SEMTECH SC2603

SC2603 Simple PWM Boost Controller POWER MANAGEMENT Description Features The SC2603 is a versatile, low-cost, voltage-mode PWM u Low cost / small size controller designed for 16V input DC/DC power supply u Switch mode efficiency up to 95% applications. A simple, fixed-voltage boost regulator can u 1% reference voltage accuracy be implemented using the SC2603 with a minimum of u Over-current protection external components. The small device footprint u 800mA output drive allows for compact circuit design. u 5V to 16V input power source u No need for external compensation network SC2603 features include a temperature compensated u SOT23-6 is fully WEEE and RoHS compliant voltage reference, triangle wave oscillator, current limit comparator, frequency shift over-current protection, and Applications an internally compensated error amplifier. Pulse by pulse current limiting is implemented by sensing the u Portable Devices differential voltage across an external resistor, or an u Flat Panel TV appropriately sized PC board trace. u TV Set Top Box u Auxiliary Supplies The SC2603 operates at a fixed frequency of 200kHz, u Peripheral Card Supplies providing an optimum compromise between efficiency, u Industrial Power Supplies external component size, and cost. u High Density DC/DC Conversion Typical Application Circuit D1 L1 VIN VOUT R1 C1 R2 C2 Q1 C3 D2 U2 GND optional 5 4 R3 VIN Gate 3 6 Enable EN/SS CS (open collector) 1 2 R4 Open Drain with < 100Ω FB GND C4 pull down impedance C5 R5 SC2603 1 Revision: Nov 14, 2006 www.semtech.com SC2603 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. Parameter Symbol Maximum Units Input Voltage V to GND -0.3 to 20 V IN Storage Temperature Range T -45 to +150 °C STG Maximum Junction Temperature T 150 °C J Lead Temperature (Soldering) 10 Sec. T 300 °C LEAD (1) Thermal Resistance, Junction to Ambient 165 °C/W θ JA Thermal Resistance, Junction to Case θ 102 °C/W JC (2) Electrical Surge Discharge ESD 2 KV Note: (1) Mounting pad has to be larger than one square inch on two sided printed circuit board with minimum 1 ounce copper (2) Human model. Electrical Characteristics V = 12V; V = 25V; T = T = -40°C to 125°C unless otherwise specified. IN O A J Parameter Symbols Conditions Min Typ Max Units Reference V 1.225 1.250 1.275 V REF Feedback Bias Current I V = V , V = 12V 2.0 8.0 μA FB FB EN/SS IN Quiescent Current I Current into V pin 5.0 8.0 mA Q IN Load Regulation V =25V ; I = 0.1A to 1A 0.5 1.0 % O O Line Regulation V =5V to 15V ; V =25V ; I = 100mA 1.4 2 % IN O O Current Limit Threshold CS 68 73 78 mV O Oscillator Frequency T = 25 C 190 200 210 kHz A Oscillator Frequency Shift V < V /2 50 kHz FB REF Max Duty Cycle 90 95 % UVLO Threshold V V ramping up 4.2 4.5 V UVLO IN UVLO Hysteresis 400 mV Driver Source Current I V = 12V, C = 10nF 0.5 0.8 1.1 A SOURCE IN GATE Driver Sink Current I V = 12V, C = 10nF 0.5 0.8 1.1 A SINK IN GATE Soft Start Charge Current I 60 μA SS Internal Ramp Peak V 1.4 V R_PEAK Internal Ramp Valley V 0.4 V R_VALLEY Pull down below this level Enable Threshold V 0.09 0.12 V TH_EN to disable the output www.semtech.com  2005 Semtech Corp. 2 SC2603 POWER MANAGEMENT Pin Configuration Ordering Information Part Numbers Package Top View (1)(2) SC2603SKTRT SOT23-6 FB CS 1 6 SC2603EVB GND 2 VIN 5 EN/SS 3 4 GATE Note: (1) Only available in tape and reel packaging. A reel contains 3000 devices. SOT23-6 (2) Lead free product. This product is fully WEEE and RoHS compliant Pin Descriptions Pin # Pin Name Pin Function 1 FB Error amplifier input (-). 2 GND Device ground. 3 EN/SS Enable/Soft Start Pin. 4 Gate Gate driver output. 5 VIN Device Input Voltage. 6 CS Current Sense Input . Block Diagram O OS SC CIIL LL LA AT TO OR R VIN S PWM Q FB Gate R GND 25K Current CS Limit EN/SS 1.25V 70mV REF UV VIN UVLO 1.25V REF  2005 Semtech Corp. 3 www.semtech.com SC2603 POWER MANAGEMENT Theory of Operation Application Information The SC2603 is a versatile, low-cost, voltage-mode PWM Soft-Start controller designed for DC/DC power supply applications. In normal condition, the SC2603 operats at a fixed Soft-start prevents a DC-DC converter from drawing 200KHz. One exception is that when the FB pin voltage excessive current from the power source during start up. drops to one half, the frequency will be shifted to one If the soft-start time is made sufficiently long, then the fouth of 200KHz. output will enter regulation without overshoot. An external capacitor is connected from the EN/SS pin to the ground. SC2603 features include a temperature compensated After the part’s input voltage surpasses the UVLO, the voltage reference, triangle wave oscillator, current limit EN/SS pin is allowed to charge its capacitor with 60µA. comparator, frequency shift over-current protection, and When 100mV is reached at the EN/SS pin, the internal an internally compensated error amplifier. Pulse by pulse comp node is at 0.4V. The SC2603 will start switching, current limiting is implemented by sensing the and the converter output comes into regulation. Because differential voltage across an external resistor, or an the FB pin voltage follows EN/SS pin voltage, finally, the appropriately sized PC board trace. EN/SS pin voltage will be clamped at 1.25V same as the refernece voltage. Setting the Output Voltage An external resistive divider R and R with its center 1 2 tap tied to the FB pin sets the output voltage. VOUT V   SC2603 OUT R1 R = R − 1   1 2 1 .25   1 FB R2 Under Voltage Lockout The under voltage lockout circuit of the SC2603 assures that the gate driver output remains in the off state when- ever the supply voltage drops below set parameters. Lock- out occurs if V falls below 3.8V. Normal operation re- IN sumes once V rises above 4.2V. IN www.semtech.com  2005 Semtech Corp. 4 SC2603 POWER MANAGEMENT Application Information Over Current Protection The over-current protection is implemented by a sensing resistor and an internal current-limit comparator with a threshold of 70mV. If the switching current through the sensing resistor causing voltage to drop at the CS pin reachs 70mV, the SC2603 will immediately turn the gate pulse off to limit the current through the power switch. The figure below shows over-current waveforms. At t1, the input current I begins to increase as the load I IN OUT builds up until it hits the OCP threshold at t2. At t2, V OUT begins to drop as I starts increasing toward t3 while V OUT IN and I remain the same. At t3, there two events are IN happening. 1) V is at half of its regulating voltage. At OUT this point, the internal oscillator runs into frequency shift mode and shifts the frequency to one fourth of the oper- ating frequency. 2) The diode starts conducting current without limit causing V to fall due to supply current limit. IN Finally, V and V both drops to zero and I becomes the IN OUT IN input supply current limit. A RC filter at the CS pin is necessary to filter out noise to ensure accurate sensing. The value of the sensing resistor can be caculated by the following equation: R = 70 mV / I S PEAK Where I is the input peak current through the power PEAK MOSFET. I IN I OUT V OUT V IN t0 t2 t3 t1 t4 Over Current Waveforms  2005 Semtech Corp. 5 www.semtech.com SC2603 POWER MANAGEMENT Applications Information Layout Guidelines Careful attention to layout requirements are necessary 5) The SC2603 is best placed over an isolated ground for successful implementation of the SC2603 PWM con- plane area. The soft-start capacitor, the V decoupling IN capacitor, and the current sensing filter capacitor should troller. High currents switching at 200kHz are present in also connected to this ground pad area. This isolated the application and their effect on ground plane voltage differentials must be understood and minimized. ground area should be connected to the main ground by a trace that runs from the GND pin to the ground side of 1) The high power parts of the circuit should be laid out the output capacitor. If this is not possible, the GND pin may be connected to the ground path between the Out- first. A ground plane should be used, the number and put Capacitor and the Cin, Q1, D1 loop. Under no cir- position of ground plane interruptions should be such as to not unnecessarily compromise ground plane integrity. cumstances should GND be returned to a ground inside Isolated or semi-isolated areas of the ground plane may the Cin, Q1, D1 loop. be deliberately introduced to constrain ground currents 6) Input voltage of the SC2603 should be supplied from to particular areas, for example the input capacitor and the power rail through a 2.2~10Ω resistor, the V pin bottom Schottky ground. IN should be decoupled directly to GND by a 0.1µF~1µf 2) The loop formed by the output Capacitor(s) (Cout), the ceramic capacitor, trace lengths should be as short as FET (Q1), the current sensing resistor, and the Schottky possible. (D1) must be kept as small as possible. This loop con- 7) An RC low pass filter is required to filter out leading tains all the high current, fast transition switching. Con- nections should be as wide and as short as possible to edge current spikes on the current sensing resistor. The minimize loop inductance. Minimizing this loop area will filter capacitor needs to be very close to the CS and reduce EMI, lower ground injection currents, resulting in GND to reduce noise pickup. electrically “cleaner” grounds for the rest of the system and minimize source ringing, resulting in more reliable gate switching signals. 3) The connection between the junction of Q1, D1 and the output capacitor should be a wide trace or copper region. It should be as short as practical. Since this con- nection has fast voltage transitions, keeping this con- nection short will minimize EMI. 4) The Output Capacitor(s) (Cout) should be located as close to the load as possible, fast transient load cur- rents are supplied by Cout only, and connections be- tween Cout and the load must be short, wide copper areas to minimize inductance and resistance. www.semtech.com  2005 Semtech Corp. 6 SC2603 POWER MANAGEMENT Applications Information (Cont.) Layout diagram for the SC2603 Vout 12VIN Ra 20uH D1 Cin + 2.2 Q1 SC2603 Cout Rb 1 5 FB VIN 4 3 Gate EN/SS 0.1uF 0.1uF Rs 2 6 CS GND Heavy lines indicate the critical loop carrying high pulsating current. The inductance of this loop needs to be minimized.  2005 Semtech Corp. 7 www.semtech.com SC2603 POWER MANAGEMENT Applications Circuit 12V to 25V @ 1A boost converter D D1 1 L L1 1 V VO OU UT T= =2 25 5V V V VIIN N = = 1 12 2V V 1 18 8u uH H R R1 1 C C1 1 3 3A A,, 4 40 0V V R R2 2 2 2..2 2 4 47 70 0u u 3 34 4K K C C2 2 C C1 11 1 1 1u u Q Q1 1 C C3 3 3 33 30 0u u//3 35 5V V A AO O4 44 44 42 2 U U2 2 1 1u u R R4 4 5 5 4 4 V VIIN N G Ga atte e 1 1..7 78 8K K R R5 5 3 3 6 6 E En na ab blle e E EN N//S SS S C CS S ((ooppeenn ddrraaiinn)) 1 1K K 1 1 2 2 Open Drain with < 100Ω F FB B G GN ND D R R6 6 C C4 4 C C5 5 pull down impedance 0 0..1 1u u 2 20 0m m 1 12 20 0p p S SC C2 26 60 03 3 Bill of Material IIt te em m Q Qu ua an nt tiit ty y R Re ef fe er re en nc ce e P Pa ar rt t f fo oo ot tp pr riin nt t V Ve en nd do or r 1 1 1 1 C C1 1 4 47 70 0u u//A Allu um m S SA AN NY YO O 2 2 1 1 C C2 2 3 33 30 0u u//A Allu um m S SA AN NY YO O 3 3 1 1 C C3 3 1 1u uF F 6 60 03 3 4 4 1 1 C C4 4 0 0..1 1u u 6 60 03 3 5 5 1 1 C C5 5 1 12 20 0p p 6 60 03 3 6 6 1 1 C C1 11 1 1 1u u 8 80 05 5 7 7 1 1 D D1 1 1 1N N5 58 81 19 9 8 8 1 1 L L1 1 1 18 8u uH H C CO OO OP PE ER R 9 9 1 1 Q Q1 1 A AO O4 44 44 42 2 A Allp ph ha a & & O Om me eg ga a 1 10 0 1 1 R R1 1 2 2..2 2 6 60 03 3 1 11 1 1 1 R R2 2 3 34 4K K 6 60 03 3 1 12 2 1 1 R R3 3 0 0 6 60 03 3 1 13 3 1 1 R R4 4 1 1..7 78 8K K 6 60 03 3 1 14 4 1 1 R R5 5 1 1K K 6 60 03 3 1 15 5 1 1 R R6 6 2 20 0m m 1 16 6 1 1 U U1 1 S SC C2 26 60 03 3 S SO OT T2 23 3- -6 6 S SE EM MT TE EC CH H www.semtech.com  2005 Semtech Corp. 8 SC2603 POWER MANAGEMENT Typical Characteristics Error Amplifier: Gain and Phase Load Regulation (V = 12V, V = 25V) IN O 40 180 35 26 30 135 25.5 25 25 20 90 15 24.5 Gain 10 45 Phase 24 5 23.5 0 0 23 -5 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 -10 -45 Output Current - (A) 100.0E+0 1.0E+3 10.0E+3 100.0E+3 1.0E+6 10.0E+6 Frequency (Hz) Efficiency (V = 12V, V = 25V) Line Regulation (V = 25V, I = 1A) IN O O O 26.000 98 96 25.500 94 25.000 92 90 24.500 88 24.000 86 84 23.500 82 80 23.000 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 4 6 8 10 12 14 16 Input Voltage - (V) Output Current - (A) Frequency Shift (V vs. F ) OCP (V = 12V, V = 25V) FB SW IN O 25.6 25.4 25.2 25 24.8 24.6 24.4 24.2 0 0.5 1 1.5 2 2.5 3 Output Current - (A)  2005 Semtech Corp. 9 www.semtech.com Output Voltage - (A) Efficiency - (%) Gain (dB) Phase (deg) Output Voltage - (V) Output Voltage - (V) SC2603 POWER MANAGEMENT Typical Characteristics UVLO Hysteresis vs Temperature Reference Voltage vs Temperature 0 .55 1.26 1.255 0.5 VIN=12V 1.25 0 .45 1.245 0.4 1.24 0 .35 VIN=5V 1.235 0.3 1.23 0 .25 1.225 0.2 1.22 0 .15 -50 -25 0 25 50 75 100 125 150 o -50 0 50 100 15 0 TEMPERATURE ( C) O T EMPER AT U R E ( C) Oscillator Frequency vs Temperature Current Limit Threshold vs Temperature 210 75 74 205 73 200 72 195 71 70 190 69 185 68 -50 -25 0 25 50 75 100 125 150 180 O -50 -25 0 25 50 75 100 125 150 TEMPERATURE ( C) O TE M P E R A TU R E ( C ) UVLO Threshold vs Temperature 4.3 0 4.2 8 4.2 5 4.2 3 4.2 0 4.1 8 4.1 5 4.1 3 4.1 0 4.0 8 4.0 5 -50 -2 5 0 2 5 5 0 7 5 1 00 12 5 1 50 O T E M P E R A T U R E ( C ) www.semtech.com  2005 Semtech Corp. 10 UVLO THRESHOLD (V) OSCILLATOR FREQUENCY (kHz) REFERENCE VOLTAGE (V) CURRENT LIMIT THRESHOLD (mV) UVLO HYSTERESIS (V) SC2603 POWER MANAGEMENT Outline Drawing - SOT23-6 DIMENSIONS INCHES MILLIMETERS A DIM MIN MAX MIN NOM MAX NOM A - - .057 0.90 1.45 e1 .035 D A1 .000 - .006 0.00 - 0.15 A2 .035 .045 .051 .90 1.15 1.30 b - - N .010 .020 0.25 0.50 2X E/2 c .003 - .009 0.08 - 0.22 EI E D .110 .114 .118 2.80 2.90 3.00 E1 .060 .063 .069 1.50 1.60 1.75 1 2 E .110 BSC 2.80 BSC ccc C e 0.95 BSC .037 BSC e1 .075 BSC 1.90 BSC 2X N/2 TIPS L .012 .018 .024 0.30 0.45 0.60 e L1 (.024) (0.60) B N 6 6 01 0° - 10° 0° - 10° aaa .004 0.10 bbb .008 0.20 D ccc .008 0.20 aaa C A2 A SEATING H PLANE H A1 C c bxN GAGE PLANE bbb C A-B D 0.25 L 01 (L1) DETAIL A SEE DETAIL A SIDE VIEW NOTES: 1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). 2. DATUMS - A - AND - B - TO BE DETERMINED AT DATUM PLANE -H- 3. DIMENSIONS "E1" AND "D" DO NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. Land Pattern - SOT23-6 X D DIIME MEN NS SIIO ON NS S D DIIM M IIN NC CH HE ES S MI MIL LL LIIME MET TE ER RS S C (.098) (2.50) C G G .055 1.40 (C) G Z P P .037 0.95 X X .024 0.60 Y Y Y .043 1.10 Z Z .141 3.60 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. 11 www.semtech.com