SC1408IMS.TR

Low Voltage, Boost DC-DC Controller POWER MANAGEMENT Description The SC1408 is a low voltage boost controller that operates from a 1.8V to 16.5V input range. The SC1408 was designed for two cell Alkaline or single cell Lithium Ion battery applications. With the proper external components it can be used as a boost converter or a buck/boost converter. A Shutdown pin allows the user to turn the controller off, reducing supply current to less than 2µA typical. Output voltage can be preset to 5V or is adjustable from 3V to 16.5V with a resistor divider. The controller changes frequency in light load conditions to improve efficiency. SC1408 Features 1.8V to 16.5V input range Preset (5V) or adjustable output Ground referenced current limit On chip precision reference Up to 300kHz switching frequency 10µA max shutdown current Industrial temperature range SO-8 and MSOP-8 packages. Lead free packages available are fully WEEE and RoHS compliant Applications PDA Power supplies Battery powered applications Positive LCD Bias generator Portable communications (cellular phones) Peripheral card supplies Industrial power supplies Typical Application Circuit Vin (1.8V to 16.5V) L1 D1 Vout (3V to 16.5V) U1 2 4 + C1 5 7 BST GATE Q1 1 8 3 6 R2 R3 SHDN ISENSE REF GND FB AGND + C2 R4 C3 SC1408 Revision: November 23, 2005 1 www.semtech.com SC1408 POWER MANAGEMENT Absolute Maximum Ratings Exceeding the specifications below may result in permanent damage to the device, or device malfunction. Operation outside of the parameters specified in the Electrical Characteristics section is not implied. Exposure to Absolute Maximum rated conditions for extended periods of time may affect device reliability. Parameter Input Voltage Small Si gnal Ground to Power Ground GATE to GND FB, SHD N, REF, ISENSE to GND Operati ng Temperature Juncti on Temperature Range Storage Temperature Range Lead Temperature (Solderi ng) 10 Sec. Thermal Resi stance, Juncti on to Ambi ent SO-8 MSOP-8 Thermal Resi stance, Juncti on to C ase SO-8 MSOP-8 Symbol BST to GND GND to AGND Maximum -0.3 to 18 +0.1 -0.3 to VBST +0.3 or 5 -0.3 to mi n. of VBST +0.3 or 5 U nits V V V V °C °C °C °C °C /W TA TJ TSTG TL θJ A -40 to +85 -40 to +150 -65 to +160 +300 128 216 50 70 θJ C °C /W Electrical Characteristics Unless specified: VOUT = 5V; ILOAD = 0mA; TA = +25°C Parameter Input Voltage Sym VIN Conditions TA = 25oC TA = -40oC to +85oC Min 1.8 1.8 Typ Max 16.5 16.5 Units V V µA Supply Current VOUT=16.5V,SHDN < 0.4V VOUT=10V, 1.6V < SHDN < 5V TA = -40oC to +85oC TA = -40oC to +85oC TA = -40oC to +85oC 4,800 110 2 5.0 60 7 140 10 5.200 Output Voltage Load Regulation Line Regulation Minimum Start Up Voltage Minimum Switch On Time Minimum Switch Off Time Efficiency Reference Voltage Reference Load Regulation Reference Line Regulation  2005 Semtech Corp. VOUT VIN = 2.0V to 5.0V V mV/A mV/V VIN = 2.0V, VOUT = 5V, ILOAD = 0mA to 500mA VIN = 2.7V to 4.0V, VOUT = 5V, ILOAD = 500mA No load tON(Max) tOFF(Min) VIN = 4V, VOUT = 5V, ILOAD = 0mA to 500mA VREF IREF =0µA TA = -40oC to +85oC 1.176 9.6 1.4 1.8 16 2.3 87 1.200 -4 40 1.224 10 100 22.4 3.2 V µs µs % V mV µV/V 0µA < IREF < 100µA 5V < VOUT < 16.5V 2 www.semtech.com SC1408 POWER MANAGEMENT Electrical Characteristics (Cont.) Unless specified: VOUT = 5V; ILOAD = 0mA; TA = +25°C Parameter FB Trip Point Voltage FB Input Current SHDN Input High Voltage SHDN Input Low Voltage SHDN Input Current Current Limit Trip Level ISENSE Input Current GATE Rise Time GATE Fall Time GATE On Resistance Sym VFB IFM VIN VIL Conditions TA = 25oC TA = -40oC to +85oC TA = 25oC TA = -40oC to +85oC VOUT = 2.7V to 16.5V VOUT = 2.7V to 16.5V VOUT = 16.5V, SHDN = 0V or 5V Min 1.176 Typ 1.200 Max 1.224 Units V nA -4 ±40 1.6 0.4 ±1 85 80 100 0.01 115 120 ±1 V V µA mV µA ns VCS VOUT = 3V to 16.5V TA = 25oC TA = -40oC to +85oC VOUT = 5V, InF from GATE to GND VOUT = 5V, InF from GATE to GND GATE = high or low 50 50 15 30 Ω NOTE: (1) This device is ESD sensitive. Use of standard ESD handling precautions is required.  2005 Semtech Corp. 3 www.semtech.com SC1408 POWER MANAGEMENT Pin Configuration TOP VIEW GATE BST FB SHDN 1 2 3 4 8 7 6 5 ISENSE GND AGND REF Ordering Information Part Number SC1408IS.TR SC1408ISTRT(2) SC1408IMS.TR SC1408IMSTRT(2) MSOP-8(3) SO-8 -40° to +85°C P ackag e (1) Temp Range (TA) (SO-8/MSOP-8) Pin Descriptions Pin # 1 2 3 4 5 6 7 8 Pin Name GATE BST FB SHDN REF AGND GND ISENSE Gate drive output. Supply voltage. Voltage feedback Notes: (1) Only available in tape and reel packaging. A reel contains 2500 devices. (2) Lead free product. This product is fully WEEE and RoHS compliant. (3) Contact factory for MSOP availability Pin Function Logic high shuts down the converter. Reference output pin. Small signal analog and digital ground. Power ground. Current sense pin. Block Diagram REF FB MODE DETECT ERROR COMP 1.20V REFERENCE + VDD + - 50mV BIAS SHDN MIN OFF TIME ONE SHOT START UP COMP Q TRIG 2.3uS + 2.5V BST S TRIG Q 16uS MAX ON TIME ONE SHOT Q R GATE GND LOW VOLTAGE OSCILLATOR CURRENT SENSE AMP + 0.1V ISENSE AGND  2005 Semtech Corp. 4 www.semtech.com SC1408 POWER MANAGEMENT Applications Information Theory of Operation The SC1408 is a modified hysteretic boost converter controller. The power switch is turned on when the output voltage falls slightly below it’s setpoint. It remains on for approximately 16µs, or until the inductor current reaches limit, whichever occurs first. The power switch is then turned off for 2.3 µs, or until the output voltage once again falls below setpoint, whichever occurs last. The SC1408 is normally powered from the output voltage. Internal circuitry, such as the bandgap, comparators and one shots, will not function properly until the BST pin voltage reaches 2.5V. To ensure start-up at low input voltages, the normal control circuitry is disabled and a special, low voltage start up oscillator generates an approximate square wave at the GATE pin, initiating boost action. When the output voltage reaches 2.5V, the normal control circuitry is enabled and the start up oscillator shuts down. To conserve power, a SHDN pin is provided which, when pulled high, shuts down most internal circuitry. The output voltage will then be 1 diode drop below the input. COMPONENT SELECTION Boost Converter RSENSE The value of the sense resistor is the primary determining factor for maximum output current. The SC1408 has a fixed current limit voltage threshold, which is developed by the peak inductor current flowing through RSENSE. RSENSE may be determined either from the maximum output current curves or from the equation below: IO (MAX ) = − V + VF − VIN VCS  1 − O  VO + VF − VFET R SENSE      The bottom resistor in the divider chain (R4 in the typical application circuits) should be 300kΩ or less and the top resistor (R3 in the application circuits) can be calculated from  V R 3 = R 4  O − 1  V   REF Inductor The SC1408 will work with a wide range of inductor values. A good choice for most applications is 22µH. Smaller inductor values result in higher peak currents and increase output ripple, while larger values will result in slower loop response. Transistor selection Normally the power switch will be an N-channel MOSFET, although in certain circumstances an NPN bipolar may be substituted. The choice of FET can be critical, especially in battery powered applications where the converter must be able to use all of the available energy in the battery. This requires that the converter be capable of starting up from very low input voltages. For example a two cell alkaline system’s terminal voltage will drop to 1.8V as it approaches full discharge. For these demanding applications, a FET with low VGS(th) is required. A good rule of thumb is that VGS(th) should be at least 0.5V less than the minimum input voltage. Diode For most applications, a Schottky diode should be used as the output rectifier. It will be subjected to reverse voltages of at least VO , and average current will be somewhat less than the Inductor peak current. Industry standard 1N5817 series or an equivalent surface mount part would be suitable. Output Capacitors Output capacitors should be low ESR to minimize ripple voltage and maximize efficiency. Low ESR tantalum or OSCON capacitors should be used. Ripple voltage will be approximately: Input Capacitors Input capacitors on a boost converter are less critical than the output capacitors, since there are no fast current pulses drawn from the input supply. A 100µF tantalum will be adequate for most applications. www.semtech.com t off  (VIN − VFET )(VO + VF − VIN )     2L  VO + VF − VFET   Where : VF = Output Diode Forward Voltage Drop VFET = Voltage across FET, RSENSE and Inductor DCR In the equation above, the use of 2.3∝s for toff may lead to slightly optimistic current values for low VO/VIN ratios. The theoretical curves use the actual value of toff, VF=0.5V, VFET=0.3V and VCS=0.08V and are generated for L=22µH. Output Voltage Output voltage can be set to 5V by connecting the FB pin to GND, or to any voltage in the 3.0V to 16.5V range using external divider resistors.  2005 Semtech Corp. 5 SC1408 POWER MANAGEMENT Applications Information (Cont.) COMPONENT SELECTION SEPIC Converter RSENSE Again, with the SEPIC topology, the value of the sense resistor is the primary determining factor for maximum output current. The simplest approach to select RSENSE is to add Vin to Vo and use this value as the output voltage in the output current curves or in the equation for Boost converter. Output Voltage Output voltage setting works exactly the same in SEPIC topology as in Boost, including the ability to set to 5V by connecting the FB pin to GND. Care must be taken to ensure that the IC supply (pin2; BST) does not exceed its 16.5V rating. In the circuit of Fig.2: This requires maximum output voltage to be limited to 16.5V-Vin. Higher output voltages are possible with different IC supply strategies. Inductor The SEPIC topology requires a coupled inductor. Again A good choice for most applications is 22µH. Smaller inductor values result in higher peak currents and increase output ripple, while larger values will result in slower loop response. Transistor selection The choice of FET can be critical, especially in battery powered applications where the converter must be able to use all of the available energy in the battery. This requires that the converter be capable of starting up from very low input voltages. For example a two cell alkaline system’s terminal voltage will drop to 1.8V as it approaches full discharge. For these demanding applications, a FET with low VGS(th) is required. A good rule of thumb is that VGS(th) should be at least 0.5V less than the minimum input voltage. Diode For most applications, a Schottky diode should be used as the output rectifier. It will be subjected to reverse voltages of at least VO +VIN and average current will be somewhat less than the Inductor peak current. Industry standard 1N5817 series or an equivalent surface mount part would be suitable. Output Capacitors Output capacitors should be low ESR to minimize ripple voltage and maximize efficiency. Low ESR tantalums, OSCONs or the newer Polymer capacitors should be used. Input Capacitors Input capacitors on a SEPIC converter are less critical than the output capacitors, since there are no fast current pulses drawn from the input supply. A 100µF tantalum will be adequate for most applications. Series Capacitors The Series capacitor(s) must be capable of handling an RMS current given by:IRMS = IO VO + 0 .5 VIN  2005 Semtech Corp. 6 www.semtech.com SC1408 POWER MANAGEMENT Typical Characteristics Figs.5 - 8: Maximum output current vs. input voltage and sense resistor value. (Boost Mode) 3.5 3.0 2.5 Io (A) 2.0 1.5 1.0 0.5 0.0 2.0 3.5 3.0 2.5 Io (A) 2.0 1.5 1.0 0.5 0.0 2.0 4.0 6.0 Vin (V) 8.0 10.0 12.0 35mOhm 50mOhm 100mOhm Vo=3.3V L=22uH 3.5 Vo=5V L=22uH 20mOhm 25mOhm Io (A) 3.0 2.5 2.0 1.5 1.0 0.5 0.0 20mOhm 25mOhm 35mOhm 50mOhm 100mOhm 2.2 2.4 2.6 Vin (V) 2.8 3.0 3.2 35mOhm 50mOhm 100mOhm 2.0 2.5 3.0 3.5 Vin (V) 4.0 4.5 5.0 Vo=12V L=22uH 20mOhm 25mOhm Io (A) 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 2.0 Vo=15V L=22uH 20mOhm 25mOhm 35mOhm 50mOhm 100mOhm 4.0 6.0 8.0 10.0 Vin (V) 12.0 14.0 16.0 Figs.9-11:Efficiency in the Boost Application circuit of Fig.1 100% Vo=5V 100% Vo=12V 90% 90% Efficiency (%) Efficiency (%) 80% Vin=5.0V Vin=4.0V Vin=3.3V Vin=3.0V 80% 70% 70% Vin=5.0V Vin=3.0V Vin=1.8V 60% 1 10 Io (mA) 100 1000 60% 1 10 Io (mA) 100 1000 100% Vo=15V 90% Efficiency (%) 80% Vin=12V Vin=9.0V Vin=5.0V Vin=3.0V Vin=1.8V 70% 60% 1 10 Io (mA) 100 1000  2005 Semtech Corp. 7 www.semtech.com SC1408 POWER MANAGEMENT Typical Characteristics Output Ripple Voltage; Vin=3V, Vo=5V, Io=470mA Ch1 = Output Ripple Ch2 = Voltage at GATE pin Output Ripple Voltage; Vin=3V, Vo=5V, Io=810mA Ch1 = Output Ripple Ch2 = Voltage at GATE pin Load Transient; Vin=3V, Vo=5V, Io=0 to 500mA Ch1 = Output Voltage Ch2 = Load Current (0.5A/div) Load Transient; Vin=2V, Vo=5V, Io=0 to 500mA Ch1 = Output Voltage Ch2 = Load Current (0.5A/div)  2005 Semtech Corp. 8 www.semtech.com SC1408 POWER MANAGEMENT Typical Application Circuit (Cont.) Fig.1: Typical Application - Boost Configuration 1.8V-16.5V IN L1 22uH D1 B130T R3 See Table Vin to 16.5V OUT Coilcraft DO3316P-223 U1 2 C2 100uF + 4 5 7 BST GATE EN ISENSE REF FB 1 8 3 6 Q1 IRLR024N C9 See Text + C8 100uF + R2 0.1Ohm R4 10.0k C3 100uF GND AGND SC1408CS C5 0.1uF Fig.2: Typical Application - Buck/Boost (SEPIC) Configuration D2 1N4148 1.8V TO 5V IN 2 L1A 22uH 1 C1 + 100uF D1 B130T 0V TO (16.5V-Vin) OUT U1 2 C2 100uF + C4 0.1uF C5 0.1uF 4 5 7 BST GATE EN ISENSE REF FB 1 8 3 6 Q1 IRLL3303 R3 See Table C9 See Text + C8 100uF + R2 0.1Ohm 4 L1B 22uH R4 10.0k C3 100uF GND AGND SC1408CS 3 L1A/L1B IS COUPLED INDUCTOR PULSE PE-53718 OR EQUIVALENT  2005 Semtech Corp. 9 www.semtech.com SC1408 POWER MANAGEMENT Typical Application Circuit (Cont.) Fig.3: Achieving output voltages greater than 16.5V D4 1N4148 3.3V IN R6 470 L1 22uH D1 B130T 25V OUT U1 2 C4 0.1uF 4 5 7 BST GATE EN ISENSE REF FB 1 8 3 6 Q1 IRL3103S R3 200k + C8 100uF C2 100uF + + R2 0.05Ohm R4 10.0k C3 100uF GND AGND SC1408CS D3 12V C5 0.1uF Fig.4: Implementing shutdown with input/output isolation 3.3V IN R5 5.1k Q2 Si2301DS L1 22uH D1 B130T 12V OUT 2 C4 0.1uF 4 5 7 U1 BST GATE EN ISENSE REF FB 1 8 3 6 Q1 IRLL3303 R3 90k + C8 100uF SHORT = RUN OPEN = SHUTDOWN J1 1 2 C2 100uF + + R2 0.05Ohm R4 10.0k C3 100uF GND AGND SC1408CS C5 0.1uF  2005 Semtech Corp. 10 www.semtech.com SC1408 POWER MANAGEMENT Outline Drawing - SO-8 A N 2X E/2 E1 E 1 ccc C 2X N/2 TIPS 2 e/2 B D aaa C SEATING PLANE A2 A C bxN bbb A1 C A-B D GAGE PLANE 0.25 SEE DETAIL SIDE VIEW NOTES: 1. 2. 3. 4. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). DATUMS -A- AND -B- TO BE DETERMINED AT DATUM PLANE -HDIMENSIONS "E1" AND "D" DO NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. REFERENCE JEDEC STD MS-012, VARIATION AA. e D DIM A A1 A2 b c D E1 E e h L L1 N 01 aaa bbb ccc DIMENSIONS MILLIMETERS INCHES MIN NOM MAX MIN NOM MAX .069 .053 .010 .004 .065 .049 .020 .012 .010 .007 .189 .193 .197 .150 .154 .157 .236 BSC .050 BSC .010 .020 .016 .028 .041 (.041) 8 0° 8° .004 .010 .008 1.75 1.35 0.25 0.10 1.65 1.25 0.31 0.51 0.17 0.25 4.80 4.90 5.00 3.80 3.90 4.00 6.00 BSC 1.27 BSC 0.25 0.50 0.40 0.72 1.04 (1.04) 8 8° 0° 0.10 0.25 0.20 h h H c A L (L1) DETAIL 01 A Minimum Land Pattern - SO-8 X DIM (C) G Z C G P X Y Z DIMENSIONS INCHES MILLIMETERS (.205) .118 .050 .024 .087 .291 (5.20) 3.00 1.27 0.60 2.20 7.40 Y P NOTES: 1. THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET. 2. REFERENCE IPC-SM-782A, RLP NO. 300A.  2005 Semtech Corp. 11 www.semtech.com SC1408 POWER MANAGEMENT Outline Drawing - MSOP-8 e/2 A N 2X E/2 PIN 1 INDICATOR ccc C 2X N/2 TIPS 12 e B E1 E D DIM A A1 A2 b c D E1 E e L L1 N 01 aaa bbb ccc DIMENSIONS INCHES MILLIMETERS MIN NOM MAX MIN NOM MAX .043 .000 .006 .030 .037 .009 .015 .003 .009 .114 .118 .122 .114 .118 .122 .193 BSC .026 BSC .016 .024 .032 (.037) 8 0° 8° .004 .005 .010 1.10 0.00 0.15 0.75 0.95 0.38 0.22 0.08 0.23 2.90 3.00 3.10 2.90 3.00 3.10 4.90 BSC 0.65 BSC 0.40 0.60 0.80 (.95) 8 0° 8° 0.10 0.13 0.25 aaa C SEATING PLANE D A2 A GAGE PLANE 0.25 H c C A1 bxN bbb C A-B D L (L1) DETAIL 01 A SIDE VIEW NOTES: 1. SEE DETAIL A CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). -B- TO BE DETERMINED AT DATUM PLANE -H- 2. DATUMS -A- AND 3. DIMENSIONS "E1" AND "D" DO NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. 4. REFERENCE JEDEC STD MO-187, VARIATION AA. Land Pattern - MSOP-8 X DIM (C) G Z C G P X Y Z DIMENSIONS INCHES MILLIMETERS (.161) .098 .026 .016 .063 .224 (4.10) 2.50 0.65 0.40 1.60 5.70 Y P NOTES: 1. THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET. Contact Information Semtech Corporation Power Management Products Division 200 Flynn Road, Camarillo, CA 93012 Phone: (805)498-2111 FAX (805)498-3804  2005 Semtech Corp. 12 www.semtech.com