SC1103 Asynchronous Voltage Mode PWM Controller for 12V Input POWER MANAGEMENT Description Features The SC1103 is a versatile, low-cost, voltage-mode PWM controller designed for 12V input DC/DC power supply applications. A simple, fixed-voltage buck regulator can be implemented using the SC1103 with a minimum of external components. Internal level shift and drive circuitry eliminates the need for an expensive p-channel, high-side switch. The small device footprint allows for compact circuit design. SC1103 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. Low cost / small size Switch mode efficiency up to 95% 1% reference voltage accuracy Over current protection 500mA output drive 5V to 12V Input power source Lead free package available. Fully WEEE and RoHS compliant Applications Pentium® P55 Core Supply Low Cost Microprocessor Supplies Peripheral Card Supplies Industrial Power Supplies High Density DC/DC Conversion The SC1103 operates at a fixed frequency of 200kHz, providing an optimum compromise between efficiency, external component size, and cost. Typical Application Circuit L1 6uH Q1 IRLR3103 Vout = 2.5V @ 10A R5 0.05 + +12V C1 1.0 C2 C3 47/16V D2 MBRD1035L 47/16V GND C8 220/4V C9 220/4V C10 220/4V C11 1.0 R6 127*see note R7 127 GND +20V R1 10 C4 0.1 R2 1k R3 1k C5 0.001 U1 SC1103 1 VCC GND 8 2 CS(-) FB 7 3 CS(+) BST 6 4 PGND DH 5 C6 0.01 R4 2.2 C7 0.1 * NOTE: R6 = R7 x (Vout/1.25 - 1) rounded to nearest 1%value 12V to 3.3V @ 10A with “flying capacitor” boost voltage. Revision: July 28, 2005 1 www.semtech.com SC1103 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 VCC to GND -0.3 to 14 V Ground Differential PGND to GND ±1 V Boost Input Voltage BST to GND -0.3 to +26 V Operating Ambient Temperature Range TAMB 0 to +70 °C Storage Temperature Range TSTG -45 to +125 °C TJ 125 °C TLEAD 300 °C Thermal Resistance, Junction to Ambient θJ A 165 °C/W Thermal Resistance, Junction to Case θJ C 40 °C/W Maximum Junction Temperature Lead Temperature (Soldering) 10 Sec. Electrical Characteristics VCC = 11.40V to 12.60V; GND = PGND = 0V; VO = 2.5V; TA = 25°C; BST = 22 ± 2V; Per test circuit, unless otherwise specified. Parameter Symbols Reference VREF Conditions Min Typ Max Units 1.238 1.250 1.263 V 1.225 1.250 1.275 2.0 8.0 µA Current into VCC pin 5.0 8.0 mA Load Regulation IO = 1A to 10A 0.5 1.0 % Line Regulation IO = 10A 0.5 % Over 0 to 125°C Temp. range Feedback Bias Current IFB Quiescent Current IQ Current Limit Threshold CS(+) to CS (-) Oscillator Frequency Oscillator Frequency Shift UVLO Threshold 75 85 mV 170 200 230 kHz VFB < VREF/2 Max Duty Cycle DH Sink/Source Current 65 90 IO VBST - VDH = 4.5V / (VDH - VPGND = 2V) 50 kHz 95 % 500 mA 3.8 VUVLO V Note: (1) This device is ESD sensitive. Use of standard ESD handling precautions is required. 2005 Semtech Corp. 2 www.semtech.com SC1103 POWER MANAGEMENT Pin Configuration Ordering Information Device Top View Package(1) Temp Range (TJ) SO - 8 0° to 125°C SC1103CS.TR SC1103CSTRT(2) 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. (SO-8) Pin Descriptions Pin # Pin Name Pin Function 1 VC C Device Input Voltage. 2 CS(-) Current Sense Input (Negative). 3 CS(+) Current Sense Input (Positive). 4 PGND Device power ground. 5 DH High side driver output. 6 BST High side driver VBST (Boost). 7 FB 8 GND Error amplifier input (-). Signal ground. Block Diagram 2005 Semtech Corp. 3 www.semtech.com SC1103 POWER MANAGEMENT Applications Information Layout Guidelines Careful attention to layout requirements are necessary for successful implementation of the SC1103 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. 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. 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. 5) The SC1103 is best placed over an isolated ground plane area. GND and PGND should be returned to this isolated ground. 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 (one of) the output capacitor(s). If this is not possible, the GND pin may be connected to the ground path between the Output Capacitor(s) and the Cin, Q1, D1 loop. Under no circumstances should GND be returned to a ground inside the Cin, Q1, D1 loop. 2). The loop formed by the Input Capacitor(s) (Cin), the Top FET (Q1) 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. 6) Vcc for the SC1103 should be supplied from the VIN supply through a 10Ω resistor, the Vcc pin should be decoupled directly to GND by a 0.1µF ceramic capacitor, trace lengths should be as short as possible. 7) The Current Sense resistor and the divider across it should form as small a loop as possible, the traces running back to CS(+) and CS(-) on the SC1103 should run parallel and close to each other. 8) To minimize noise pickup at the sensitive FB pin, the feedback resistors should both be close to the SC1103 with the bottom resistor (Rb) returned to ground at the GND pin. 3). The connection between the junction of Q1, D1 and the output inductor 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. The connection between the output inductor and the sense resistor should be a wide trace or copper area, there are no fast voltage or current transitions in this connection and length is not so important, however adding unnecessary impedance will reduce efficiency. 2005 Semtech Corp. Under Voltage Lockout The under voltage lockout circuit of the SC1103 assures that the high-side MOSFET driver outputs remain in the off state whenever the supply voltage drops below set parameters. Lockout occurs if VCC falls below 3.8V. Normal operation resumes once VCC rises above 3.8V. 4 www.semtech.com SC1103 POWER MANAGEMENT Applications Information (Cont.) Layout diagram for the SC1103 VO = VREF (1 + Ra/Rb) 12VIN 20-24V BST 10 0.1uF Q1 SC1103CS 1 2 3 4 0.001uF VCC GND CS(-) CS(+) PGND FB BST DH Cin + 8 Vout 7 6uH Rb 6 + D1 Cout 5 Ra Heavy lines indicate high current paths. Application Circuit 12V to 2.5V @ 10A (Bootstrapped) D1 LL4148 C7 0.1 L1 6uH Q1 IRLR3103 R5 0.05 + +12V C1 1.0 C2 47/16V C3 47/16V D2 MBRD1035L C8 220/4V C9 220/4V C10 220/4V C11 1.0 R6 76.8 *see note R7 127 Vout = 2.5V @ 10A GND GND R1 10 R2 1k C4 R3 1k U1 SC1103 1 VCC GND 8 2 CS(-) FB 7 3 CS(+) BST 6 4 PGND DH 5 C6 0.01 R4 2.2 C5 0.001 0.1 * NOTE: R6 = R7 x (Vout/1.25 - 1) rounded to nearest 1%value 2005 Semtech Corp. 5 www.semtech.com SC1103 POWER MANAGEMENT Typical Characteristics Error Amplifier, Gain and Phase Load Regulation @ VIN = 12V 40 180 1.0% 35 0.8% 30 0.6% 135 90 15 Gain 10 45 Phase Load Regulation 20 Phase (deg) Gain (dB) 25 5 0 0.4% Vo= 1.8V 2.5V 3.3V 5.0V 0.2% 0.0% -0.2% -0.4% -0.6% 0 -0.8% -5 -1.0% -10 100.0E+0 1.0E+3 10.0E+3 100.0E+3 -45 10.0E+6 1.0E+6 0 2 4 6 8 10 12 14 Output Current, (A) Frequency (Hz) VRIPPLE @ VIN = 12V, VO = 3.3V, IO = 10A Line Regulation @ VO = 3.3V, IO = 10A 0.5% 0.4% Line Regulation 0.3% 0.2% 0.1% 0.0% -0.1% -0.2% -0.3% -0.4% -0.5% 11.4 11.6 11.8 12.0 12.2 12.4 12.6 Input Voltage, (V) Efficiency @ VIN = 12V 100% 90% Efficiency 80% 1.8V 2.5V 3.3V 5V 70% 60% 50% 40% 0 2 4 6 8 10 12 14 Output Current, (A) 2005 Semtech Corp. 6 www.semtech.com SC1103 POWER MANAGEMENT Outline Drawing - SO-8 A D e N DIM E1 E 1 2 ccc C 2X N/2 TIPS .069 .053 .010 .004 .065 .049 .012 .020 .007 .010 .189 .193 .197 .150 .154 .157 .236 BSC .050 BSC .010 .020 .016 .028 .041 (.041) 8 0° 8° .004 .010 .008 A A1 A2 b c D E1 E e h L L1 N 01 aaa bbb ccc 2X E/2 e/2 B D DIMENSIONS MILLIMETERS INCHES MIN NOM MAX MIN NOM MAX aaa C SEATING PLANE h A2 A C A1 bxN bbb 1.35 1.75 0.25 0.10 1.65 1.25 0.31 0.51 0.25 0.17 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 0° 8° 0.10 0.25 0.20 h H C A-B D c GAGE PLANE 0.25 SEE DETAIL A L (L1) DETAIL SIDE VIEW 01 A 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. 4. REFERENCE JEDEC STD MS-012, VARIATION AA. Minimum Land Pattern - SO-8 X DIM (C) G Z Y 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 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. 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. 7 www.semtech.com