing little improvement in output current capability. The minimum inductance value is given by: L> ( VIN(MIN) • VOUT(MAX) – VIN(MIN) 2 • Ripple • VOUT(MAX) ) µH where: Ripple = Allowable inductor current ripple (amps peakpeak) VOUT(MAX) = Maximum output voltage CIN 8 VIN 7 SGND FB 2 LTC3528-2 COUT Inductor Selection VIN(MIN) = Minimum input voltage + SHDN 1 VOUT 4 COMPONENT SELECTION PCB LAYOUT GUIDELINES PGOOD 3 the recommended component placement. A large ground copper area with the package backside metal pad properly soldered will help to lower the chip temperature. A multilayer board with a separate ground plane is ideal, but not absolutely necessary. 6 PGND 5 SW 35282 F02 MULTIPLE VIAS TO GROUND PLANE Figure 2. Recommended Component Placement for Single Layer Board 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 handle the peak inductor current without saturating. Molded chokes and some chip inductors usually do not have enough core area to support the peak inductor currents of 1.5A seen on the LTC3528-2. To minimize radiated noise, use a shielded inductor. See Table 1 for suggested components and suppliers. 35282fb 12 LTC3528-2 APPLICATIONS INFORMATION Table 1. Recommended Inductors VENDOR PART/STYLE Coilcraft (847) 639-6400 www.coilcraft.com DO1606T, MSS5131, MSS5121 MSS6122, MOS6020 ME3220, DO1608C 1812PS Coiltronics SD12, SD14, SD20 SD25, SD52 Sumida (847) 956-0666 www.sumida.com CD43 CDC5D23B CDRH5D18 TDK VLP, VLF VLCF, SLF, VLS Toko (408) 432-8282 www.tokoam.com D53, D62, D63 D73, D75 Wurth (201) 785-8800 www.we-online.com WE-TPC type M, MH 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 10µF to 22µF output capacitor is sufficient for most applications. Values larger than 22µF 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 LTC3528-2 is designed to be stable with output capacitor values of 10µF or greater. 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 which 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 68pF 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 10µF input capacitor is sufficient for most applications. Larger values may be used without limitations. Table 2 shows a list of several ceramic capacitor manufacturers. Consult the manufacturers directly for detailed information on their selection of ceramic parts. Table 2. Capacitor Vendor Information SUPPLIER PHONE AVX (803) 448-9411 www.avxcorp.com Murata (714) 852-2001 www.murata.com Taiyo-Yuden (408) 573-4150 www.t-yuden.com TDK (847) 803-6100 www.component.tdk.com TYPICAL APPLICATIONS Efficiency 1 Cell to 1.8V 100 2.2µH 90 VIN 4.7µF VOUT LTC3528-2 PGOOD OFF ON SHDN GND 499k 68pF VOUT 1.8V 250mA 10µF FB 80 EFFICIENCY (%) SW VIN 0.88V TO 1.6V WEBSITE 70 60 50 1M VIN = 0.9V VIN = 1.2V VIN = 1.5V 40 35282 TA02a 30 0.01 0.1 1 10 100 1000 LOAD CURRENT (mA) 35282 TA02b 35282fb 13 LTC3528-2 TYPICAL APPLICATIONS Dual 1 Cell to 1.8V, 3V Sequenced Supply 2.2µH SW VIN 0.88V TO 1.6V VOUT VIN 4.7µF 475k LTC3528-2 SHDN Output Voltage Sequencing 10µF FB PGOOD OFF ON 68pF 499k VOUT1 1.8V 250mA 1M GND VOUT2 SW VIN 4.7µF VOUT1 VIN PGOOD1 0.5V/DIV 2.2µH VOUT LTC3528-2 PGOOD SHDN GND 68pF 499k VOUT2 3V 200mA 35282 TA03b 200µs/DIV 10µF FB 324k 3528 TA03a Efficiency 1 Cell to 3.3V 100 2.2µH 90 VIN 4.7µF VOUT LTC3528-2 PGOOD OFF ON SHDN GND 499k 68pF VOUT 3.3V 200mA 10µF FB 80 EFFICIENCY (%) SW VIN 0.88V TO 1.6V 70 60 50 287k 35282 TA04a VIN = 0.9V VIN = 1.2V VIN = 1.5V 40 30 0.01 0.1 1 10 100 1000 LOAD CURRENT (mA) 35282 TA04b 35282fb 14 LTC3528-2 TYPICAL APPLICATIONS Efficiency 2 Cell to 3.3V 100 90 2.2µH SW VIN 1.8V TO 3.2V VIN 4.7µF VOUT 68pF 10µF FB PGOOD OFF ON 499k LTC3528-2 SHDN VOUT 3.3V 400mA EFFICIENCY (%) 80 60 50 287k GND 70 VIN = 1.8V VIN = 2.4V VIN = 3V 40 30 0.01 35282 TA05a 0.1 1 10 1000 100 LOAD CURRENT (mA) 35282 TA05b 2 Cell to 5V Efficiency 100 2.2µH 90 VIN 4.7µF VOUT LTC3528-2 68pF 22µF FB PGOOD OFF ON 1M SHDN VOUT 5V 300mA 80 EFFICIENCY (%) SW VIN 1.8V TO 3.2V 60 50 316k GND 70 VIN = 1.8V VIN = 2.4V VIN = 3V 40 35282 TA06a 30 0.01 0.1 1 10 100 1000 LOAD CURRENT (mA) 35282 TA06b Li-Ion to 5V Efficiency 100 2.2µH 90 VIN 4.7µF VOUT LTC3528-2 PGOOD OFF ON SHDN GND 1M FB 68pF VOUT 5V 400mA 22µF 80 EFFICIENCY (%) SW VIN 2.7V TO 4.2V 70 60 50 316k 35282 TA07a VIN = 2.8V VIN = 3.6V VIN = 4.2V 40 30 0.01 0.1 1 10 100 1000 LOAD CURRENT (mA) 35282 TA07b 35282fb 15 LTC3528-2 PACKAGE DESCRIPTION DDB Package 8-Lead Plastic DFN (3mm × 2mm) (Reference LTC DWG # 05-08-1702 Rev B) 0.61 ±0.05 (2 SIDES) 0.70 ±0.05 2.55 ±0.05 1.15 ±0.05 PACKAGE OUTLINE 0.25 ± 0.05 0.50 BSC 2.20 ±0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 3.00 ±0.10 (2 SIDES) R = 0.115 TYP 5 R = 0.05 TYP 0.40 ± 0.10 8 2.00 ±0.10 (2 SIDES) PIN 1 BAR TOP MARK (SEE NOTE 6) 0.56 ± 0.05 (2 SIDES) 0.200 REF 0.75 ±0.05 0 – 0.05 4 0.25 ± 0.05 1 PIN 1 R = 0.20 OR 0.25 × 45° CHAMFER (DDB8) DFN 0905 REV B 0.50 BSC 2.15 ±0.05 (2 SIDES) BOTTOM VIEW—EXPOSED PAD NOTE: 1. DRAWING CONFORMS TO VERSION (WECD-1) IN JEDEC PACKAGE OUTLINE M0-229 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 35282fb 16 LTC3528-2 REVISION HISTORY REV DATE DESCRIPTION A 01/11 Change in Operating Temperature Range PAGE NUMBER Update to Note 2 reflected in Electrical Characteristics B 12/11 2 2,3 Replaced graphs G14, G15, G16 and G17 5 Operations section update Pin 9 to read GND 7 Operations section update to Shutdown 9 Added capacitor to the output in “Li-Ion to 5V” Typical Application 15 35282fb 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. 17 LTC3528-2 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC3528/LTC3528 1A (ISW), 1MHz Synchronous Step-Up DC/DC Converters 94% Efficiency, VIN: 0.7V to 5.5V, VOUT(MAX) = 5.25V, IQ = 12µA, ISD < 1µA, 3mm × 2mm DFN8 Package with Output Disconnect LTC3528B-2 1A (ISW), 2MHz Synchronous Step-Up DC/DC Converter with Output Disconnect 94% Efficiency, VIN: 0.7V to 5.5V, VOUT(MAX) = 5.25V, IQ = 12µA, ISD < 1µA, 3mm × 2mm DFN8 Package 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, ThinSOTTM Package LTC3421 3A (ISW), 3MHz, Synchronous Step-Up DC/DC Converter with Output Disconnect 94% Efficiency VIN: 0.85V to 4.5V, VOUT(MAX) = 5.25V, IQ = 12µA, ISD < 1µA, 4mm × 4mm QFN24 Package LTC3422 1.5A (ISW), 3MHz Synchronous Step-Up DC/DC Converter with Output Disconnect 94% Efficiency VIN: 0.85V to 4.5V, VOUT(MAX) = 5.25V, IQ = 25µA, ISD < 1µA, 3mm × 3mm DFN10 Package LTC3426 2A (ISW), 1.5MHz, Step-Up DC/DC Converter 92% Efficiency VIN: 1.6V to 5.5V, VOUT(MAX) = 5V, IQ = 600µA, ISD < 1µA, ThinSOT Package LTC3427 500mA (ISW), 1.25MHz, Synchronous Step-Up DC/DC Converter with Output Disconnect 94% Efficiency VIN: 1.8V to 5V, VOUT(MAX) = 5.25V, IQ = 350µA ISD < 1µA, 2mm × 2mm DFN6 Package LTC3429/LTC3429B 600mA (ISW), 550kHz, Synchronous Step-Up DC/DC Converter with Output Disconnect and Soft-Start 96% Efficiency VIN: 0.85V to 4.3V, VOUT(MAX) = 5V, IQ = 20µA, ISD < 1µA, ThinSOT Package LTC3458/LTC3458L 1.4A/1.7A (ISW), 1.5MHz, Synchronous Step-Up DC/DC Converter 94% Efficiency VIN: 0.85V to 6V, VOUT(MAX) = 7.5V/6V, IQ = 15µA, ISD < 1µA, 3mm × 4mm DFN12 Package LTC3459 80mA (ISW), Synchronous Step-Up DC/DC Converter 92% Efficiency VIN: 1.5V to 5.5V, VOUT(MAX) = 10V, IQ = 10µA, ISD < 1µA, ThinSOT Package LT®3494/LT3494A 180mA/350mA (ISW), High Efficiency Step-Up DC/DC Converter with Output Disconnect 85% Efficiency VIN: 2.3V to 16V, VOUT(MAX) = 38V, IQ = 65µA, ISD < 1µA, 2mm × 3mm DFN6, ThinSOT Packages LTC3523/LTC3523-2 600mA (ISW), Step-Up and 400mA Synchronous Step-Down 1.2MHz/2.4MHz DC/DC Converters with Output Disconnect 94% Efficiency VIN: 1.8V to 5.5V, VOUT(MAX) = 5.25V, IQ = 45µA, ISD < 1µA, 3mm × 3mm QFN16 LTC3526/LTC3526L LTC3526B 500mA (ISW), 1MHz Synchronous Step-Up DC/DC Converters with Output Disconnect 94% Efficiency, VIN: 0.85V to 5V, VOUT(MAX) = 5.25V, IQ = 9µA, ISD < 1µA, 2mm × 2mm DFN6 Package LTC3527/LTC3527-1 Dual 800mA/400mA (ISW), 2.2MHz, Synchronous Step-Up DC/DC Converter with Output Disconnect 94% Efficiency, VIN: 0.7V to 5V, VOUT(MAX) = 5.25V, IQ = 12µA, ISD < 1µA, 3mm × 3mm QFN16 Package LTC3537 600mA, 2.2MHz Synchronous Step-Up DC/DC Converter with Output Disconnect and 100mA LDO 94% Efficiency, VIN: 0.7V to 5V, VOUT(MAX) = 5.25V, IQ = 30µA, ISD < 1µA, 3mm × 3mm QFN16 Package 35282fb 18 Linear Technology Corporation LT 1211 REV B • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com  LINEAR TECHNOLOGY CORPORATION 2009