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1、1Linear Technology Chronicle November 1996A Showcase of Linear Technologys Focus ProductsLinear Technology ChronicleNovember 1996Vol. 5 No. 11Products of the MonthSoftware-Selectable Multiprotocol Chip Set Simplifies Data Networking Interface DesignC-Load is a trademark of Linear Technology Corporat
2、ion., LTC and LT are registered trademarks of Linear Technology Corporation.Controller IC Allows Safe Hot Swapping of Circuit Boards . 2 First Dual 12-Bit Voltage Output DAC in SO-8 Runs on 3V Supply. 2Micropower Dual JFET Op Amps Feature pA Input Bias Currents and C-LoadTM Drive Capability. 3Find L
3、inear Technologys Products on CD-ROMFast and Free!. 4Dual DAC Adds Features to Single 5V Supply, 12-Bit Family . 4Inside This Issue:Figure 1. The LTC1343 and LTC1344 Address the Problem of Easily Switching the Terminations for Different Protocols Using a Single Connector. Here it is Configured for S
4、ingle Port DCE and V.35NCNCCABLE1343 F1117?18?19?21LTC1343LTC1343CONNECTOR2021?19?18?172221M2M1LTC1344LATCHM0 (DATA)23241CTRL/CLK22(DATA)?M0?M1?M2?DCE/DTELATCH20CTRL/CLK22DCE/DTE?M2?M1?M0?(DATA)LATCHVCCDCE/? DTER1, 10k VCCR2, 10k VCCR3, 10k VCCR4, 10k VCCV.36 and X.21 protocols that are both NET1 an
5、d NET2 compliant. This chip set is ideal for space limited networking applications and supports all major telecom protocols for remote access serial ports.In a typical application, the first LTC1343 is connected to the clock and data signal lines along with the diagnostic LL (local loop-back) and TM
6、 (test mode) signals. The second LTC1343 is connected to the con- trol signal lines along with the diagnostic RL (remote loop-back) signals. Switching between modes is simplejust three mode select pins are required for both the LTC1343 and LTC1344, as shown in Figure 1. The mode pins are latched int
7、ernally to allow shar- ing of the select lines between multiple interface ports. DTE or DCE is set with one pin, as is the designation for whether the transceiver is used for data and clock signals or control signals. This greatly simplifies the task of switching eight different types of serial port
8、s to the same DB-25 connector, as shown in Figure 2. Other routing tasks, such as loop- back testing or echo clocking, are also easily performed.The LTC1343 is packaged in a 44-lead SSOP and the LTC1344 in a 28-lead SSOP. Together they eliminate the switches, relays and jumpers normally required to
9、switch between drivers, receivers and associated ter- mination schemes. The three chips together occupy only 8 cm2 of board area, ideal for space constrained applications. For a data sheet and evaluation samples of this multiprotocol chip set, contact your local Linear Technology sales office.Figure
10、 2. Single 5V Complete Multiprotocol Serial PortThe LTC1343 multiprotocol trans- ceiver and companion LTC1344 cable terminator form a complete software-select- able multiprotocol serial port, operating from a single 5V supply. This is the first integrated solution to pass the stringent NET1 and NET2
11、 tests of the European Telecommunications Institute.The LTC1343 contains four drivers and four receivers and the configuration logic to do protocol selection, loopback testing as well13 12 11 109876543225 24 23 22 21 20 19 18 17 16 15 141CLK AND DATADB-25CONTROLCLK AND? DATAMODE? SELECT3LTC1343RS232
12、? EIA-530? EIA-530-A? RS449? V.35? V.36? X.21LTC1343LTC1344CONTROLas turning on and off the echo clock and the low power shutdown mode. The LTC1343/ LTC1344 can be used in both DTE and DCE equipment. The LTC1344 cable terminator contains six switchable resistive terminations to configure a single DB
13、-25 connector for up to eight different serial protocols. Two LTC1343 transceivers and a single LTC1344 terminator form a DTE or DCE interface port, capable of supporting RS232 (V.28), RS423 (V.10), EIA530, EIA530-A, RS449, V.35,2Linear Technology Chronicle November 1996Controller IC Allows Safe Hot
14、 Swapping of Circuit BoardsThe LTC1421 hot swap controller safely limits the inrush currents that can destroy components and traces on circuit boards and prevents glitches that disrupt the system bus when a circuit board is plugged into a live backplane. The device can turn on up to three board supp
15、ly voltages at pro- grammable rates. The LTC1421 is ideal for backplanes and rack systems that must run continuously or cannot tolerate glitches on the supply rails when inserting or removing circuit boards. It is appropriate for power systems supplying 3V/5V, 5V/12V or even 48V/5V telecom voltages.The key to controlling the inrush cur- rent is the user-programmable power-up rate. An external capacitor sets the timing for the ramp-up of the positive FET voltages result- ing in the switches being
