SC2603 Simple PWM Boost Controller POWER MANAGEMENT Description Features u u u u u u SC2603 features include a temperature compensated u voltage reference, triangle wave oscillator, current limit u The SC2603 is a versatile, low-cost, voltage-mode PWM controller designed for 16V input DC/DC power supply applications. A simple, fixed-voltage boost regulator can be implemented using the SC2603 with a minimum of external components. The small device footprint allows for compact circuit design. comparator, frequency shift over-current protection, and an internally compensated error amplifier. Pulse by pulse current limiting is implemented by sensing the differential voltage across an external resistor, or an appropriately sized PC board trace. Low cost / small size Switch mode efficiency up to 95% 1% reference voltage accuracy Over-current protection 800mA output drive 5V to 16V input power source No need for external compensation network SOT23-6 is fully WEEE and RoHS compliant Applications u u u u The SC2603 operates at a fixed frequency of 200kHz, u providing an optimum compromise between efficiency, u external component size, and cost. u Portable Devices Flat Panel TV TV Set Top Box Auxiliary Supplies Peripheral Card Supplies Industrial Power Supplies High Density DC/DC Conversion Typical Application Circuit D1 L1 VIN VOUT R1 R2 C1 C2 Q1 C3 D2 U2 GND optional 5 3 Enable (openDrain collector) Open with < 100Ω pull down impedance 1 C4 VIN Gate EN/SS CS FB GND R3 4 6 R4 2 C5 R5 SC2603 Revision: Nov 14, 2006 1 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 VIN to GND -0.3 to 20 V TSTG -45 to +150 °C TJ 150 °C TLEAD 300 °C Thermal Resistance, Junction to Ambient(1) θJA 165 °C/W Thermal Resistance, Junction to Case θJC 102 °C/W ESD 2 KV Input Voltage Storage Temperature Range Maximum Junction Temperature Lead Temperature (Soldering) 10 Sec. Electrical Surge Discharge(2) 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 VIN= 12V; VO = 25V; TA = TJ = -40°C to 125°C unless otherwise specified. Parameter Symbols Reference VREF C onditions Min Typ Max U nits 1.225 1.250 1.275 V Feedback Bi as C urrent IFB VFB = VEN/SS, VIN = 12V 2.0 8.0 µA Qui escent C urrent IQ C urrent i nto VIN pi n 5.0 8.0 mA Load Regulati on VO=25V ; IO = 0.1A to 1A 0.5 1.0 % Li ne Regulati on VIN=5V to 15V ; VO=25V ; IO = 100mA 1.4 2 % C urrent Li mi t Threshold Osci llator Frequency CS 68 73 78 mV TA = 25OC 190 200 210 kHz VFB < VREF/2 Osci llator Frequency Shi ft Max D uty C ycle UVLO Threshold 90 VUVLO VIN rampi ng up 50 kHz 95 % 4.2 UVLO Hysteresi s 4.5 400 V mV ISOURCE VIN = 12V, C GATE = 10nF 0.5 0.8 1.1 A D ri ver Si nk C urrent ISINK VIN = 12V, C GATE = 10nF 0.5 0.8 1.1 A Soft Start C harge C urrent ISS 60 µA Internal Ramp Peak VR_PEAK 1.4 V Internal Ramp Valley VR_VALLEY 0.4 V 0.12 V D ri ver Source C urrent Enable Threshold 2005 Semtech Corp. VTH_EN Pull down below thi s level to di sable the output 2 0.09 www.semtech.com SC2603 POWER MANAGEMENT Pin Configuration Ordering Information Top View FB 1 6 CS GND 2 5 VIN EN/SS 3 4 GATE P art N umbers P ackag e S C 2603S K TRT (1)(2) S OT23-6 S C 2603E V B Note: (1) Only available in tape and reel packaging. A reel contains 3000 devices. (2) Lead free product. This product is fully WEEE and RoHS compliant SOT23-6 Pin Descriptions Pin # Pin Name Pin Function 1 FB 2 GND 3 EN/SS 4 Gate Gate driver output. 5 VIN Device Input Voltage. 6 CS Current Sense Input . Error amplifier input (-). Device ground. Enable/Soft Start Pin. Block Diagram OSCILLATOR VIN S PWM FB Q Gate R GND 25K Current Limit CS EN/SS 1.25V REF 70mV UV VIN 1.25V REF 2005 Semtech Corp. UVLO 3 www.semtech.com SC2603 POWER MANAGEMENT Theory of Operation Application Information The SC2603 is a versatile, low-cost, voltage-mode PWM controller designed for DC/DC power supply applications. In normal condition, the SC2603 operats at a fixed 200KHz. One exception is that when the FB pin voltage drops to one half, the frequency will be shifted to one fouth of 200KHz. Soft-Start Soft-start prevents a DC-DC converter from drawing excessive current from the power source during start up. If the soft-start time is made sufficiently long, then the output will enter regulation without overshoot. An external capacitor is connected from the EN/SS pin to the ground. After the part’s input voltage surpasses the UVLO, the EN/SS pin is allowed to charge its capacitor with 60µA. When 100mV is reached at the EN/SS pin, the internal comp node is at 0.4V. The SC2603 will start switching, and the converter output comes into regulation. Because the FB pin voltage follows EN/SS pin voltage, finally, the EN/SS pin voltage will be clamped at 1.25V same as the refernece voltage. SC2603 features include a temperature compensated voltage reference, triangle wave oscillator, current limit comparator, frequency shift over-current protection, and an internally compensated error amplifier. Pulse by pulse current limiting is implemented by sensing the differential voltage across an external resistor, or an appropriately sized PC board trace. Setting the Output Voltage An external resistive divider R1 and R2 with its center tap tied to the FB pin sets the output voltage. VOUT V R 1 = R 2 OUT − 1 1 . 25 SC2603 R1 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 whenever the supply voltage drops below set parameters. Lockout occurs if VIN falls below 3.8V. Normal operation resumes once VIN rises above 4.2V. 2005 Semtech Corp. 4 www.semtech.com 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 IIN begins to increase as the load IOUT builds up until it hits the OCP threshold at t2. At t2, VOUT begins to drop as IOUT starts increasing toward t3 while VIN and IIN remain the same. At t3, there two events are happening. 1) VOUT is at half of its regulating voltage. At this point, the internal oscillator runs into frequency shift mode and shifts the frequency to one fourth of the operating frequency. 2) The diode starts conducting current without limit causing VIN to fall due to supply current limit. Finally, VIN and VOUT both drops to zero and IIN becomes the 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 S = 70 mV / I PEAK Where IPEAK is the input peak current through the power MOSFET. IIN IOUT VOUT VIN t0 t2 t1 t3 t4 Over Current Waveforms 2005 Semtech Corp. 5 www.semtech.com SC2603 POWER MANAGEMENT Applications Information Layout Guidelines 5) The SC2603 is best placed over an isolated ground plane area. The soft-start capacitor, the VIN decoupling capacitor, and the current sensing filter capacitor should also connected to this ground pad area. This isolated ground area should be connected to the main ground by a trace that runs from the GND pin to the ground side of the output capacitor. If this is not possible, the GND pin may be connected to the ground path between the Output Capacitor and the Cin, Q1, D1 loop. Under no circumstances should GND be returned to a ground inside the Cin, Q1, D1 loop. Careful attention to layout requirements are necessary for successful implementation of the SC2603 PWM controller. High currents switching at 200kHz are present in the application and their effect on ground plane voltage differentials must be understood and minimized. 1) The high power parts of the circuit should be laid out first. A ground plane should be used, the number and position of ground plane interruptions should be such as to not unnecessarily compromise ground plane integrity. Isolated or semi-isolated areas of the ground plane may be deliberately introduced to constrain ground currents to particular areas, for example the input capacitor and bottom Schottky ground. 6) Input voltage of the SC2603 should be supplied from the power rail through a 2.2~10Ω resistor, the VIN pin should be decoupled directly to GND by a 0.1µF~1µf ceramic capacitor, trace lengths should be as short as possible. 2) The loop formed by the output Capacitor(s) (Cout), the FET (Q1), the current sensing resistor, and the Schottky (D1) must be kept as small as possible. This loop contains all the high current, fast transition switching. Connections should be as wide and as short as possible to minimize loop inductance. Minimizing this loop area will reduce EMI, lower ground injection currents, resulting in electrically “cleaner” grounds for the rest of the system and minimize source ringing, resulting in more reliable gate switching signals. 7) An RC low pass filter is required to filter out leading edge current spikes on the current sensing resistor. The filter capacitor needs to be very close to the CS and GND to reduce noise pickup. 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 connection has fast voltage transitions, keeping this connection short will minimize EMI. 4) The Output Capacitor(s) (Cout) should be located as close to the load as possible, fast transient load currents are supplied by Cout only, and connections between Cout and the load must be short, wide copper areas to minimize inductance and resistance. 2005 Semtech Corp. 6 www.semtech.com SC2603 POWER MANAGEMENT Applications Information (Cont.) Layout diagram for the SC2603 Vout 12VIN Ra 20uH D1 Cin 2.2 5 3 0.1uF Q1 SC2603 VIN FB EN/SS Gate CS GND Rb 1 Cout 4 0.1uF 6 + Rs 2 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 D1 L1 VOUT=25V VIN = 12V R1 C1 2.2 470u 18uH 3A, 40V 34K U2 C2 C11 1u Q1 AO4442 C3 1u R2 330u/35V R4 5 3 Enable (open drain) Open Drain with < 100Ω pull down impedance 1 C4 0.1u VIN Gate EN/SS CS FB GND 4 1.78K R5 6 1K 2 C5 120p SC2603 R6 20m Bill of Material Item Quantity Reference Part 1 1 C1 470u/Alum SANYO 2 1 C2 330u/Alum SANYO 3 1 C3 1uF 603 4 1 C4 0.1u 603 5 1 C5 120p 603 6 1 C11 1u 805 7 1 D1 1N5819 8 1 L1 18uH COOPER 9 1 Q1 AO4442 Alpha & Omega 10 1 R1 2.2 603 11 1 R2 34K 603 12 1 R3 0 603 13 1 R4 1.78K 603 14 1 R5 1K 603 15 1 R6 20m 16 1 U1 SC2603 2005 Semtech Corp. 8 footprint SOT23-6 Vendor SEMTECH www.semtech.com SC2603 POWER MANAGEMENT Typical Characteristics Load Regulation (VIN = 12V, VO = 25V) Error Amplifier: Gain and Phase 40 180 35 26 30 135 25.5 90 15 Gain 10 45 Phase Phase (deg) Gain (dB) 20 Output Voltage - (V) 25 5 0 25 24.5 24 23.5 0 23 -5 0.0 -10 100.0E+0 1.0E+3 10.0E+3 100.0E+3 0.1 0.2 0.3 0.4 -45 10.0E+6 1.0E+6 0.5 0.6 0.7 0.8 0.9 1.0 1.1 Output Current - (A) Frequency (Hz) Efficiency (VIN = 12V, VO = 25V) Line Regulation (VO = 25V, IO = 1A) 26.000 98 96 Output Voltage - (V) 25.500 Efficiency - (%) 94 92 90 88 86 84 25.000 24.500 24.000 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 V oltage - (V ) Output Current - (A) Frequency Shift (VFB vs. FSW) OCP (VIN = 12V, VO = 25V) 25.6 Output Voltage - (A) 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 SC2603 POWER MANAGEMENT Typical Characteristics UVLO Hysteresis vs Temperature Reference Voltage vs Temperature 0 .5 5 0 .5 VIN=12V 1.25 UVLO HYSTERESIS (V) REFERENCE VOLTAGE (V) 1.26 1.255 1.245 1.24 VIN=5V 1.235 1.23 0 .4 5 0 .4 0 .3 5 0 .3 0 .2 5 1.225 0 .2 1.22 -50 -25 0 25 50 75 100 125 0 .1 5 150 -5 0 TEMPERATURE (oC) CURRENT LIMIT THRESHOLD (mV) OSCILLATOR FREQUENCY (kHz) 205 200 195 190 185 25 50 75 150 75 74 73 72 71 70 69 68 -50 180 0 100 Current Limit Threshold vs Temperature 210 -2 5 50 T E M P E R A T U R E (OC ) Oscillator Frequency vs Temperature -5 0 0 100 125 150 125 150 -25 0 25 50 75 100 125 150 TEMPERATURE (OC) T E M P E R A T U R E (OC ) UVLO Threshold vs Temperature 4.3 0 UVLO THRESHOLD (V) 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 -5 0 -2 5 0 25 50 75 100 T E M P E R A T U R E (O C ) 2005 Semtech Corp. 10 www.semtech.com SC2603 POWER MANAGEMENT Outline Drawing - SOT23-6 DIM A e1 2X E/2 A .035 .057 A1 .000 .006 A2 .035 .045 .051 b .020 .010 c .003 .009 D .110 .114 .118 E1 .060 .063 .069 E .110 BSC e .037 BSC e1 .075 BSC L .012 .018 .024 (.024) L1 N 6 01 0° 10° aaa .004 bbb .008 ccc .008 D N EI 1 DIMENSIONS MILLIMETERS INCHES MIN NOM MAX MIN NOM MAX E 2 ccc C 2X N/2 TIPS e B D 1.45 0.90 0.00 0.15 .90 1.15 1.30 0.25 0.50 0.08 0.22 2.80 2.90 3.00 1.50 1.60 1.75 2.80 BSC 0.95 BSC 1.90 BSC 0.30 0.45 0.60 (0.60) 6 0° 10° 0.10 0.20 0.20 aaa C A2 SEATING PLANE A H H A1 C bxN bbb C A-B D c GAGE PLANE 0.25 L 01 (L1) SEE DETAIL DETAIL A A SIDE VIEW NOTES: 1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). 2. DATUMS -A- AND -B- TO BE DETERMINED AT DATUM PLANE -H3. DIMENSIONS "E1" AND "D" DO NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. Land Pattern - SOT23-6 X DIM (C) G Z Y P C G P X Y Z DIMENSIONS MILLIMETERS INCHES (.098) .055 .037 .024 .043 .141 (2.50) 1.40 0.95 0.60 1.10 3.60 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