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1、1Linear Technology Chronicle June 1996Products of the MonthA Showcase of Linear Technologys Focus ProductsLinear Technology ChronicleJune 1996Vol. 5 No. 6, LTC and LT are registered trademarks of Linear Technology Corporation.12-Bit Micropower Voltage Output Digital-to-Analog Converters in SSOP Pack
2、age Have Excellent DNLThe LTC1450 and LTC1450L are complete single supply micropower voltage output 12-bit digital-to-analog converters (DACs) in 24-pin SSOP and PDIP pack- ages. The 3V powered LTC1450L and 5V powered LTC1450 draw only 250A and 400A of supply current, respectively. Maximum Different
3、ial Nonlinearity error is only 0.5LSB. Figure 1 shows the highly ac- curate DNL of the LTC1450 and LTC1450L. These new DACs include a rail-to-rail output buffer amplifier, refer- ence and a double buffered parallel digital interface. The parallel interface can be con- figured as a 12-bit or 8 + 4-bi
4、t digital I/O.The 5V powered LTC1450 contains a 2.048V internal reference and an output that can be pin selected for a 4.095V or 2.047V full-scale range. The 3V powered LTC1450L contains a 1.22V reference and the output can be configured for a 2.5V or 1.22V full-scale range. An external refer- ence
5、can be applied to convert the device to a true rail-to-rail output DAC. Internal power-on reset is also provided to assure a zero output at system start-up. Figure 2 shows a typical LTC1450 simplified circuit diagram. The reference output, high and low reference inputs and gain setting resis- tors a
6、re user accessible to provide maximum flexibility.The LTC1450 and LTC1450L micropower DACs are ideal for use in industrial process control, automatic test equipment, function generators and portable battery-powered data acquisition and con- version products. The LTC1450 and LTC1450L are specified ov
7、er 4.5V to 5.5V and 2.7V to 5.5V supply voltage ranges, respectively. These DACs are available specified for either the 0C to 70C range or the industrial 40C to 85C range. Contact your local Linear Technology sales office for a data sheet and free evaluation samples of the LTC1450 and LTC1450L.CODE0
8、DNL ERROR (LSBs) 0.5?0.0?0.5 10242048 25601450/50L TA0251215363072 3584 4095Inside This Issue:Industrial Grade 3V, 8-Bit A/D Converters Are Micropower and Micro Sized . 2 Constant Voltage Load Box for Battery Simulation. 312-Bit, 1.25Msps Sampling A/D Converter Now Available in Industrial Grade . 4F
9、igure 1. LTC1450/LTC1450L Have a Maximum 0.5LSB DNL ErrorContinued on page 22A Battery Charger IC Has Automatic Buck-to- Boost and Boost-to-Buck SwitchoverThe LT1513 is a 500kHz current mode switching regulator specifically configured to create a constant-current/constant-voltage battery charger. Th
10、is new charger IC auto- matically transfers from buck to boost mode, allowing the input voltage to range above or below the battery voltage. Also known as a SEPIC (Single-Ended Primary Inductance Converter) circuit, the LT1513 can be usedLTC1450VOUTDATA (0:11)?CSLSB?CSMSB?WR?LDAC?CLRVCCREF OUTGNDREF
11、 HIREF LOGAIN1/GAIN2FROM P? DATA BUSFROM P AND? DECODE LOGICFROM ? SYSTEM RESET5V0.1FCONTROL? OUTPUT? 0V TO 4.095VLTC1450/50L TA01Figure 2. LTC1450 Simplified Circuit2Linear Technology Chronicle June 1996cell. Charging current can be easily pro- grammed for all battery types. Figure 2 shows the maxi
12、mum charging current versus input voltage of the LT1513.The LT1513 is designed for battery charging when the input voltage is above and below the charge voltage. Other LT1513 family members include the LT1510, LT1511 and LT1512. These other devices are optimized for various input/output condi-tions
13、and different battery types as shown in Table 1. These power devices are available in various package types, including an 8-lead SO surface mount package. The LT1513 is available in a 7-lead TO-220 and a 7-lead surface mount DD package. Devices are specified for operation from 0C to 70C and 40C to 8
14、5C. For a data sheet and evalua- tion samples of the LT1513, contact your local Linear Technology sales office.for either voltage step-down (buck) or volt- age boost mode with no component changes. This power IC charges any number of Li-Ion, NiMH and NiCd battery cells up to 20V. The LT1513 includes
15、 1% output volt- age accuracy as required by rechargeable lithium-ion batteries. The LT1513 is avail- able in a surface mount 7-lead DD package and the switching frequency of 500kHz minimizes external component size.In addition to the usual voltage feed- back mode, the LT1513 has a current sense fee
16、dback circuit for accurately controlling the output current of a flyback or SEPIC topology charger. These topologies allow the current sense circuit to be ground re- ferred and completely separated from the battery itself, simplifying battery switching and eliminating ground loop errors. Figure 1 shows a typical LT1513 battery charger circuit.Maximum sw
