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1、Linear Technology Chronicle April 20001Product of the Month, LTC and LT are registered trademarks of Linear Technology Corporation. OPTI-LOOP, Burst Mode and Hot Swap are a trade- marks of Linear Technology Corporation.A Showcase of Linear Technologys Focus ProductsLinear Technology ChronicleApril 2
2、000Vol. 9 No. 4Inside This Issue:500mA, SOT-23 Step-Down Regulator Switches at 1MHzLTC1701 . 2 Single/Dual/Quad 400MHz Current Feedback AmplifiersLT1395/LT1396/LT1397. 2 Simple Converter for 5V to 48VLTC1624 . 3 Dual Hot SwapTM with Independent “ON” Pins for Supply SequencingLTC1647 . 3 Parallel 16-
3、Bit Rail-to-Rail Micropower DACLTC1657 . 4Figure 1. LTC1599 Achieves 4-Quadrant Multiplication with On-Chip Precision Resistors16-Bit, 2-Byte Parallel Input, Low Glitch Multiplying DAC with 4-Quadrant ResistorsLTC1599The LTC1599 is a 16-bit multiplying current output DAC. Both INL and DNL are accura
4、te to 1LSB over temperature, guaranteeing true 16-bit performance and eliminating external calibrations. True 4-quadrant multiplication is achieved with on-chip precision multiplication resistors, allowing output ranges of 0V to 10V, 0V to 10V or 10V. The LTC1599 operates off a single 5V supply, typ
5、ically consuming only 10mW of power. The LTC1599 offers a 2-byte parallel input. An asynchronous clear pin resets theoutput to midscale or zero scale, depending on user settings. A low glitch impulse of less than 2nV-s improves the performance of the device in industrial control systems. The LTC1599
6、 is available in 24-pin PDIP and SSOP packages and is specified over the commercial and industrial tempera- ture ranges. For a full 16-bit parallel inter- face current output DAC, Linear Technology offers the LTC1597. For serial interface 16-bit current output DACs, the LTC1595 and LTC1596 offer com
7、parable performance.VCCLTC1599RFBRFBROFSROFS5VLDLD432633621211241020819R1RCOM2R21REF560.1F7IOUT115pF15pFVOUT1599 TA01IOUT2F9IOUT2SDGND+LT1468WR14 TO 18, 21 TO 2313WRMLBYTEMLBYTECLRCLVLCLR CLVL+LT146816-BIT DACR1R28 DATA INPUTSComplete Charger for Lithium-Ion Batteries in MSOPLTC1731The LTC1731 is a
8、complete, constant- current/constant-voltage linear charge con- troller for lithium-ion batteries. It offers the highest level of integration in the market to create the smallest, simplest charger pos- sible. The device employs internal resistor dividers to achieve 1% charge voltage accu- racy witho
9、ut the need for external precision resistors (Figure 1). The charge current can be programmed with 5% accuracy using an external sense resistor (RSENSE) in combina- tion with the program resistor (RPROGRAM). The output float voltage of the LTC1731-4.2 version is set at 4.2V. Other versions provide a
10、n output of 4.1V, 8.2V or 8.4V to serve 1- and 2-cell systems. The LTC1731 controls a low cost, external P-channel MOSFET selected for the desired charging current. An internal com- parator monitors the charge current and pro- vides a flag output when the charge current drops to 10% of the programme
11、d currentVCCVIN 5V TO 15VSENSEDRV1kRSENSE 0.2RPROG* 19.6kLi-Ion CELLLTC1731-4.2*SHUTDOWN INVOKED BY FLOATING THE PROG PIN OR PULLING IT HIGHBATCHRG87MBRM120T310F1731 TA011FIBAT = 500mACTIMER 0.1FQ1 Si9430DY6154+23TIMERPROGGNDFigure 1. 500mA Li-Ion ChargerContinued on page 22Linear Technology Chronic
12、le April 2000Contact your local Linear Technology sales office for a data sheet and evaluation samples. For more information, visit our web site at www.linear-.500mA, SOT-23 Step-Down Regulator Switches at 1MHzLTC1701(C/10). This flag output will drive a charge- status LED. A built-in timer, program
13、med with a single external capacitor, sets the total charge termination time. Deeply discharged cells are automatically trickle charged at10% of the programmed charge current until the cell voltage exceeds 2.5V. The LTC1731 has a wide input voltage range of 4.5V to 15V, so that inexpensive wall adap
14、ters can be used to power the charger. It will charge nickel-cadmiumLTC1731 from page 1The LTC1701 is the industrys first step-down, current mode DC/DC converter in a SOT-23 package. It operates from an input of 2.5V to 5.5V (6V maximum) for long life in single cell Li-Ion or 3-/4-cell NiCd/NiMH bat
15、tery systems. It switches at 1MHz to allow the use of tiny, low cost capacitors and inductors that are 2mm or less in height. The area used by the complete regulator is less than 2cm2, as shown in Fig- ure 1. The LTC1701 may be configured as a zeta converter for buck/boost applications. The output voltage is adjustable from 1.25V to 5V. The built-in 0.28 switch fur- nishes up to 500mA of output current at 94% efficiency in the step-down mode.The LTC1701 incorporates a current mode, constant off-time architecture for superior line regulation with a varying input.
