LTC3440 Micropower Synchronous Buck-Boost DC/DC Converter Features Description n Single Inductor The LTC®3440 is a high efficiency, fixed frequency, Buck- n Fixed Frequency Operation with Battery Voltages Boost DC/DC converter that operates from input voltages Above, Below or Equal to the Output above, below or equal to the output voltage. The topology n Synchronous Rectification: Up to 96% Efficiency incorporated in the IC provides a continuous transfer n 25µA Quiescent Current in Burst Mode® Operation function through all operating modes, making the prod- n Up to 600mA Continuous Output Current uct ideal for single lithium-ion, multicell alkaline or NiMH n No Schottky Diodes Required (V < 4.3V) applications where the output voltage is within the battery OUT n V Disconnected from V During Shutdown voltage range. OUT IN n 2.5V to 5.5V Input and Output Range The device includes two 0.19Ω N-channel MOSFET n Programmable Oscillator Frequency switches and two 0.22Ω P-channel switches. Switch- from 300kHz to 2MHz ing frequencies up to 2MHz are programmed with an n Synchronizable Oscillator external resistor and the oscillator can be synchronized n Burst Mode Enable Control to an external clock. Quiescent current is only 25µA in n <1µA Shutdown Current Burst Mode operation, maximizing battery life in portable n Small Thermally Enhanced 10-Pin MSOP and applications. Burst Mode operation is user controlled and (3mm × 3mm) DFN Packages can be enabled by driving the MODE/SYNC pin high. If the MODE/SYNC pin has either a clock or is driven low, then applications fixed frequency switching is enabled. Other features include a 1µA shutdown, soft-start con- n Palmtop Computers trol, thermal shutdown and current limit. The LTC3440 n Handheld Instruments is available in the 10-pin thermally enhanced MSOP and n MP3 Players (3mm × 3mm) DFN packages. n Digital Cameras L, LT, LTC, LTM, Linear Technology, Burst Mode and the Linear logo are registered trademarks and ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. typical application Li-Ion to 3.3V at 600mA Buck-Boost Converter Efficiency vs V IN L1 100 10µH V3.O3UVT 98 VIOOUUTT = = 1 30.03mVA 600mA 96 fOSC = 1MHz 3 4 SW1 SW2 94 VIN = 2.7V TO 4.2V 7 LTC3440 6 R1 %) VIN VOUT 340k Y ( 92 C 8 9 N 90 Li-Ion+ C1 * 2 SMHODDNE//SSSYNC VFBC 10C5 1.5nFR3 C222µF EFFICIE 8886 10µF 1 RT GND 5 15k R2 84 200k RT 82 60.4k 80 2.5 3.0 3.5 4.0 4.5 5.0 5.5 *1 = Burst Mode OPERATION C1: TAIYO YUDEN JMK212BJ106MG 0 = FIXED FREQUENCY C2: TAIYO YUDEN JMK325BJ226MM 3440 TA01 VIN (V) L1: SUMIDA CDRH6D38-100 3440 TA02 3440fd 1 For more information www.linear.com/LTC3440

LTC3440 absolute MaxiMuM ratings (Note 1) V , V Voltage ....................................... –0.3V to 6V Operating Temperature Range (Note 2)....–40°C to 85°C IN OUT SW1, SW2 Voltage ...................................... –0.3V to 6V Storage Temperature Range ..................–65°C to 125°C V , R , FB, SHDN/SS, Lead Temperature (Soldering, 10 sec) ...................300°C C T MODE/SYNC Voltage .................................. –0.3V to 6V pin conFiguration TOP VIEW TOP VIEW RT 1 10 VC MODE/SYNRCT 12 190 VFBC MODE/SYNC 2 9 FB SW1 3 8 SHDN/SS SW1 3 11 8 SHDN/SS SW2 4 7 VIN SW2 4 7 VIN GND 5 6 VOUT GND 5 6 VOUT MS PACKAGE 10-LEAD PLASTIC MSOP DD PACKAGE TJMAX = 125°C, 10-LEAD (3mm × 3mm) PLASTIC DFN θJA = 130°C/W 1 LAYER BOARD EXPOSED PAD (PIN 11) IS GND θJA = 100°C/W 4 LAYER BOARD MUST BE SOLDERED TO PCB θJC = 45°C/W TJMAX = 125°C, θJA = 43°C/W, θJC = 3°C/W orDer inForMation http://www.linear.com/product/LTC3440#orderinfo LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LTC3440EDD#PBF LTC3440EDD#TRPBF LBKT 10-Lead (3mm × 3mm) Plastic DFN –40°C to 85°C LTC3440EMS#PBF LTC3440EMS#TRPBF LTNP 10-Lead Plastic MSOP –40°C to 85°C Consult LTC Marketing for parts specified with wider operating temperature ranges. Consult LTC Marketing for information on nonstandard 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/. Some packages are available in 500 unit reels through designated sales channels with #TRMPBF suffix. electrical characteristics The ● denotes specifications that apply over the full operating temperature range, otherwise specifications are at T = 25°C. V = V = 3.6V, R = 60k, unless otherwise noted. A IN OUT T PARAMETER CONDITIONS MIN TYP MAX UNITS Input Start-Up Voltage l 2.4 2.5 V Input Operating Range l 2.5 5.5 V Output Voltage Adjust Range l 2.5 5.5 V Feedback Voltage l 1.196 1.22 1.244 V Feedback Input Current V = 1.22V 1 50 nA FB Quiescent Current, Burst Mode Operation V = 0V, MODE/SYNC = 3V (Note 3) 25 40 µA C Quiescent Current, Shutdown SHDN = 0V, Not Including Switch Leakage 0.1 1 µA Quiescent Current, Active V = 0V, MODE/SYNC = 0V (Note 3) 600 1000 µA C NMOS Switch Leakage Switches B and C 0.1 5 µA 3440fd 2 For more information www.linear.com/LTC3440

LTC3440 electrical characteristics The ● denotes specifications that apply over the full operating temperature range, otherwise specifications are at T = 25°C. V = V = 3.6V, R = 60k, unless otherwise noted. A IN OUT T PARAMETER CONDITIONS MIN TYP MAX UNITS PMOS Switch Leakage Switches A and D 0.1 10 µA NMOS Switch On Resistance Switches B and C 0.19 Ω PMOS Switch On Resistance Switches A and D 0.22 Ω Input Current Limit l 1 A Maximum Duty Cycle Boost (% Switch C On) l 55 75 % Buck (% Switch A On) l 100 % Minimum Duty Cycle l 0 % Frequency Accuracy l 0.8 1 1.2 MHz MODE/SYNC Threshold 0.4 2 V MODE/SYNC Input Current V = 5.5V 0.01 1 µA MODE/SYNC Error Amp AVOL 90 dB Error Amp Source Current 15 µA Error Amp Sink Current 380 µA SHDN/SS Threshold When IC is Enabled l 0.4 1 1.5 V When EA is at Maximum Boost Duty Cycle 2.2 V SHDN/SS Input Current V = 5.5V 0.01 1 µA SHDN Note 1: Absolute Maximum Ratings are those values beyond which the temperature range are assured by design, characterization and life of the device may be impaired. correlation with statistical process controls. Note 2: The LTC3440E is guaranteed to meet performance specifications Note 3: Current measurements are performed when the outputs are not from 0°C to 70°C. Specifications over the –40°C to 85°C operating switching. typical perForMance characteristics Li-Ion to 3.3V Efficiency Li-Ion to 3.3V Efficiency, Li-Ion to 3.3V Efficiency (fOSC = 300kHz) Power Loss (fOSC = 1MHz) (fOSC = 2MHz) 100 100 1000 100 90 Burst Mode 90 Burst Mode 90 Burst Mode OPERATION OPERATION OPERATION 80 80 100 80 EFFICIENCY (%) 576000 VIN = 2.5V VIN = 3.3VVIN = 4.2V EFFICIENCY (%) 576000 VIN = 2.5V VINV I=VN I3N=. 33=V. 34V.2V 10 POWER LOSS (mW EFFICIENCY (%) 576000 VIN = 2.5V VIN V=I N3 .=3 V4.2V 40 40 1 ) 40 30 30 30 20 fOSC = 300kHz 20 fOSC = 1MHz 0.1 20 fOSC = 2MHz 0.1 1 10 100 1000 0.1 1 10 100 1000 0.1 1 10 100 1000 OUTPUT CURRENT (mA) OUTPUT CURRENT (mA) OUTPUT CURRENT (mA) 3440 G01 3440 G02 3440 G03 3440fd 3 For more information www.linear.com/LTC3440

LTC3440 typical perForMance characteristics Switch Pins on the Edge of Switch Pins on the Edge of Switch Pins During Buck/Boost Buck/Boost and Approaching Boost Buck/Boost and Approaching Buck SW1 SW1 SW1 2V/DIV 2V/DIV 2V/DIV SW2 SW2 SW2 2V/DIV 2V/DIV 2V/DIV VIN = 3.78V 50ns/DIV 3440 G04 VIN = 3.42V 50ns/DIV 3440 G05 VIN = 4.15V 50ns/DIV 3440 G06 VOUT = 3.3V VOUT = 3.3V VOUT = 3.3V IOUT = 250mA IOUT = 250mA IOUT = 250mA V Ripple During Buck, OUT Switch Pins in Buck Mode Switch Pins in Boost Mode Buck/Boost and Boost Modes Buck SW1 SW1 VIN = 5V 2V/DIV 2V/DIV VOUT Buck/Boost 10mV/DIV AC Coupled VIN = 3.78V Boost SW2 SW2 VIN = 2.5V 2V/DIV 2V/DIV VIN = 5V 250ns/DIV 3440 G07 VIN = 2.5V 250ns/DIV 3440 G08 L = 10µH 1µs/DIV 3440 G09 VOUT = 3.3V VOUT = 3.3V COUT = 22µF IOUT = 250mA IOUT = 250mA IOUT = 250mA fOSC = 1MHz Active Quiescent Current Burst Mode Quiescent Current Error Amp Source Current 550 40 20 VIN = VOUT = 3.6V VIN = VOUT = 3.6V VIN = VOUT = 3.6V V + V CURRENT (µA)INOUT455000 V + V CURRENT (µA)INOUT2300 E/A SOURCE CURRENT (µA)1105 400 10 5 –55 –25 5 35 65 95 125 –55 –25 5 35 65 95 125 –55 –25 5 35 65 95 125 TEMPERATURE (°C) TEMPERATURE (°C) TEMPERATURE (°C) 3440 G10 3440 G11 3440 G12 3440fd 4 For more information www.linear.com/LTC3440

LTC3440 typical perForMance characteristics Output Frequency NMOS R Feedback Voltage DS(ON) 1.10 0.30 1.236 VIN = VOUT = 3.6V VIN = VOUT = 3.6V VIN = VOUT = 3V SWITCHES B AND C 1.05 0.25 V) NCY (MHz)1.00 (Ω)DS(ON)0.20 VOLTAGE (1.216 FREQUE NMOS R EDBACK 0.95 0.15 FE 0.90 0.10 1.196 –55 –25 5 35 65 95 125 –55 –25 5 35 65 95 125 –55 –25 5 35 65 95 125 TEMPERATURE (°C) TEMPERATURE (°C) TEMPERATURE (°C) 3440 G13 3440 G14 3440 G15 Feedback Voltage Line Regulation Error Amp Sink Current PMOS R DS(ON) 90 430 0.30 VIN = VOUT = 2.5V TO 5.5V VIN = VOUT = 3.6V VIN = VOUT = 3.6V SWITCHES A AND D B) A) 410 0.25 EGULATION (d 80 K CURRENT (µ 390 S R (Ω)DS(ON)0.20 R N O E 70 SI M LIN E/A 370 P0.15 60 350 0.10 –55 –25 5 35 65 95 125 –55 –25 5 35 65 95 125 –55 –25 5 35 65 95 125 TEMPERATURE (°C) TEMPERATURE (°C) TEMPERATURE (°C) 3440 G16 3440 G17 3440 G18 Boost Max Duty Cycle Minimum Start Voltage Current Limit 90 2.40 3000 VIN = VOUT = 3.6V VIN = VOUT = 3.6V RT = 60k V) PEAK SWITCH 85 E ( 2500 UTY CYCLE (%) 80 M START VOLTAG2.35 RRENT LIMIT (A)2000 D U2.30 U AVERAGE INPUT M C 75 NI 1500 MI 70 2.25 1000 –55 –25 5 35 65 95 125 –55 –25 5 35 65 95 125 –55 –25 5 35 65 95 125 TEMPERATURE (°C) TEMPERATURE (°C) TEMPERATURE (°C) 3440 G19 3440 G20 3440 G21 3440fd 5 For more information www.linear.com/LTC3440

LTC3440 pin Functions R (Pin 1): Timing Resistor to Program the Oscillator GND (Pin 5): Signal and Power Ground for the IC. T Frequency. The programming frequency range is 300kHz V (Pin 6): Output of the Synchronous Rectifier. A filter OUT to 2MHz. capacitor is placed from V to GND. OUT 10 6•10 V (Pin 7): Input Supply Pin. Internal V for the IC. A f = Hz IN CC OSC R ceramic bypass capacitor as close to the V pin and GND T IN (Pin 5) is required. MODE/SYNC (Pin 2): MODE/SYNC = External CLK : Syn- SHDN/SS (Pin 8): Combined Soft-Start and Shutdown. chronization of the internal oscillator. A clock frequency Grounding this pin shuts down the IC. Tie to >1.5V to of twice the desired switching frequency and with a pulse enable the IC and >2.5V to ensure the error amp is not width between 100ns and 2µs is applied. The oscillator clamped from soft-start. An RC from the shutdown com- free running frequency is set slower than the desired mand signal to this pin will provide a soft-start function synchronized switching frequency to guarantee sync. by limiting the rise time of the V pin. The oscillator R component value required is given by: C T FB (Pin 9): Feedback Pin. Connect resistor divider tap 10 8•10 R = here. The output voltage can be adjusted from 2.5V to T fSW 5.5V. The feedback reference voltage is typically 1.22V. ⎛ R1⎞ where fSW = desired synchronized switching frequency. V =1.22V•⎜1+ ⎟ OUT ⎝ R2⎠ SW1 (Pin 3): Switch Pin Where the Internal Switches A and B are Connected. Connect inductor from SW1 to V (Pin 10): Error Amp Output. A frequency compensa- C SW2. An optional Schottky diode can be connected from tion network is connected from this pin to the FB pin to SW1 to ground. Minimize trace length to keep EMI down. compensate the loop. See the section “Compensating the Feedback Loop” for guidelines. SW2 (Pin 4): Switch Pin Where the Internal Switches C and D are Connected. For applications with output voltages Exposed Pad (Pin 11, DFN Package Only): Ground. This over 4.3V, a Schottky diode is required from SW2 to VOUT pin must be soldered to the PCB and electrically connected to ensure the SW pin does not exhibit excess voltage. to ground. 3440fd 6 For more information www.linear.com/LTC3440

LTC3440 block DiagraM SW1 SW2 2.5V VTION 5.5V SW A 3 4 SW D VOUT 2.5VV TOOU T5.5V 7 6 + GATE DRIVERS AND –0.4A SW B ANTICROSS SW C – + CONDUCTION ISENSE REVERSE AMP CURRENT LIMIT SUPPLY CURRENT LIMIT + – ERROR AMP + 1.22V 2.7A – PWM + R1 LOGIC PWM – 9 FB UVLO OUATNPDU T COMPARATORS + PHASING – CLAMP 2.4V – + VC RT RT 10 1 OSC R2 SYNC Burst Mode SLEEP OPERATION CONTROL SHDN/SS RSS SHUTDOWN 8 VIN 5µs DELAY MODE/SYNC 2 CSS 1 = Burst Mode 5 OPERATION GND 0 = FIXED FREQUENCY 3440 BD 3440fd 7 For more information www.linear.com/LTC3440

LTC3440 operation The LTC3440 provides high efficiency, low noise power Error Amp for applications such as portable instrumentation. The The error amplifier is a voltage mode amplifier. The loop LTC proprietary topology allows input voltages above, compensation components are configured around the below or equal to the output voltage by properly phasing amplifier to provide loop compensation for the converter. the output switches. The error amp output voltage on the The SHDN/SS pin will clamp the error amp output, V , to C V pin determines the output duty cycle of the switches. C provide a soft-start function. Since the V pin is a filtered signal, it provides rejection C of frequencies from well below the switching frequency. Supply Current Limit The low R , low gate charge synchronous switches DS(ON) The current limit amplifier will shut PMOS switch A off provide high frequency pulse width modulation control at once the current exceeds 2.7A typical. The current ampli- high efficiency. Schottky diodes across the synchronous fier delay to output is typically 50ns. switch D and synchronous switch B are not required, but provide a lower drop during the break-before-make time Reverse Current Limit (typically 15ns). The addition of the Schottky diodes will improve peak efficiency by typically 1% to 2% at 600kHz. The reverse current limit amplifier monitors the inductor High efficiency is achieved at light loads when Burst Mode current from the output through switch D. Once a nega- operation is entered and when the IC’s quiescent current tive inductor current exceeds –400mA typical, the IC will is a low 25µA. shut off switch D. Output Switch Control LOW NOISE FIXED FREQUENCY OPERATION Figure 1 shows a simplified diagram of how the four internal Oscillator switches are connected to the inductor, V , V and GND. IN OUT The frequency of operation is user programmable and is Figure 2 shows the regions of operation for the LTC3440 set through a resistor from the R pin to ground where: as a function of the internal control voltage, V . The V T CI CI voltage is a level shifted voltage from the output of the ⎛6e10⎞ error amp (V pin) (see Figure 5). The output switches are f=⎜ ⎟Hz C ⎝ R ⎠ properly phased so the transfer between operation modes T is continuous, filtered and transparent to the user. When An internally trimmed timing capacitor resides inside the V approaches V the Buck/Boost region is reached IN OUT IC. The oscillator can be synchronized with an external where the conduction time of the four switch region is clock applied to the MODE/SYNC pin. A clock frequency typically 150ns. Referring to Figures 1 and 2, the various of twice the desired switching frequency and with a pulse regions of operation will now be described. width between 100ns and 2µs is applied. The oscillator R component value required is given by: T 10 R = 8•10 VIN VOUT T f 7 6 VOUT SW PMOS A PMOS D where f = desired synchronized switching frequency. SW SW1 SW2 3 4 For example to achieve a 1.2MHz synchronized switching frequency the applied clock frequency to the MODE/SYNC NMOS B NMOS C pin is set to 2.4MHz and the timing resistor, R , is set to T 66.5k (closest 1% value). 3440 F01 Figure 1. Simplified Diagram of Output Switches 3440fd 8 For more information www.linear.com/LTC3440

LTC3440 operation The input voltage, V , where the four switch region begins IN 75% is given by: DMAX V4 (≈2.05V) BOOST A ON, B OFF V PWM CD SWITCHES BOOST REGION V = OUT V IN DMIN V3 (≈1.65V) 1–(150ns•f) BOOST FOUR SWITCH PWM BUCK/BOOST REGION DMAX V2 (≈1.55V) The point at which the four switch region ends is given by: BUCK D ON, C OFF BUCK REGION V = V (1 – D) = V (1 – 150ns • f) V PWM AB SWITCHES IN OUT OUT 0% V1 (≈0.9V) Boost Region (V < V ) IN OUT DUTY INTERNAL CYCLE 3440 F02 CONTROL Switch A is always on and switch B is always off during VOLTAGE, VCI this mode. When the internal control voltage, V , is CI Figure 2. Switch Control vs Internal Control Voltage, V CI above voltage V3, switch pair CD will alternately switch to provide a boosted output voltage. This operation is Buck Region (V > V ) typical to a synchronous boost regulator. The maximum IN OUT duty cycle of the converter is limited to 75% typical and Switch D is always on and switch C is always off during is reached when V is above V4. this mode. When the internal control voltage, V , is above CI CI voltage V1, output A begins to switch. During the off time of Burst Mode Operation switch A, synchronous switch B turns on for the remainder of the time. Switches A and B will alternate similar to a Burst Mode operation is when the IC delivers energy to typical synchronous buck regulator. As the control volt- the output until it is regulated and then goes into a sleep age increases, the duty cycle of switch A increases until mode where the outputs are off and the IC is consuming the maximum duty cycle of the converter in Buck mode only 25µA. In this mode the output ripple has a variable reaches D _ , given by: frequency component that depends upon load current. MAX BUCK D _ = 100 – D4 % During the period where the device is delivering energy to MAX BUCK SW the output, the peak current will be equal to 400mA typical where D4 = duty cycle % of the four switch range. SW and the inductor current will terminate at zero current for D4 = (150ns • f) • 100 % each cycle. In this mode the maximum average output SW current is given by: where f = operating frequency, Hz. 0.1•V Beyond this point the “four switch,” or Buck/Boost region I ≈ IN A OUT(MAX)BURST is reached. VOUT+VIN Buck/Boost or Four Switch (V ~ V ) Burst Mode operation is user controlled, by driving the IN OUT MODE/SYNC pin high to enable and low to disable. When the internal control voltage, V , is above voltage V2, CI switch pair AD remain on for duty cycle D , and The peak efficiency during Burst Mode operation is less MAX_BUCK the switch pair AC begins to phase in. As switch pair AC than the peak efficiency during fixed frequency because phases in, switch pair BD phases out accordingly. When the part enters full-time 4-switch mode (when servicing the V voltage reaches the edge of the Buck/Boost range, the output) with discontinuous inductor current as illus- CI at voltage V3, the AC switch pair completely phase out the trated in Figures 3 and 4. During Burst Mode operation, BD pair, and the boost phase begins at duty cycle D4 . the control loop is nonlinear and cannot utilize the control SW voltage from the error amp to determine the control mode, 3440fd 9 For more information www.linear.com/LTC3440

LTC3440 operation therefore full-time 4-switch mode is required to main- Burst Mode Operation to Fixed Frequency Transient tain the Buck/Boost function. The efficiency below 1mA Response becomes dominated primarily by the quiescent current and When transitioning from Burst Mode operation to fixed not the peak efficiency. The equation is given by: frequency, the system exhibits a transient since the modes (ηbm)•I of operation have changed. For most systems this transient Efficiency Burst ≈ LOAD 25µA+I is acceptable, but the application may have stringent input LOAD current and/or output voltage requirements that dictate a where (ηbm) is typically 79% during Burst Mode opera- broad-band voltage loop to minimize the transient. Low- tion for an ESR of the inductor of 50mΩ. For 200mΩ of ering the DC gain of the loop will facilitate the task (10M inductor ESR, the peak efficiency (ηbm) drops to 75%. FB to V ) at the expense of DC load regulation. Type 3 C compensation is also recommended to broad band the loop and roll off past the two pole response of the LC of the converter (see Closing the Feedback Loop). VIN VOUT 7 6 A dI≈VIN D dT L + – 3 4 400mA L OR SW1 SW2 T C U B C ND II 0mA T1 3440 F03 5 GND Figure 3. Inductor Charge Cycle During Burst Mode Operation VIN VOUT 7 6 A dI≈ –VOUT D dT L – + 3 4 400mA L OR SW1 SW2 T C U B C ND II 0mA T2 3440 F04 5 GND Figure 4. Inductor Discharge Cycle During Burst Mode Operation 3440fd 10 For more information www.linear.com/LTC3440

LTC3440 operation SOFT-START the V pin. A detailed diagram of this function is shown C in Figure 5. The components R and C provide a The soft-start function is combined with shutdown. SS SS slow ramping voltage on the SHDN/SS pin to provide a When the SHDN/SS pin is brought above typically 1V, soft-start function. the IC is enabled but the EA duty cycle is clamped from ERROR AMP VIN 15µA VOUT + 1.22V FB R1 – 9 R2 SOFT-START VC CP1 CLAMP 10 TO PWM VCI COMPARATORS SHDN/SS RSS 8 ENABLE SIGNAL CSS 3440 F05 + CHIP ENABLE – 1V Figure 5. Soft-Start Circuitry 3440fd 11 For more information www.linear.com/LTC3440

LTC3440 applications inForMation COMPONENT SELECTION For high efficiency, choose an inductor with a high fre- quency core material, such as ferrite, to reduce core loses. The inductor should have low ESR (equivalent series resistance) to reduce the I2R losses, and must be able to 1 RT LTC3440 VC 10 handle the peak inductor current without saturating. Molded 2 MODE/SYNC FB 9 chokes or chip inductors usually do not have enough core L1 3 SW1 D2 SHDN/SS 8 R1 R2 to support the peak inductor currents in the 1A to 2A SW2 region. To minimize radiated noise, use a toroid, pot core 4 VIN 7 VIN D1 or shielded bobbin inductor. See Table 1 for suggested 5 GND VOUT 6 components and Table 2 for a list of component suppliers. C1 MULTIPLE Table 1. Inductor Vendor Information VIAS C2 VOUT SUPPLIER PHONE FAX WEB SITE Coilcraft (847) 639-6400 (847) 639-1469 www.coilcraft.com GND Coiltronics (561) 241-7876 (561) 241-9339 www.coiltronics.com 3440 F06 Murata USA: USA: www.murata.com (814) 237-1431 (814) 238-0490 Figure 6. Recommended Component Placement. Traces Carrying (800) 831-9172 High Current are Direct. Trace Area at FB and V Pins are Kept C Low. Lead Length to Battery Should be Kept Short Sumida USA: www.japanlink.com/ (847) 956-0666 (847) 956-0702 sumida Japan: Inductor Selection 81(3) 3607-5111 81(3) 3607-5144 The high frequency operation of the LTC3440 allows the Output Capacitor Selection use of small surface mount inductors. The inductor cur- rent ripple is typically set to 20% to 40% of the maximum The bulk value of the capacitor is set to reduce the ripple inductor current. For a given ripple the inductance terms due to charge into the capacitor each cycle. The steady are given as follows: state ripple due to charge is given by: V •(V −V ) L> IN(MIN) OUT IN(MIN) µH I •(V –V )•100 OUT(MAX) OUT IN(MIN) f•I •Ripple•V %Ripple_Boost= % OUT(MAX) OUT 2 C •V •f OUT OUT V •(V −V ) L> OUT IN(MAX) OUT µH I •(V –V )•100 OUT(MAX) IN(MAX) OUT f•I •Ripple•V %Ripple_Buck= % OUT(MAX) IN(MAX) C •V •V •f OUT IN(MAX) OUT where f = operating frequency, MHz where C = output filter capacitor, F OUT Ripple = allowable inductor current ripple (e.g., 0.2 = 20%) The output capacitance is usually many times larger in order to handle the transient response of the converter. For V = minimum input voltage, V IN(MIN) a rule of thumb, the ratio of the operating frequency to the V = maximum input voltage, V IN(MAX) unity-gain bandwidth of the converter is the amount the VOUT = output voltage, V output capacitance will have to increase from the above I = maximum output load current calculations in order to maintain the desired transient OUT(MAX) response. 3440fd 12 For more information www.linear.com/LTC3440

LTC3440 applications inForMation The other component of ripple is due to the ESR (equiva- Input Voltage > 4.5V lent series resistance) of the output capacitor. Low ESR For applications with input voltages above 4.5V which could capacitors should be used to minimize output voltage exhibit an overload or short-circuit condition, a 2Ω/1nF ripple. For surface mount applications, Taiyo Yuden ceramic series snubber is required between the SW1 pin and GND. capacitors, AVX TPS series tantalum capacitors or Sanyo A Schottky diode such as the Phillips PMEG2010EA or POSCAP are recommended. equivalent from SW1 to V should also be added as close IN to the pins as possible. For the higher input voltages V Input Capacitor Selection IN bypassing becomes more critical, therefore, a ceramic Since the VIN pin is the supply voltage for the IC it is bypass capacitor as close to the VIN and GND pins as recommended to place at least a 4.7µF, low ESR bypass possible is also required. capacitor. Operating Frequency Selection Table 2. Capacitor Vendor Information There are several considerations in selecting the operat- SUPPLIER PHONE FAX WEB SITE ing frequency of the converter. The first is, what are the AVX (803) 448-9411 (803) 448-1943 www.avxcorp.com sensitive frequency bands that cannot tolerate any spec- Sanyo (619) 661-6322 (619) 661-1055 www.sanyovideo.com tral noise? For example, in products incorporating RF Taiyo Yuden (408) 573-4150 (408) 573-4159 www.t-yuden.com communications, the 455kHz IF frequency is sensitive to Optional Schottky Diodes any noise, therefore switching above 600kHz is desired. Some communications have sensitivity to 1.1MHz and in To achieve a 1%-2% efficiency improvement above that case a 2MHz converter frequency may be employed. 50mW, Schottky diodes can be added across synchronous switches B (SW1 to GND) and D (SW2 to V ). The Other considerations are the physical size of the converter OUT Schottky diodes will provide a lower voltage drop during and efficiency. As the operating frequency goes up, the the break-before-make time (typically 15ns) of the NMOS to inductor and filter capacitors go down in value and size. PMOS transition. General purpose diodes such as a 1N914 The trade off is in efficiency since the switching losses due are not recommended due to the slow recovery times and to gate charge are going up proportional with frequency. will compromise efficiency. If desired a large Schottky Additional quiescent current due to the output switches diode, such as an MBRM120T3, can be used from SW2 to GATE charge is given by: V . A low capacitance Schottky diode is recommended OUT Buck: (0.5 • V • f) mA from GND to SW1 such as a Phillips PMEG2010EA or IN equivalent. Boost: [0.25 • (V + V ) • f] mA IN OUT Buck/Boost: f • (0.75 • V + 0.25 • V ) mA Output Voltage > 4.3V IN OUT where f = switching frequency in MHz A Schottky diode from SW to V is required for output OUT voltages over 4.3V. The diode must be located as close to the pins as possible in order to reduce the peak voltage on SW2 due to the parasitic lead and trace inductance. 3440fd 13 For more information www.linear.com/LTC3440

LTC3440 applications inForMation Closing the Feedback Loop Most applications demand an improved transient response to allow a smaller output filter capacitor. To achieve a higher The LTC3440 incorporates voltage mode PWM control. The bandwidth, Type III compensation is required. Two zeros control to output gain varies with operation region (Buck, are required to compensate for the double-pole response. Boost, Buck-Boost), but is usually no greater than 15. The 1 output filter exhibits a double pole response is given by: f ≈ Hz POLE1 3 2•π•32e •R1•C 1 P1 fFILTER_POLE = Hz(inBuckmode) WhichisextremelyclosetoDC 2•π• L•C OUT 1 f = Hz f = VIN Hz(inBoostmode) ZERO1 2•π•RZ •CP1 FILTER_POLE 2•V •π• L•C OUT OUT 1 f = Hz ZERO2 2•π•R1•C where L is in Henries and C is the output filter capaci- Z1 OUT tor in Farads. 1 f = Hz POLE2 The output filter zero is given by: 2•π•RZ •CP2 1 f = Hz FILTER_ZERO 2•π•R •C ESR OUT VOUT where R is the capacitor equivalent series resistance. + 1.22V ESR ERROR R1 A troublesome feature in Boost mode is the right-half AMP FB – 9 plane zero (RHP), and is given by: VC CP1 R2 V 2 10 f = IN Hz 3440 F07 RHPZ 2•π•I •L•V OUT OUT Figure 7. Error Amplifier with Type I Compensation The loop gain is typically rolled off before the RHP zero frequency. A simple Type I compensation network can be incorporated VOUT to stabilize the loop but at a cost of reduced bandwidth and slower transient response. To ensure proper phase + 1.22V R1 CZ1 margin, the loop requires to be crossed over a decade ERROR AMP FB before the LC double pole. – 9 The unity-gain frequency of the error amplifier with the VC RZ CP1 R2 Type I compensation is given by: 10 CP2 1 3440 F08 f = Hz UG 2•π•R1•CP1 Figure 8. Error Amplifier with Type III Compensation 3440fd 14 For more information www.linear.com/LTC3440

LTC3440 applications inForMation Short-Circuit Improvements Simple Average Input Current Control The LTC3440 is current limited to 2.7A peak to protect A simple average current limit circuit is shown in the IC from damage. At input voltages above 4.5V a cur- Figure 10. Once the input current of the IC is above ap- rent limit condition may produce undesirable voltages proximately 1A, Q1 will start sourcing current into the FB to the IC due to the series inductance of the package, as pin and lower the output voltage to maintain the average well as the traces and external components. Following input current. Since the voltage loop is utilized to perform the recommendations for output voltage >4.3V and input average current limit, the voltage control loop is main- voltage >4.5V will improve this condition. Additional tained and the V voltage does not slam. The averaging C short-circuit protection can be accomplished with some function of current comes from the fact that voltage loop external circuitry. compensation is also used with this circuit. In an overload or short-circuit condition the LTC3440 volt- VIN age loop opens and the error amp control voltage on the V C pin slams to the upper clamp level. This condition forces R1 boost mode operation in order to attempt to provide more 1M R2 D1 output voltage and the IC hits a peak switch current limit of 1M 1N4148 2.7A. When switch current limit is reached switches B and M2 SOFT-START NMOS D turn on for the remainder of the cycle to reverse the volts SO/SS VN2222 M1 • seconds on the inductor. Although this prevents current C1 C2 NMOS VOUT 4.7nF 10nF VN2222 run away, this condition produces four switch operation producing a current foldback characteristic and the aver- 3440 F09 age input current drops. The IC is trimmed to guarantee greater than 1A average input current to meet the maximum Figure 9. Soft-Start Reset Circuitry for a Sustained Short-Circuit load demand, but in a short-circuit or overload condition the foldback characteristic will occur producing higher peak switch currents. To minimize this affect during this condition the following circuits can be utilized. INPUT_VOLTAGE C1 V1 10µF R1 Restart Circuit 0.5Ω For a sustained short-circuit the circuit in Figure 9 will force Q1 VIN_PIN 2N3906 a soft-start condition. The only design constraint is that FB_PIN R2/C2 time constant must be longer than the soft-start components R1/C1 to ensure start-up. Figure 10. Simple Input Current Control Utilizing the Voltage Loop 3440fd 15 For more information www.linear.com/LTC3440

LTC3440 typical applications 3-Cell to 3.3V at 600mA Converter L1 D2 4.7µH VOUT 3.3V D1 C3 600mA 3 4 33pF SW1 SW2 VIN = 2.7V TO 4.5V 7 LTC3440 6 R1 R5 VIN VOUT 340k 10k 8 9 SHDN/SS FB C4 150pF C2 + 2 10 R3 15k 22µF C1 * MODE/SYNC VC 3 CELLS 10µF 1 5 RT GND R2 200k RT fOSC = 1.5MHz C5 10pF 45.3k *1 = Burst Mode OPERATION C1: TAIYO YUDEN JMK212BJ106MG 3440 TA03a 0 = FIXED FREQUENCY C2: TAIYO YUDEN JMK325BJ226MM D1, D2: CENTRAL SEMICONDUCTOR CMDSH2-3 L1: SUMIDA CDR43-4R7M 3-Cell to 3.3V Efficiency 100 90 Burst Mode 80 OPERATION 70 %) VIN = 2.7V CY ( 60 VIN = 4.5V N 50 FICIE 40 VIN = 3.3V F E 30 20 10 fOSC = 1.5MHz 0 0.1 1 10 100 1000 OUTPUT CURRENT (mA) 3440 TA03b 3440fd 16 For more information www.linear.com/LTC3440

LTC3440 typical applications 3-Cell to 5V Boost Converter with Output Disconnect 3-Cell to 5V Boost Efficiency L1 D1** 100 10µH VOUT VIN = 4.5V 5V 90 Burst Mode 3 4 300mA 80 OPERATION SW1 SW2 VIN = 2+.7V TO 4.5VR4 1M 782 VSIHNDNLT/SCS3440VOFUBT 6910 15k R6119k C222µ*F* FICIENCY (%) 57640000 VIN = 3.6V VIN = 2.7V CELLS3 C101µF C0.31µF* 1 MODE/SYNC VC 5 C4 EF 30 RT GND 1.5nF R2 20 200k SD R60T.4k fOSC = 1MHz 10 fOSC = 1MHz 0 *1 = Burst Mode OPERATION C1: TAIYO YUDEN JMK212BJ106MG 0.1 1 10 100 1000 3440 TA06a 0 = FIXED FREQUENCY C2: TAIYO YUDEN JMK325BJ226MM OUTPUT CURRENT (mA) ** LOCATE COMPONENTS AS D1: ON SEMICONDUCTOR MBRM120T3 3440 TA06b CLOSE TO IC AS POSSIBLE L1: SUMIDA CDRH4D28-100 Low Profile (<1.1mm) Li-Ion to 3.3V at 200mA Converter L1 4.7µH VOUT 3.3V 200mA 3 4 SW1 SW2 VIN = 2.5V TO 4.2V 7 LTC3440 6 R3410k VIN VOUT 8 9 SHDN/SS FB C2 + 2 10 4.7µF Li-Ion C1 * MODE/SYNC VC 4.7µF 1 RT GND 5 1R53k 1.C54nF R2 200k RT 30.1k *1 = Burst Mode OPERATION C1: TAIYO YUDEN JMK212BJ475MG 3440 TA04a 0 = FIXED FREQUENCY C2: TAIYO YUDEN JMK212BJ475MG fOSC = 2MHz L1: COILCRAFT LPO1704-472M Efficiency 100 90 Burst Mode 80 OPERATION 70 %) CY ( 60 VIN = 2.5V VIN = 4.2V N 50 FICIE 40 VIN = 3.3V F E 30 20 10 0 0.1 1 10 100 1000 OUTPUT CURRENT (mA) 3440 TA04b 3440fd 17 For more information www.linear.com/LTC3440

LTC3440 typical applications WCDMA Power Amp Power Supply with Dynamic Voltage Control Efficiency of the WCDMA Power Amp Power Supply DAC VOUT = 3.3V – 1.7V • (VDAC – 1.22V) 100 VOUT = 3.4V L1 98 D1** 3.3µH VOUT 96 IOUT = 100mA 0.4V TO 5V 3 SW1 SW2 4 C333pF %) 94 VIN = 2.5V TO 4.2V 7 LTC3440 6 R1 R5 CY ( 92 IOUT = 250mA VIN VOUT 340k 10k EN 90 8 9 R6 FICI 88 + 2 SHDN/SS FB 10 R3 15kC4 150pF 200k EF 86 IOUT = 600mA Li-Ion C1 * MODE/SYNC VC 84 10µF 1 5 RT GND R2 C2** 82 RT C5 10pF 200k 10µF 80 30.1k fOSC = 2MHz 2.5 3 3.5 4 4.5 5 INPUT VOLTAGE (V) *1 = Burst Mode OPERATION C1, C2: TAIYO YUDEN JMK212BJ106MM 0 = FIXED FREQUENCY D1: ON SEMICONDUCTOR MBRM120T3 3440 TA07a 3440 TA07b ** LOCATE COMPONENTS AS L1: SUMIDA CDRH4D28-3R3 CLOSE TO IC AS POSSIBLE GSM Modem Powered from USB or PCMCIA with 500mA Input Current Limit L1 10µH VOUT 3.6V 2A 3 4 (PULSED) 2.5V TO 5V.5IVN 0R.1SΩ 7 SW1LTC3440SW2 6 R3912k USB/PCM5C0I0Am PAO WMAERX 8 VIN VOUT 9 1R306k 1N914 + C6 TO C9 SHDN/SS FB 1/2 LT1490A 470µF ×4 2 10 – C1 * MODE/SYNC VC R2 10µF 1 5 C5 200k RT GND 10nF RT R5 60.4k 24k + C1: TAIYO YUDEN JMK212BJ106MG 3440 TA08 C2: TAIYO YUDEN JMK325BJ226MM R4 1/2 LT1490A 2N3906 L1: SUMIDA CDRH-4D28-100 1k *1 = Burst Mode OPERATION – ICURRENTLIMIT = 1R.252 • • R RS4 0 = FIXED FREQUENCY 3440fd 18 For more information www.linear.com/LTC3440

LTC3440 package Description Please refer to http://www.linear.com/product/LTC3440#packaging for the most recent package drawings. DD Package DD Package 10-Lead Plastic DFN (3mm × 3mm) 10-Lead Plastic DFN (3mm × 3mm) (Reference LTC DWG # 05-08-1699 Rev C) (Reference LTC DWG # 05-08-1699 Rev C) 0.70 ±0.05 3.55 ±0.05 1.65 ±0.05 2.15 ±0.05 (2 SIDES) PACKAGE OUTLINE 0.25 ±0.05 0.50 BSC 2.38 ±0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS R = 0.125 0.40 ±0.10 TYP 6 10 3.00 ±0.10 1.65 ±0.10 (4 SIDES) (2 SIDES) PIN 1 NOTCH PIN 1 R = 0.20 OR TOP MARK 0.35 × 45° (SEE NOTE 6) CHAMFER (DD) DFN REV C 0310 5 1 0.200 REF 0.75 ±0.05 0.25 ±0.05 0.50 BSC 2.38 ±0.10 (2 SIDES) 0.00 – 0.05 BOTTOM VIEW—EXPOSED PAD NOTE: 1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2). CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT 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 3440fd 19 For more information www.linear.com/LTC3440

LTC3440 package Description Please refer to http://www.linear.com/product/LTC3440#packaging for the most recent package drawings. MS Package MS Package 10-Lead Plastic MSOP 10-Lead Plastic MSOP (Reference LTC DWG # 05-08-1661 Rev F) (Reference LTC DWG # 05-08-1661 Rev F) 0.889 ±0.127 (.035 ±.005) 5.10 3.20 – 3.45 (.201) (.126 – .136) MIN 3.00 ±0.102 0.305 ±0.038 0.50 (.118 ±.004) 0.497 ±0.076 (.0120 ±.0015) (.0197) (NOTE 3) (.0196 ±.003) 10 9 8 76 TYP BSC REF RECOMMENDED SOLDER PAD LAYOUT 3.00 ±0.102 4.90 ±0.152 DETAIL “A” (.193 ±.006) (.118 ±.004) 0.254 (NOTE 4) (.010) 0° – 6° TYP GAUGE PLANE 1 2 3 4 5 0.53 ±0.152 (.021 ±.006) 1.10 0.86 (.043) (.034) DETAIL “A” MAX REF 0.18 (.007) SEATING PLANE 0.17 – 0.27 0.1016 ±0.0508 (.007 – .011) (.004 ±.002) 0.50 TYP (.0197) MSOP (MS) 0213 REV F NOTE: BSC 1. DIMENSIONS IN MILLIMETER/(INCH) 2. DRAWING NOT TO SCALE 3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX 3440fd 20 For more information www.linear.com/LTC3440

LTC3440 revision history (Revision history begins at Rev C) REV DATE DESCRIPTION PAGE NUMBER C 8/14 Modified filter pole equation in Closing the Feedback Loop section 13 D 10/16 Added equation to calculate V 6 OUT Modified Operating Frequency Selection section 13 3440fd Information furnished by Linear Technology Corporation is believed to be accurate and reliable. 21 However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa- tion that the interconneFcotiro nm oof irtes cinircfouritms aast idoensc wribwedw h.leinreeina rw.cilol nmo/tL inTfCri3ng4e4 o0n existing patent rights.

LTC3440 typical application Li-Ion to 3.3V at 600mA Buck-Boost Converter Efficiency L1 100 10µH V3.O3UVT 90 Burst Mode 600mA 80 OPERATION 3 4 SW1 SW2 70 VIN = 2.7V TO 4.2V 7 LTC3440 6 R1 %) VIN = 4.2V VIN VOUT 340k CY ( 60 VIN = 3.3V 8 9 N 50 Li-Ion+ C1 * 2 SMHODDNE//SSSYNC VFBC 10C5 1.5nFR3 C222µF EFFICIE 4300 10µF 1 RT GND 5 15k R2 20 200k RT 10 60.4k 0 0.1 1.0 10 100 1000 *1 = Burst Mode OPERATION C1: TAIYO YUDEN JMK212BJ106MG 3440 TA01 OUTPUT CURRENT (mA) 0 = FIXED FREQUENCY C2: TAIYO YUDEN JMK325BJ226MM L1: SUMIDA CDRH6D38-100 3440 TA05 relateD parts PART NUMBER DESCRIPTION COMMENTS LT1613 550mA(I ), 1.4MHz, High Efficiency Step-Up DC/DC 90% Efficiency, V : 0.9V to 10V, V = 34V, I = 3mA, SW IN OUT(MIN) Q Converter I = <1µA, ThinSOT™ Package SD LT1618 1.5A(I ), 1.25MHz, High Efficiency Step-Up DC/DC 90% Efficiency, V : 1.6V to 18V, V = 35V, I = 1.8mA, SW IN OUT(MIN) Q Converter I = <1µA, MS10 Package SD LTC1877 600mA(I ), 550kHz, Synchronous Step-Down DC/DC 95% Efficiency, V : 2.7V to 10V, V = 0.8V, I = 10µA, OUT IN OUT(MIN) Q Converter I = <1µA, MS8 Package SD LTC1878 600mA(I ), 550kHz, Synchronous Step-Down DC/DC 95% Efficiency, V : 2.7V to 6V, V = 0.8V, I = 10µA, OUT IN OUT(MIN) Q Converter I = <1µA, MS8 Package SD LTC1879 1.2A(I ), 550kHz, Synchronous Step-Down DC/DC 95% Efficiency, V : 2.7V to 10V, V = 0.8V, I = 15µA, OUT IN OUT(MIN) Q Converter I = <1µA, TSSOP16 Package SD LT1961 1.5A(I ), 1.25MHz, High Efficiency Step-Up DC/DC 90% Efficiency, V : 3V to 25V, V = 35V, I = 0.9mA, SW IN OUT(MIN) Q Converter I = 6µA, MS8E Package SD LTC3400/LTC3400B 600mA(I ), 1.2MHz, Synchronous Step-Up DC/DC 92% Efficiency, V : 0.85V to 5V, V = 5V, I = 19µA/300µA, SW IN OUT(MIN) Q Converter I = <1µA, ThinSOT Package SD LTC3401 1A(I ), 3MHz, Synchronous Step-Up DC/DC Converter 97% Efficiency, V : 0.5V to 5V, V = 6V, I = 38µA, SW IN OUT(MIN) Q I = <1µA, MS10 Package SD LTC3402 2A(I ), 3MHz, Synchronous Step-Up DC/DC Converter 97% Efficiency, V : 0.5V to 5V, V = 6V, I = 38µA, SW IN OUT(MIN) Q I = <1µA, MS10 Package SD LTC3405/LTC3405A 300mA(I ), 1.5MHz, Synchronous Step-Down DC/DC 95% Efficiency, V : 2.7V to 6V, V = 0.8V, I = 20µA, OUT IN OUT(MIN) Q Converter I = <1µA, ThinSOT Package SD LTC3406/LTC3406B 600mA(I ), 1.5MHz, Synchronous Step-Down DC/DC 95% Efficiency, V : 2.5V to 5.5V, V = 0.6V, I = 20µA, OUT IN OUT(MIN) Q Converter I = <1µA, ThinSOT Package SD LTC3411 1.25A(I ), 4MHz, Synchronous Step-Down DC/DC 95% Efficiency, V : 2.5V to 5.5V, V = 0.8V, I = 60µA, OUT IN OUT(MIN) Q Converter I = <1µA, MS10 Package SD LTC3412 2.5A(I ), 4MHz, Synchronous Step-Down DC/DC 95% Efficiency, V : 2.5V to 5.5V, V = 0.8V, I = 60µA, OUT IN OUT(MIN) Q Converter I = <1µA, TSSOP16E Package SD LTC3441/LTC3443 1.2A(I ), 1MHz/0.6MHz, Micropower Synchronous 95% Efficiency, V : 2.4V to 5.5V, V : 2.4V to 5.25V, I = 25µA, OUT IN OUT(MIN) Q Buck-Boost DC/DC Converter I = <1µA, DFN Package SD 3440fd 22 Linear Technology Corporation LT 1016 REV D • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 For more information www.linear.com/LTC3440 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com/LTC3440  LINEAR TECHNOLOGY CORPORATION 2001