SEMTECH SC1103 handbook
Contents
1. 10 45 100 0 0 1 0E 3 10 0E 3 100 0 3 1 0E 6 10 0E 6 Frequency Hz Fig 1 Error Amplifier Gain and Phase Tek EIBTEE 20MS s M z 5us Chi F z4mv 20mV Fig 3 Vy 12V Vo 3 3V lo 10A Phase deg Efficiency 6 8 Output Current A Fig 5 Efficiency V 12V 2A Voltage Change V Normalized to 0 at lo Fig Load Regulation Fig Line Regulation Fig Current Amps 2 Load Regulation Vo 3 3V V 12V 6 8 Output Current A 4 Load Regulation V 12V 11 8 12 0 12 2 Input Voltage V 6 Line Regulation Vo 3 3V 1 10A 4 2000 SEMTECH CORP 652 MITCHELL ROAD NEWBURY PARK CA day s Results Tomorrow s P SEMITECH VOLTAGE MODE PWM CONTROLLER PRELIMINARY February 29 2000 LAYOUT GUIDELINES SC1103 and the output inductor should be a wide trace or cop Careful attention to layout requirements are necessary Per region It should be as short as practical Since for successful implementation of the SC1103 PWM controller High currents switching at 200kHz are pre this connection has fast voltage transitions keeping this connection short will minimize EMI The connec sent in the application and their effect2. on the SC1103 should run parallel and close to each other The 0 1uF capaci tor should be mounted as close to the CS and CS pins as possible 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 TYPICAL APPLICATIONS Q1 IRL31038 Under Voltage Lockout The under voltage lockout circuit of the SC1103 as sures that the high side MOSFET driver outputs remain in the off state whenever the supply voltage drops be low set parameters Lockout occurs if Vec falls below 3 8V Normal operation resumes once rises above 3 8V TTC2 TC3 1500 6 3V 1500 6 3V S12 1500 63 150063 15006 0 DI 1530 T Ul SC1103 Fig 8 5V to 3 3V 8A 2000 SEMTECH CORP 6 652 MITCHELL ROAD NEWBURY PARK CA foday s Results Tomorrow s P SEMTECH VOLTAGE MODE PWM CONTROLLER SC1103 PRELIMINARY February 29 2000 TYPICAL APPLICATIONS cont 01 Si4420DY lal TC C 1500 6 3V T 1500 6 3V DI MBRD340 T Ul SC1103 Vout C9 C10 C11 C12 1500 6 3 1500 6 3 1500 6 3V 0 1 Vout Fig 10 12V to 3 3V 10A with flying
3. SEMTECH CORP 40 2 652 MITCHELL ROAD NEWBURY PARK CA foday s Results Tomorrow s P SEMTECH VOLTAGE MODE PWM CONTROLLER SC1103 PRELIMINARY February 29 2000 ELECTRICAL CHARACTERISTICS Voc 11 50V to 12 50V GND Peno OV Vo 3 3V 25 C BST 24 1V Output current 2A Per test circuit unless otherwise specified PARAMETER SYMBOL CONDITIONS Reference VREF Over Temp Feedback Bias Current Quiescent Current Current into Vec pin Regulation Load lo 1A to 10A Regulation Line lo 10A Current Limit Threshold CS to CS Oscillator Frequency Oscillator Frequency Shift Veg lt Vper 2 Max Duty Cycle DH Sink Source Current Vest 4 5V Vou Veanp 2V UVLO Threshold TEST CIRCUIT 01 IRL3103S Vout I co C10 Cl CI2 c2 C3 CA c 1500 6 3 1500 6 3 1500 6 3V 0 X 5 820 16V D i MBSRHISMOT 7 Vout Ut SC1103 NOTE R6 124 x Vout 1 25 1 rounded to nearest 1 value 20 to 24V 3 2000 SEMTECH CORP 652 MITCHELL ROAD NEWBURY PARK CA Today s Results Tomorrow s Vision P SEMITECH VOLTAGE MODE PWM CONTROLLER SC1103 PRELIMINARY February 29 2000 a 5
4. on ground plane tion between the output inductor and the sense resis voltage differentials must be understood and mini mized 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 con strain ground currents to particular areas for example the input capacitor and bottom Schottky ground 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 tor 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 unnec essary impedance will reduce efficiency 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 5 The SC1103 is best placed over an isolated ground plane area GND and PGND should be returned to this isolated ground This
5. ICATIONS Pentium P55 Core Supply Low Cost Microprocessor Supplies Peripheral Card Supplies Industrial Power Supplies High Density DC DC Conversion ORDERING INFORMATION DEVICE PACKAGE TEMP RANGE T SC1103CS SO 8 0 to 125 C Note 1 Add suffix TR for tape and reel BLOCK DIAGRAM Cs Cs lt lt O B CURRENT LIMIT d m OSCILLAT Pentium is a registered trademark of Intel Corporation 1 652 MITCHELL ROAD NEWBURY PARK CA foday s Results Tomorrow s pjsEvrTECH PRELIMINARY February 29 2000 PIN DESCRIPTION Pin Name VOLTAGE MODE PWM CONTROLLER Pin Function SC1103 Device Input Voltage Current Sense Input Negative Current Sense Input Positive Device Power Ground High Side Driver Output High Side Driver Boost Error Amplifier Input ABSOLUTE MAXIMUM RATINGS Parameter Small Signal Ground Symbol Maximum Input Voltage Voc to GND 0 3 to 14 Ground Differential Pau to GND t1 Boost Input Voltage BST to GND 0 3 to 26 Operating Temperature 0 to 70 Storage Temperature 45 to 125 Lead Temperature Soldering 10 seconds 300 Thermal Resistance Junction to Ambient 165 Thermal Resistance Junction to Case 2000
6. OO SC1103 O oday s Results Tomorrow s P SSEMITECHI VOLTAGE MODE PWM CONTROLLER PRELIMINARY February 29 2000 DESCRIPTION The SC1103 is a versatile low cost voltage mode PWM controller designed for use in single ended DC DC power supply applications A sim ple fixed voltage buck regulator can be imple mented using the SC1103 with a minimum of ex ternal components Internal level shift and drive circuitry eliminates the need for an expensive p channel high side switch The small device foot print allows for compact circuit design 561103 features include a temperature compen sated 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 The SC1103 operates at a fixed frequency of 200kHz providing an optimum compromise be tween efficiency external component size and cost PIN CONFIGURATION Top View 2000 SEMTECH CORP SC1103 TEL 805 498 2111 FAX 805 498 3804 WEB http www semtech com FEATURES Low cost small size Switch mode efficiency 90 196 reference voltage accuracy Over current protection 500mA output drive 5V to 12V Input power source APPL
7. capacitor boost voltage 7 2000 SEMTECH CORP 652 MITCHELL ROAD NEWBURY PARK CA foday s Results Tomorrow s P SEMTECH VOLTAGE MODE PWM CONTROLLER SC1103 PRELIMINARY February 29 2000 OUTLINE DRAWING JEDEC REF MS 012AA ENSIONS ES M MIN se 4 80 5 00 5 80 4 00 0 8016 20 250010 ETAIL A D x 25 010 MI 1901195 7h uw SEE DETAIL A ACIE LAND PATTERN SO 8 ENSIONS E M lt X EF GRID PLACEMENT COURTYARD IS EMENTS 6 mm X 8mm IN ACCORDANCE E INTERNATIONAL GRID DETAILED IN ICATION 97 CONTROLLING DIMENSION MILLIM ECNO00 899 8 2000 SEMTECH CORP 652 MITCHELL ROAD NEWBURY PARK CA
8. 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 lower ground injection currents resulting in electrically Output Capacitor s and the Cin Q1 D1 loop Under cleaner grounds for the rest of the system and mini mize source ringing resulting in more reliable gate switching signals 3 The connection between the junction of Q1 D1 24V IN o no circumstances should GND be returned to a ground inside the Cin Q1 D1 loop 6 Vcc for the SC1103 should be supplied from the VIN supply through 100 resistor the Vcc pin should 10 0 1uF SC1103CS ai 1 VCC GND 8 23J cs FB 7 Rb d 3 CS BST Di 0 tuF H PGND DH 1 Ra Heavy lines indicate x7 high current paths Vout Fig 7 Layout diagram for the SC1103 2000 SEMTECH CORP 5 652 MITCHELL ROAD NEWBURY PARK CA foday s Results Tomorrow s P SEMTECH VOLTAGE MODE PWM CONTROLLER SC1103 PRELIMINARY February 29 2000 be decoupled directly to GND by a 0 1uF ceramic ca pacitor 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 run ning back to CS and CS
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SEMTECH SC1103 handbook