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LT1785A Dataheets PDF



Part Number LT1785A
Manufacturers Linear Technology
Logo Linear Technology
Description 60V Fault Protected RS485/RS422 Transceivers
Datasheet LT1785A DatasheetLT1785A Datasheet (PDF)

LT1785/LT1785A LT1791/LT1791A 60V Fault Protected RS485/RS422 Transceivers FEATURES s s s s DESCRIPTIO s s s s s s U APPLICATIO S s s s Protected from Overvoltage Line Faults to ±60V Pin Compatible with LTC485 and LTC491 High Input Impedance Supports Up to 128 Nodes No Damage or Latchup to ESD IEC-1000-4-2 Level 4: ±15kV Air Discharge IEC-1000-4-2 Level 2: ± 4kV Contact Discharge Controlled Slew Rates for EMI Emissions Control Guaranteed High Receiver Output State for Floating, Shorted or .

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LT1785/LT1785A LT1791/LT1791A 60V Fault Protected RS485/RS422 Transceivers FEATURES s s s s DESCRIPTIO s s s s s s U APPLICATIO S s s s Protected from Overvoltage Line Faults to ±60V Pin Compatible with LTC485 and LTC491 High Input Impedance Supports Up to 128 Nodes No Damage or Latchup to ESD IEC-1000-4-2 Level 4: ±15kV Air Discharge IEC-1000-4-2 Level 2: ± 4kV Contact Discharge Controlled Slew Rates for EMI Emissions Control Guaranteed High Receiver Output State for Floating, Shorted or Inactive Inputs Outputs Assume a High Impedance When Off or Powered Down Drives Low Cost, Low Impedance Cables Short-Circuit Protection on All Outputs Thermal Shutdown Protection The LT®1785/LT1791 are half-duplex and full-duplex differential bus transceivers for RS485 and RS422 applications which feature on-chip protection from overvoltage faults on the data transmission lines. Receiver input and driver output pins can withstand voltage faults up to ±60V with respect to ground with no damage to the device. Faults may occur while the transceiver is active, shut down or powered off. Data rates to 250kbaud on networks of up to 128 nodes are supported. Controlled slew rates on the driver outputs control EMI emissions and improve data transmission integrity on improperly terminated lines. Drivers are specified to operate with inexpensive cables as low as 72Ω characteristic impedance. The LT1785A/LT1791A devices have “fail-safe” receiver inputs to guarantee a receiver output high for shorted, open or inactive data lines. On-chip ESD protection eliminates need for external protection devices. The LT1785/LT1785A are available in 8-lead DIP and SO packages and the LT1791/LT1791A in 14-lead DIP and SO packages. , LTC and LT are registered trademarks of Linear Technology Corporation. Industrial Control Data Networks CAN Bus Applications HVAC Controls TYPICAL APPLICATIO RO1 RE1 DE1 DI1 RX LT1785 Normal Operation Waveforms at 250kBaud VCC1 RTERM RO TX GND1 Y-Z VCC2 RO2 RE2 DE2 DI2 RX LT1785 RTERM DI TX GND2 1785/91 TA01 U 1785/91 TA02 U 1 LT1785/LT1785A LT1791/LT1791A ABSOLUTE AXI U RATI GS Supply Voltage (VCC) .............................................. 18V Receiver Enable Input Voltage .................... – 0.3V to 6V Driver Enable Input Voltage ........................ – 0.3V to 6V Driver Input Voltage .................................. – 0.3V to 18V Receiver Input Voltage ............................... – 60V to 60V Driver Output Voltage ............................... – 60V to 60V Receiver Output Voltage ................ – 0.3V to (VCC + 6V) PACKAGE/ORDER I FOR ATIO ORDER PART NUMBER TOP VIEW RO 1 RE 2 DE 3 DI 4 N8 PACKAGE 8-LEAD PDIP D R 8 7 6 5 VCC B A GND LT1785CN8 LT1785CS8 LT1785IN8 LT1785IS8 LT1785ACN8 LT1785ACS8 S8 PACKAGE 8-LEAD PLASTIC SO TJMAX = 150°C, θJA = 130°C/ W (N8) TJMAX = 150°C, θJA = 150°C/ W (S8) S8 PART MARKING 1785 1785I 1785A TJMAX = 150°C, θJA = 130°C/ W (N) TJMAX = 150°C, θJA = 150°C/ W (S) Consult factory for Military grade parts. 2 U U W W W U W (Note 1) Operating Temperature Range LT1785C/LT1791C/ LT1785AC/LT1791AC ............................. 0°C to 70°C LT1785I/LT1791I ............................... – 40°C to 85°C Storage Temperature Range ................ – 65°C to 150°C Lead Temperature (Soldering, 10 sec)................. 300°C ORDER PART NUMBER TOP VIEW NC 1 RO 2 RE 3 DE 4 DI 5 GND 6 GND 7 N PACKAGE 14-LEAD PDIP D R 14 VCC 13 NC 12 A 11 B 10 Z 9 8 Y NC LT1791CN LT1791CS LT1791IN LT1791IS LT1791ACN LT1791ACS S PACKAGE 14-LEAD PLASTIC SO LT1785/LT1785A LT1791/LT1791A DC ELECTRICAL CHARACTERISTICS SYMBOL VOD1 VOD2 PARAMETER Differential Driver Output Voltage (Unloaded) Differential Driver Output Voltage (With Load) The q denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C, VCC = 5V. CONDITIONS IO = 0 R = 50Ω (RS422), Figure 1 R = 27Ω (RS485), Figure 1 R = 18Ω R = 27Ω or R = 50Ω, Figure 1 R = 27Ω or R = 50Ω, Figure 1 R = 27Ω or R = 50Ω, Figure 1 DI, DE, RE DI, DE, RE DI, DE, RE VIN = 12V VIN = – 7V – 60V ≤ VIN ≤ 60V LT1785/LT1791: – 7V ≤ VCM ≤ 12V LT1785A/LT1791A: – 7V ≤ VCM ≤ 12V – 7V < VCM < 12V IO = – 400µA, VID = 200mV IO = 1.6mA, VID = – 200mV RE > 2V or Power Off – 7V ≤ VCM ≤ 12V – 60V ≤ VCM ≤ 60V – 7V ≤ VCM ≤ 12V VOUT = HIGH, Force VO = – 7V VOUT = LOW, Force VO = 12V VO = 60V VO = – 60V 0V ≤ VO ≤ VCC –7V ≤ VO ≤ 12V – 60V ≤ VO ≤ 60V No Load, RE = 0V, DE = 5V No Load, RE = 5V, DE = 5V No Load, RE = 0V, DE = 0V No Load, RE = 5V, DE = 0V q q q q q q q q q q q q q q q q q q q q MIN 2.0 1.5 1.2 TYP 4.1 2.70 2.45 2.2 MAX 5 UNITS V V V V ∆VOD VOC ∆VOC VIH VIL IIN1 IIN2 Change in Magnitude of Driver Differential Output Voltage for Complementary Output States Driver Common Mode Output Voltage Change in Magnitude of Driver Common Mode Output Voltage for Complementary Output States Input High Voltage Input Low Voltage Input Current Input Current (A, B); (LT1791 or LT1785 with DE = 0V) Di.


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