SC1486 Semtech Corporation, SC1486 Datasheet
SC1486
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SC1486 Summary of contents
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... POWER MANAGEMENT Description The SC1486 is a dual output constant on synchronous- buck PWM controller optimized for cost effective mobile DDR applications. Features include high efficiency, a fast dynamic response with no minimum on time, a REFIN input and a buffered REFOUT pin capable of sourcing 3mA. The excellent transient response means that SC1486 based solutions will require less output capacitance than competing fixed frequency converters ...
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... SC1486 ...
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... SC1486 = 2. 1.25 1M, R VDDQ VTT TON1 TON2 2 ° ° ° ...
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... SC1486 = 2. 1.25 1M, R VDDQ VTT TON1 2 ° ° ° ...
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... SC1486 = 2. 1.25 1M, R VDDQ VTT TON1 2 ° ° ° ...
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... SC1486 ° ...
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... SC1486 . ...
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... LOGIC 10 PWM REFOUT 11 REF VCCA2 TOFF BUFFER OC ZEROI FBK2 - PWM FAULT OV 13 MONITOR UV PGOOD2 REF + 10% 14 REF - 10% AGND2 REF - 30% FIGURE 1 - SC1486 Block Diagram 8 SC1486 AGND1 FBK1 + X3 26 FB1 1.5V VCCA1 TOFF 25 VOUT +5V 24 VDDQ TON TON1 23 EN/PSV1 22 POR/SS VBAT VCCA VCCA1 ...
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... POWER MANAGEMENT Application Information +5V Bias Supplies The SC1486 requires an external +5V bias supply in ad- dition to the battery. If stand-alone capability is required, the +5V supply can be generated with an external linear regulator such as the Semtech LP2951A. To minimize channel to channel crosstalk, each controller has 4 sup- ply pins, VDDP, PGND, VCCA and AGND. ...
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... ILIM pin and LX set the over current threshold. This resistor R is connected to a 10uA cur- ILIM rent source within the SC1486 which is turned on when the low side MOSFET turns on. When the voltage drop across the sense resistor or low side MOSFET equals the voltage across the R resistor, current limit will activate ...
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... The selection of the ripple current is based on the maximum output cur- rent and tends to be between 20% to 50% of the maxi- mum load current. Again, cost, size and efficiency all play a part in the selection process. 11 SC1486 ) is determined by the MAX www.semtech.com ...
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... ESR should be increased. 2002 Semtech Corp. SC1486 ESR Requirements The constant on-time control used in the SC1486 regulates the ripple voltage at the output capacitor. This signal consists of a term generated by the output ESR of the capacitor and a term based on the increase in voltage across the capacitor due to charging and discharging during the switching cycle ...
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... Thus, the percentage error is the sum of the reference variation over supply and temperature and the offset in the error comparator or 1.5%. The on pulse in the SC1486 is calculated to give a pseudo fixed frequency. Nevertheless, some frequency variation with line and load can be expected. This variation changes the output ripple voltage. Because constant on regulators regulate to the valley of the output ripple, ½ ...
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... POWER MANAGEMENT Application Information (Cont.) DDR Supply Selection The SC1486 can be configured so that VTT and VDQ are generated directly from the battery. Alternatively, the VTT supply can be generated from the VDDQ supply. Since the battery configuration generally yields better efficiency and performance, the eval board is configured to generate both supplies from the battery ...
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... SC1486 www.semtech.com ...
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... 2002 Semtech Corp SC1486 www.semtech.com ...
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... POWER MANAGEMENT Outline Drawing - TSSOP-28 Land Pattern - TSSOP-28 Contact Information Phone: (805)498-2111 FAX (805)498-3804 2002 Semtech Corp. Semtech Corporation Power Management Products Division 200 Flynn Road, Camarillo, CA 93012 17 SC1486 www.semtech.com ...