《电子集成线性技术资料（LT公司器件）41》由会员分享，可在线阅读，更多相关《电子集成线性技术资料（LT公司器件）41（4页珍藏版）》请在金锄头文库上搜索。
1、1Linear Technology Chronicle October 1997A Showcase of Linear Technologys Focus ProductsLinear Technology ChronicleOctober 1997Vol. 6 No. 10Product of the MonthThe switching frequency may be exter- nally set with a single capacitor up to 250kHz and may be synchronized to an external clock source of
2、up to 375kHz. Pro- tection features include cycle-by-cycle current limiting, undervoltage lockout and thermal shutdown. For unregulated DC/DC conversion, the LT1533 may be configured to operate in a fixed 50% duty cycle mode.The LT1533 is available from stock in a 16-lead narrow SO package, screened
3、 to the commercial and industrial temperature ranges. For a data sheet and evaluation samples, contact your local Linear Technology sales office or visit our web site at www.linear- for more information., LTC and LT are registered trademarks of Linear Technology Corporation. Hot Swap is a trademark
4、of Linear Technology Corporation.Inside This Issue:LTC1422: Hot SwapTM Controller IC in SO-8 Permits Safe PC Board Insertion and Removal .2LTC1536: Triple Reset Generator for PCI Applications Offers 0.75% Threshold Accuracy .2LT1300: A 4-Cell to 5V Power Supply . 3LTC1329 and LTC1428: Push-Button DA
5、Cs in SO-8 Packages Tweak Adjustable Regulators . 4The LT1533 can be configured in low noise step-up/step-down, inverting and iso- lated DC/DC converters to regulate both positive and negative output voltages. Because the voltage and current slew rates are independently adjustable using external res
6、istors, the designer is given the flexibility to select the optimum noise vs efficiency operating point for any application.The LT1533 operates from an input supply voltage of 2.7V to 23V (input volt- age is limited to 15V for push-pull configurations). It draws 9mA (typ) quies- cent current and shu
7、ts down to only 12A, making the part suitable for portable, battery-powered applications.Ultralow Noise Switching Regulator Is Quieter Than Linear RegulatorsThe LT1533 is a DC/DC converter that produces less than 100V peak-to-peak output noisefar less than linear regulators. The first in a new class
8、 of switching regula- tors, the LT1533 dramatically reduces both conducted and radiated noise by accurately controlling the voltage and current slew rates of the two internal power switches. Using this novel technique, high frequency har- monic noise can be reduced by as much as 40dB over typical sw
9、itching regulators, with a relatively minor impact on power conver- sion efficiency. Figure 1 shows the comparison in output noise between a con- ventional switcher and the LT1533. Its ability to provide high efficiency voltage conversion with very low noise makes it ideal in such noise-sensitive ap
10、plications as precision instrumentation and wireless com- munications.The LT1533 is a complete current mode switching regulator that includes an oscilla- tor, error amplifier, protection circuitry and two 1A power switches (Figure 2). Byemploying a push-pull switching topology to drive a center-tapp
11、ed transformer, it signifi- cantly reduces the RMS ripple current observed at the converters input and output. This topology and the ability to control switching harmonics can greatly reduce and even eliminate power supply shielding requirements in sensitive applications.Figure 2. The LT1533 as a 5V
12、 to 12V Push-Pull Converter for Low EMI ApplicationsSHDN?DUTY?SYNC?COL A?COL B?PGND?RVSL?RCSL?FBNFBLT1533GNDVIN5V142?15?16?13?12?711?3?4?5610?CT? 3300pFRT, 18kCVC? 0.01FRVSL,15kNote 1CIN? 4.7FRCSL,15k+T1*DS1? 1N4148BAL2*? 100H10 : 36L3*? 100HDS2? 1N4148R2? 2.49k? 1%*? *? NOTE1:89R1? 21.5k? 1%C3? 47F
13、+C4? 47FCOILTRONICS CTX02-13716-X1? COILTRONICS CTX100-3? 25nH TRACE INDUCTANCE OR COILCRAFT B10T12V? 200mA1533 TA01+CT?RTVC10mV/DIV10mV/DIVLT1533TYPICAL SWITCHERSFigure 1. The LT1533 Produces Less Than 100V Peak-to-Peak Output Noise over a 100MHz Bandwidth, Considerably Less Than Conventional Switc
14、hers2Linear Technology Chronicle October 1997Hot Swap Controller IC in SO-8 Permits Safe PC Board Insertion and Removalfailures. All that is required is an external N-channel MOSFET along with resistors and capacitors to set the timing and reset thresholds as shown in Figure 1. The LTC1422 is flexib
15、le enough to cover supply voltages ranging from 2.7V to 12V as well as 48V applications.Hot swap means plugging a component into a socket that is already powered. The inrush current required to charge up all of the bypass capacitors can be several amps which can damage the connector and other in-lin
16、e components as well as cause the sys- tem supply to glitch. The LTC1422 eliminates glitches on the system supply and allows the user to set the maximum current limit. Similarly, a user-programmable RESET threshold notifies the processor when supply voltage drops below the selected voltage.The LTC1422 is available in the 8-pin PDIP and SO pack
