LTC1324 Single Supply LocalTalk® Transceiver U DESCRIPTION FEATURES ■ ■ ■ ■ ■ ■ ■ Single Chip 5V LocalTalk Port Low Power: ICC = 1mA Typ Shutdown Pin Reduces ICC to 1µA 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 The LTC®1324 is a single 5V line transceiver designed to operate on Apple®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 1µA 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. LocalTalk Peripherals Notebook and Palmtop Computers Battery-Powered Systems The LTC1324 is available in a 16-pin SO Wide package. U APPLICATIONS ■ ■ ■ , LTC and LT are registered trademarks of Linear Technology Corporation. Apple and LocalTalk are registered trademarks of Apple Computer, Inc. U TYPICAL APPLICATION Waveform of Driver Typical LocalTalk Connection for Low EMI 5V 16 SLEW RATE CONTROL DATA IN TX ENABLE SHUTDOWN RX ENABLE DATA OUT 12 2 3 6 DIN 5V/DIV 120Ω 11 4 5 LocalTalk TRANSFORMER DOUT 1V/DIV LTC1324 10 7 8 9 1324 TA01 TIME (0.5µs/DIV) 1324 TA02 1 LTC1324 U W U U W W W ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION (Note 1) 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 .................... 0°C to 70°C Storage Temperature Range ................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec).................. 300°C ORDER PART NUMBER TOP VIEW NC 1 16 VCC SR 2 15 TXDEN 14 RXEN TXD 3 TXDEN 4 SHDN 5 12 TXD – RXEN 6 11 TXD + RXO 7 10 RXD – RX 9 GND 8 N PACKAGE 16-LEAD PDIP LTC1324CN LTC1324CSW 13 NC DX RXD + SW PACKAGE 16-LEAD PLASTIC SO WIDE TJMAX = 150°C, θJA = 110°C/ W (N) TJMAX = 150°C, θJA = 150°C/ W (SW) Consult factory for Industrial and Military grade parts. ELECTRICAL CHARACTERISTICS SYMBOL PARAMETER VCC = 5V, TA = 0°C to 70°C (Notes 2, 3), unless otherwise noted. CONDITIONS MIN TYP MAX 1 1 2 10 UNITS Supplies ICC Normal Operation Supply Current Shutdown Supply Current No Load, SHDN = 0V, TXDEN = 0V, RXEN = 0V No Load, SHDN = VCC ● ● ● ● mA µA Differential Driver ±4.0 ±2.0 VOD Differential Output Voltage No Load RL = 50Ω (Figure 1) ∆VOD Change in Magnitude of Differential Output Voltage RL = 50Ω (Figure 1) 0.2 V VOC Differential Common Mode Output Voltage RL = 50Ω (Figure 1) 3.0 V ISS Short-Circuit Current 0V ≤ VO ≤ 5V ● IOZ Three-State Output Current (TXDEN = VCC and TXDEN = GND) or SHDN = VCC or Power Off, – 10V ≤ VO ≤ 10V ● 35 V V 120 250 mA ±2 ±200 µA Logic Inputs VIH Input High Voltage All Logic Input Pins ● VIL Input Low Voltage All Logic Input Pins ● IIN Input Current SHDN, TXDEN, RXDEN, V = 0V to VCC ● IDN Pull-Down Current RXDEN, TXDEN, SR, V = 0V to VCC ● 2.4 V 0.8 V ±1 ±20 µA 15 60 µA Receiver Input Resistance – 7V ≤ VIN ≤ 7V Receiver Threshold Voltage – 7V ≤ VCM ≤ 7V Receiver Input Hysteresis – 7V ≤ VCM ≤ 7V VOH Output High Voltage IO = – 4mA ● VOL Output Low Voltage IO = 4mA ● ISS Output Short-Circuit Current 0V ≤ VO ≤ 5V ● IOZ Output Three-State Current 0V ≤ VO ≤ 5V, RXEN = VCC, RXEN = GND ● RIN 2 12 ● kΩ – 200 200 70 mV mV 3.5 V 7 ±2 0.4 V 85 mA ±100 µA LTC1324 ELECTRICAL CHARACTERISTICS SYMBOL PARAMETER VCC = 5V, TA = 0°C to 70°C (Notes 2, 3), unless otherwise noted. CONDITIONS MIN TYP MAX UNITS Switching Characteristics tPLH, tPHL tSKEW t r, t f t Hdis, t Ldis t ENH, t ENL Driver Propagation Delay Without Slew Rate Control RL = 100Ω, CL = 100pF (Figures 2, 4) SR = GND ● 40 120 ns Driver Propagation Delay with Slew Rate Control RL = 100Ω, CL = 100pF (Figures 2, 4) SR = VCC ● 0.4 1.2 µs Receiver Propagation Delay CL = 15pF (Figures 2, 6) ● 40 120 ns Driver Output to Output Without Slew Rate Control RL = 100Ω, CL = 100pF (Figures 2, 4) SR = GND ● 10 35 ns Driver Output to Output with Slew Rate Control RL = 100Ω, CL = 100pF (Figures 2, 4) SR = VCC ● 25 100 ns Driver Rise/Fall Time Without Slew Rate Control RL = 100Ω, CL = 100pF (Figures 2,4) SR = GND ● 20 50 ns Driver Rise/Fall Time with Slew Rate Control RL = 100Ω, CL = 100pF (Figures 2, 4) SR = VCC ● 0.4 1.2 µs Driver Output Active to Disable Without Slew Rate Control CL = 15pF (Figures 3, 5) SR = GND ● 50 150 ns Driver Output Active to Disable with Slew Rate Control CL = 15pF (Figures 3, 5) SR = VCC ● 0.7 2 µs Receiver Output Active to Disable CL = 15pF (Figures 3, 7) ● 30 100 ns Driver Enable to Output Active Without Slew Rate Control CL = 15pF (Figures 3, 5) SR = GND ● 50 150 ns Driver Enable to Output Active with Slew Rate Control CL = 15pF (Figures 3, 5) SR = VCC ● 250 750 ns Receiver Enable to Output Active CL = 15pF (Figures 3, 7) ● 30 100 ns The ● 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 = 25°C. U W TYPICAL PERFORMANCE CHARACTERISTICS Driver Differential Output Voltage vs Output Current Driver Output Low Voltage vs Output Current 120 80 TA = 25°C –90 50 40 30 20 OUTPUT CURRENT (mA) 100 60 80 60 40 20 10 0 –105 TA = 25°C TA = 25°C OUTPUT CURRENT (mA) OUTPUT CURRENT (mA) 70 Driver Output High Voltage vs Output Current 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 DRIVER DIFFERENTIAL OUTPUT VOLTAGE (V) 1324 G01 0 –75 –60 –45 –30 –15 0 0.5 1.0 1.5 2.0 OUTPUT VOLTAGE (V) 2.5 3.0 1324 G02 0 1.0 2.0 2.5 3.0 3.5 4.0 4.5 DRIVER OUTPUT HIGH VOLTAGE (V) 1.5 5.0 1324 G03 3 LTC1324 U W TYPICAL PERFORMANCE CHARACTERISTICS Receiver Output High Voltage vs Output Current Receiver Output Low Voltage vs Output Current 30 –16 110 TA = 25°C 20 15 10 5 100 –12 OUTPUT CURRENT (mA) OUTPUT CURRENT (mA) OUTPUT CURRENT (mA) TA = 25°C –14 25 0 –10 –8 –6 –4 0 0.4 0.8 1.2 1.6 OUTPUT VOLTAGE (V) 0 2.0 2.0 18 875 17 850 2.5 3.0 3.5 4.0 OUTPUT VOLTAGE (V) 4.5 13 12 5 25 45 65 85 105 125 TEMPERATURE (°C) Driver Skew vs Temperature 3.8 825 800 775 3.6 3.4 750 3.2 700 –55 –35 –15 5 25 45 65 85 105 125 TEMPERATURE (°C) 3.0 –55 –35 –15 5 25 45 65 85 105 125 TEMPERATURE (°C) 1324 G08 Receiver Output Low Voltage vs Temperature 1324 G09 Receiver Output High Voltage vs Temperature 0.8 4.00 I = 8mA I = 8mA 0.7 3.75 0.6 3.50 OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) 1324 G06 4.0 1324 G07 0.5 0.4 0.3 0.2 0.1 0 –55 –35 –15 3.25 3.00 2.75 2.50 2.25 5 25 45 65 85 105 125 TEMPERATURE (°C) 1324 G10 4 5 25 45 65 85 105 125 TEMPERATURE (°C) 4.2 725 11 10 –55 –35 –15 60 40 –55 –35 –15 5.0 TIME (ns) SUPPLY CURRENT (µA) 900 14 70 Supply Current (Driver and Receiver Enabled) vs Temperature 19 15 80 1324 G05 Receiver Short-Circuit Current vs Temperature 16 90 50 –2 1324 G04 OUTPUT CURRENT (mA) Driver Short-Circuit Current vs Temperature 2.00 –55 –35 –15 5 25 45 65 85 105 125 TEMPERATURE (°C) 1324 G11 LTC1324 U W TYPICAL PERFORMANCE CHARACTERISTICS Receiver t PLH – t PHL vs Temperature Driver Differential Output Voltage vs Temperature 3.1 8 RL = 100Ω 7 2.9 6 2.8 5 TIME (ns) DIFFERENTIAL VOLTAGE (V) 3.0 2.7 2.6 4 3 2.5 2 2.4 1 2.3 –55 –35 –15 5 25 45 65 85 105 125 TEMPERATURE (°C) 0 –55 –35 –15 5 25 45 65 85 105 125 TEMPERATURE (°C) 1324 G12 1324 G13 U U U PIN FUNCTIONS NC (Pins 1, 13): No Internal Connection. GND (Pin 8): Ground. 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. 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. TXD (Pin 3): RS485 Driver Input (TTL Compatible). TXD + (Pin 11): RS485 Driver Noninverting Output. 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. TXD – (Pin 12): RS485 Driver Inverting Output. 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 1µA. 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. RXD – (Pin 10): RS485 Receiver Inverting Input. 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 1µF bypass capacitor to ground. 5 LTC1324 TEST CIRCUITS VCC TXD + RL CL TXD + TXI VOD TXD – RL RXD + RL CL S1 RXDO 500Ω RXD – OUTPUT 15pF VOC CL TXD – 1324 F02 1324 F01 1324 F03 Figure 1 Figure 2 Figure 3 U W SWITCHING WAVEFORMS 3V 1.5V TXD f = 1MHz: t r ≤ 10ns: t f ≤ 10ns 1.5V 0V t PLH tPHL VO VDIFF = V(TXD+) – V(TXD –) 90% 50% 10% –VO 90% 50% 10% 1/2 VO tr tf TXD – VO TXD + tSKEW tSKEW 1324 F04 Figure 4. Differential Driver 3V 1.5V TXDEN 0V f = 1MHz: t r ≤ 10ns: t f ≤ 10ns t ZL 1.5V t LZ 5V TXD +, TXD – 2.3V OUTPUT NORMALLY LOW VOL t ZH OUTPUT NORMALLY HIGH VOH 0.5V t HZ 0.5V TXD –, TXD + 2.3V 0V 1324 F05 Figure 5. Differential Driver Enable and Disable V OD2 (RXD +) – (RXD –) 0V f = 1MHz: tr ≤ 10ns: tf ≤ 10ns 0V –V OD2 tPLH tPHL VOH RXDO 1.5V VOL 1.5V 1324 F06 Figure 6. Differential Receiver 6 S2 LTC1324 U W SWITCHING WAVEFORMS 3V 1.5V RXEN 1.5V f = 1MHz: tr ≤ 10ns: tf ≤ 10ns 0V tZL t LZ 5V RXO, RXO, RXDO 2.3V OUTPUT NORMALLY LOW VOL tZH OUTPUT NORMALLY HIGH VOH 0.5V t HZ 0.5V 2.3V RXO, RXO, RXDO 0V 1324 F07 Figure 7. Receiver Enable and Disable U U W U 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 150°C, the thermal shutdown circuit turns off the driver outputs. When the die cools to about 130°C, 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. 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 5.1Ω 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. Power Shutdown 5.1Ω 5.1Ω 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 1µA and the driver and receiver outputs are three-stated. TXD + 100pF TXD 120Ω TXD – 5.1Ω 5.1Ω 100pF 1324 F08 Figure 8 Supply Bypassing The LTC1324 requires VCC be bypassed to prevent data errors. A 1µF capacitor from VCC to ground is adequate. FERRITE BEAD FERRITE BEAD 100pF EMI Filters and Slew Rate Control 1324 F09 Most LocalTalk applications need to use an electromagnetic interference (EMI) filter consisting of a resistor- Figure 9 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. 7 LTC1324 U U W U APPLICATIONS INFORMATION 1324 F10 1324 F11 Figure 10. High Slew Rate Mode U PACKAGE DESCRIPTION Figure 11. Low Slew Rate Mode Dimensions in inches (millimeters) unless otherwise noted. N Package 16-Lead PDIP (Narrow 0.300) (LTC DWG # 05-08-1510) 0.130 ± 0.005 (3.302 ± 0.127) 0.300 – 0.325 (7.620 – 8.255) 0.009 – 0.015 (0.229 – 0.381) ( +0.635 8.255 –0.381 0.045 – 0.065 (1.143 – 1.651) 0.015 (0.381) MIN +0.025 0.325 –0.015 ) 0.770* (19.558) MAX 0.065 (1.651) TYP 0.045 ± 0.015 (1.143 ± 0.381) 0.125 (3.175) MIN 16 15 14 13 12 11 10 1 2 3 4 5 6 7 0.255 ± 0.015* (6.477 ± 0.381) 0.018 ± 0.003 (0.457 ± 0.076) 0.100 ± 0.010 (2.540 ± 0.254) 9 8 N16 0694 *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTURSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm). SW Package 16-Lead Plastic Small Outline (Wide 0.300) (LTC DWG # 05-08-1620) 0.005 (0.127) RAD MIN 0.291 – 0.299 (7.391 – 7.595) (NOTE 2) 0.010 – 0.029 × 45° (0.254 – 0.737) 0.093 – 0.104 (2.362 – 2.642) NOTE 1 16 15 14 13 12 11 10 9 0.037 – 0.045 (0.940 – 1.143) 0.394 – 0.419 (10.007 – 10.643) NOTE 1 0° – 8° TYP 0.009 – 0.013 (0.229 – 0.330) 0.398 – 0.413 (10.109 – 10.490) (NOTE 2) 0.050 (1.270) TYP 0.004 – 0.012 (0.102 – 0.305) 0.014 – 0.019 (0.356 – 0.482) TYP 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). 1 2 3 4 5 6 7 8 SOL16 0392 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC1318 Single 5V Powered RS232/RS422 Transceiver Pin Selectable RS232/RS422 Receiver. Available in 24-Pin SO Wide Package LTC1320 RS422/RS562 Transceiver Available in 18-Pin SO Wide Package LTC1323 Single 5V Powered RS422/RS562 Transceiver Available in 16-Pin and 24-Pin SO Wide Packages 8 Linear Technology Corporation LT/GP 0596 7K • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● TELEX: 499-3977 LINEAR TECHNOLOGY CORPORATION 1995