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| LTC1324 Single Supply LocalTalk(R) Transceiver FEATURES s s s s DESCRIPTION The LTC(R)1324 is a single 5V line transceiver designed to operate on Apple(R)LocalTalk networks. The driver features a digitally selectable low slew rate mode for reduced EMI emissions. The chip draws only 1mA quiescent current when active and 1A in shutdown. The differential driver outputs three-state when disabled, during shutdown or when the power is off. The driver outputs will maintain high impedance even with output common mode voltages beyond the power supply rails. Both the driver outputs and receiver inputs are protected against ESD damage to 10kV. The LTC1324 is available in a 16-pin SO Wide package. , LTC and LT are registered trademarks of Linear Technology Corporation. Apple and LocalTalk are registered trademarks of Apple Computer, Inc. s s s Single Chip 5V LocalTalk Port Low Power: ICC = 1mA Typ Shutdown Pin Reduces ICC to 1A Typ Digitally Selectable Low Slew Rate Mode for Reduced EMI Emmisions Drivers Maintain High Impedance in Three-State or with Power Off Thermal Shutdown Protection Drivers Are Short-Circuit Protected APPLICATIONS s s s LocalTalk Peripherals Notebook and Palmtop Computers Battery-Powered Systems TYPICAL APPLICATION Typical LocalTalk Connection for Low EMI 5V 16 SLEW RATE CONTROL DATA IN TX ENABLE SHUTDOWN RX ENABLE DATA OUT 2 3 4 5 6 7 8 9 1324 TA01 Waveform of Driver 12 LocalTalk TRANSFORMER 120 DIN 5V/DIV 11 LTC1324 10 DOUT 1V/DIV U U U TIME (0.5s/DIV) 1324 TA02 1 LTC1324 ABSOLUTE MAXIMUM RATINGS (Note 1) PACKAGE/ORDER INFORMATION TOP VIEW NC 1 SR 2 TXD 3 TXDEN 4 SHDN 5 RXEN 6 RXO 7 GND 8 N PACKAGE 16-LEAD PDIP RX DX Supply Voltage (VCC) ................................................ 7V Input Voltage (Logic Inputs) ........ - 0.3V to (VCC + 0.3V) Input Voltage (Receiver Inputs) ............................ 1 5V Driver Output Voltage (Forced) ............................. 15V Driver Short-Circuit Duration .......................... Indefinite Operating Temperature Range .................... 0C to 70C Storage Temperature Range ................. - 65C to 150C Lead Temperature (Soldering, 10 sec).................. 300C 16 VCC 15 TXDEN 14 RXEN 13 NC 12 TXD - 11 TXD + 10 RXD - 9 RXD + ORDER PART NUMBER LTC1324CN LTC1324CSW SW PACKAGE 16-LEAD PLASTIC SO WIDE TJMAX = 150C, JA = 110C/ W (N) TJMAX = 150C, JA = 150C/ W (SW) Consult factory for Industrial and Military grade parts. ELECTRICAL CHARACTERISTICS SYMBOL PARAMETER Supplies ICC Normal Operation Supply Current Shutdown Supply Current VCC = 5V, TA = 0C to 70C (Notes 2, 3), unless otherwise noted. MIN TYP MAX UNITS CONDITIONS No Load, SHDN = 0V, TXDEN = 0V, RXEN = 0V No Load, SHDN = VCC q q 1 1 4.0 2.0 0.2 3.0 2 10 Differential Driver VOD VOD VOC ISS IOZ Differential Output Voltage Change in Magnitude of Differential Output Voltage Differential Common Mode Output Voltage Short-Circuit Current Three-State Output Current No Load RL = 50 (Figure 1) RL = 50 (Figure 1) RL = 50 (Figure 1) 0V VO 5V (TXDEN = VCC and TXDEN = GND) or SHDN = VCC or Power Off, - 10V VO 10V q q q q 35 120 2 250 200 Logic Inputs VIH VIL IIN IDN Receiver RIN Input Resistance Receiver Threshold Voltage Receiver Input Hysteresis VOH VOL ISS IOZ Output High Voltage Output Low Voltage Output Short-Circuit Current Output Three-State Current - 7V VIN 7V - 7V VCM 7V - 7V VCM 7V IO = - 4mA IO = 4mA 0V VO 5V 0V VO 5V, RXEN = VCC, RXEN = GND q q q q q Input High Voltage Input Low Voltage Input Current Pull-Down Current All Logic Input Pins All Logic Input Pins SHDN, TXDEN, RXDEN, V = 0V to VCC RXDEN, TXDEN, SR, V = 0V to VCC q q q q 2.4 0.8 1 15 20 60 12 - 200 70 3.5 0.4 7 2 85 100 200 2 U W U U WW W mA A V V V V mA A V V A A k mV mV V V mA A LTC1324 ELECTRICAL CHARACTERISTICS SYMBOL tPLH, tPHL PARAMETER Driver Propagation Delay Without Slew Rate Control Driver Propagation Delay with Slew Rate Control Receiver Propagation Delay tSKEW Driver Output to Output Without Slew Rate Control Driver Output to Output with Slew Rate Control t r, t f Driver Rise/Fall Time Without Slew Rate Control Driver Rise/Fall Time with Slew Rate Control t Hdis, t Ldis Driver Output Active to Disable Without Slew Rate Control Driver Output Active to Disable with Slew Rate Control Receiver Output Active to Disable t ENH, t ENL Driver Enable to Output Active Without Slew Rate Control Driver Enable to Output Active with Slew Rate Control Receiver Enable to Output Active Switching Characteristics VCC = 5V, TA = 0C to 70C (Notes 2, 3), unless otherwise noted. MIN q q q q q q q q q q q q q CONDITIONS RL = 100, CL = 100pF (Figures 2, 4) SR = GND RL = 100, CL = 100pF (Figures 2, 4) SR = VCC CL = 15pF (Figures 2, 6) RL = 100, CL = 100pF (Figures 2, 4) SR = GND RL = 100, CL = 100pF (Figures 2, 4) SR = VCC RL = 100, CL = 100pF (Figures 2,4) SR = GND RL = 100, CL = 100pF (Figures 2, 4) SR = VCC CL = 15pF (Figures 3, 5) SR = GND CL = 15pF (Figures 3, 5) SR = VCC CL = 15pF (Figures 3, 7) CL = 15pF (Figures 3, 5) SR = GND CL = 15pF (Figures 3, 5) SR = VCC CL = 15pF (Figures 3, 7) TYP 40 0.4 40 10 25 20 0.4 50 0.7 30 50 250 30 MAX 120 1.2 120 35 100 50 1.2 150 2 100 150 750 100 UNITS ns s ns ns ns ns s ns s ns ns ns ns The q denotes specifications which apply over the full operating temperature range. Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: All currents into device pins are positive and all currents out of device pins are negative. All voltages are reference to ground unless otherwise specified. Note 3: All typicals are given at VCC = 5V, TA = 25C. TYPICAL PERFORMANCE CHARACTERISTICS Driver Differential Output Voltage vs Output Current 80 70 OUTPUT CURRENT (mA) TA = 25C 100 OUTPUT CURRENT (mA) OUTPUT CURRENT (mA) 60 50 40 30 20 10 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 DRIVER DIFFERENTIAL OUTPUT VOLTAGE (V) 1324 G01 UW Driver Output Low Voltage vs Output Current 120 TA = 25C -90 -75 -60 -45 -30 -15 -105 Driver Output High Voltage vs Output Current TA = 25C 80 60 40 20 0 0 0.5 1.0 1.5 2.0 OUTPUT VOLTAGE (V) 2.5 3.0 1324 G02 0 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 DRIVER OUTPUT HIGH VOLTAGE (V) 5.0 1324 G03 3 LTC1324 TYPICAL PERFORMANCE CHARACTERISTICS Receiver Output Low Voltage vs Output Current 30 TA = 25C 25 OUTPUT CURRENT (mA) OUTPUT CURRENT (mA) OUTPUT CURRENT (mA) 20 15 10 5 0 0 0.4 0.8 1.2 1.6 OUTPUT VOLTAGE (V) Receiver Short-Circuit Current vs Temperature 19 18 900 875 SUPPLY CURRENT (A) OUTPUT CURRENT (mA) 17 16 15 14 13 12 11 10 -55 -35 -15 5 25 45 65 85 105 125 TEMPERATURE (C) 1324 G07 800 775 750 725 700 -55 -35 -15 5 25 45 65 85 105 125 TEMPERATURE (C) 1324 G08 TIME (ns) Receiver Output Low Voltage vs Temperature 0.8 I = 8mA 0.7 OUTPUT VOLTAGE (V) 0.5 0.4 0.3 0.2 0.1 0 -55 -35 -15 5 25 45 65 85 105 125 TEMPERATURE (C) 1324 G10 OUTPUT VOLTAGE (V) 0.6 4 UW 1324 G04 Receiver Output High Voltage vs Output Current -16 -14 -12 -10 -8 -6 -4 -2 2.0 110 Driver Short-Circuit Current vs Temperature 100 90 80 70 60 50 40 -55 -35 -15 TA = 25C 0 2.0 2.5 3.0 3.5 4.0 OUTPUT VOLTAGE (V) 4.5 5.0 1324 G05 5 25 45 65 85 105 125 TEMPERATURE (C) 1324 G06 Supply Current (Driver and Receiver Enabled) vs Temperature 4.2 4.0 3.8 3.6 3.4 3.2 Driver Skew vs Temperature 850 825 3.0 -55 -35 -15 5 25 45 65 85 105 125 TEMPERATURE (C) 1324 G09 Receiver Output High Voltage vs Temperature 4.00 I = 8mA 3.75 3.50 3.25 3.00 2.75 2.50 2.25 2.00 -55 -35 -15 5 25 45 65 85 105 125 TEMPERATURE (C) 1324 G11 LTC1324 TYPICAL PERFORMANCE CHARACTERISTICS Driver Differential Output Voltage vs Temperature 3.1 3.0 DIFFERENTIAL VOLTAGE (V) 2.9 2.8 2.7 2.6 2.5 2.4 2.3 -55 -35 -15 5 25 45 65 85 105 125 TEMPERATURE (C) 1324 G12 TIME (ns) PIN FUNCTIONS NC (Pins 1, 13): No Internal Connection. SR (Pin 2): Slew Rate Control (TTL Compatible). A high level on this pin forces the RS485 driver into the low slew rate mode. A low level forces the driver into the high slew rate or normal mode. Connected to an internal pull-down. TXD (Pin 3): RS485 Driver Input (TTL Compatible). TXDEN (Pin 4): Driver Output Enable (TTL Compatible). A high level on this pin and a low level on TXDEN (Pin 15) forces the RS485 driver into three-state. A low level enables the driver. SHDN (Pin 5): Shutdown Input (TTL Compatible). When this pin is high, the chip is shut down; the driver and receiver outputs three-state; and the supply current drops to 1A. A low level on this pin allows normal operation. RXEN (Pin 6): Receiver Enable (TTL Compatible). A high level on this pin and a low level on RXEN (Pin 14) disables the receiver and three-states the logic outputs. A low level allows normal operation. RXDO (Pin 7): RS485 Receiver Output. GND (Pin 8): Ground. RXD + (Pin 9): RS485 Receiver Noninverting Input. When this pin is 200mV above RXD -, RXDO will be high. When this pin is 200mV below RXD -, RXDO will be low. RXD - (Pin 10): RS485 Receiver Inverting Input. TXD + (Pin 11): RS485 Driver Noninverting Output. TXD - (Pin 12): RS485 Driver Inverting Output. RXEN (Pin 14): Receiver Enable (TTL Compatible). A low level on this pin and a high level on RXEN (Pin 6) disables the receiver and three-states the logic outputs. A high level allows normal operation. Connected to an internal pulldown. TXDEN (Pin 15): Driver Output Enable (TTL Compatible). A low level on this pin and a high level on TXDEN (Pin 4) forces the RS485 driver into three-state. A high level enables the driver. Connected to an internal pull-down. VCC (Pin 16): The Positive Supply Input. 4.75V VCC 5.25V. Requires a 1F bypass capacitor to ground. UW Receiver t PLH - t PHL vs Temperature 8 7 6 5 4 3 2 1 0 -55 -35 -15 5 25 45 65 85 105 125 TEMPERATURE (C) 1324 G13 RL = 100 U U U 5 LTC1324 TEST CIRCUITS TXD + RL VOD RL TXD - 1324 F01 VCC TXD + RL TXD - CL RXD - CL RXD + TXI RXDO S1 500 15pF OUTPUT CL S2 VOC 1324 F02 1324 F03 Figure 1 Figure 2 Figure 3 SWITCHING WAVEFORMS 3V TXD 0V t PLH VO -VO TXD - VO TXD + tSKEW tSKEW 1324 F04 3V TXDEN 0V t ZL 5V TXD +, TXD - VOL t ZH VOH TXD -, TXD + 0V 1324 F05 V OD2 (RXD +) - (RXD -) -V OD2 tPLH VOH RXDO VOL 0V 6 W U 1.5V f = 1MHz: t r 10ns: t f 10ns 1.5V tPHL 90% 50% 10% tr VDIFF = V(TXD+) - V(TXD -) 90% 50% 10% tf 1/2 VO Figure 4. Differential Driver 1.5V f = 1MHz: t r 10ns: t f 10ns 1.5V t LZ 2.3V OUTPUT NORMALLY LOW OUTPUT NORMALLY HIGH 2.3V t HZ 0.5V 0.5V Figure 5. Differential Driver Enable and Disable f = 1MHz: tr 10ns: tf 10ns 0V tPHL 1.5V 1.5V 1324 F06 Figure 6. Differential Receiver LTC1324 SWITCHING WAVEFORMS 3V RXEN 0V tZL 5V RXO, RXO, RXDO VOL tZH VOH RXO, RXO, RXDO 0V 1324 F07 APPLICATIONS INFORMATION Thermal Shutdown Protection The LTC1324 includes a thermal shutdown circuit which protects against prolonged shorts at the driver outputs. If a driver output is shorted to another output, ground or to the power supply, the current will be initially limited to a maximum of 250mA. When the die temperature rises above 150C, the thermal shutdown circuit turns off the driver outputs. When the die cools to about 130C, the outputs turn on. If the short still exists, the part will heat again and the cycle will repeat. This oscillation occurs at about 10Hz and prevents the part from being damaged by excessive power dissipation. When the short is removed, the part will return to normal operation. Power Shutdown The power shutdown feature of the LTC1324 is designed for battery-powered systems. When SHDN is forced high, the part enters shutdown mode. In shutdown, the supply current typically drops from 1mA to 1A and the driver and receiver outputs are three-stated. Supply Bypassing The LTC1324 requires VCC be bypassed to prevent data errors. A 1F capacitor from VCC to ground is adequate. EMI Filters and Slew Rate Control Most LocalTalk applications need to use an electromagnetic interference (EMI) filter consisting of a resistorFERRITE BEAD FERRITE BEAD Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. U W W U U U 1.5V f = 1MHz: tr 10ns: tf 10ns 1.5V t LZ 2.3V OUTPUT NORMALLY LOW OUTPUT NORMALLY HIGH 2.3V t HZ 0.5V 0.5V Figure 7. Receiver Enable and Disable capacitor T network between each driver, receiver and the connector. Unfortunately, the resistors will attenuate the driver's output signal applied to the cable. Because the LTC1324 uses a single 5V supply, the resistors' values should be reduced to 5.1 to ensure enough voltage swing on the cable (Figure 8). Another way to get maximum swing and EMI immunity is to use a ferrite bead and capacitor as the T network (Figure 9). For data rates below 250kbps, the LTC1324 features a low EMI mode which limits the rise time of the drivers to 400ns. With a lower rise time, the EMI network can be eliminated, allowing more signal voltage to reach the cable. Figures 10 and 11 show the output signals of the driver with different slew rates. 5.1 TXD + TXD TXD - 5.1 5.1 100pF 120 5.1 100pF 1324 F08 Figure 8 100pF 1324 F09 Figure 9 7 LTC1324 APPLICATIONS INFORMATION U W U U 1324 F10 Figure 10. High Slew Rate Mode 1324 F11 Figure 11. Low Slew Rate Mode PACKAGE DESCRIPTION 0.300 - 0.325 (7.620 - 8.255) 0.130 0.005 (3.302 0.127) 0.015 (0.381) MIN 0.009 - 0.015 (0.229 - 0.381) ( +0.025 0.325 -0.015 +0.635 8.255 -0.381 ) 0.125 (3.175) MIN 0.100 0.010 (2.540 0.254) *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTURSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm). 0.005 (0.127) RAD MIN 0.291 - 0.299 (7.391 - 7.595) (NOTE 2) 0.010 - 0.029 x 45 (0.254 - 0.737) 0 - 8 TYP 0.050 (1.270) TYP 0.009 - 0.013 (0.229 - 0.330) NOTE 1 0.016 - 0.050 (0.406 - 1.270) NOTE: 1. PIN 1 IDENT, NOTCH ON TOP AND CAVITIES ON THE BOTTOM OF PACKAGES ARE THE MANUFACTURING OPTIONS. THE PART MAY BE SUPPLIED WITH OR WITHOUT ANY OF THE OPTIONS. 2. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006 INCH (0.15mm). RELATED PARTS PART NUMBER LTC1318 LTC1320 LTC1323 DESCRIPTION Single 5V Powered RS232/RS422 Transceiver RS422/RS562 Transceiver Single 5V Powered RS422/RS562 Transceiver COMMENTS Pin Selectable RS232/RS422 Receiver. Available in 24-Pin SO Wide Package Available in 18-Pin SO Wide Package Available in 16-Pin and 24-Pin SO Wide Packages LT/GP 0596 7K * PRINTED IN USA 8 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 q FAX: (408) 434-0507 q TELEX: 499-3977 U Dimensions in inches (millimeters) unless otherwise noted. N Package 16-Lead PDIP (Narrow 0.300) (LTC DWG # 05-08-1510) 0.045 - 0.065 (1.143 - 1.651) 0.770* (19.558) MAX 16 15 14 13 12 11 10 9 0.065 (1.651) TYP 0.045 0.015 (1.143 0.381) 0.255 0.015* (6.477 0.381) 1 0.018 0.003 (0.457 0.076) 2 3 4 5 6 7 8 N16 0694 SW Package 16-Lead Plastic Small Outline (Wide 0.300) (LTC DWG # 05-08-1620) 0.093 - 0.104 (2.362 - 2.642) 0.037 - 0.045 (0.940 - 1.143) 16 15 0.398 - 0.413 (10.109 - 10.490) (NOTE 2) 14 13 12 11 10 9 NOTE 1 0.394 - 0.419 (10.007 - 10.643) 0.004 - 0.012 (0.102 - 0.305) 0.014 - 0.019 (0.356 - 0.482) TYP 1 2 3 4 5 6 7 8 SOL16 0392 (c) LINEAR TECHNOLOGY CORPORATION 1995 |
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