LTC3441 High Current Micropower Synchronous Buck-Boost DC/DC Converter FeaTures DescripTion n Regulated Output with Input Above, Below or Equal The LTC®3441 is a high efficiency, fixed frequency, buck- to the Output boost DC/DC converter that operates efficiently from input n Single Inductor, No Schottky Diodes voltages above, below or equal to the output voltage. The n High Efficiency: Up to 95% topology incorporated in the IC provides a continuous n 25µA Quiescent Current in Burst Mode® Operation transfer function through all operating modes, making n Up to 1.2A Continuous Output Current from a Single the product ideal for single lithium ion or multicell ap- Lithium-Ion plications where the output voltage is within the battery n True Output Disconnect in Shutdown voltage range. n 2.4V to 5.5V Input Range The device includes two 0.10Ω N-channel MOSFET n 2.4V to 5.25V Output Range switches and two 0.11Ω P-channel switches. External n 1MHz Fixed Frequency Operation Schottky diodes are optional, and can be used for a mod- n Synchronizable Oscillator erate efficiency improvement. The operating frequency n Selectable Burst Mode or Fixed Frequency Operation is internally set to 1MHz and can be synchronized up to n <1µA Quiescent Current in Shutdown 1.7MHz. Quiescent current is only 25µA in Burst Mode n Small, Thermally Enhanced 12-Lead (4mm × 3mm) operation, maximizing battery life in portable applica- DFN package tions. Burst Mode operation is user controlled and can be enabled by driving the MODE/SYNC pin high. If the applicaTions MODE/SYNC pin is driven low or with a clock, then fixed frequency switching is enabled. n Handheld Computers n Handheld Instruments Other features include a 1µA shutdown, soft-start control, n MP3 Players thermal shutdown and current limit. The LTC3441 is n Digital Cameras available in a thermally enhanced 12-lead (4mm × 3mm) DFN package. 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 1A Buck-Boost Converter Efficiency vs V IN 100 L1 VOUT = 3.3V IOUT = 200mA 4.7µH VOUT 95 3.3V 90 1A 4 5 9 SW1 SW2 8 340k %) 85 IOUT = 1A 2.5V TO 4.2V 10 PVINLTC3441VOUT 12 CY ( 80 Li-Ion * 17 VSMIHONDDNE//SSSYNC GNVFDBC 121 15k 1.5nF 2C2OµUFT EFFICIEN 767055 CIN 3 6 200k 10µF PGND PGND 60 55 * 10 == BFIuXrEsDt M FRodEeQ UOEPNERCYATION CCIONU: TT:A TIAYIOY OY UYDUEDNE NJM JMK2K1322B5JB1J0262M6MGM 3441 TA01 502.5 3 3.5 4 4.5 5 5.5 L1: TOKO A916CY-4R7M VIN (V) 3441 TA02 3441fc 1 For more information www.linear.com/LTC3441

LTC3441 absoluTe MaxiMuM raTings pin conFiguraTion (Note 1) V , V Voltage ....................................... –0.3V to 6V TOP VIEW IN OUT SW1, SW2 Voltage SHDN/SS 1 12 FB DC ............................................................–0.3V to 6V GND 2 11 VC Pulsed < 100ns ....................................... –0.3V to 7V PGND 3 10 VIN 13 SHDN/SS, MODE/SYNC Voltage ................ –0.3V to 6V SW1 4 9 PVIN Operating Temperature Range (Note 2) ..–40°C to 85°C SW2 5 8 VOUT Maximum Junction Temperature (Note 4).............125°C PGND 6 7 MODE/SYNC Storage Temperature Range .................. –65°C to 125°C DE12 PACKAGE 12-LEAD (4mm × 3mm) PLASTIC DFN TJMAX = 125°C θJA = 53°C/W 1-LAYER BOARD, θJA = 43°C/W 4-LAYER BOARD θJC = 4.3°C/W, EXPOSED PAD IS PGND (PIN 13) MUST BE SOLDERED TO PCB orDer inForMaTion http://www.linear.com/product/LTC3441#orderinfo LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LTC3441EDE#PBF LTC3441EDE#TRPBF 3441 12-Lead (4mm × 3mm) Plastic DFN –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 l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T = 25°C. V = V = 3.6V,unless otherwise noted. A IN OUT PARAMETER CONDITIONS MIN TYP MAX UNITS Input Start-Up Voltage ● 2.3 2.4 V Output Voltage Adjust Range ● 2.4 5.25 V Feedback Voltage ● 1.19 1.22 1.25 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—SHDN V = SHDN = 0V, Not Including Switch Leakage 0.1 1 µA OUT Quiescent Current—Active MODE/SYNC = 0V (Note 3) 520 900 µA NMOS Switch Leakage Switches B and C 0.1 7 µA PMOS Switch Leakage Switches A and D 0.1 10 µA NMOS Switch On Resistance Switches B and C 0.10 Ω PMOS Switch On Resistance Switches A and D 0.11 Ω Input Current Limit ● 2 3.2 A Max Duty Cycle Boost (% Switch C On) ● 70 88 % Buck (% Switch A In) ● 100 % Min Duty Cycle ● 0 % Frequency Accuracy ● 0.85 1 1.15 MHz MODE/SYNC Threshold ● 0.4 1.4 V 3441fc 2 For more information www.linear.com/LTC3441

LTC3441 elecTrical characTerisTics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T = 25°C. V = V = 3.6V,unless otherwise noted. A IN OUT PARAMETER CONDITIONS MIN TYP MAX UNITS MODE/SYNC Input Current V = 5.5V 0.01 1 µA MODE/SYNC Error Amp AV 90 dB OL Error Amp Source Current 14 µA Error Amp Sink Current 300 µA SHDN/SS Threshold When IC is Enabled ● 0.4 1 1.4 V SHDN/SS Threshold When EA is at Max Boost Duty Cycle 2 2.4 V SHDN/SS Input Current V = 5.5V 0.01 1 µA SHDN Note 1: Stresses beyond those listed under Absolute Maximum Ratings Note 3: Current measurements are preformed when the outputs are not may cause permanent damage to the device. Exposure to any Absolute switching. Maximum Rating condition for extended periods may affect device Note 4: This IC includes overtemperature protection that is intended reliability and lifetime. to protect the device during momentary overload conditions. Junction Note 2: The LTC3441E is guaranteed to meet performance specifications temperature will exceed 125°C when overtemperature protection is active. from 0°C to 70°C. Specifications over the –40°C to 85°C operating Continuous operation above the specified maximum operating junction temperature range are assured by design, characterization and correlation temperature may result in device degradation or failure. with statistical process controls. Typical perForMance characTerisTics Efficiency V Ripple at 1A Load OUT 100 90 Burst Mode OPERATION BUCK 80 VIN = 4.2V 70 %) VOUT BUCK-BOOST CY ( 60 VIN = 4.2V AC-1C0OmUVP/LDEIDV VIN = 3.3V N 50 EFFICIE 40 VIN = 2.7V VIN = 3.6V BVOINO =S 2T.7V 30 20 10 L = 4.7µH 1µs/DIV 3441 G02 VOUT = 3.3V COUT = 47µF 0 IOUT = 1A 0.1 1 10 100 1000 VOUT = 3.3V IOUT (mA) 3441 G17 Load Transient Response, Switch Pins Entering 100mA to 1A Switch Pins in Buck-Boost Mode Buck-Boost Mode SW1 SW1 VOUT 2V/DIV 2V/DIV 100mV/DIV 1A SW2 SW2 2V/DIV 2V/DIV 100mA 100µs/DIV 3441 G01 VIN = 3.3V 50ns/DIV 3441 G03 VIN = 4.2V 50ns/DIV 3441 G04 VOUT = 3.3V VOUT = 3.3V IOUT = 500mA IOUT = 500mA 3441fc 3 For more information www.linear.com/LTC3441

LTC3441 Typical perForMance characTerisTics Switch Pins Before Entering Boost Mode Active Quiescent Current Feedback Voltage 630 1.241 VIN = VOUT = 3.6V VIN = VOUT = 3.6V 620 1.236 SW1 610 2V/DIV NT (µA)569000 GE (V)11..223216 E A 2VS/DWIV2 + V CURRNOUT555558760000 EEDBACK VOLT111...222211161 VI F1.206 540 VIN = 3V 50ns/DIV 3441 G05 530 1.201 VOUT = 3.3V IOUT = 500mA 520 1.196 –55 –25 5 35 65 95 125 –55 –25 5 35 65 95 125 TEMPERATURE (°C) TEMPERATURE (°C) 3441 G06 3441 G07 Burst Mode Quiescent Current Feedback Voltage Line Regulation Error Amp Source Current 50 90 20 VIN = VOUT = 3.6V VIN = VOUT = 2.4V TO 5.5V VIN = VOUT = 3.6V V + V CURRENT (µA)INOUT 243000 LINE REGULATION (dB) 7800 EA SOURCE CURRENT (µA) 1105 10 60 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) 3441 G08 3441 G09 3441 G10 Error Amp Sink Current Output Frequency Current Limit 400 1.2 3.4 VIN = VOUT = 3.6V VIN = VOUT = 3.6V VIN = VOUT = 3.6V A)350 1.1 URRENT (µ300 NCY (MHz) 1.0 T LIMIT (A) 3.2 SINK C REQUE URREN 3.0 A F C E250 0.9 200 0.8 2.8 –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) 3441 G11 3441 G12 3441 G13 3441fc 4 For more information www.linear.com/LTC3441

LTC3441 Typical perForMance characTerisTics NMOS R PMOS R Minimum Start Voltage DS(ON) DS(ON) 0.15 0.15 2.30 VIN = VOUT = 3.6V VIN = VOUT = 3.6V SWITCHES B AND C 0.14 SWITCHES A AND D 0.13 0.13 E (V)2.25 Ω) Ω) 0.12 TAG NMOS R (DS(ON)00..0191 PMOS R (DS(ON)0000....01019180 MUM START VOL2.20 NI2.15 0.07 0.07 MI 0.06 0.05 0.05 2.10 –55 –25 5 35 65 95 125 –50 –25 5 35 65 95 125 –55 –25 5 35 65 95 125 TEMPERATURE (°C) TEMPERATURE (°C) TEMPERATURE (°C) 3441 G14 3441 G15 3441 G16 pin FuncTions SHDN/SS (Pin 1): Combined Soft-Start and Shutdown. the output, the inductor peak inductor current will reach Applied voltage < 0.4V shuts down the IC. Tie to >1.4V to 0.8A and return to zero current on each cycle. In Burst enable the IC and >2.4V to ensure the error amp is not Mode operation the operation is variable frequency, clamped from soft-start. An RC from the shutdown com- which provides a significant efficiency improvement at mand signal to this pin will provide a soft-start function light loads. The Burst Mode operation will continue until by limiting the rise time of the V pin. the pin is driven low. C GND (Pin 2): Signal Ground for the IC. MODE/SYNC = Low: Disable Burst Mode operation and maintain low noise, constant frequency operation . PGND (Pins 3, 6, 13 Exposed Pad): Power Ground for the Internal NMOS Power Switches MODE/SYNC = External CLK : Synchronization of the internal oscillator and Burst Mode operation disable. A SW1 (Pin 4): Switch pin where the internal switches A clock pulse width between 100ns and 2µs and a clock and B are connected. Connect inductor from SW1 to SW2. frequency between 2.3MHz and 3.4MHz (twice the An optional Schottky diode can be connected from this desired frequency) is required to synchronize the IC. SW1 to ground. Minimize trace length to keep EMI down. f = f /2 SW2 (Pin 5): Switch pin where the internal switches C OSC SYNC and D are connected. An optional Schottky diode can V (Pin 8): Output of the Synchronous Rectifier. A filter OUT be connected from SW2 to V (it is required where capacitor is placed from V to GND. A ceramic bypass OUT OUT V > 4.3V). Minimize trace length to keep EMI down. capacitor is recommended as close to the V and GND OUT OUT pins as possible. MODE/SYNC (Pin 7): Burst Mode Select and Oscillator Synchronization. PV (Pin 9): Power V Supply Pin. A 10µF ceramic ca- IN IN pacitor is recommended as close to the PV and PGND MODE/SYNC = High: Enable Burst Mode Operation. IN pins as possible During the period where the IC is supplying energy to 3441fc 5 For more information www.linear.com/LTC3441

LTC3441 pin FuncTions V (Pin 10): Input Supply Pin. Internal V for the IC. FB (Pin 12): Feedback Pin. Connect resistor divider tap IN CC here. The output voltage can be adjusted from 2.4V to V (Pin 11): Error Amp Output. A frequency compensa- C 5.25V. The feedback reference voltage is typically 1.22V. tion network is connected from this pin to the FB pin to compensate the loop. See the section “Compensating the ⎛ R1⎞ V =1.22V•⎜1+ ⎟ Feedback Loop” for guidelines. OUT ⎝ R2⎠ block DiagraM VIN SW1 4 5 SW2 VOUT 2.4V TO 5.5V PVIN SW A SW D VOUT 2.4V TO 5.25V 9 8 + VIN GATE 10 DRIVERS AND –0.8A SW B ANTICROSS SW C – + CONDUCTION ISENSE REVERSE AMP CURRENT + LIMIT gm = 1100k PGND 3.2A – AVERAGE CURRENT LIMIT THERMAL SUPPLY SHUTDOWN CURRENT LIMIT + – ERROR AMP + 1.22V 4A – PWM + R1 VINCTCERNAL UVLO OLUAOTNGPDIUC T COMPPAWRMATORS – FB 12 + PHASING – CLAMP 2.4V – + VC 1MHz 11 OSC R2 SYNC Burst Mode SLEEP OPERATION CONTROL SHDN/SS RSS ÷2 SHUTDOWN 1 VIN 5µs DELAY 7 MODE/SYNC CSS 1 = Burst Mode GND PGND 2 6 OPERATION 0 = FIXED FREQUENCY 3440 BD 3441fc 6 For more information www.linear.com/LTC3441

LTC3441 operaTion The LTC3441 provides high efficiency, low noise power Reverse Current Limit for applications such as portable instrumentation. The The reverse current limit amplifier monitors the inductor LTC proprietary topology allows input voltages above, current from the output through switch D. Once a nega- below or equal to the output voltage by properly phasing tive inductor current exceeds –800mA typical, the IC will the output switches. The error amp output voltage on the shut off switch D. V pin determines the output duty cycle of the switches. C Since the V pin is a filtered signal, it provides rejection C Output Switch Control of frequencies from well below the switching frequency. Figure 1 shows a simplified diagram of how the four in- The low R , low gate charge synchronous switches DS(ON) ternal switches are connected to the inductor, V , V provide high frequency pulse width modulation control at IN OUT and GND. Figure 2 shows the regions of operation for the high efficiency. Schottky diodes across the synchronous LTC3441 as a function of the internal control voltage, V . switch D and synchronous switch B are not required, CI The V voltage is a level shifted voltage from the output of but provide a lower drop during the break-before-make CI the error amp (V pin) (see Figure 5). The output switches time (typically 15ns). The addition of the Schottky diodes C are properly phased so the transfer between operation will improve peak efficiency by typically 1% to 2%. High modes is continuous, filtered and transparent to the efficiency is achieved at light loads when Burst Mode user. When V approaches V the Buck/Boost region operation is entered and when the IC’s quiescent current IN OUT is reached where the conduction time of the four switch is a low 25µA. region is typically 150ns. Referring to Figures 1 and 2, the various regions of operation will now be described. LOW NOISE FIXED FREQUENCY OPERATION PVIN VOUT Oscillator 9 8 VOUT The frequency of operation is factory trimmed to 1MHz. PMOS A PMOS D The oscillator can be synchronized with an external clock SW1 SW2 applied to the MODE/SYNC pin. A clock frequency of twice 4 5 the desired switching frequency and with a pulse width NMOS B NMOS C of at least 100ns is applied. The oscillator sync range is 1.15MHz to 1.7MHz (2.3MHz to 3.4MHz sync frequency). 3441 F01 Figure 1. Simplified Diagram of Output Switches Error Amp The error amplifier is a voltage mode amplifier. The loop compensation components are configured around the 75% DMAX V4 (≈2.05V) amplifier to obtain stability of the converter. The SHDN/ BOOST A ON, B OFF SS pin will clamp the error amp output, V , to provide a BOOST REGION C PWM CD SWITCHES soft-start function. DMIN V3 (≈1.65V) BOOST FOUR SWITCH PWM BUCK/BOOST REGION Supply Current Limit BDUMCAKX V2 (≈1.55V) D ON, C OFF The current limit amplifier will shut PMOS switch A off PWM AB SWITCHES BUCK REGION once the current exceeds 4A typical. Before the switch 0% V1 (≈0.9V) current limit, the average current limit amp (3.2A typical) DUTY INTERNAL will source current into the FB pin to drop the output volt- CYCLE 3441 F02 CONTROL VOLTAGE, VCI age. The current amplifier delay to output is typically 50ns. Figure 2. Switch Control vs Internal Control Voltage, V CI 3441fc 7 For more information www.linear.com/LTC3441

LTC3441 operaTion Buck Region (V > V ) above voltage V3, switch pair CD will alternately switch IN OUT to provide a boosted output voltage. This operation is Switch D is always on and switch C is always off during typical to a synchronous boost regulator. The maximum this mode. When the internal control voltage, V , is above CI duty cycle of the converter is limited to 88% typical and voltage V1, output A begins to switch. During the off time of is reached when V is above V4. switch A, synchronous switch B turns on for the remainder CI of the time. Switches A and B will alternate similar to a typical synchronous buck regulator. As the control volt- Burst Mode OPERATION age increases, the duty cycle of switch A increases until Burst Mode operation is when the IC delivers energy to the maximum duty cycle of the converter in Buck mode the output until it is regulated and then goes into a sleep reaches D _ , given by: MAX BUCK mode where the outputs are off and the IC is consuming D _ = 100 – D4 % only 25µA. In this mode the output ripple has a variable MAX BUCK SW frequency component that depends upon load current. where D4 = duty cycle % of the four switch range. SW During the period where the device is delivering energy to D4 = (150ns • f) • 100 % SW the output, the peak current will be equal to 800mA typical where f = operating frequency, Hz. and the inductor current will terminate at zero current for each cycle. In this mode the typical maximum average Beyond this point the “four switch,” or Buck/Boost region output current is given by: is reached. 0.2•V I ≈ IN A Buck/Boost or Four Switch (VIN ~ VOUT) OUT(MAX)BURST VOUT+VIN When the internal control voltage, V , is above voltage V2, CI Burst Mode operation is user controlled, by driving the switch pair AD remain on for duty cycle D , and MAX_BUCK MODE/SYNC pin high to enable and low to disable. the switch pair AC begins to phase in. As switch pair AC phases in, switch pair BD phases out accordingly. When The peak efficiency during Burst Mode operation is less the V voltage reaches the edge of the Buck/Boost range, than the peak efficiency during fixed frequency because CI at voltage V3, the AC switch pair completely phase out the the part enters full-time 4-switch mode (when servicing BD pair, and the boost phase begins at duty cycle D4 . the output) with discontinuous inductor current as illus- SW trated in Figures 3 and 4. During Burst Mode operation, The input voltage, V , where the four switch region begins IN the control loop is nonlinear and cannot utilize the control is given by: voltage from the error amp to determine the control mode, V V = OUT V therefore full-time 4-switch mode is required to main- IN 1–(150ns•f) tain the Buck/Boost function. The efficiency below 1mA becomes dominated primarily by the quiescent current and The point at which the four switch region ends is given by: not the peak efficiency. The equation is given by: V = V (1 – D) = V (1 – 150ns • f) V IN OUT OUT (ηbm) • I LOAD Efficiency Burst ≈ Boost Region (VIN < VOUT) 25µA+ILOAD Switch A is always on and switch B is always off during where (ηbm) is typically 75% during Burst Mode this mode. When the internal control voltage, V , is operation. CI 3441fc 8 For more information www.linear.com/LTC3441

LTC3441 operaTion Burst Mode Operation to Fixed Frequency Transient SOFT-START Response The soft-start function is combined with shutdown. When transitioning from Burst Mode operation to fixed When the SHDN/SS pin is brought above typically 1V, frequency, the system exhibits a transient since the modes the IC is enabled but the EA duty cycle is clamped from of operation have changed. For most systems this transient the V pin. A detailed diagram of this function is shown C is acceptable, but the application may have stringent input in Figure 5. The components R and C provide a SS SS current and/or output voltage requirements that dictate a slow ramping voltage on the SHDN/SS pin to provide a broad-band voltage loop to minimize the transient. Lower- soft-start function. ing the DC gain of the loop will facilitate the task (5M from 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). PVIN VOUT PVIN VOUT 9 8 9 8 A dI≈VIN D A dI≈ –VOUT D dt L dt L + – – + B SW41 L SW52 C IINDUCTOR8000mmAA B SW41 L SW52 C IINDUCTOR8000mmAA T1 3441 F03 T2 3441 F04 6 6 GND GND Figure 3. Inductor Charge Cycle During Burst Mode Operation Figure 4. Inductor Discharge Cycle During Burst Mode Operation VIN ERROR AMP 14µA VOUT + 1.22V FB R1 – 12 SOFT-START VC CP1 R2 CLAMP 11 TO PWM VCI COMPARATORS SHDN/SS RSS 1 ENABLE SIGNAL CSS 3441 F05 + CHIP ENABLE – 1V Figure 5. Soft-Start Circuitry 3441fc 9 For more information www.linear.com/LTC3441

LTC3441 applicaTions inForMaTion COMPONENT SELECTION handle the peak inductor current without saturating. Molded chokes or chip inductors usually do not have enough core to support the peak inductor currents in the 1A to 2A 1 SHDN/SS FB 12 region. To minimize radiated noise, use a toroid, pot core 2 GND VC 11 or shielded bobbin inductor. See Table 1 for suggested 3 PGND VIN 10 VIN components and Table 2 for a list of component suppliers. 4 SW1 PVIN 9 Table 1. Inductor Vendor Information 5 SW2 VOUT 8 VOUT SUPPLIER PHONE FAX WEB SITE 6 PGND MODE 7 Coilcraft (847) 639-6400 (847) 639-1469 www.coilcraft.com Coiltronics (561) 241-7876 (561) 241-9339 www.coiltronics.com Murata USA: USA: www.murata.com (814) 237-1431 (814) 238-0490 3441 F06 (800) 831-9172 GND MULTIPLE VIAS Sumida USA: www.japanlink.com/ (847) 956-0666 (847) 956-0702 sumida Japan: Figure 6. Recommended Component Placement. Traces Carrying 81(3) 3607-5111 81(3) 3607-5144 High Current are Direct. Trace Area at FB and V Pins are Kept C Low. Lead Length to Battery Should be Kept Short. V and V OUT IN Ceramic Capacitors Close to the IC Pins Output Capacitor Selection The bulk value of the capacitor is set to reduce the ripple Inductor Selection due to charge into the capacitor each cycle. The steady The high frequency operation of the LTC3441 allows the state ripple due to charge is given by: use of small surface mount inductors. The inductor cur- rent ripple is typically set to 20% to 40% of the maximum I •(V –V )•100 OUT(MAX) OUT IN(MIN) inductor current. For a given ripple the inductance terms %Ripple_Boost= % 2 C •V •f are given as follows: OUT OUT V •(V –V )•100 IOUT(MAX)•(VIN(MAX)–VOUT)•100 IN(MIN) OUT IN(MIN) %Ripple_Buck= % L> H, C •V •V •f f•IOUT(MAX)•%Ripple•VOUT OUT IN(MAX) OUT L> VOUT •(VIN(MAX)–VOUT)•100 H where COUT = output filter capacitor, F f•I •%Ripple•V OUT(MAX) IN(MAX) The output capacitance is usually many times larger in order to handle the transient response of the converter. For where f = operating frequency, Hz a rule of thumb, the ratio of the operating frequency to the %Ripple = allowable inductor current ripple, % unity-gain bandwidth of the converter is the amount the output capacitance will have to increase from the above V = minimum input voltage, V IN(MIN) calculations in order to maintain the desired transient V = maximum input voltage, V IN(MAX) response. V = output voltage, V OUT The other component of ripple is due to the ESR (equiva- I = maximum output load current OUT(MAX) lent series resistance) of the output capacitor. Low ESR For high efficiency, choose an inductor with a high fre- capacitors should be used to minimize output voltage quency core material, such as ferrite, to reduce core loses. ripple. For surface mount applications, Taiyo Yuden ceramic The inductor should have low ESR (equivalent series capacitors, AVX TPS series tantalum capacitors or Sanyo resistance) to reduce the I2R losses, and must be able to POSCAP are recommended. 3441fc 10 For more information www.linear.com/LTC3441

LTC3441 applicaTions inForMaTion Input Capacitor Selection input voltages, V bypassing becomes more critical; IN therefore, a ceramic bypass capacitor as close to the V Since the V pin is the supply voltage for the IC it is IN IN and GND pins as possible is also required. recommended to place at least a 4.7µF, low ESR bypass capacitor. Operating Frequency Selection Table 2. Capacitor Vendor Information Additional quiescent current due to the output switches SUPPLIER PHONE FAX WEB SITE GATE charge is given by: AVX (803) 448-9411 (803) 448-1943 www.avxcorp.com Buck: (0.8 • V • f) mA Sanyo (619) 661-6322 (619) 661-1055 www.sanyovideo.com IN Taiyo Yuden (408) 573-4150 (408) 573-4159 www.t-yuden.com Boost: [0.4 • (VIN + VOUT) • f] mA Buck/Boost: [f • (1.2 • V + 0.4 • V )] mA Optional Schottky Diodes IN OUT where f = switching frequency in MHz The Schottky diodes across the synchronous switches B and D are not required (V < 4.3V), but provide a lower OUT Closing the Feedback Loop drop during the break-before-make time (typically 15ns) of the NMOS to PMOS transition, improving efficiency. Use a The LTC3441 incorporates voltage mode PWM control. The Schottky diode such as an MBRM120T3 or equivalent. Do control to output gain varies with operation region (Buck, not use ordinary rectifier diodes, since the slow recovery Boost, Buck/Boost), but is usually no greater than 15. The times will compromise efficiency. For applications with an output filter exhibits a double pole response is given by: output voltage above 4.3V, a Schottky diode is required 1 from SW2 to V . f = Hz OUT FILTER_POLE 2•π• L•C OUT Output Voltage < 2.4V (in buck mode) The LTC3441 can operate as a buck converter with out- put voltages as low as 0.4V. The part is specified at 2.4V f = VIN Hz FILTER_POLE minimum to allow operation without the requirement of a 2•V •π• L•C OUT OUT Schottky diode. Synchronous switch D is powered from V and the R will increase at low output voltages, (in boost mode) OUT DS(ON) therefore a Schottky diode is required from SW2 to V OUT Where L is in Henries and C is the output filter capaci- OUT to provide the conduction path to the output. tor in Farads. Output Voltage > 4.3V The output filter zero is given by: A Schottky diode from SW to V is required for output 1 OUT f = Hz voltages over 4.3V. The diode must be located as close to FILTER_ZERO 2•π•R •C ESR OUT the pins as possible in order to reduce the peak voltage where R is the capacitor equivalent series resistance. on SW2 due to the parasitic lead and trace inductance. ESR A troublesome feature in Boost mode is the right-half Input Voltage > 4.5V plane zero (RHP), and is given by: For applications with input voltages above 4.5V which V 2 f = IN Hz could exhibit an overload or short-circuit condition, a RHPZ 2•π•I •L•V OUT OUT 2Ω/1nF series snubber is required between the SW1 pin The loop gain is typically rolled off before the RHP zero and GND. A Schottky diode from SW1 to V should also IN frequency. be added as close to the pins as possible. For the higher 3441fc 11 For more information www.linear.com/LTC3441

LTC3441 applicaTions inForMaTion A simple Type I compensation network can be incorporated VOUT to stabilize the loop but at a cost of reduced bandwidth + 1.22V and slower transient response. To ensure proper phase ERAMROPR FB R1 margin, the loop requires to be crossed over a decade – 12 before the LC double pole. VC CP1 R2 11 The unity-gain frequency of the error amplifier with the 3441 F07 Type I compensation is given by: Figure 7. Error Amplifier with Type I Compensation 1 f = Hz UG 2•π•R1•CP1 Most applications demand an improved transient response VOUT to allow a smaller output filter capacitor. To achieve a higher bandwidth, Type III compensation is required. Two zeros + 1.22V R1 CZ1 ERROR are required to compensate for the double-pole response. AMP FB – 12 1 fPOLE1≈ 2•π•32e3 •R1•C Hz VC RZ CP1 R2 P1 11 CP2 WhichisextremelyclosetoDC 3441 F08 1 f = Hz ZERO1 2•π•R •C Figure 8. Error Amplifier with Type III Compensation Z P1 1 f = Hz ZERO2 2•π•R1•C Z1 1 f = Hz POLE2 2•π•R •C Z P2 Load Transient Response, L1 100mA to 1A 4.7µH VOUT 3.3V 4 5 220pF 1A SW1 SW2 2.5V TO 4.2V 190 PVINLTC3441VOUT 812 R3418k 2.2k 100mVV/ODUIVT VIN FB C2 1 11 R3 15k 47µF SHDN/SS VC 7 2 Li-Ion * MODE/SYNC GND C4 220pF 1A C1 3 6 10µF PGND PGND 5M R2 200k 100mA *1 = Burst Mode OPERATION C1: TAIYO YUDEN JMK212BJ106MG 3441 F09 0 = FIXED FREQUENCY C2: TAIYO YUDEN JMK325BJ476MM 100µs/DIV 3441 G01 L1: TOKO A916CY-4R7M Figure 9. Fast Transient Response Compensation for Step Load or Mode Change 3441fc 12 For more information www.linear.com/LTC3441

LTC3441 Typical applicaTions Li-Ion to 3.3V at 1.2A Converter L1 Efficiency 4.7µH D1 100 4 5 VOUT 90 SW1 SW2 3.3V 4.2VIN BURST 9 8 R1 1.2A 80 2.8V TO 4.2V PVIN VOUT 340k 10 LTC3441 12 70 Li-Ion DC21 * 173 VSMPIHGONDNDNDE//SSSYNCPGGNNVFDDBC 1261 R3 15k C4 1.5nF R2020k C222µF EFFICIENCY (%) 645000 2.8VIN PWM 3.6VIN P4W.2MVIN PWM 10µF 30 20 *1 = Burst Mode OPERATION C1: TAIYO YUDEN JMK212BJ106MG 0 = FIXED FREQUENCY C2: TAIYO YUDEN JMK325BJ226MM 3441 TA03a 10 D1, D2: ON SEMICONDUCTOR MBRM120LT3 0 L1: TOKO A916CY-3R3M 0.1 1 10 100 1000 10000 IOUT (mA) 3441 TA03b Li-Ion to 5V at 600mA Boost Converter with Output Disconnect Efficiency L1 D1 4.7µH VOUT 100 5V VIN = 4.2V 600mA 90 4 5 Burst Mode SW1 SW2 R1 80 OPERATION VIN = 3.6 V 9 8 619k 2.5V TO 4.2V PVIN VOUT 70 VIN = 2.7V 1M 101 VSIHNDNL/TSCS3441 VFBC 1121 R3 15k 2C2OµUFT NCY (%) 5600 Li-Ion 0.047µF * 73 MODE/SYNC GND 26 C4 1.5nF R2 FFICIE 40 C1 PGND PGND 200k E 30 10µF 20 *1 = Burst Mode OPERATION C1: TAIYO YUDEN JMK212BJ106MG 10 3441 TA04a 0 = FIXED FREQUENCY C2: TAIYO YUDEN JMK325BJ226MM D1: MBRM120LT3 0 L1: TOKO A916CY-4R7M 0.1 1 10 100 1000 OUTPUT CURRENT (mA) 3441 TA04b 3441fc 13 For more information www.linear.com/LTC3441

LTC3441 package DescripTion Please refer to http://www.linear.com/product/LTC3441#packaging for the most recent package drawings. DE/UE Package 12-Lead Plastic DFN (4mm × 3mm) (Reference LTC DWG # 05-08-1695 Rev D) 0.70 ±0.05 3.30 ±0.05 3.60 ±0.05 2.20 ±0.05 1.70 ±0.05 PACKAGE OUTLINE 0.25 ±0.05 0.50 BSC 2.50 REF RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 4.00 ±0.10 R = 0.115 0.40 ±0.10 (2 SIDES) TYP 7 12 R = 0.05 TYP 3.30 ±0.10 3.00 ±0.10 (2 SIDES) 1.70 ±0.10 PIN 1 PIN 1 NOTCH TOP MARK R = 0.20 OR (NOTE 6) 0.35 × 45° CHAMFER 6 1 (UE12/DE12) DFN 0806 REV D 0.200 REF 0.75 ±0.05 0.25 ±0.05 0.50 BSC 2.50 REF 0.00 – 0.05 BOTTOM VIEW—EXPOSED PAD NOTE: 1. DRAWING PROPOSED TO BE A VARIATION OF VERSION (WGED) 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 3441fc 14 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 representa- tion that the interconneFcotiro nm oof irtes cinircfouritms aast idoensc wribwedw h.leinreeina rw.cilol nmo/tL inTfCri3ng4e4 o1n existing patent rights.

LTC3441 revision hisTory (Revision history begins at Rev B) REV DATE DESCRIPTION PAGE NUMBER B 8/14 Modified filter pole equation in Closing the Feedback Loop section 11 C 10/16 Added equation to calculate V 6 OUT Modified Operating Frequency Selection section 11 3441fc 15 For more information www.linear.com/LTC3441

LTC3441 Typical applicaTion PCMCIA Powered GSM Modem L1 10µH VOUT 3.6V 2A (PULSED) 4 5 R1 SW1 SW2 392k VIN 0.R05SΩ 190 PVINLTC3441VOUT 812 2R46k 1N914 + 2.5V TO 5.5V VIN FB 1/2 LT1490A COUT 1A MAX 1 SHDN/SS VC 11 – 2200µF 7 2 MODE/SYNC GND C4 C1 3 6 10nF 10µF PGND PGND R5 R2 24k 200k 3441 TA05 + C1: TAIYO YUDEN JMK212BJ106MG R4 1/2 LT1490A 2N3906 C2: SANYO MV-AX SERIES 1k L1: TOKO A916CY-4R7M – ICURRENTLIMIT =1R.252 • • R RS4 AVERAGE INPUT CURRENT CONTROL relaTeD parTs PART NUMBER DESCRIPTION COMMENTS LT®1613 550mA (I ) 1.4MHz High Efficiency Step-Up DC/DC Converter V : 0.9V to 10V, V : 34V, I : 3mA, SW IN OUT(MAX) Q I : ≤ 1µA, ThinSOT™ SD LT1615/LT1615-1 300mA/80mA (I ) Constant Off-Time, High Efficiency Step-Up V : 1.2V to 15V, V : 34V, I : 20µA, SW IN OUT(MAX) Q DC/DC Converter I : ≤ 1µA, ThinSOT SD LT1616 500mA (I ) 1.4MHz High Efficiency Step-Down DC/DC Converter High Efficiency, V : 3.6V to 25V, V : 1.25V, I : 1.9mA, OUT IN OUT(MIN) Q I : ≤ 1µA, ThinSOT SD LT1776 500mA (I ) 200kHz High Efficiency Step-Down DC/DC Converter High Efficiency, V : 7.4V to 40V, V : 1.24V, I : 3.2mA, OUT IN OUT(MIN) Q I : 30µA, N8, S8 SD LTC1877 600mA (I ) 550kHz Synchronous Step-Down DC/DC Converter 95% Efficiency, V : 2.7V to 10V, V : 0.8V, I : 10µA, OUT IN OUT(MIN) Q I : ≤ 1µA, MS8 SD LTC1878 600mA (I ) 550kHz Synchronous Step-Down DC/DC Converter 95% Efficiency, V : 2.7V to 6V, V : 0.8V, I : 10µA, OUT IN OUT(MIN) Q I : ≤ 1µA, MS8 SD LTC1879 1.2A (I ) 550kHz Synchronous Step-Down DC/DC Converter 95% Efficiency, V : 2.7V to 10V, V : 0.8V, I : 15µA, OUT IN OUT(MIN) Q I : ≤ 1µA, TSSOP16 SD LT1930/LT1930A 1A (I ) 1.2MHz/2.2MHz High Efficiency Step-Up DC/DC Converter V : 2.6V to 16V, V : 34V, I : 5.5mA, SW IN OUT(MAX) Q I : ≤ 1µA, ThinSOT SD LTC3405/ 300mA (I ) 1.5MHz Synchronous Step-Down DC/DC Converter 95% Efficiency, V : 2.7V to 6V, V : 0.8V, I : 20µA, OUT IN OUT(MIN) Q LTC3405A I : ≤ 1µA, ThinSOT SD LTC3406/ 600mA (I ) 1.5MHz Synchronous Step-Down DC/DC Converter 95% Efficiency, V : 2.5V to 5.5V, V : 0.6V, I : 20µA, OUT IN OUT(MIN) Q LTC3406B I : ≤ 1µA, ThinSOT SD LTC3407 600mA (IOUT) ×2 1.5MHz Dual Synchronous Step-Down 96% Efficiency, VIN: 2.5V to 5.5V, VOUT(MIN): 0.6V, IQ: 40µA, DC/DC Converter I : ≤ 1µA, 10-Lead MS SD LTC3411 1.25A (I ) 4MHz Synchronous Step-Down DC/DC Converter 95% Efficiency, V : 2.5V to 5.5V, V : 0.8V, I : 60µA, OUT IN OUT(MIN) Q I : ≤ 1µA, 10-Lead MS SD LTC3412 2.5A (I ) 4MHz Synchronous Step-Down DC/DC Converter 95% Efficiency, V : 2.5V to 5.5V, V : 0.8V, I : 60µA, OUT IN OUT(MIN) Q I : ≤ 1µA, TSSOP16E SD LTC3440 600mA (I ) 2MHz Synchronous Buck-Boost DC/DC Converter 95% Efficiency, V : 2.5V to 5.5V, V : 2.5V, I : 25µA, OUT IN OUT(MIN) Q I : ≤ 1µA, 10-Lead MS SD 3441fc 16 Linear Technology Corporation LT 1016 REV C • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 For more information www.linear.com/LTC3441 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com/LTC3441  LINEAR TECHNOLOGY CORPORATION 2003