LT3461ES6#TRPBF

LT3461/LT3461A 1.3MHz/3MHz Step-Up DC/DC Converters with Integrated Schottky in ThinSOT FEATURES DESCRIPTION Integrated Schottky Rectifier nn Fixed Frequency 1.3MHz/3MHz Operation nn High Output Voltage: Up to 38V nn Low V CESAT Switch: 260mV at 250mA nn 12V at 70mA from 5V Input nn 5V at 115mA from 3.3V Input nn Wide Input Range: 2.5V to 16V nn Uses Small Surface Mount Components nn Low Shutdown Current: 15V 80 40 0 6 14 22 30 38 VOUT (V) 3461 F03a Figure 3a. LT3461 Operating Region     V – 0.6 π •Ω  IP = IN exp  –   L L – 1Ω2 – 1Ω2   2   C C 160 VIN = 5V where L is the inductance, r is the resistance of the inductor and C is the output capacitance. Table 3 gives inrush peak currents for some component selections. Table 3. Inrush Peak Current VIN (V) L (µH) C (µF) IP (A) 5 4.7 1 1.1 5 10 1 0.9 Thermal Considerations Significant power dissipation can occur on the LT3461 and LT3461A, 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 LT3461 does not exceed the absolute maximum operating junction temperature of 125°C over the operating ambient temperature range. Generally, for supply voltages below 5V the integrated current limit function provides adequate protection for nonfault conditions. For supply voltages above 5V, Figures 3a and 3b show the recommended operating region of the LT3461 and LT3461A, respectively. These graphs are based on 250mW on-chip dissipation. Improvement of these numbers can be expected if the LT3461 is supplied from a separate low voltage rail. IOUT (mA) 120 VIN = 8V VIN = 12V VIN >15V 80 40 0 6 14 22 30 38 VOUT (V) 3461 F03b Figure 3b. LT3461A Operating Region Switching Frequency The key difference between the LT3461 and LT3461A is the faster switching frequency of the LT3461A. At 3MHz, the LT3461A switches at twice the rate of the LT3461. The higher switching frequency of the LT3461A 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 LT3461. Generally if efficiency and maximum output current are crucial, or a high output voltage is being generated, the LT3461 should be used. If application size and cost are more important, the LT3461A will be the better choice. 3461afa 6 For more information www.linear.com/LT3461 LT3461/LT3461A APPLICATIONS INFORMATION Inductor Selection The inductors used with the LT3461/LT3461A should havea saturation current rating of 0.3A 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 LT3461, an inductor value between 10µH and 47µH, depending upon output voltage, will usually be the best choice for most designs. For the LT3461A, inductor values between 4.7µH and 15µH inductor will suffice for most applications. For best loop stability results, the inductor value selected should provide a ripple current of 70mA or more. For a given VIN and VOUT the inductor value to use with LT3461A is estimated by the formula: L (in microhenries) = D • VIN • VOUT •1sec 1A • 1V VOUT +1V – VIN VOUT +1V Use twice this value for the LT3461. where D = they have a low ESR and maintain capacitance over wide voltage and temperature range. A 2.2µF output capacitor is sufficient for most applications using the LT3461, while a 1µF capacitor is sufficient for most applications using the LT3461A. 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 LT3461/LT3461A. A 1µF capacitor is sufficient for most applications. Phase Lead Capacitor A small value capacitor can be added across resistor R1 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: CPL = 500kΩ •1pF R2 Capacitor Selection Low ESR capacitors should be used at the output to minimize the output voltage ripple. Multilayer ceramic capacitors using X5R/X7R dielectrics are preferred as For an application running 50µA in the feedback divider, capacitor values from 10pF to 22pF work well. TYPICAL APPLICATIONS L1 10µH VIN 5V C1 1µF CONTROL SIGNAL 47k 47nF 1 SW 5 VIN VOUT LT3461A 4 3 SHDN FB GND 2 Input Current and Output Voltage 6 C1, C2: TAIYO YUDEN EMK212BJ105 L1: MURATA LQH32CN100K53 R1 261k R2 30.1k 15pF VOUT 12V 70mA C2 1µF 3461a TA02a CONTROL SIGNAL 5V/DIV IIN 50mV/DIV VOUT 5V/DIV 1ms/DIV 3461 TA02b Figure 4. 5V to 12V with Soft-Start Circuit (LT3461A) 3461afa For more information www.linear.com/LT3461 7 LT3461/LT3461A TYPICAL APPLICATIONS 3.3V to 5V Step-Up Converter Efficiency 80 3.3V to 5V Step-Up Converter (LT3461A) L1 4.7µH 75 1 SW 5 VIN VOUT LT3461A 4 3 SHDN FB GND 2 6 C1 1µF OFF ON R1 45.3k 15pF EFFICIENCY (%) VIN 3.3V VOUT 5V 115mA C2 1µF R2 15k C1, C2: TAIYO YUDEN X7R LMK212BJ105 L1: MURATA LQH32CN4R7M33 OR EQUIVALENT 70 65 3461a TA03a 60 0 30 60 90 LOAD CURRENT (mA) 120 3461a TA03b PACKAGE DESCRIPTION Please refer to http://www.linear.com/product/LT3461#packaging for the most recent package drawings. S6 Package 6-Lead Plastic TSOT-23 (Reference LTC DWG # 05-08-1636) 0.62 MAX 2.90 BSC (NOTE 4) 0.95 REF 1.22 REF 2.80 BSC 1.4 MIN 3.85 MAX 2.62 REF 1.50 – 1.75 (NOTE 4) PIN ONE ID RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR 0.30 – 0.45 6 PLCS (NOTE 3) 0.95 BSC 0.80 – 0.90 0.20 BSC 0.01 – 0.10 1.00 MAX DATUM ‘A’ 0.30 – 0.50 REF 0.09 – 0.20 (NOTE 3) NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DRAWING NOT TO SCALE 3. DIMENSIONS ARE INCLUSIVE OF PLATING 1.90 BSC S6 TSOT-23 0302 4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR 5. MOLD FLASH SHALL NOT EXCEED 0.254mm 6. JEDEC PACKAGE REFERENCE IS MO-193 3461afa 8 For more information www.linear.com/LT3461 LT3461/LT3461A REVISION HISTORY (Revision history begins at Rev B) REV DATE DESCRIPTION A 01/16 Modified inrush current IP equation. PAGE NUMBER 6 3461afa 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. For more information www.linear.com/LT3461 9 LT3461/LT3461A TYPICAL APPLICATION Low Profile (1mm) 3.3V to 15V Step-Up Converter 3.3V to 15V Efficiency 75 L1 10µH 1 SW 5 VIN VOUT LT3461A 4 3 SHDN FB GND 2 70 VOUT 15V 25mA 6 C1 1µF OFF ON 332k 22pF EFFICIENCY (%) VIN 3.3V C2 2.2µF 30.1k C1: TAIYO YUDEN LMK107BJ105KA C2: TAIYO YUDEN EMK316BJ225KD (X5R) L1: MURATA LQH2MCN100K02 65 60 55 3461a TA04a 50 0 5 5V to 36V Step-Up Converter (LT3461) OFF ON 30 3461a TA04b 5V to 36V Efficiency 75 280k VOUT 36V 18mA 22pF C2 0.47µF 50V 10k C1: TAIYO YUDEN X7R LMK212BJ105 C2: MURATA GRM42-6X7R474K50 L1: MURATA LQH32CN470 70 EFFICIENCY (%) C1 1µF 1 SW 6 5 VIN VOUT LT3461 4 3 SHDN FB GND 2 25 80 L1 47µH VIN 5V 10 15 20 LOAD CURRENT (mA) 65 60 55 3461 TA05a 50 0 2 4 6 8 10 12 14 16 18 LOAD CURRENT (mA) 3.3V to ±5V Dual Output Converter C3 1µF L1 4.7µH VIN 3.3V 1 SW 5 VIN VOUT LT3461A 4 3 SHDN FB GND 2 3461 TA05b VOUT 5V 100mA 6 C1 1µF OFF ON 45.3k 15pF C2 1µF 15k D1 C1, C2, C3, C4: TAIYO YUDEN JMK107BJ105 D1, D2: PHILIPS PMEG2005EB L1: MURATA LQH2MCN4R7M02 D2 C4 1µF 10Ω –5V 15mA 3461 TA06 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1615/LT1615-1 300mA/80mA (ISW) Constant Off-Time, High Efficiency Step-Up DC/DC Converter VIN: 1.2V to 15V, VOUT(MAX) = 34V, IQ = 20µA, ISD