SC2604ULTRT

SC2604 Simple PWM Boost Controller with Input Disconnect FET Drive POWER MANAGEMENT Features „„ „„ „„ „„ „„ „„ „„ „„ „„ „„ „„ „„ „„ „„ Description Input Voltage Range: 4.5V to 16V 1% Voltage Reference Accuracy Up to 95% Efficiency Input Disconnect FET Drive In-rush Current Control Internal Compensation Programmable Current Limit Programmable Soft Start 800mA Typical PWM Gate Drive 400kHz Switching Frequency Under Voltage Lockout O U T IN on the OCP/EN pin 0and pin can trigger a .625the SS/VREF 750 hiccup event because of the charging current demanded by the boost regulator output capacitor. 72mV Voltage SettingRthe =Output CS IPEAK In Figure 1, an external resistive divider R3 and R5 with its center tap tied to the FB pin sets the output voltage.  V  R3 = R 5  OUT − 1 1 . 25 V   In some applications, a RC branch (R6, C12 in the Typical Schematic on page 12) will be needed for loop stability. Maximum Duty Cycle The maximum duty cycle, Dmax defines the upper limit of VO U T 1ratio power conversion = VIN 1 − DMA X VO U T 1 = VIN 1 − DMA X Calculating Current Sense Resistor C ( V − Vd ) R C S C O C P/ E N > O U T IN 0.625 750 Current sense resistor is placed at the input to sense C ( V V ) R − O U T IN d C inductor current of the boostSregulator. The value of C Opeak C P/ E N > 0.625 by750 the resistor can be calculated 72mV IPEAK 72mV R CSis=the allowed boost inductor peak current. where IPEAK IPEAK R CS = In many applications,  V a noise  filter circuit (R1=200, C10=10nF R3 = R 5  OUT − 1 in the Typical Schematic  1.25 V on  page 12) may be needed for the input current sensing.  V  R3 = R 5  OUT − 1  1.25 V  © 2010 Semtech Corp. C O C P/ E N > C O U T( VIN − Vd ) R C S 0.625 750 Disconnect FET Selection 72mV IPEAK voltage of DRV pin drops slightly as The floating driving R CS = the supply voltage VIN is below 7.5V (Typical Characteristics on page 8), where a FET with low gate threshold voltage (VGS(TH)) has to be used for the disconnect FET. In a 5V input  VOUT  R3 = Ra5FET −GS(TH) 1 =2V, such as FDD6672A from  with V application,  1.25 V  Fairchild, is needed. Layout Guidelines Careful attentions to layout requirements are necessary for successful implementation of the SC2604 PWM controller. High currents switching at 400kHz 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. 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, as shown on the layout diagram in Figure 4. 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, www.semtech.com 10 yout SC2604 Applications Information (Cont.) 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. 5) The SC2604 is best placed over an isolated ground plane area. The soft-start capacitor and the Vin decoupling 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. 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 diagram inductance and resistance. 6) Input voltage of the SC2604 should be supplied from the power rail through a 1Ω 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. Vout VIN Ra D1 4.7uH Rcs Cin 1 + SC2604 2 5 1uF 0.1uF 1 3 VIN SS/VREF CS DRV FB GATE OCP/EN GND 6 Rb Cout 8 7 4 0.1uF Note: Heavy lines indicate the critical loop carrying high pulsating current. The inductance of the loop needs to be minimized. Figure 4. SC2604 Layout Diagram © 2010 Semtech Corp. www.semtech.com 11 SC2604 Applications Information (Cont.) Typical application schematic with 12V input and 25V/1.5A output Rs 10m, Sen. Res. 12V INPUT + C1 220uF C3 1uF Rcc 1R0 Q1 IRF7821 C11 1uF Da MA729 1 D1 2 C4 15uH 1uF R1 200 C10 10nF L1(CD1-150) A 25V/1.5A OUTPUT C C6 4.7uF CMSH2-40L Q2 AO4412 + C7 220uF U1 1 CS DRV 8 2 VIN OCP/EN 7 3 GATE FB 6 SS/VREF 5 4 GND SC2604 R3 499k C12 C13 0.33uF C14 0.1uF 0.33uF R6 1.43k R5 26.3k Note: A small Schottky diode (Da) may be required in some applications to clamp negative spike at the GATE pin. Bill of materials 5 Item Quantity Reference 1 1 C1 2 3 C3,C4,C11 3 1 C6 4 1 C7 5 1 C10 6 1 C12 7 1 C13 8 1 C14 9 1 D1 10 1 Da 11 1 L1 12 1 Q1 13 1 Q2 14 1 Rs 15 1 R1 16 1 Rcc 17 1 R3 18 1 R5 19 1 R6 20 1 U1 © 2010 Semtech Corp. Part (P/N of Vender) 220uF/10V 1uF/16V 4.7uF/50V 220uF/35V/160m 10nF 0.33uF 0.33uF 0.1uF CMSH2-40L (Schottky diode) MA729 (Schottky diode) 15uH/3.5A (CD1-150) 4 IRF7821 AO4412 15m(Sensing Res.) 200 1R0 499k 26.1k 1.43k SC2604 Vendor Rubycon, ZL Vishay Murata Rubycon, YXF Vishay Vishay Vishay Vishay Central Semi Panasonic Coiltronics 3 IR Alpha & Omega Semi. Vishay Vishay Vishay Vishay Vishay Vishay Semtech Title Size A Date: SEMTECH CORPORATIO SC2604 (MSOP-8) EVB Sc Document Number 12V Input, 25V/1.5A Output, 4 Tuesday, October 23, 2007 2 www.semtech.com 12 Sheet SC2604 12V Input (5V/DIV) Applications Information (Cont.) Start up 12V Input (5V/DIV) 25V output (10V/DIV) SS/VREF (1V/DIV) OCP/EN (1V/DIV) X=5ms/DIV Inductor current and DRV pin voltage at OCP 25V Output (1V/DIV) OCP/EN (1V/DIV) Inductor Current (5A/DIV) DRV Voltage (5V/DIV) © 2010 Semtech Corp. X=10ms/DIV www.semtech.com 13 SC2604 MSOP-8 Outline Outline Drawing - MSOP-8 ü DIM A A A1 A2 b c D E1 E e L L1 N 01 aaa bbb ccc D N 2X E/2 E1 PIN 1 INDICATOR ü C E 1 2 2X N/2 TIPS e B ü D C A .043 .006 .037 .015 .009 .118 .122 .118 .122 .193 BSC .026 BSC .016 .024 .032 (.037) 8 8° 0° .004 .005 .010 1.10 0.00 0.15 0.75 0.95 0.22 0.38 0.08 0.23 2.90 3.00 3.10 2.90 3.00 3.10 4.90 BSC 0.65 BSC 0.40 0.60 0.80 (.95) 8 0° 8° 0.10 0.13 0.25 ü ü c GAGE PLANE A1 C .000 .030 .009 .003 .114 .114 H A2 SEATING PLANE DIMENSIONS INCHES üüüüü MIN NOM MAX MIN NOM MAX 0.25 C A-B D L (L1) DETAIL SEE DETAIL SIDE VIEW 01 A A MSOP-8 Landing Pattern NOTES: 1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). 2. DATUMS -A- AND -B- TO BE DETERMINED AT DATUM PLANE ü 3. DIMENSIONS "E1" AND "D" DO NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. 4. REFERENCE JEDEC STD MO-187, VARIATION AA. Land Pattern - MSOP-8 X DIM ü G Y Z C G P X Y Z DIMENSIONS INCHES üüüüü (.161) .098 .026 .016 .063 .224 (4.10) 2.50 0.65 0.40 1.60 5.70 P NOTES: 1. © 2010 Semtech Corp. THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET. www.semtech.com 14 SC2604 Outline Drawing - 2x3 MLPD-UT8 A B D DIM E PIN 1 INDICATOR (LASER MARK) A ü C A2 A1 SEATING PLANE A A1 A2 b D D1 E E1 e L N aaa bbb DIMENSIONS üüüüü INCHES MIN NOM MAX MIN NOM MAX - .024 .002 (.006) .007 .010 .012 .075 .079 .083 .059 .065 .069 .114 .118 .122 .065 .071 .075 .020 BSC .012 .016 .020 8 .003 .003 .020 .000 0.50 0.60 0.00 0.05 (0.1524) 0.18 0.25 0.30 1.90 2.00 2.10 1.50 1.65 1.75 2.90 3.00 3.10 1.65 1.80 1.90 0.50 BSC 0.30 0.40 0.50 8 0.08 0.08 C D1 1 2 ü ü E1 N ü e ü C A B ü ü NOTES: 1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). 2. COPLANARITY APPLIES TO THE EXPOSED PAD AS WELL AS THE TERMINALS. Land Pattern - 2x3 MLPD-UT8 K DIM ü G H Y X Z C G H K P X Y Z DIMENSIONS INCHES üüüüü (.116) .087 .071 .069 .020 .012 .030 .146 (2.95) 2.20 1.80 1.75 0.50 0.30 0.75 3.70 P NOTES: 1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). 2. THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY. CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR COMPANY'S MANUFACTURING GUIDELINES ARE MET. 3. THERMAL VIAS IN THE LAND PATTERN OF THE EXPOSED PAD SHALL BE CONNECTED TO A SYSTEM GROUND PLANE. FAILURE TO DO SO MAY COMPROMISE THE THERMAL AND/OR FUNCTIONAL PERFORMANCE OF THE DEVICE. © 2010 Semtech Corp. www.semtech.com 15 SC2604 © Semtech 2010 All rights reserved. Reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. The information presented in this document does not form part of any quotation or contract, is believed to be accurate and reliable and may be changed without notice. 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Should a customer purchase or use Semtech products for any such unauthorized application, the customer shall indemnify and hold Semtech and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs damages and attorney fees which could arise. Contact Information Semtech Corporation Power Mangement Products Division 200 Flynn Road, Camarillo, CA 93012 Phone: (805) 498-2111 Fax: (805) 498-3804 www.semtech.com © 2010 Semtech Corp. www.semtech.com 16