V OUT 12V 300mA 1930 F01

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Abraham Briggs
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1 FEATRES 1.MHz Switching Frequency High Output Voltage: p to V Wide Input Range:.6V to 16V Low V CESAT Switch: mv at 1A ses Small Surface Mount Components 5V at 8mA from.v Input 1V at ma from 5V Input Low Shutdown Current: <1µA 5-Lead SOT- Package Pin-for-Pin Compatible with the LT161 APPLICATIO S Digital Cameras Cordless Phones Battery Backup LCD Bias Medical Diagnostic Equipment Local 5V or 1V Supply External Modems PC Cards xdsl Power Supply DESCRIPTIO LT19 1.MHz Boost DC/DC Converter in SOT- Final Electrical Specifications June The LT 19 is the industry s highest power SOT- switching regulator. Its internal 1A, 6V switch allows high current outputs to be generated in a small footprint. Intended for space-conscious applications, the LT19 switches at 1.MHz, allowing the use of tiny, low cost capacitors and inductors mm or less in height. Multiple output power supplies can now use a separate regulator for each output voltage, replacing cumbersome quasiregulated approaches using a single regulator and custom transformers. A constant frequency, internally compensated, current mode PWM architecture results in low, predictable output noise that is easy to filter. Low ESR ceramic capacitors can be used on the output, further reducing noise to the millivolt level. The high voltage switch on the LT19 is rated at 6V, making the device ideal for boost converters up to V as well as for single-ended primary inductance converter (SEPIC) and flyback designs. The device can generate 5V at up to 8mA from a.v supply or 5V at ma from four alkaline cells in a SEPIC design. The LT19 is available in the 5-lead SOT- package., LTC and LT are registered trademarks of Linear Technology Corporation. TYPICAL APPLICATIO Efficiency 5V.µF 1µH LT19 : TAIYO-YDEN X5R LMK1BJ5MG C: TAIYO-YDEN X5R EMK16BJ75ML : ON SEMICONDCTOR MBR5 : SMIDA CR-1 *OPTIONAL 11k R 1.k C* 1pF C.7µF 19 F1 Figure 1. 5V to 1V, ma Step-p DC/DC Converter 1V ma EFFICIENCY (%) = 5V =.V 1 LOAD CRRENT (ma) 19 TA1 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. 1

2 LT19 ABSOLTE AXI RATI GS (Note 1) W W W Voltage... 16V Voltage....V to 6V Voltage....5V Current Into Pin... ±1mA Voltage... 1V Maximum Junction Temperature C Operating Temperature Range (Note ).. C to 85 C Storage Temperature Range C to 15 C Lead Temperature (Soldering, 1 sec)... C W PACKAGE/ORDER I FOR ATIO 1 TOP VIEW 5 S5 PACKAGE 5-LEAD PLASTIC SOT- T JMAX = 15 C, θ JA = 56 C/ W Consult factory for Industrial and Military grade parts. ORDER PART NMBER LT19ES5 S5 PART MARKING LTKS ELECTRICAL CHARACTERISTICS The denotes specifications which apply over the full operating temperature range, otherwise specifications are T A = 5 C. = V, V = unless otherwise noted. (Note ) PARAMETER CONDITIONS MIN TYP MAX NITS Minimum Operating Voltage.5.6 V Maximum Operating Voltage 16 V Feedback Voltage V V Pin Bias Current 1 6 na Quiescent Current V =.V, Not Switching. 6 ma Quiescent Current in Shutdown V = V, = V.1 1 µa Reference Line Regulation.6V 16V.1.5 %/V Switching Frequency MHz.8.6 MHz Maximum Duty Cycle 8 9 % Switch Current Limit (Note ) 1 1. A Switch V CESAT I = 9mA 5 5 mv Switch Leakage Current V = 5V.1 1 µa Input Voltage High. V Input Voltage Low.5 V Pin Bias Current V = V 16 µa V = V.1.1 µa Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note : The LT19ES5 is guaranteed to meet performance specifications from C to 7 C. Specifications over the C to 85 C operating temperature range are assured by design, characterization and correlation with statistical process controls. Note : Current limit guaranteed by design and/or correlation to static test.

3 LT19 TYPICAL PERFOR A CE CHARACTERISTICS W QIESCENT CRRENT (ma) Quiescent Current V = 1.V NOT ITCHING =.V = 5V FEEDBACK VOLTAGE (V) Feedback Pin Voltage SHTDOWN PIN CRRENT (µa) Shutdown Pin Current 5 T A = 5 C T A = 1 C TEMPERATRE (C) TEMPERATRE ( C) SHTDOWN PIN VOLTAGE (V) 6 19 G1 19 G 19 G CRRENT LI MIT (A) Current Limit Switch Saturation Voltage Oscillator Frequency V CESAT (V) FREQENCY (MHz) DTY CYCLE (%) ITCH CRRENT (A) TEMPERATRE ( C) 19 G 19 G5 19 G6 PI F CTIO S (Pin 1): Switch Pin. Connect inductor/diode here. Minimize trace area at this pin to reduce EMI. (Pin ): Ground. Tie directly to local ground plane. (Pin ): Feedback Pin. Reference voltage is 1.55V. Connect resistive divider tap here. Minimize trace area at. Set according to = 1.55V(1 /R). (Pin ): Shutdown Pin. Tie to.v or more to enable device. Ground to shut down. (Pin 5): Input Supply Pin. Must be locally bypassed.

4 LT19 BLOCK DIAGRA W V REFERENCE (EXTERNAL) R (EXTERNAL) A1 R C C C Σ RAMP GENERATOR COMPARATOR A R S Q DRIVER 1 Q1.1Ω SHTDOWN 1.MHz OSCILLATOR 199 BD Figure. Block Diagram OPERATIO The LT19 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, turning on the power switch Q1. 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 error amplifier A1, and is simply an amplified version of the difference between the feedback voltage and the reference voltage of 1.55V. In this manner, 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. One function present in the LT19 but not shown in Figure is current limit. The switch current is constantly monitored and not allowed to exceed the nominal value of 1A. If the switch current reaches 1A, the SR latch is reset regardless of the state of comparator A. This current limit protects the power switch as well as the external components connected to the LT19. APPLICATIONS INFORMATION Inductor Selection W Several inductors that work well with the LT19 are listed in Table 1, 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, as many different sizes and shapes are available. Ferrite core inductors should be used to obtain the best efficiency, as core losses at 1.MHz are much lower for ferrite cores than for the cheaper powdered-iron cores. Choose an inductor that can handle at least 1A without saturating, and ensure that the inductor has a low DCR (copper wire resistance) to minimize I R power losses. A.7µH or 1µH inductor will be the best choice for most LT19 designs. Note that in some applications, the current handling requirements of the inductor can be lower, such as in the SEPIC topology where each inductor only carries one-half of the total switch current.

5 LT19 APPLICATIONS INFORMATION Table 1. Recommended Inductors W MAX L DCR HEIGHT PART (µh) mω (mm) VENDOR CDRH Sumida CDRH (87) CR-R CR DS Coilcraft DS (87) D5LC-R7M.7 8. Toko D5LC-1M (8) Capacitor Selection Low ESR (equivalent series resistance) capacitors should be used at the output to minimize the output ripple voltage. Multilayer ceramic capacitors are an excellent choice, as they have extremely low ESR and are available in very small packages. X5R dielectrics are preferred, followed by X7R, as these materials retain the capacitance over wide voltage and temperature ranges. A.7µF to 1µF output capacitor is sufficient for most applications, but systems with very low output current may need only a 1µF or.µf output capacitor. Solid tantalum 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, and should be placed as close as possible to the LT19. A 1µF to.7µf input capacitor is sufficient for most applications. Table shows a list of several ceramic capacitor manufacturers. Consult the manufacturers for detailed information on their entire selection of ceramic parts. Table. Ceramic Capacitor Manufacturers Taiyo-Yuden (8) AVX (8) Murata (71) The decision to use either low ESR (ceramic) capacitors or the higher ESR (tantalum or OS-CON) capacitors can affect the stability of the overall system. The ESR of any capacitor, along with the capacitance itself, contributes a zero to the system. For the tantalum and OS-CON capacitors, this zero is located at a lower frequency due to the higher value of the ESR, while the zero of a ceramic capacitor is at a much higher frequency and can generally be ignored. A phase lead zero can be intentionally introduced by placing a capacitor (C) in parallel with the resistor () between and V as shown in Figure 1. The frequency of the zero is determined by the following equation. ƒ = Z 1 π C By choosing the appropriate values for the resistor and capacitor, the zero frequency can be designed to slightly improve the phase margin of the overall converter. The typical target value for the zero frequency is between 5kHz to 15kHz. Figure shows the transient response of the step-up converter from Figure 1 without the phase lead capacitor C. The phase margin is reduced as evidenced by more ringing in both the output voltage and inductor current. A 1pF capacitor for C results in better phase margin, which is revealed in Figure as a more damped response and less overshoot. Figure 5 shows the transient response when a µf tantalum capacitor with no phase lead capacitor is used on the output. The higher output voltage ripple is revealed in the upper waveform as a set of double lines. The transient response is not greatly improved which implies that the ESR zero frequency is too high to increase the phase margin..v/div AC COPLED I LI.5A/DIV AC COPLED LOAD 5mA CRRENT 15mA 5µs/DIV 19 F Figure. Transient Response of Step-p Converter Without Phase Lead Capacitor 5

6 LT19 APPLICATIONS INFORMATION.V/DIV AC COPLED I LI.5A/DIV AC COPLED LOAD 5mA CRRENT 15mA W 5µs/DIV 19 F Layout Hints The high speed operation of the LT19 demands careful attention to board layout. You will not get advertised performance with careless layout. Figure 6 shows the recommended component placement. Make the ground pin copper area large. This helps to lower the die temperature. Figure. Transient Response of Step-p Converter with 1pF Phase Lead Capacitor.V/DIV AC COPLED I LI.5A/DIV AC COPLED C R SHTDOWN LOAD 5mA CRRENT 15mA µs/div 19 F C 19 F6 Figure 5. Transient Response of Step-p Converter with µf Tantalum Output Capacitor and No Phase Lead Capacitor Diode Selection A Schottky diode is recommended for use with the LT19. The ON Semiconductor MBR5 is a very good choice. Where the input to output voltage differential exceeds V, use the MBR5 (a V diode). These diodes are rated to handle an average forward current of.5a. In applications where the average forward current of the diode exceeds.5a, a Microsemi PS5817 rated at 1A is recommended. Setting Output Voltage To set the output voltage, select the values of and R (see Figure 1) according to the following equation: VOT = R V A good value for R is 1.k which sets the current in the resistor divider chain to 1.55V/1.k = 9.µA. Figure 6. Suggested Layout Driving Above 1V The maximum voltage allowed on the pin is 1V. If you wish to use a higher voltage, you must place a resistor in series with. A good value is 11k. Figure 7 shows a circuit where = 16V and is obtained from. The voltage on the pin is kept below 1V. 16V 11k LT19 R Figure 7. Keeping Below 1V C 19 F7 6

7 LT19 TYPICAL APPLICATIO S -CELL BATTERY V TO 6.5V.µF -Cell to 5V SEPIC Converter 1µH LT19 C 1µF k 8.5k L 1µH : TAIYO-YDEN X5R LMK1BJ5MG C: TAIYO-YDEN X5R JMK16BJ16ML : ON SEMICONDCTOR MBR5 C: TAIYO-YDEN X5R LMK1BJ15MG : MRATA LQHK 5V ma C 1µF 19 TAa EFFICIENCY (%) Efficiency = 6.5V = V 1 5 LOAD CRRENT (ma) 19 TAb -Cell to 5V SEPIC Converter with Coupled Inductors -CELL BATTERY V TO 6.5V.µF 1µH LT19 C 1µF k 8.5k L 1µH 5V ma C 1µF : TAIYO-YDEN X5R LMK1BJ5MG C: TAIYO-YDEN X5R JMK16BJ16ML C: TAIYO-YDEN X5R LMK1BJ15MG : ON SEMICONDCTOR MBR5, L: SMIDA CLS TA PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted..6. (.1.118) (.59.69) S5 Package 5-Lead Plastic SOT- (LTC DWG # )..15 (..6) (.5.57).8. ( ) (NOTE ).5.55 (.1.).9. (..8) (NOTE ) NOTE: 1. DIMENSIONS ARE IN MILLIMETERS. DIMENSIONS ARE INCLSIVE OF PLATING. DIMENSIONS ARE EXCLSIVE OF MOLD FLASH AND METAL BRR. MOLD FLASH SHALL NOT EXCEED.5mm 5. PACKAGE EIAJ REFERENCE IS SC-7A (EIAJ).5.5 (.1.) FIVE PLACES (NOTE ).9 1. (.5.51) 1.9 (.7) REF.95 (.7) REF S5 SOT

8 LT19 TYPICAL APPLICATIO S 5V to 8V Boost Converter 5V.7µF 1µH LT M 8V 1mA C.µF R 75k : TAIYO-YDEN X5R EMK16BJ75ML C: TAIYO-YDEN X5R GMK5BJ5MN : ON SEMICONDCTOR MBR5 : SMIDA CR-1 19 TA Boost Converter with Reverse Battery Protection V to 6V M1.µF.7µH LT19 6.k R 11.k C 7pF 8V 5mA AT = 6V ma AT = V C µf : TAIYO-YDEN X5R LMKBJ6MM C: TAIYO-YDEN X5R LMK1BJ5MG : ON SEMICONDCTOR MBR5 : SMIDA CR-R7 M1: SILICONIX Si6DQ 19 TA5 RELATED PARTS PART NMBER DESCRIPTION COMMENTS LT17 Single Cell Micropower 6kHz PWM DC/DC Converter.V at 75mA from Single Cell, MSOP Package LT116 Burst Mode TM Operation DC/DC Converter with Programmable Current Limit 1.5V Minimum, Precise Control of Peak Current Limit LT117 -Cell Micropower DC/DC Converter with Low-Battery Detector.V at ma from Cells, 6kHz Fixed Frequency LT161 Single Cell Micropower DC/DC Converter V at ma from 1V, 1.7MHz Fixed Frequency LT1611 Inverting 1.MHz Switching Regulator in 5-Lead SOT- 5V at 15mA from 5V Input, Tiny SOT- Package LT161 1.MHz Switching Regulator in 5-Lead SOT- 5V at ma from.v Input, Tiny SOT- Package LT1615 Micropower Constant Off-Time DC/DC Converter in 5-Lead SOT- V at 1mA from.5v, Tiny SOT- Package LT1617 Micropower Inverting DC/DC Converter in 5-Lead SOT- 15V at 1mA from.5v Input, Tiny SOT- Package LTC 16 High Efficiency, N-Channel Switching Regulator Controller 95% DC,.5V to 6V Range, SO-8 Burst Mode is a trademark of Linear Technology Corporation. 8 Linear Technology Corporation 16 McCarthy Blvd., Milpitas, CA (8) -19 FAX: (8) is, sn19 LT/TP 6 K PRINTED IN SA LINEAR TECHNOLOGY CORPORATION

FEATURES. LT1612 Synchronous, Step-Down 800kHz PWM DC/DC Converter DESCRIPTIO APPLICATIO S TYPICAL APPLICATION

FEATURES. LT1612 Synchronous, Step-Down 800kHz PWM DC/DC Converter DESCRIPTIO APPLICATIO S TYPICAL APPLICATION Synchronous, Step-Down 8kHz PWM DC/DC Converter FEATRES Operates from Input Voltage As Low As 2V Internal.7A Synchronous Switches ses Ceramic Input and Output Capacitors 62mV Reference Voltage 8kHz Fixed