LT3461/LT3461A 1.3MHz/3MHz Step-Up DC/DC Converters with Integrated Schottky in ThinSOT APPLICATIONS TYPICAL APPLICATION

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1 LT6/LT6A.MHz/MHz Step-Up DC/DC Converters with Integrated Schottky in ThinSOT FEATURES Integrated Schottky Rectifier Fixed Frequency.MHz/MHz Operation High Output Voltage: Up to 8V Low V CESAT Switch: 6mV at ma V at 7mA from V Input V at ma from.v Input Wide Input Range:.V to 6V Uses Small Surface Mount Components Low Shutdown Current: <µa Soft-Start Low Profile (mm) SOT- (ThinSOT ) Package APPLICATIONS Digital Cameras CCD Bias Supply XDSL Power Supply TFT-LCD Bias Supply Local V or V Supply Medical Diagnostic Equipment Battery Backup DESCRIPTION The LT 6/LT6A are general purpose fixed frequency current mode step-up DC/DC converters. Both devices feature an integrated Schottky and a low V CESAT switch allowing a small converter footprint and lower parts cost. The LT6 switches at.mhz while the LT6A switches at MHz. These high switching frequencies enable the use of tiny, low cost and low height capacitors and inductors. The constant switching frequency results in predictable output noise that is easy to filter, and the inductor based topology ensures an input free from switching noise typically present with charge pump solutions. The high voltage switch in the LT6/LT6A is rated at V making the device ideal for boost converters up to 8V. The LT6/LT6A are available in a low profile (mm) SOT- package. L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and ThinSOT is a trademark of Linear Technology Corporation. TYPICAL APPLICATION V to V, 7mA Step-Up DC/DC Converter Efficiency V OFF ON µh LT6A SHDN FB 6k.k pf V 7mA C EFFICIENCY (%) =.V = V 6 TAa LOAD CURRENT (ma) 6 TAOb For more information

2 LT6/LT6A ABSOLUTE MAXIMUM RATINGS (Note ) Input Voltage ( )...6V, SW Voltage...V FB Voltage...V SHDN Voltage...6V Operating Ambient Temperature Range (Note )... C to 8 C Maximum Junction Temperature... C Storage Temperature Range... 6 C to C Lead Temperature (Soldering, sec)... C PIN CONFIGURATION SW FB TOP VIEW 6 SHDN S6 PACKAGE 6-LEAD PLASTIC TSOT- T JMAX = C, θ JA = C ON BOARD OVER GROUND PLANE, θ JC = C/W ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LT6AES6#PBF LT6AES6#TRPBF LTAHG 8-Lead Plastic TSOT- C to 8 C LT6ES6#PBF LT6ES6#TRPBF LTAEB 8-Lead Plastic TSOT- C to 8 C Consult LTC Marketing for parts specified with wider operating temperature ranges. For more information on lead free part marking, go to: For more information on tape and reel specifications, go to: Some packages are available in unit reels through designated sales chaels with #TRMPBF suffix. For more information

3 ELECTRICAL CHARACTERISTICS LT6/LT6A The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T A = C, = V, V SHDN = V, unless otherwise noted. PARAMETER CONDITIONS MIN TYP MAX UNITS Minimum Operating Voltage. V Maximum Operating Voltage 6 V Feedback Voltage...7 V l..8 V Feedback Line Regulation. %/V FB Pin Bias Current l na Supply Current FB =.V, Not Switching SHDN = V ma µa Switching Frequency (LT6A) l...9 MHz Switching Frequency (LT6) l...7 MHz Maximum Duty Cycle (LT6A) l 8 % Maximum Duty Cycle (LT6) l 9 % Switch Current Limit 6 ma Switch V CESAT I SW = ma 6 mv Switch Leakage Current V SW = V. µa Schottky Forward Voltage I SCHOTTKY = ma 8 mv Schottky Reverse Leakage SW = V. µa SHDN Voltage High. V SHDN Voltage Low. V SHDN Pin Bias Current µa Note : 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 : The LT6E/LT6AE is guaranteed to meet specifications from C to 7 C. Specifications over the C to 8 C operating temperature range are assured by design, characterization and correlation with statistical process controls. For more information

LT6/LT6A TYPICAL PERFORMANCE CHARACTERISTICS.6 Oscillator Frequency (LT6) Current Limit FB Pin Voltage 8.8 T A = C FREQUENCY (MHz)..... CURRENT LIMIT (ma) 6 FB VOLTAGE (V).7.6.... 6 8 TEMPERATURE ( C) 6 7 DUTY CYCLE (%) 8 9.

Oscillator Frequency (LT6A) Current Limit in Soft-Start Mode SHDN Pin Current CURRENT LIMIT (ma) 8 T A = C 6 8 6 SHDN PIN CURRENT (µa) T A = C 8 6 8. 6 6 8 TEMPERATURE ( C)...7.9.

4 LT6/LT6A TYPICAL PERFORMANCE CHARACTERISTICS.6 Oscillator Frequency (LT6) Current Limit FB Pin Voltage 8.8 T A = C FREQUENCY (MHz)..... CURRENT LIMIT (ma) 6 FB VOLTAGE (V) TEMPERATURE ( C) 6 7 DUTY CYCLE (%) TEMPERATURE ( C) 6a G 6a G 6a G FREQUENCY (MHz) Oscillator Frequency (LT6A) Current Limit in Soft-Start Mode SHDN Pin Current CURRENT LIMIT (ma) 8 T A = C SHDN PIN CURRENT (µa) T A = C TEMPERATURE ( C) SHDN PIN VOLTAGE (V) 8 SHDN PIN VOLTAGE (V) 6 6a G 6a G 6a G6 Switching Waveform Circuit of Figure Load Transient Response Circuit of Figure 7mA I LOAD ma V SW V/DIV mv/div mv/div I LOAD = 6mA.µs/DIV 6a G8 µs/div 6a G9 For more information

5 LT6/LT6A PIN FUNCTIONS SW (Pin ): Switch Pin. Coect inductor here. Minimize trace at this pin to reduce EMI. (Pin ): Ground Pin. Tie directly to local ground plane. FB (Pin ): Feedback Pin. Reference voltage is.v. Coect resistor divider tap here. Minimize trace area at FB. Set according to =.V ( + R/R). SHDN (Pin ): Shutdown Pin. Tie to.v or higher to enable device;.v or less to disable device. Also functions as soft-start. Use RC filter (7k, 7nF typ) as shown in Figure. (Pin ): Output Pin. Coect to resistor divider. Put capacitor close to pin and close to plane. (Pin 6): Input Supply Pin. Must be locally bypassed. BLOCK DIAGRAM 6 R (EXTERNAL) FB R (EXTERNAL).V REFERENCE FB + A R C C C COMPARATOR + A R S Q DRIVER + SW Q.Ω R S (EXTERNAL) SHUTDOWN SHDN RAMP GENERATOR C S (EXTERNAL) R S, C S OPTIONAL SOFT-START COMPONENTS MHz* OSCILLATOR *LT6 IS.MHz 6a F Figure. Block Diagram OPERATION The LT6/LT6A uses a constant frequency, current mode control scheme to provide excellent line and load regulation. Operation can be best understood by referring to the block diagram in Figure. At the start of each oscillator cycle, the SR latch is set, which turns on the power switch Q. A voltage proportional to the switch current is added to a stabilizing ramp and the resulting sum is fed into the positive terminal of the PWM comparator A. When this voltage exceeds the level at the negative input of A, the SR latch is reset turning off the power switch. The level at the negative input of A is set by the error amplifier A, and is simply an amplified version of the difference between the feedback voltage and the reference voltage of.v. In this maer, the error amplifier sets the correct peak current level to keep the output in regulation. If the error amplifier s output increases, more current is delivered to the output; if it decreases, less current is delivered. For more information Layout Hints The high speed operation of the LT6/LT6A demands careful attention to board layout. You will not get advertised performance with careless layout. Figure shows the recommended component placement. R + R C C + 6a F Figure. Suggested Layout SHUTDOWN

6 LT6/LT6A APPLICATIONS INFORMATION Inrush Current The LT6 has a built-in Schottky diode. When supply voltage is applied to the pin, the voltage difference between and generates inrush current flowing from input through the inductor and the Schottky diode to charge the output capacitor. The maximum nonrepetitive surge current the Schottky diode in the LT6 can sustain is.a. The selection of inductor and capacitor value should ensure the peak of the inrush current to be below.a. In addition, turn-on of the LT6 should be delayed until the inrush current is less than the maximum current limit. The peak inrush current can be calculated as follows: I P =.6 π Ω exp L C Ω L C Ω where L is the inductance, r is the resistance of the inductor and C is the output capacitance. Table gives inrush peak currents for some component selections. I OUT (ma) I OUT (ma) = V = 8V = V >V (V) 6 Fa Figure a. LT6 Operating Region = V = 8V = V >V 8 Table. Inrush Peak Current (V) L (µh) C (µf) I P (A).7..9 Thermal Considerations Significant power dissipation can occur on the LT6 and LT6A, particularly at high input voltage. Device load, voltage drops in the power path components, and switching losses are the major contributors. It is important to measure device power dissipation in an application to ensure that the LT6 does not exceed the absolute maximum operating junction temperature of C over the operating ambient temperature range. Generally, for supply voltages below V the integrated current limit function provides adequate protection for nonfault conditions. For supply voltages above V, Figures a and b show the recommended operating region of the LT6 and LT6A, respectively. These graphs are based on mw on-chip dissipation. Improvement of these numbers can be expected if the LT6 is supplied from a separate low voltage rail. 6 6 For more information (V) 6 Fb Figure b. LT6A Operating Region Switching Frequency The key difference between the LT6 and LT6A is the faster switching frequency of the LT6A. At MHz, the LT6A switches at twice the rate of the LT6. The higher switching frequency of the LT6A allows physically smaller inductors and capacitors to be used in a given application, but with a slight decrease in efficiency and maximum output current when compared to the LT6. Generally if efficiency and maximum output current are crucial, or a high output voltage is being generated, the LT6 should be used. If application size and cost are more important, the LT6A will be the better choice. 8

7 APPLICATIONS INFORMATION Inductor Selection The inductors used with the LT6/LT6A should havea saturation current rating of.a or greater. If the device is used in an application where the input supply will be hot-plugged, then the saturation current rating should be equal to or greater than the peak inrush current. For the LT6, an inductor value between µh and 7µH, depending upon output voltage, will usually be the best choice for most designs. For the LT6A, inductor values between.7µh and µh inductor will suffice for most applications. For best loop stability results, the inductor value selected should provide a ripple current of 7mA or more. For a given and the inductor value to use with LT6A is estimated by the formula: L (in microhenries) = D sec A V where D = +V +V Use twice this value for the LT6. Capacitor Selection Low ESR capacitors should be used at the output to minimize the output voltage ripple. Multilayer ceramic capacitors using XR/X7R dielectrics are preferred as LT6/LT6A they have a low ESR and maintain capacitance over wide voltage and temperature range. A.µF output capacitor is sufficient for most applications using the LT6, while a capacitor is sufficient for most applications using the LT6A. High output voltages typically require less capacitance for loop stability. Always use a capacitor with sufficient voltage rating. Either ceramic or solid tantalum capacitors may be used for the input decoupling capacitor, which should be placed as close as possible to the LT6/LT6A. A capacitor is sufficient for most applications. Phase Lead Capacitor A small value capacitor can be added across resistor R between the output and the FB pin to reduce output perturbation due to a load step and to improve transient response. This phase lead capacitor introduces a pole-zero pair to the feedback that boosts phase margin near the cross-over frequency. The following formula is useful to estimate the capacitor value needed: C PL = kω R pf For an application ruing µa in the feedback divider, capacitor values from pf to pf work well. TYPICAL APPLICATIONS V CONTROL SIGNAL 7k 7nF µh LT6A SHDN FB, C: TAIYO YUDEN EMKBJ : MURATA LQHCNK R 6k R.k pf Figure. V to V with Soft-Start Circuit (LT6A) V 7mA C 6a TAa CONTROL SIGNAL V/DIV I IN mv/div V/DIV Input Current and Output Voltage ms/div 6 TAb For more information 7

8 LT6/LT6A TYPICAL APPLICATIONS.V to V Step-Up Converter (LT6A).V to V Step-Up Converter Efficiency 8.V OFF ON.7µH LT6A SHDN FB R.k R k pf V ma C EFFICIENCY (%) 7 7 6, C: TAIYO YUDEN X7R LMKBJ : MURATA LQHCNR7M OR EQUIVALENT 6a TAa LOAD CURRENT (ma) 6a TAb PACKAGE DESCRIPTION Please refer to for the most recent package drawings. S6 Package 6-Lead Plastic TSOT- (Reference LTC DWG # -8-66).6 MAX.9 REF.9 BSC (NOTE ). REF.8 MAX.6 REF. MIN.8 BSC..7 (NOTE ) PIN ONE ID RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR.9 BSC.. 6 PLCS (NOTE ).8.9. BSC DATUM A. MAX.... REF.9..9 BSC (NOTE ) S6 TSOT- 8 NOTE:. DIMENSIONS ARE IN MILLIMETERS. DRAWING NOT TO SCALE. DIMENSIONS ARE INCLUSIVE OF PLATING. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR. MOLD FLASH SHALL NOT EXCEED.mm 6. JEDEC PACKAGE REFERENCE IS MO-9 For more information

9 REVISION HISTORY (Revision history begins at Rev B) LT6/LT6A REV DATE DESCRIPTION PAGE NUMBER A /6 Modified inrush current I P equation. 6 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 intercoection For more of its circuits information as described herein will not infringe on existing patent rights. 9

10 LT6/LT6A TYPICAL APPLICATION Low Profile (mm).v to V Step-Up Converter.V to V Efficiency.V OFF ON µh LT6A SHDN FB k.k pf V ma C.µF EFFICIENCY (%) : TAIYO YUDEN LMK7BJKA C: TAIYO YUDEN EMK6BJKD (XR) : MURATA LQHMCNK 6a TAa LOAD CURRENT (ma) 6a TAb V to 6V Step-Up Converter (LT6) V to 6V Efficiency V OFF ON 7µH LT6 SHDN FB 8k k pf 6V 8mA C.7µF V EFFICIENCY (%) : TAIYO YUDEN X7R LMKBJ C: MURATA GRM-6X7R7K : MURATA LQHCN7 6 TAa.V to ±V Dual Output Converter 6 8 LOAD CURRENT (ma) 6 6 TAb 8.V OFF ON.7µH LT6A SHDN FB.k k C pf V ma C, C, C, C: TAIYO YUDEN JMK7BJ D, D: PHILIPS PMEGEB : MURATA LQHMCNR7M D D Ω C V ma 6 TA6 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT6/LT6- LT9/LT9- ma/8ma (I SW ) Constant Off-Time, High Efficiency Step-Up DC/DC Converter Dual Output ma/ma (I SW ), Constant Off-Time, High Efficiency Step-Up DC/DC Converter Linear Technology Corporation 6 McCarthy Blvd., Milpitas, CA 9-77 For more information (8) -9 FAX: (8) -7 :.V to V, (MAX) = V, I Q = µa, I SD <µa, ThinSOT Package :.V to V, (MAX) = V, I Q = µa, I SD <µa, MS Package LTC/LTCB 6mA (I SW ),.MHz, Synchronous Step-Up DC/DC Converter :.8V to V, (MAX) = V, I Q = 9µA/µA, I SD <µa, ThinSOT Package LT6.A (I SW ),.MHz, High Efficiency Step-Up DC/DC Converter :.V to 6V, (MAX) = 6V, I Q = ma, I SD <µa, SC7, ThinSOT Packages LT6/LT6A Constant Current,.MHz/.7MHz, High Efficiency White LED Boost Regulator with Integrated Schottky Diode :.7V to 6V, (MAX) = V, I Q =.9mA, I SD <µa, ThinSOT Package LT 6 REV A PRINTED IN USA LINEAR TECHNOLOGY CORPORATION

LT3572 Dual Full-Bridge Piezo Driver with 900mA Boost Converter DESCRIPTION FEATURES APPLICATIONS TYPICAL APPLICATION

LT3572 Dual Full-Bridge Piezo Driver with 900mA Boost Converter DESCRIPTION FEATURES APPLICATIONS TYPICAL APPLICATION Dual Full-Bridge Piezo Driver with 900mA Boost Converter FEATURES 2.7V to 0V Input Voltage Range 900mA Boost Converter Dual Full-Bridge Piezo Drivers Up to 00kHz PWM Frequency Programmable Switching Frequency