SC1101_05 SEMTECH | Alldatasheet

Document overview

  • Manufacturer or author: Provided By ALLDATASHEET.COM(FREE DATASHEET DOWNLOAD SITE)
  • PDF pages: 7

Technical content

Features

Applications

Revision: May 25, 2005 Typical Application Circuit

Description

‹ Low cost / small size ‹ Switch mode efficiency up to 95% ‹ 1% reference voltage accuracy ‹ Over current protection ‹ 500mA output drive ‹ SO-8 package ‹ Pentium® P55 Core Supply ‹ Low Cost Microprocessor Supplies ‹ Peripheral Card Supplies ‹ Industrial Power Supplies ‹ High Density DC/DC Conversion The SC1101 is a versatile, low-cost, voltage-mode PWM controller designed for low output voltage DC/DC power supply applications. A simple, fixed-voltage buck regulator can be implemented using the SC1101 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. SC1101 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. The SC1101 operates at a fixed frequency of 200kHz, providing an optimum compromise between efficiency, external component size, and cost. IRLR3103 2.2 MBRD1035L 4uH 330/2.5V 330/2.5V C10 330/2.5V 150/6.3V 150/6.3V 0.001 127 76.8 *see note 1.0 0.01 ++5V GND 0.1 C11 1.0 0.05 GND VCC1 CS(-)2 CS(+)3 PGND4 DH 5 BST 6 FB 7 GND 8 SC1101 * NOTE: R6 = R7 x (Vout/1.25 - 1) rounded to nearest 1%value 0.1 Vout = 2V @ 10A +12V

2 2005 Semtech Corp. www.semtech.com POWER MANAGEMENT SC1101

Electrical Characteristics

retemaraPl obmySm umixaMs tinU egatloVtupnIV CC DNGot7 +ot3.0-V laitnereffiDdnuorGP DNG DNGot1 ±V egatloVtupnItsooBD NGotTSB5 1+ot3.0-V egnaRerutarepmeTtneibmAgnitarepOT BMA 07+ot0C ° egnaRerutarepmeTegarotST GTS 521ot54-C ° erutarepmeTnoitcnuJmumixaMT J 521C ° .ceS01)gniredloS(erutarepmeTdaeLT DAEL 003C ° tneibmAotnoitcnuJecnatsiseRlamrehT θ AJ 561W /C° esaCotnoitcnuJecnatsiseRlamrehT θ CJ 04W /C° retemaraPl obmySs noitidnoCn iMp yTx aMs tinU ecnerefeRV FER 832.10 52.13 62.1V egnar.pmeTC°521ot0revO5 22.10 52.15 72.1 tnerruCsaiBkcabdeeFI BF 0.20 .8A u tnerruCtnecseiuQI Q VotnitnerruC CC nip0 .50 .8A m noitalugeRdaoLI O A01otA1=5 .00 .1% noitalugeReniLI O A01=5 .0% dlohserhTtimiLtnerruC) -(SCot)+(SC0 60 70 8V m ycneuqerFrotallicsO 0710 020 32z Hk tfihSycneuqerFrotallicsOV BF V< FER 2/0 5z Hk elcyCytuDxaM 095 9% tnerruCecruoS/kniSHDI O V TSB V- HD V/V5.4= HD V- DNGP V2=0 05A m dlohserhTOLVUV OLVU 8.3V Unless specified: VCC = 4.75 to 5.25, GND = PGND = 0V, VO = 2.5V, TA = 25°C, BST = 12V. Per test circuit, unless otherwise specified. Note: (1) This device is ESD sensitive. Use of standard ESD handling precautions is required. Exceeding the specifications below may result in permanent damage to the device, or device malfunction. Operation outside of th e parameters specified in the Electrical Characteristics section is not implied.

3 2005 Semtech Corp. www.semtech.com POWER MANAGEMENT SC1101 Pin Configuration Ordering Information Pin Descriptions eciveD )1( egakcaPT (egnaRpmeT J) RT.SC1011CS 8-OSC °521ot°0 TRTSC1011CS )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. rebmuNniPe maNniPn oitcnuFniP 1C CV. egatlovtupnieciveD 2) -(SC. )evitageN(tupniesnestnerruC 3) +(SC. )evitisoP(tupniesnestnerruC 4D NGP. dnuorgrewopeciveD 5H D. tuptuorevirdedishgiH 6T SBV revirdedishgiH CC .)tsooB( 7B F. )-(tupnireifilpmarorrE 8D NG. dnuorglangiS Top View (8 Lead Plastic SOIC) 4 5 BST DH GND PGND VCC CS(+) CS(-) FB Block Diagram

4 2005 Semtech Corp. www.semtech.com POWER MANAGEMENT SC1101 Careful attention to layout requirements are necessary for successful implementation of the SC1101 PWM controller. High currents switching at 200kHz are present in the application and their effect on ground plane volt- age 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. 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. Mini- mizing this loop area will reduce EMI, lower ground injec- tion currents, resulting in 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 inductor 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. 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. 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 between Cout and the load must be short, wide copper areas to minimize inductance and resistance. 5) The SC1101 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 con- nected 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 circum- stances should GND be returned to a ground inside the Cin, Q1, D1 loop. 6) Vcc for the SC1101 should be supplied from the 5V supply through a 10 Ω 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 run- ning back to CS(+) and CS(-) on the SC1101 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 SC1101 with the bottom resistor (Rb) returned to ground at the GND pin. Under Voltage Lockout The under voltage lockout circuit of the SC1101 assures that the high-side MOSFET driver outputs remain in the off state whenever the supply voltage drops below set parameters. Lockout occurs if V CC falls below 3.8V. Nor- mal operation resumes once V CC rises above 3.8V. Layout Guidelines Applications Information

5 2005 Semtech Corp. www.semtech.com POWER MANAGEMENT SC1101 Vout 4uH Cout +Cin 0.1uF 0.001uF 12V IN Heavy lines indicate high current paths. SC1101CS GND 8VCC1 CS(-)2 CS(+)3 PGND4 DH 5 BST 6 FB 7 Rb Ra Applications Information (Cont.) Layout diagram for the SC1101 VO = V REF (1 + Ra/Rb) IRLR3103 2.2 MBRD1035L L14uH 330/2.5V 330/2.5V C10 330/2.5V 150/6.3V 150/6.3V 0.001 127 76.8 *see note 1.0 0.01 ++5V GND 0.1 C11 1.0 R50.05 GND VCC1 CS(-)2 CS(+)3 PGND4 DH 5 BST 6 FB 7 GND 8 SC1101 * NOTE: R6 = R7 x (Vout/1.25 - 1) rounded to nearest 1%value 0.1 LL42 Vout = 2V @ 10A Application Circuit 5V to 2.0V @ 10A (Bootstrapped)

6 2005 Semtech Corp. www.semtech.com POWER MANAGEMENT SC1101 PIN Descriptions Typical Characteristics Error Amplifier, Gain and Phase Load Regulation VIN = 5V Line Regulation VO = 2.5V; I O = 10A Efficiency VIN = 5V -10 Frequency (Hz) Gain (dB) -45 135 180 Phase (deg) Gain Phase -2.0% -1.5% -1.0% -0.5% 0.0% 0.5% 1.0% 1.5% 2.0% Input Voltage, (V) -1.0% -0.8% -0.6% -0.4% -0.2% 0.0% 0.2% 0.4% 0.6% 0.8% 1.0% 02468 1 0 1 2 Output Current, (A) 3.3V 2.5V 1.8V 60% 65% 70% 75% 80% 85% 90% 95% 100% 02468 1 0 1 2 Output Current, (A) 3.3V 2.5V 1.8V Output Ripple Voltage VIN = 5V; V O = 3.3V; I O = 10A

7 2005 Semtech Corp. www.semtech.com POWER MANAGEMENT SC1101 Outline Drawing - SO-8 Minimum Land Pattern - SO-8 Semtech Corporation Power Management Products Division

200 Flynn Road, Camarillo, CA 93012

Phone: (805)498-2111 FAX (805)498-3804 Contact Information SEE DETAIL DETAIL AA .050 BSC .236 BSC .010 .150 .189 .154 .193 .012 - 0.25

1.27 BSC

6.00 BSC

3.90 4.90 .157 .197 3.80 4.80 .020 0.31 4.00 5.00 0.51 bxN 2X N/2 TIPS SEATING aaa C E/22X N A D bbb C A-B D ccc C e/2 (.041) .004 .008 .028 .016 .007 .049 .004 .053 8° 0° 0.20 0.10 - 8° 0.40 0.17 1.25 0.10 .041 .010 .069 .065 .010 1.35 (1.04) 0.72 1.04 0.25 - 1.75 1.65 0.25 c L (L1) 01 0.25 GAGE PLANE h h 3. DIMENSIONS "E1" AND "D" DO NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. -B- CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). DATUMS AND TO BE DETERMINED AT DATUM PLANE NOTES: 2. -A- -H- SIDE VIEW A B C De H PLANE REFERENCE JEDEC STD MS-012, VARIATION AA.4. N bbb aaa ccc A b D E L h e c DIM MIN MILLIMETERS NOM DIMENSIONS INCHES MIN MAX MAX NOM E (.205) (5.20) ZG Y P (C) 3.00.118 1.27.050 0.60.024 2.20.087 7.40.291 X INCHES DIMENSIONS Z P Y X DIM C G MILLIMETERS THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET. NOTES: REFERENCE IPC-SM-782A, RLP NO. 300A.2.