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1、1Linear Technology Chronicle July 1996Products of the MonthA Showcase of Linear Technologys Focus ProductsLinear Technology ChronicleJuly 1996Vol. 5 No. 7, LTC and LT are registered trademarks of Linear Technology Corporation.Complete 12-Bit, 400ksps A/D Converter in SO-8 PackageThe LTC1400 is the w
2、orlds first 400ksps 12-bit analog-to-digital (A/D) con- verter that fits in an SO-8 package. It is complete with a 200ns sample-and-hold and a precision reference. The LTC1400 con- verts 0V to 4.096V unipolar analog signals from a single 5V supply and 2.048V bipo- lar inputs from a 5V supply. Unipol
3、ar and bipolar conversion modes and a 3-wire serial port make this device quite flexible for a variety of microprocessor, microcontroller and DSP applications where speed and small size are essential. Figure 1 shows the main parts of this complete A/D converter.SAMPLE RATE (Hz)0.01SUPPLY CURRENT (mA
4、)100?10?1?0.1?0.01?0.001 101k1MLTC1400 TA020.1110010k 100kNORMAL CONVERSIONNAP MODE ? BETWEEN CONVERSIONSLEEP AND NAP MODE? BETWEEN CONVERSIONSLEEP MODE BETWEEN? CONVERSION6.4MHz CLOCKThe LTC1400 draws 75mW from a 5V or 5V source while performing conversions at 400ksps. It also operates under two po
5、wer saving modes. In Nap mode, it consumes only 6mW and can wake up and convert immediately. In Sleep mode, it uses just 30W, where a reference ready signal is available in the serial data word to indicate that the reference has settled and the chip is ready to convert. These Nap and Sleep modes can
6、 be used for reducing power con- sumption at lower sample rates (Figure 2).Excellent DC specs include 1LSB maximum differential nonlinearity (DNL), 1LSB integral nonlinearity (INL), and a 25ppm/C drift over temperature. Guaran- teed AC performance over temperature includes 70dB signal-to-noise + dis
7、tortion S/(N + D) and 76dB total harmonic distor- tion (THD) at an input frequency of 100kHz. The LTC1400 is ideally suited for telecom, portable test equipment, PCMCIA data acquisition and DSP applications. It is available in commercial and industrial tem- perature versions. Contact your local Line
8、ar Technology sales office for a data sheet and evaluation samples.Figure 2. Using Sleep and Nap Modes Reduces Power Consumption at Low Sample RatesRail-To-Rail Input and Output, Precision Op Amps Draw Only 50AThe dual LT1490 and quad LT1491 are rail-to-rail input and output op amps requiring less t
9、han 50A of supply current per amplifier. They can operate on any split or single supply with a total voltage of 2.5V up to 44V, the widest among any micropower rail-to-rail op amp. The output voltage swings to within 50mV of the supply rail at no load while the input common mode voltage can range up
10、 to 44V above the op amps negative rail independent of the volt- age on the positive rail.Continued on page 2Precision Quad Filter Building Block Fits in 28-Lead SSOP, Works on 3.3V Supply . 2 Power Supplies for Subscriber Line Interface Circuits. 3 200V/s Op Amp Uses Only 250A Supply Current. 41.1A
11、 Output, Current Feedback Amp Has 35MHz Bandwidth, 700V/s Slew Rate. 4Inside This Issue:LTC1400 BD0112-BIT CAPACITIVE DACCOMPSUCCESSIVE APPROXIMATION ? REGISTER/PARALLEL TO ? SERIAL CONVERTERZEROING SWITCHCONTROL? LOGIC2.42V REFDOUTVCCCONVCLKVREFAINCSAMPLE12GNDVSSSO-8Figure 1. Functional Block Diagr
12、am of the LTC14002Linear Technology Chronicle July 1996LT1490/LT1491 from page 1monitor, where current is measured into or out of the battery.The LT1490 is offered in 8-pin PDIP and SO-8 packages. The LT1491 is available in 14-pin PDIP and SO packages. Call your local Linear Technology sales office
13、for a data sheet and evaluation samples.wide supply voltage range and low power consumption make the LT1490 and LT1491 well suited for portable and higher voltage industrial applications, such as battery- or solar-powered systems, portable instrumen- tation, micropower active filters and 4mA to 20mA
14、 current loop transmitters. Figure 1 illustrates the LT1491 used as a battery+RA? 2kQ2? 2N3904S1S1 = OPEN, GAIN = 1? S1 = CLOSED, GAIN = 10RA = RB? VS = 5V, 0V10k90.9kVOUTLOGIC149091 TA01LOGIC HIGH (5V) = CHARGING? LOGIC LOW (0V) = DISCHARGINGRG? 10k? ?Q1? 2N3904RS? 0.2CHARGER? VOLTAGE 1/4 LT1491? A
15、1/4 LT1491? BRA? 2kRB? 2kVBATT = 12VIBATT+RB? 2k LOAD+1/4 LT1491? C1/4 LT1491? D?VOUT? (RS)(RG/RA)(GAIN)VOUT? GAINIBATT = = AMPS Figure 1. The LT1491s Wide Input Voltage Range Makes it Suitable as a Battery MonitorPrecision Quad Filter Building Block Fits in 28-Lead SSOP, Works on 3.3V SupplyThe LTC1068 quad universal filter building block consists of four identical 2nd order filters that fit in a small 28-pin SSOP package. It allows building high precision, high performance filters using a single power supply as low as 3.3V. Each building block, togeth
