DEMO CIRCUIT 827 QUICK LTC4260CGN START GUIDE LTC2803 and LTC2804 1.8V to 5.5V RS-232 Dual Transceiver DESCRIPTION Demonstration circuit 827 is a 1.8V to 5.5V RS-232 Dual Transceiverfeaturing the LTC2803 and LTC2804. VERSION DC827A-A DC827A-B P/N LTC2803CDHC LTC2804CDHC Design files for this circuit board are available. Call the LTC factory. , LTC and LT are registered trademarks of Linear Technology Corporation. ThinSOT and PowerPath are trademarks of Linear Technology Corporation. PERFORMANCE SUMMARY SYMBOL VCC VL SR(D) -- PARAMETER Input Supply Voltage Logic Supply Voltage Driver Slew Rate Maximum Data Rate CONDITIONS MIN 1.8 1.8 RL=3k, 50pF<CL<2.5nF LTC2803: LTC2804: RL = 3k, CL = 2.5nF RL = 3k, CL = 1.0nF RL = 3k, CL = 250pF (LTC2804) 4 4 100 250 1000 TYP MAX 5.5 5.5 UNITS V V 30 150 V/s V/s kbps kbps kbps JUMPERS SCH NAME JP1, MODE, JP2 PS JP3 LOGIC SUPPLY JP4, TD/RD, JP5 RTS/CTS PURPOSE Mode control, as follows: PS MODE MODE NAME OFF L Shutdown OFF H Receivers Active ON L Drivers Disabled ON H Normal Selects supply for VL pin. Use setting "VL" for a separate logic supply, or "VCC" to share a single supply. Selects Receiver loopback mode, for use with the DB9 connector. In this configuration, R1OUT is connected to T1IN and R2OUT is connected to T2IN. SCH NAME PURPOSE For the UART connected to the DB9, this wraps TD back to RD and RTS back to CTS. 1 QUICK START PROCEDURE Demonstration circuit827is easyto setupforevaluating the LTC2803 and LTC2804. Refer to Figure 1 or Figure 2 for proper setup andfollow the procedure below: 1. Check for the proper generated supply voltages: VDD = 6.5V to 7.5V, and VEE = -6.8V to -5.8V. 8. Send data! Placejumpersinthe following positions: JP1 JP2 MODE PS H ON 2. With power off, connect the primary power supply to VCC and GND. 3. Set JP3 "Logic Supply"to the correct position.If a separate logic supply isn't needed, use the "VCC" setting.Ifa separate Logic Supply willbe used, use the"VL" setting and, with the power off,connectthe supplyto VL and GND. 4. For transmitterloopback mode (Figure 1), connect each driver outputto a receiverinput. Connectinput sources to the driverinputs.(Make sure thatinput voltages don't exceed 7V.) Omit Loopback jumpers JP4 and JP5 forthis mode. 5. Alternatively,to operatethe partinreceiverloopback mode (Figure 2),connecta 9-wire RS-232 cable between DB9 connector J1 and the serial port of a computer. Placejumpersin thetwo LOOPBACK positions: JP4 JP5 TD/RD CTS/RTS Data may be transmitted and monitored using a terminal emulation program such as Terminal, HyperTerminal,Tera Term Pro, or RealTerm. 6. 7. Turn on the input supply/supplies in any order. (Note: Make sure that the voltage doesn't exceed 7V.) 2 Notes: 1. Inputs PS and MODE may be driven by signalsinstead of set with jumpers.If done, ensure thatthe voltage of PS doesn'texceed VL. 2. The terminal emulation program RealTerm can lock up when RTS/CTS flow controlis used in receiver loopback mode. LTC2803 AND LTC2804 Figure 1. Setup for Transmitter Loopback Mode Figure 2. Setup for Receiver Loopback Mode 3 4