DESCRIPTIO FEATURES APPLICATIO S. LT1615/LT Micropower Step-Up DC/DC Converters in ThinSOT TYPICAL APPLICATIO

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1 LT6/LT6- Micropower Step-p DC/DC Converters in ThinSOT FEATRES Low Quiescent Current: 0µA in Active Mode <µa in Shutdown Mode Operates with as Low as V Low V CESAT Switch: 0mV at 00mA ses Small Surface Mount Components High Output Voltage: p to V Low Profile (mm) ThinSOT TM Package APPLICATIO S LCD Bias Handheld Computers Battery Backup Digital Cameras DESCRIPTIO The LT 6/LT6- are micropower step-up DC/DC converters in a -lead low profile (mm) ThinSOT package. The LT6 is designed for higher power systems with a 0mA current limit and an input voltage range of.v to V, whereas the LT6- is intended for lower power and single-cell applications with a 00mA current limit and an extended input voltage range of V to V. Otherwise, the two devices are functionally equivalent. Both devices feature a quiescent current of only 0µA at no load, which further reduces to 0.µA in shutdown. A current limited, fixed off-time control scheme conserves operating current, resulting in high efficiency over a broad range of load current. The 6V switch allows high voltage outputs up to V to be easily generated in a simple boost topology without the use of costly transformers. The LT6 s low off-time of 00ns permits the use of tiny, low profile inductors and capacitors to minimize footprint and cost in space-conscious portable applications., LTC and LT are registered trademarks of Linear Technology Corporation. ThinSOT is a trademark of Linear Technology Corporation. TYPICAL APPLICATIO -Cell Li-Ion to 0V Converter for LCD Bias Efficiency.V TO.V.7µF 0µH LT6 SHDN FB R M R 0k 0V ma µf EFFICIENCY (%) =.V =.V =.V : TAIYO YDEN LMK6BJ7 : TAIYO YDEN TMK6BJ0 : MOTOROLA MBR00 : MRATA LQH00K 6/- TA LOAD CRRENT (ma) 6/- TA0a sn6 6fas

2 LT6/LT6- ABSOLTE AXI RATI GS (Note ) W W W, SHDN Voltage... V Voltage... 6V FB Voltage... Current into FB Pin... ma Junction Temperature... C Operating Temperature Range (Note ).. 0 C to 8 C Storage Temperature Range... 6 C to 0 C Lead Temperature (Soldering, 0 sec) C W PACKAGE/ORDER I FOR ATIO FB TOP VIEW S PACKAGE -LEAD PLASTIC SOT- SHDN T JMAX = C, θ JA = 6 C/W ORDER PART NMBER LT6ES LT6ES- LT6IS LT6IS- S PART MARKING LTIZ LTKH LTXZ LTBHT Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T A = C. =.V, V SHDN =.V unless otherwise noted. PARAMETER CONDITIONS MIN TYP MAX NITS Minimum Input Voltage LT6-.0 V LT6. V Quiescent Current Not Switching 0 0 µa V SHDN = 0V µa FB Comparator Trip Point.0.. V FB Comparator Hysteresis 8 mv Output Voltage Line Regulation.V < < V %/V FB Pin Bias Current (Note ) V FB =.V 0 80 na Switch Off Time V FB > V 00 ns V FB < 0.6V. µs Switch V CESAT I = 70mA (LT6-) 8 0 mv I = 00mA (LT6) 0 0 mv Switch Current Limit LT ma LT ma SHDN Pin Current V SHDN =.V µa V SHDN = V 8 µa SHDN Input Voltage High 0.9 V SHDN Input Voltage Low 0. V Switch Leakage Current Switch Off, V = V 0.0 µa Note : Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note : The LT6E and LT6E- are guaranteed to meet performance specifications from 0 C to 70 C. Specifications over the 0 C to 8 C operating temperature range are assured by design, characterization and correlation with statistical process controls. The LT6I/LT6I- is guaranteed to meet performance specifications over the 0 C to 8 C operating temperature range. Note : Bias current flows into the FB pin. sn6 6fas

3 LT6/LT6- TYPICAL PERFOR A CE CHARACTERISTICS W ITCH VOLTAGE (V) Switch Saturation Voltage Feedback Pin Voltage and (V CESAT ) Bias Current Quiescent Current I ITCH = 00mA I ITCH = 00mA TEMPERATRE ( C) FEEDBACK VOLTAGE (V) VOLTAGE CRRENT TEMPERATRE ( C) BIAS CRRENT (na) QIESCENT CRRENT (µa) 9 7 V FB =.V NOT ITCHING = V =.V TEMPERATRE ( C) 6/- G0 6/- G0 6/- G0 Switch Off Time Switch Current Limit Shutdown Pin Current ITCH OFF TIME (ns) =.V = V PEAK CRRENT (ma) = V LT6 LT6- =.V = V =.V SHTDOWN PIN CRRENT (µa) 0 0 C 00 C TEMPERATRE ( C) TEMPERATRE ( C) SHTDOWN PIN VOLTAGE (V) 6/- G0 6/- G0 6/- G0 PI F CTIO S (Pin ): Switch Pin. This is the collector of the internal NPN power switch. Minimize the metal trace area connected to this pin to minimize EMI. (Pin ): Ground. Tie this pin directly to the local ground plane. FB (Pin ): Feedback Pin. Set the output voltage by selecting values for R and R (see Figure ): V R R OT =. SHDN (Pin ): Shutdown Pin. Tie this pin to 0.9V or higher to enable the device. Tie below 0.V to turn off the device. (Pin ): Input Supply Pin. Bypass this pin with a capacitor as close to the device as possible. sn6 6fas

4 LT6/LT6- BLOCK DIAGRA W + V OT SHDN R 0k R6 0k + A ENABLE R (EXTERNAL) R (EXTERNAL) V OT FB Q Q X0 R 0k 00ns ONE-SHOT RESET DRIVER Q R 0k A mv* 0.Ω 6/- BD * mv FOR LT6- Figure. LT6 Block Diagram OPERATIO The LT6 uses a constant off-time control scheme to provide high efficiencies over a wide range of output current. Operation can be best understood by referring to the block diagram in Figure. Q and Q along with R and R form a bandgap reference used to regulate the output voltage. When the voltage at the FB pin is slightly above.v, comparator A disables most of the internal circuitry. Output current is then provided by capacitor, which slowly discharges until the voltage at the FB pin drops below the lower hysteresis point of A (typical hysteresis at the FB pin is 8mV). A then enables the internal circuitry, turns on power switch Q, and the current in inductor begins ramping up. Once the switch current reaches 0mA, comparator A resets the oneshot, which turns off Q for 00ns. then delivers current to the output through diode as the inductor current ramps down. Q turns on again and the inductor current ramps back up to 0mA, then A resets the oneshot, again allowing to deliver current to the output. This switching action continues until the output voltage is charged up (until the FB pin reaches.v), then A turns off the internal circuitry and the cycle repeats. The LT6 contains additional circuitry to provide protection during start-up and under short-circuit conditions. When the FB pin voltage is less than approximately 600mV, the switch off-time is increased to.µs and the current limit is reduced to around 0mA (70% of its normal value). This reduces the average inductor current and helps minimize the power dissipation in the LT6 power switch and in the external inductor and diode. The LT6- operates in the same manner, except the switch current is limited to 00mA (the A reference voltage is mv instead of mv). sn6 6fas

5 LT6/LT6- APPLICATIO S I FOR Choosing an Inductor Several recommended inductors that work well with the LT6 and LT6- are listed in Table, although there are many other manufacturers and devices that can be used. Consult each manufacturer for more detailed information and for their entire selection of related parts. Many different sizes and shapes are available. se the equations and recommendations in the next few sections to find the correct inductance value for your design. Table. Recommended Inductors PART VALE (µh) MAX DCR (Ω) VENDOR LQHCR Murata LQH (8) 7- LQH CD-R Sumida CD (87) CDRH8-R CDRH DO Coilcraft DO (87) DO Inductor Selection Boost Regulator The formula below calculates the appropriate inductor value to be used for a boost regulator using the LT6 or LT6- (or at least provides a good starting point). This value provides a good tradeoff in inductor size and system performance. Pick a standard inductor close to this value. A larger value can be used to slightly increase the available output current, but limit it to around twice the value calculated below, as too large of an inductance will increase the output voltage ripple without providing much additional output current. A smaller value can be used (especially for systems with output voltages greater than V) to give a smaller physical size. Inductance can be calculated as: V V + V L = I OT IN MIN D LIM ( ) t OFF ATIO W where V D = 0.V (Schottky diode voltage), I LIM = 0mA or 00mA, and t OFF = 00ns; for designs with varying such as battery powered applications, use the minimum value in the above equation. For most systems with output voltages below 7V, a.7µh inductor is the best choice, even though the equation above might specify a smaller value. This is due to the inductor current overshoot that occurs when very small inductor values are used (see Current Limit Overshoot section). For higher output voltages, the formula above will give large inductance values. For a V to 0V converter (typical LCD Bias application), a µh inductor is called for with the above equation, but a 0µH inductor could be used without excessive reduction in maximum output current. Inductor Selection SEPIC Regulator The formula below calculates the approximate inductor value to be used for a SEPIC regulator using the LT6. As for the boost inductor selection, a larger or smaller value can be used. V L = OT I + V LIM D t OFF Current Limit Overshoot For the constant off-time control scheme of the LT6, the power switch is turned off only after the 0mA (or 00mA) current limit is reached. There is a 00ns delay between the time when the current limit is reached and when the switch actually turns off. During this delay, the inductor current exceeds the current limit by a small amount. The peak inductor current can be calculated by: I PEAK V = ILIM + IN( MAX) V L SAT 00ns Where V SAT = 0.V (switch saturation voltage). The current overshoot will be most evident for systems with high input voltages and for systems where smaller inductor values are used. This overshoot can be beneficial as it helps increase the amount of available output current for smaller inductor values. This will be the peak current seen by the inductor (and the diode) during normal operation. For designs using small inductance values (especially at sn6 6fas

6 LT6/LT6- APPLICATIO S I FOR ATIO W input voltages greater than V), the current limit overshoot can be quite high. Although it is internally current limited to 0mA, the power switch of the LT6 can handle larger currents without problem, but the overall efficiency will suffer. Best results will be obtained when I PEAK is kept below 700mA for the LT6 and below 00mA for the LT6-. Capacitor Selection Low ESR (Equivalent Series Resistance) capacitors should be used at the output to minimize the output ripple voltage. Multilayer ceramic capacitors are the best choice, as they have a very low ESR and are available in very small packages. Their small size makes them a good companion to the LT6 s SOT- package. Solid tantalum capacitors (like the AVX TPS, Sprague 9D families) or OS-CON capacitors can be used, but they will occupy more board area than a ceramic and will have a higher ESR. Always use a capacitor with a sufficient voltage rating. Ceramic capacitors also make a good choice for the input decoupling capacitor, which should be placed as close as possible to the LT6. A.7µF input capacitor is sufficient for most applications. Table shows a list of several capacitor manufacturers. Consult the manufacturers for more detailed information and for their entire selection of related parts. Diode Selection For most LT6 applications, the Motorola MBR00 surface mount Schottky diode (0.A, 0V) is an ideal choice. Schottky diodes, with their low forward voltage drop and fast switching speed, are the best match for the LT6. For higher output voltage applications the 0V MBR00 can be used. Many different manufacturers make equivalent parts, but make sure that the component is rated to handle at least 0.A. For LT6- applications, a Philips BAT or Central Semiconductor CMDSH- works well. Lowering Output Voltage Ripple sing low ESR capacitors will help minimize the output ripple voltage, but proper selection of the inductor and the output capacitor also plays a big role. The LT6 provides energy to the load in bursts by ramping up the inductor current, then delivering that current to the load. If too large of an inductor value or too small of a capacitor value is used, the output ripple voltage will increase because the capacitor will be slightly overcharged each burst cycle. To reduce the output ripple, increase the output capacitor value or add a.7pf feed-forward capacitor in the feedback network of the LT6 (see the circuits in the Typical Applications section). Adding this small, inexpensive.7pf capacitor will greatly reduce the output voltage ripple. Table. Recommended Capacitors CAPACITOR TYPE VENDOR Ceramic Taiyo Yuden (08) Ceramic AVX (80) Ceramic Murata (7) sn6 6fas

7 LT6/LT6- TYPICAL APPLICATIO S -Cell to.v Boost Converter -Cell to.v Converter Efficiency.V TO V.7µH.7pF M LT6.7µF 60k : TAIYO YDEN LMK6BJ7 (08) 7-0 : TAIYO YDEN JMKBJ6 (08) 7-0 : MRATA LQHCR7M (8) 7- : MOTOROLA MBR00 (800) -7.V 60mA µf 6/- TA0 EFFICIENCY (%) = V =.V 0 00 LOAD CRRENT (ma) 6/- TA0a -Cell Li-Ion to.v SEPIC Converter -Cell to V SEPIC Converter.V TO.V 0µH LT6.7µF C µf L 0µH M 60k.7pF.V 0mA 0µF V TO 6V 0µH C µf LT6.7µF L 0µH M k.7pf V 0mA 0µF : TAIYO YDEN LMK6BJ7 (08) 7-0 : TAIYO YDEN JMK6BJ06 (08) 7-0 C: TAIYO YDEN JMK07BJ0 (08) 7-0, L: MRATA LQH00K (8) 7- : MOTOROLA MBR00 (800) -7 6/- TA07 : TAIYO YDEN LMK6BJ7 (08) 7-0 : TAIYO YDEN JMK6BJ06 (08) 7-0 C: TAIYO YDEN JMK07BJ0 (08) 7-0, L: MRATA LQH00K (8) 7- : MOTOROLA MBR00 (800) -7 6/- TA07 PIN Diode Driver -Cell to.v Boost Converter V TO 6V µh LT6-.7µF 0M 6k V 00µA µf V TO.V µh LT6-.7µF M 60k.7pF.V ma 0µF : TAIYO YDEN EMK6BJ7 (08) 7-0 : TAIYO YDEN GMK6BJ0 (08) 7-0 : MRATA LQH0K (8) 7- : MOTOROLA MBR00 (800) -7 6/- TA09 : TAIYO YDEN LMK6BJ7 (08) 7-0 : TAIYO YDEN JMK6BJ06 (08) 7-0 : MRATA LQH0K (8) 7- : CENTRAL SEMICONDCTOR CMDSH- (6) -0 6/- TA0 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. sn6 6fas 7

8 LT6/LT6- TYPICAL APPLICATIO S ±0V Dual Output Converter with Output Disconnect.V TO V C µf C µf 0µH LT6.7µF D D D.7pF M 0k 0V ma C µf µf 0V ma : TAIYO YDEN LMK6BJ7 (08) 7-0, C, C: TAIYO YDEN TMK6BJ0 (08) 7-0 C: TAIYO YDEN LMKBJ0 (08) 7-0 : MRATA LQH00K (8) 7-, D, D, D: MOTOROLA MBR00 (800) -7 6/- TA0 PACKAGE DESCRIPTIO S Package -Lead Plastic SOT- (Reference LTC DWG # ) (Reference LTC DWG # ).80.0 (.0.8) (NOTE ).0 (.008) DATM A A A (.0.8).0.7 ( ) (NOTE ) L NOTE:. CONTROLLING DIMENSION: MILLIMETERS MILLIMETERS. DIMENSIONS ARE IN (INCHES).09.0 ( ) (NOTE ). DRAWING NOT TO SCALE. DIMENSIONS ARE INCLSIVE OF PLATING. DIMENSIONS ARE EXCLSIVE OF MOLD FLASH AND METAL BRR 6. MOLD FLASH SHALL NOT EXCEED.mm 7. PACKAGE EIAJ REFERENCE IS: SC-7A (EIAJ) FOR ORIGINAL JEDEL MO-9 FOR THIN A A A L SOT- (Original).90. (.0.07).00. ( ).90.0 (.0.0).. (.0.0).90 (.07) REF SOT- (ThinSOT).00 MAX (.09 MAX).0.0 ( ) (.0.0).0.0 REF (.0.09 REF) A PIN ONE.9 (.07) REF..0 (.00.00) (PLCS, NOTE ) S SOT- 00 RELATED PARTS PART NMBER DESCRIPTION COMMENTS LT07 Single-Cell Micropower 600kHz PWM DC/DC Converter.V at 7mA from One Cell, MSOP Package LT6 Burst Mode TM Operation DC/DC with Programmable Current Limit.V Minimum, Precise Control of Peak Current Limit LT7 -Cell Micropower DC/DC with Low-Battery Detector.V at 00mA from Two Cells, 600kHz Fixed Frequency LT60 Single-Cell Micropower DC/DC Converter V at 0mA from V,.7MHz Fixed Frequency LT6.MHz Inverting Switching Regulator in -Lead ThinSOT V at 0mA from V Input, Tiny ThinSOT Package LT6.MHz Switching Regulator in -Lead ThinSOT V at 00mA from.v Input, Tiny ThinSOT Package LT67 Micropower Inverting DC/DC Converter in -Lead ThinSOT V at ma from.v Input, Tiny ThinSOT Package Burst Mode is a trademark of Linear Technology Corporation 8 sn6 6fas 6fa LT/TP 060.K REV A PRINTED IN SA Linear Technology Corporation 60 McCarthy Blvd., Milpitas, CA (08)-900 FAX: (08) LINEAR TECHNOLOGY CORPORATION 998