LTC2850/LTC2851/LTC2852 3.3V 20Mbps RS485/RS422 Transceivers Features n n n n n n n n n n n n Description 3.3V Supply Voltage 20Mbps Maximum Data Rate No Damage or Latchup Up to 15kV HBM High Input Impedance Supports 256 Nodes (C, IGrade) Operation Up to 125C (H-Grade) Guaranteed Failsafe Receiver Operation Over the Entire Common Mode Range Current Limited Drivers and Thermal Shutdown Delayed Micropower Shutdown: 5A Maximum (C, I-Grade) Power Up/Down Glitch-Free Driver Outputs Low Operating Current: 370A Typical in Receive Mode Compatible with TIA/EIA-485-A Specifications Available in 8-Pin and 10-Pin 3mm x 3mm DFN, 8-Pin and 10-Pin MSOP, and 8-Pin and 14-Pin SO Packages Applications n n n Low Power RS485/RS422 Transceiver Level Translator Backplane Transceiver The LTC(R)2850, LTC2851 and LTC2852 are low power, 20Mbps RS485/RS422 transceivers operating on 3.3V supplies. The receiver has a one-eighth unit load supporting up to 256 nodes per bus (C, I-grade), and a failsafe feature that guarantees a high output state under conditions of floating or shorted inputs. The driver maintains a high output impedance over the entire common mode range when disabled or when the supply is removed. Excessive power dissipation caused by bus contention or a fault is prevented by current limiting all outputs and by thermal shutdown. Enhanced ESD protection allows these parts to withstand up to 15kV (human body model) on the transceiver interface pins without latchup or damage. PART NUMBER DUPLEX PACKAGE LTC2850 Half SO-8, MSOP-8, DFN-8 LTC2851 Full SO-8, MSOP-8, DFN-8 LTC2852 Full SO-14, MSOP-10, DFN-10 L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Typical Application LTC2850 at 20Mbps Into 54 LTC2850 RO1 RE1 R VCC1 DI1 DI RT DE1 D A GND1 B 2V/DIV A-B LTC2850 RO2 RE2 R VCC2 20ns/DIV DE2 DI2 RT D 285012 TA01b GND2 285012 TA01a 285012fd LTC2850/LTC2851/LTC2852 Absolute Maximum Ratings (Note 1) Supply Voltage (VCC).................................... -0.3V to 7V Logic Input Voltages (RE, DE, DI)................. -0.3V to 7V Interface I/O: A, B, Y, Z........................................ (VCC - 15V) to 15V Receiver Output Voltage (RO)........-0.3V to (VCC + 0.3V) Operating Temperature (Note 4) LTC285xC................................................. 0C to 70C LTC285xI..............................................-40C to 85C LTC285xH........................................... -40C to 125C LTC285xMP........................................ -55C to 125C Storage Temperature Range................... -65C to 150C Lead Temperature (Soldering, 10 sec) MSOP................................................................ 300C PIN CONFIGURATION LTC2850 TOP VIEW TOP VIEW RO 1 8 VCC RE 2 7 B DE 3 6 A DI 4 5 GND 9 DD PACKAGE 8-LEAD (3mm x 3mm) PLASTIC DFN TOP VIEW RO RE DE DI 1 2 3 4 8 7 6 5 VCC B A GND MS8 PACKAGE 8-LEAD PLASTIC MSOP TJMAX = 150C, JA = 200C/W, JC = 40C/W TJMAX = 150C, JA = 43C/W, JC = 3C/W EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB LTC2851 RO 1 8 VCC RE 2 7 B DE 3 6 A DI 4 5 GND S8 PACKAGE 8-LEAD PLASTIC SO TJMAX = 150C, JA = 150C/W, JC = 39C/W TOP VIEW TOP VIEW VCC 1 8 A RO 2 7 B DI 3 6 Z GND 4 5 Y 9 DD PACKAGE 8-LEAD (3mm x 3mm) PLASTIC DFN TOP VIEW VCC RO DI GND 1 2 3 4 8 7 6 5 A B Z Y MS8 PACKAGE 8-LEAD PLASTIC MSOP TJMAX = 150C, JA = 200C/W, JC = 40C/W TJMAX = 150C, JA = 43C/W, JC = 3C/W EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB LTC2852 VCC 1 8 A RO 2 7 B DI 3 6 Z GND 4 5 Y S8 PACKAGE 8-LEAD PLASTIC SO TJMAX = 150C, JA = 150C/W, JC = 39C/W TOP VIEW TOP VIEW RO 1 10 VCC RE 2 9 A DE 3 DI 4 GND 5 11 8 B 7 Z 6 Y DD PACKAGE 10-LEAD (3mm x 3mm) PLASTIC DFN TJMAX = 150C, JA = 43C/W, JC = 3C/W EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB TOP VIEW RO RE DE DI GND 1 2 3 4 5 10 9 8 7 6 VCC A B Z Y MS PACKAGE 10-LEAD PLASTIC MSOP TJMAX = 150C, JA = 120C/W, JC = 45C/W NC 1 14 VCC RO 2 13 NC RE 3 12 A DE 4 11 B DI 5 10 Z GND 6 9 Y GND 7 8 NC S PACKAGE 14-LEAD PLASTIC SO TJMAX = 150C, JA = 88C/W, JC = 37C/W 285012fd LTC2850/LTC2851/LTC2852 order information LTC2850 C DD #TR PBF LEAD FREE DESIGNATOR PBF = Lead Free TAPE AND REEL TR = Tape and Reel PACKAGE TYPE DD = 8-Lead Plastic DFN DD = 10-Lead Plastic DFN MS8 = 8-Lead Plastic MSOP MS = 10-Lead Plastic MSOP S8 = 8-Lead Plastic SO S = 14-Lead Plastic SO TEMPERATURE GRADE C = Commercial Temperature Range (0C to 70C) I = Industrial Temperature Range (-40C to 85C) H = Automotive Temperature Range (-40C to 125C) MP = Military Temperature Range (-55C to 125C) PRODUCT PART NUMBER LTC2850 = Half Duplex, with Enables LTC2851 = Full Duplex, No Enables LTC2852 = Full Duplex, with Enables Consult LTC Marketing for information on non-standard lead based finish parts. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ PRODUCT SELECTION GUIDE PART NUMBER PART MARKING DUPLEX LOW POWER SHUTDOWN MODE PACKAGE LTC2850 2850/I/H, LTCQD, LCQC Half Yes SO-8, MSOP-8, DFN-8 LTC2851 2851/I/H, LTCWF, LCWD Full No SO-8, MSOP-8, DFN-8 LTC2852 2852CS/IS/HS, LTCRX, LCRY Full Yes SO-14, MSOP-10, DFN-10 LTC2850MP 2850MP, LTFYD, LFYC Half Yes SO-8, MSOP-8, DFN-8 LTC2851MP 2851MP, LTFYG, LFYF Full No SO-8, MSOP-8, DFN-8 LTC2852MP 2852MPS, LTFYH, LFYJ Full Yes SO-14, MSOP-10, DFN-10 285012fd LTC2850/LTC2851/LTC2852 Electrical Characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VCC = 3.3V, unless otherwise noted. (Note 2) SYMBOL PARAMETER CONDITIONS |VOD| Differential Driver Output Voltage R = , VCC = 3V (Figure 1) R = 27, VCC = 3V (Figure 1) R = 50, VCC = 3.13V (Figure 1) |VOD| Difference in Magnitude of Driver Differential R = 27 or 50 (Figure 1) Output Voltage for Complementary Output States VOC Driver Common Mode Output Voltage |VOC| MIN TYP MAX UNITS VCC VCC VCC V V V l 0.2 V R = 27 or 50 (Figure 1) l 3 V Difference in Magnitude of Driver Common Mode Output Voltage for Complementary Output States R = 27 or 50 (Figure 1) l 0.2 V IOZD Driver Three-State (High Impedance) Output Current on Y and Z DE = 0V, (Y or Z) = -7V, 12V (LTC2852) l 10 A IOSD Maximum Driver Short-Circuit Current -7V (Y or Z) 12V (Figure 2) 250 300 mA mA 125 A Driver l l l l 1.5 2 -250 180 Receiver IIN RIN Receiver Input Current (A, B) Receiver Input Resistance DE = TE = 0V, VCC = 0V or 3.3V, VIN = 12V (Figure 3) (C, I-Grade) DE = TE = 0V, VCC = 0V or 3.3V, VIN = -7V, (Figure 3) (C, I-Grade) l DE = TE = 0V, VCC = 0V or 3.3V, VIN = 12V (Figure 3) (H-Grade) DE = TE = 0V, VCC = 0V or 3.3V, VIN = -7V, (Figure 3) (H-Grade) l l -145 RE = VCC or 0V, DE = TE = 0V, VIN = -7V, -3V, 3V, 7V, 12V (Figure 3) (C, I-Grade) l 96 125 kW RE = VCC or 0V, DE = TE = 0V, VIN = -7V, -3V, 3V, 7V, 12V (Figure 3) (H-Grade) l 48 125 kW l -100 A 250 A A VTH Receiver Differential Input Threshold Voltage -7V B 12V VTH Receiver Input Hysteresis B = 0V 0.2 VOH Receiver Output High Voltage I(RO) = -4mA, A-B = 200mV, VCC = 3V l VOL Receiver Output Low Voltage I(RO) = 4mA, A-B = -200mV, VCC = 3V l 0.4 V IOZR Receiver Three-State (High Impedance) Output Current on RO RE = VCC, 0V RO VCC (LTC2850, LTC2852) l 1 A IOSR Receiver Short-Circuit Current 0V RO VCC l 85 mA VIH Logic Input High Voltage VCC = 3.6V l VIL Logic Input Low Voltage VCC = 3V l IINL Logic Input Current l 25 V mV 2.4 V Logic l 2 V 0 0.8 V 10 A 285012fd LTC2850/LTC2851/LTC2852 Electrical Characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VCC = 3.3V, unless otherwise noted. (Note 2) SYMBOL PARAMETER CONDITIONS MIN Supply Current in Shutdown Mode DE = 0V, RE = VCC, LTC2850, LTC2852 (C and I-Grade) LTC2850, LTC2852 (H-Grade) TYP MAX UNITS l 0 5 A l 0 15 A Supplies ICCS ICCR Supply Current in Receive Mode DE = 0V, RE = 0V (LTC2850, LTC2852) l 370 900 A ICCT Supply Current in Transmit Mode No Load, DE = VCC, RE = VCC (LTC2850, LTC2852) l 450 1000 A ICCTR Supply Current with Both Driver and Receiver Enabled No Load, DE = VCC, RE = 0V l 450 1000 A Switching Characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VCC = 3.3V, unless otherwise noted. (Note 2) SYMBOL PARAMETER CONDITIONS MIN Maximum Data Rate (Note 3) l TYP MAX UNITS Driver fMAX tPLHD, tPHLD Driver Input to Output 20 Mbps RDIFF = 54, CL = 100pF (Figure 4) l 10 50 ns tPD Driver Input to Output Difference |tPLHD - tPHLD| RDIFF = 54, CL = 100pF (Figure 4) l 1 6 ns tSKEWD Driver Output Y to Output Z RDIFF = 54, CL = 100pF (Figure 4) l 1 6 ns tRD, tFD Driver Rise or Fall Time RDIFF = 54, CL = 100pF (Figure 4) l 4 12.5 ns tZLD, tZHD, tLZD, tHZD Driver Enable or Disable Time RL = 500, CL = 50pF, RE = 0V (Figure 5) (LTC2850, LTC2852) l 70 ns tZHSD, tZLSD Driver Enable from Shutdown RL = 500, CL = 50pF, RE = VCC (Figure 5) (LTC2850, LTC2852) l 8 s tSHDN RL = 500, CL = 50pF, (DE = , RE = VCC) or (DE = 0V, RE = ) (Figure 5) (LTC2850, LTC2852) l 100 ns tPLHR, tPHLR Receiver Input to Output CL = 15pF, VCM = 1.5V, |VAB| = 1.5V, tR and tF < 4ns (Figure 6) l 50 70 ns tSKEWR Differential Receiver Skew |tPLHR - tPHLR| CL = 15pF (Figure 6) l 1 6 ns tRR, tFR Receiver Output Rise or Fall Time CL = 15pF (Figure 6) l 3 12.5 ns tZLR, tZHR, tLZR, tHZR Receiver Enable/Disable RL =1k, CL =15pF, DE = VCC (Figure 7) (LTC2850, LTC2852) l 50 ns RL = 1k, CL = 15pF, DE = 0V (Figure 7) (LTC2850, LTC2852) l 8 s Time to Shutdown Receiver tZHSR, tZLSR Receiver Enable from Shutdown Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. High temperatures degrade operating lifetimes. Operating lifetime is derated at temperatures greater than 105C. Note 2: All currents into device pins are positive; all currents out of device pins are negative. All voltages are referenced to device ground unless otherwise specified. Note 3: Maximum data rate is guaranteed by other measured parameters and is not tested directly. Note 4: This IC includes overtemperature protection that is intended to protect the device during momentary overload conditions. Overtemperature protection activates at a junction temperature exceeding 150C. Continuous operation above the specified maximum operating junction temperature may result in device degradation or failure. 285012fd LTC2850/LTC2851/LTC2852 Test Circuits Y GND OR VCC DI Y + DRIVER VOD - R R GND OR VCC + - IOSD DI DRIVER VOC Z + - Z 285012 F01 -7V TO 12V 285012 F02 Figure 1. Driver DC Characteristics Figure 2. Driver Output Short-Circuit Current IIN VIN + - A OR B RECEIVER B OR A 285012 F03 V RIN = IN IIN Figure 3. Receiver Input Current and Input Resistance DI Y DI VCC 0V tPLHD tPHLD tSKEWD CL DRIVER Y, Z RDIFF VO 1/2 VO CL Z 285012 F04a (Y-Z) 90% 10% 0 0 tRD 90% 10% tFD 285012 F04b Figure 4. Driver Timing Measurement 285012fd LTC2850/LTC2851/LTC2852 Test Circuits RL Y VCC OR GND DI CL DRIVER VCC DE GND OR VCC DE Z CL VCC OR GND 285012 F05a tZLD, tZLSD VCC Y OR Z RL 1/2 VCC 0V VO VOL Z OR Y tLZD 1/2 VCC VOH 0.5V 0.5V 1/2 VCC 0V tZHD, tZHSD 285012 F05b tHZD, tSHDN Figure 5. Driver Enable and Disable Timing Measurements tR VAB A-B -VAB A VAB/2 VCM B VAB/2 RECEIVER RO CL RO 285012 F06a VCC 0 90% 10% tF 90% 0 10% tPLHR VO tPHLR 90% 1/2 VCC 10% 90% 10% 1/2 VCC tRR tSKEWR = |tPLHR - tPHLR| tFR 285012 F06b Figure 6. Receiver Propagation Delay Measurements RE 0V OR VCC VCC OR 0V 1/2 VCC 0V A B VCC RECEIVER RE RL RO CL VCC OR GND RO VOL RO DI = 0V OR VCC 285012 F07a VCC tZLR, tZLSR VO 1/2 VCC VOH 0V tLZR 0.5V 0.5V 1/2 VCC tZHR, tZHSR 285012 F07b tHZR Figure 7. Receiver Enable/Disable Time Measurements 285012fd LTC2850/LTC2851/LTC2852 Typical Performance Characteristics Receiver Skew vs Temperature Driver Propagation Delay vs Temperature Driver Skew vs Temperature 1.5 VAB = 1.5V CL = 15pF 0 16 0.5 PROP DELAY (ns) 1 18 RDIFF = 54 CL = 100pF 1.0 DRIVER SKEW (ns) RECEIVER SKEW (ns) 2 TA = 25C. VCC = 3.3V, unless otherwise noted. 0 -0.5 -1.0 -1 -40 -20 0 20 40 60 80 TEMPERATURE (C) 0 20 40 60 80 TEMPERATURE (C) 285012 G01 12 10 8 4 -40 -20 100 120 Driver Output Low/High Voltage vs Output Current 3.5 140 3.0 3.0 RDIFF = VOH 110 100 SOURCE VOUT = 0V 90 80 -40 -20 0 2.5 2.0 1.5 VOL 1.0 0.5 20 40 60 80 TEMPERATURE (C) 0 100 120 0 10 20 30 40 50 OUTPUT CURRENT (mA) 1.5 1.0 0 1 2 3 4 OUTPUT CURRENT (mA) 5 1.0 0 -40 -20 70 6 285012 G07 0 20 40 60 80 TEMPERATURE (C) Supply Current vs Data Rate 60 65 50 60 55 50 45 35 -40 -20 100 120 285012 G06 70 CL = 100pF RDIFF = 54 40 30 RDIFF = 100 20 RDIFF = 10 40 SINK 0 60 SUPPLY CURRENT (mA) PROP DELAY (ns) OUTPUT VOLTAGE (V) SOURCE 2.0 RDIFF = 54 1.5 Receiver Propagation Delay vs Temperature 3.5 0.5 2.0 285012 G05 Receiver Output Voltage vs Output Current (Source and Sink) 2.5 RDIFF = 100 2.5 0.5 285012 G04 3.0 OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) 120 100 120 Driver Differential Output Voltage vs Temperature 3.5 SINK VOUT = 3.3V 20 40 60 80 TEMPERATURE (C) 285012 G03 150 130 0 285012 G02 Driver Output Short-Circuit Current vs Temperature OUTPUT SHORT-CIRCUIT CURRENT (mA) 14 6 -1.5 -40 -20 100 120 RDIFF = 54 CL = 100pF 0 20 40 60 80 TEMPERATURE (C) 100 120 285012 G08 0 0.1 1 10 DATA RATE (Mbps) 100 285012 G09 285012fd LTC2850/LTC2851/LTC2852 Pin Functions RO: Receiver Output. If the receiver output is enabled (RE low) and A > B by 200mV, then RO will be high. If A < B by 200mV, then RO will be low. If the receiver inputs are open, shorted, or terminated without a valid signal, RO will be high. RE: Receiver Enable. A low enables the receiver. A high input forces the receiver output into a high impedance state. DE: Driver Enable. A high on DE enables the driver. A low input will force the driver outputs into a high impedance. If RE is high with DE low, the part will enter a low power shutdown state. DI: Driver Input. If the driver outputs are enabled (DE high), then a low on DI forces the driver positive output low and negative output high. A high on DI, with the driver outputs enabled, forces the driver positive output high and negative output low. Y: Noninverting Driver Output for LTC2851 and LTC2852. High impedance when driver disabled or unpowered. Z: Inverting Driver Output for LTC2851 and LTC2852. High impedance when driver disabled or unpowered. A: Noninverting Receiver Input (and Noninverting Driver Output for LTC2850). Impedance is >96k in receive mode or unpowered. B: Inverting Receiver Input (and Inverting Driver Output for LTC2850). Impedance is >96k in receive mode or unpowered. VCC: Positive Supply. 3V < VCC < 3.6V. Bypass with 0.1F ceramic capacitor. Exposed Pad: Ground. The exposed pads on the DFN packages must be soldered to ground. GND: Ground. Function Tables LTC2850 Logic Inputs Mode A, B RO 0 Receive RIN Driven 0 1 Shutdown RIN Hi-Z 1 0 Transceive Driven Driven 1 1 Transmit Driven Hi-Z DE RE 0 LTC2852 Logic Inputs Mode A, B Y, Z RO 0 Receive RIN Hi-Z Driven 0 1 Shutdown RIN Hi-Z Hi-Z 1 0 Transceive RIN Driven Driven 1 1 Transmit RIN Driven Hi-Z DE RE 0 285012fd LTC2850/LTC2851/LTC2852 Block Diagram LTC2850 LTC2851 VCC VCC A (15kV) RO RE DE DI RECEIVER RO RECEIVER B (15kV) A (15kV) SLEEP/SHUTDOWN LOGIC AND DELAY B (15kV) Z (15kV) DRIVER DI DRIVER Y (15kV) 285012 BDa 285012 BDb GND GND LTC2852 VCC A (15kV) RO RECEIVER B (15kV) RE DE SLEEP/SHUTDOWN LOGIC AND DELAY Z (15kV) DI DRIVER Y (15kV) 285012 BDc GND 285012fd 10 LTC2850/LTC2851/LTC2852 Applications Information Driver The driver provides full RS485/RS422 compatibility. When enabled, if DI is high, Y-Z is positive for the full-duplex devices (LTC2851, LTC2852) and A-B is positive for the half-duplex device (LTC2850). When the driver is disabled, both outputs are high impedance. For the full-duplex devices, the leakage on the driver output pins is guaranteed to be less than 10A over the entire common mode range of -7V to 12V. On the half-duplex LTC2850, the impedance is dominated by the receiver input resistance, RIN. These parts have a failsafe feature that guarantees the receiver output to be in a logic-high state when the inputs are either shorted, left open, or terminated but not driven. This failsafe feature is guaranteed to work for inputs spanning the entire common mode range of -7V to 12V. The receiver output is internally driven high (to VCC) or low (to ground) with no external pull-up needed. When the receiver is disabled the RO pin becomes Hi-Z with leakage of less than 1A for voltages within the supply range. Driver Overvoltage and Overcurrent Protection Receiver Input Resistance The driver outputs are protected from short-circuits to any voltage within the Absolute Maximum range of (VCC - 15V) to 15V. The typical peak current in this condition does not exceed 180mA. The receiver input resistance from A or B to ground is guaranteed to be greater than 96k (C, I-grade). This is 8x higher than the requirements for the RS485 standard and thus this receiver represents a one-eighth unit load. This, in turn, means that 8x the standard number of receivers, or 256 total, can be connected to a line without loading it beyond what is specified in the RS485 standard. The receiver input resistance from A or B to ground on high temperature H-grade parts is greater than 48k providing a one-quarter unit load. The high input resistance of the receiver is maintained whether it is enabled or disabled, powered or unpowered. If a high driver output is shorted to a voltage just above VCC, a reverse current will flow into the supply. When this voltage exceeds VCC by about 1.4V, the reverse current turns off. Preventing the driver from turning off with outputs shorted to output voltages just above VCC keeps the driver active even for receiver loads that have a positive common mode with respect to the driver-- a valid condition. The worst-case peak reverse short-circuit current can be as high as 300mA in extreme cold conditions. If this current can not be absorbed by the supply, a 3.6V Zener diode can be added in parallel with the supply to sink this current. All devices also feature thermal shutdown protection that disables the driver and receiver in case of excessive power dissipation (see Note 4 in the Electrical Characteristics section). Receiver and Failsafe With the receiver enabled, when the absolute value of the differential voltage between the A and B pins is greater than 200mV, the state of RO will reflect the polarity of (A-B) Supply Current The unloaded static supply currents in these devices are very low, typically under 500A for all modes of operation. In applications with resistively terminated cables, the supply current is dominated by the driver load. For example, when using two 120 terminators with a differential driver output voltage of 2V, the DC load current is 33mA, which is sourced by the positive voltage supply. Power supply current increases with toggling data due to capacitive loading and this term can increase significantly at high data rates. Figure 13 shows supply current vs data rate for two different capacitive loads for the circuit configuration of Figure 4. 285012fd 11 LTC2850/LTC2851/LTC2852 Applications Information pins causing an unintended state change. This can be avoided by maintaining normal logic levels on the pins and by slewing inputs through their thresholds by faster than 1V/s when transitioning. Good supply decoupling and proper driver termination also reduce glitches caused by driver transitions. RDIFF = 54 SUPPLY CURRENT (mA) 70 CL = 1000pF 60 50 40 CL = 100pF Cable Length vs Data Rate 30 20 0.1 1 10 DATA RATE (Mbps) 100 285012 F13 Figure 13. Supply Current vs Data Rate High Speed Considerations A ground plane layout is recommended. A 0.1F bypass capacitor less than one-quarter inch away from the VCC pin is also recommended. The PC board traces connected to signals A/B and Z/Y should be symmetrical and as short as possible to maintain good differential signal integrity. To minimize capacitive effects, the differential signals should be separated by more than the width of a trace and should not be routed on top of each other if they are on different signal planes. Care should be taken to route outputs away from any sensitive inputs to reduce feedback effects that might cause noise, jitter, or even oscillations. For example, in the full-duplex devices, DI and A/B should not be routed near the driver or receiver outputs. The logic inputs have 150mV of hysteresis to provide noise immunity. Fast edges on the outputs can cause glitches in the ground and power supplies which are exacerbated by capacitive loading. If a logic input is held near its threshold (typically 1.5V), a noise glitch from a driver transition may exceed the hysteresis levels on the logic and data input For a given data rate, the maximum transmission distance is bounded by the cable properties. A curve of cable length vs data rate compliant with the RS485/RS422 standards is shown in Figure 14. Three regions of this curve reflect different performance limiting factors in data transmission. In the flat region of the curve, maximum distance is determined by resistive losses in the cable. The downward sloping region represents limits in distance and data rate due to AC losses in the cable. The solid vertical line represents the specified maximum data rate in the RS485/RS422 standards. The dashed lines at 20Mbps show the maximum data rates of the LTC2850, LTC2851 and LTC2852. 10k CABLE LENGTH (FT) 80 1k LTC2850/ LTC2851/LTC2852 MAX DATA RATE 100 RS485/RS422 MAX DATA RATE 10 10k 100k 1M 10M DATA RATE (bps) 100M 285012 F14 Figure 14. Cable Length vs Data Rate (RS485/RS422 Standard Shown in Solid Line) 285012fd 12 LTC2850/LTC2851/LTC2852 Typical Applications Failsafe "0" Application (Idle State = Logic "0") VCC 100k I1 RO R B A DI I2 "A" "B" D LTC2850 285012 TA02 Multinode Network with End Termination Using the LTC2850 and LTC2854 R D LTC2850 R D LTC2850 R R TE = 3.3V TE = 3.3V D D LTC2854 LTC2854 285012 TA03 285012fd 13 LTC2850/LTC2851/LTC2852 Package Description DD Package 8-Lead Plastic DFN (3mm x 3mm) (Reference LTC DWG # 05-08-1698 Rev C) 0.70 p0.05 3.5 p0.05 1.65 p0.05 2.10 p0.05 (2 SIDES) PACKAGE OUTLINE 0.25 p 0.05 0.50 BSC 2.38 p0.05 RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 3.00 p0.10 (4 SIDES) PIN 1 TOP MARK (NOTE 6) R = 0.125 TYP 5 1.65 p 0.10 (2 SIDES) 0.75 p0.05 0.200 REF 0.40 p 0.10 8 4 0.25 p 0.05 (DD8) DFN 0509 REV C 1 0.50 BSC 2.38 p0.10 0.00 - 0.05 BOTTOM VIEW--EXPOSED PAD NOTE: 1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-1) 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON TOP AND BOTTOM OF PACKAGE DD Package 10-Lead Plastic DFN (3mm x 3mm) (Reference LTC DWG # 05-08-1699 Rev B) R = 0.125 TYP 6 0.40 p 0.10 10 0.70 p0.05 3.55 p0.05 1.65 p0.05 2.15 p0.05 (2 SIDES) 3.00 p0.10 (4 SIDES) 1.65 p 0.10 (2 SIDES) PIN 1 NOTCH R = 0.20 OR 0.35 s 45o CHAMFER PIN 1 PACKAGE TOP MARK OUTLINE (SEE NOTE 6) 0.25 p 0.05 0.50 BSC 2.38 p0.05 (2 SIDES) 0.200 REF 0.75 p0.05 0.00 - 0.05 5 1 (DD) DFN REV C 0310 0.25 p 0.05 0.50 BSC 2.38 p0.10 (2 SIDES) BOTTOM VIEW--EXPOSED PAD RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS NOTE: 1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2). CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE 285012fd 14 LTC2850/LTC2851/LTC2852 Package Description MS8 Package 8-Lead Plastic MSOP (Reference LTC DWG # 05-08-1660 Rev F) 3.00 p 0.102 (.118 p .004) (NOTE 3) 0.889 p 0.127 (.035 p .005) 5.23 (.206) MIN 0.254 (.010) 7 6 5 0.52 (.0205) REF 3.00 p 0.102 (.118 p .004) (NOTE 4) 4.90 p 0.152 (.193 p .006) DETAIL "A" 0o - 6o TYP GAUGE PLANE 3.20 - 3.45 (.126 - .136) 0.53 p 0.152 (.021 p .006) DETAIL "A" 0.42 p 0.038 (.0165 p .0015) TYP 8 0.65 (.0256) BSC 1 2 3 4 1.10 (.043) MAX 0.86 (.034) REF 0.18 (.007) SEATING PLANE RECOMMENDED SOLDER PAD LAYOUT NOTE: 1. DIMENSIONS IN MILLIMETER/(INCH) 2. DRAWING NOT TO SCALE 3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX 0.22 - 0.38 (.009 - .015) TYP 0.65 (.0256) BSC 0.1016 p 0.0508 (.004 p .002) MSOP (MS8) 0307 REV F MS Package 10-Lead Plastic MSOP (Reference LTC DWG # 05-08-1661 Rev E) 3.00 0.102 (.118 .004) (NOTE 3) 0.889 0.127 (.035 .005) 0.254 (.010) 10 9 8 7 6 3.00 0.102 (.118 .004) (NOTE 4) 4.90 0.152 (.193 .006) DETAIL "A" 0.497 0.076 (.0196 .003) REF 0 - 6 TYP GAUGE PLANE 5.23 (.206) MIN 1 2 3 4 5 3.20 - 3.45 (.126 - .136) 0.53 0.152 (.021 .006) DETAIL "A" 0.18 0.50 0.305 0.038 (.007) (.0197) (.0120 .0015) SEATING BSC TYP PLANE RECOMMENDED SOLDER PAD LAYOUT NOTE: 1. DIMENSIONS IN MILLIMETER/(INCH) 2. DRAWING NOT TO SCALE 3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX 0.86 (.034) REF 1.10 (.043) MAX 0.17 - 0.27 (.007 - .011) TYP 0.50 (.0197) BSC 0.1016 0.0508 (.004 .002) MSOP (MS) 0307 REV E 285012fd 15 LTC2850/LTC2851/LTC2852 Package Description S8 Package 8-Lead Plastic Small Outline (Narrow .150 Inch) (Reference LTC DWG # 05-08-1610) .189 - .197 (4.801 - 5.004) NOTE 3 .045 .005 .050 BSC 7 8 .245 MIN .160 .005 5 6 .150 - .157 (3.810 - 3.988) NOTE 3 .228 - .244 (5.791 - 6.197) .030 .005 TYP 1 RECOMMENDED SOLDER PAD LAYOUT .010 - .020 x 45 (0.254 - 0.508) 3 2 4 .053 - .069 (1.346 - 1.752) .008 - .010 (0.203 - 0.254) .004 - .010 (0.101 - 0.254) 0- 8 TYP .016 - .050 (0.406 - 1.270) .050 (1.270) BSC .014 - .019 (0.355 - 0.483) TYP NOTE: 1. DIMENSIONS IN INCHES (MILLIMETERS) 2. DRAWING NOT TO SCALE 3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm) SO8 0303 S Package 14-Lead Plastic Small Outline (Narrow .150 Inch) (Reference LTC DWG # 05-08-1610) .337 - .344 (8.560 - 8.738) NOTE 3 .045 .005 .050 BSC 14 N 12 11 10 9 8 N .245 MIN .160 .005 .228 - .244 (5.791 - 6.197) 1 .030 .005 TYP 13 2 3 N/2 N/2 RECOMMENDED SOLDER PAD LAYOUT .010 - .020 x 45 (0.254 - 0.508) .008 - .010 (0.203 - 0.254) 1 2 3 4 5 .053 - .069 (1.346 - 1.752) NOTE: 1. DIMENSIONS IN .014 - .019 (0.355 - 0.483) TYP INCHES (MILLIMETERS) 2. DRAWING NOT TO SCALE 3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm) 7 .004 - .010 (0.101 - 0.254) 0 - 8 TYP .016 - .050 (0.406 - 1.270) 6 .150 - .157 (3.810 - 3.988) NOTE 3 .050 (1.270) BSC S14 0502 285012fd 16 LTC2850/LTC2851/LTC2852 Revision History (Revision history begins at Rev D) REV DATE DESCRIPTION PAGE NUMBER D 05/10 Added military grade parts. 2, 3 285012fd 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. 17 LTC2850/LTC2851/LTC2852 Typical Application SLAVE SLAVE LTC2852 LTC2852 R D R D MASTER SLAVE 120 D R TE = 3.3V TE = 3.3V R D LTC2855 LTC2855 285012 TA04 Full Duplex Network Using the LTC2852 and LTC2855 Related Parts PART NUMBER DESCRIPTION COMMENTS LTC485 Low Power RS485 Interface Transceiver ICC = 300A (Typ) LTC491 Differential Driver and Receiver Pair ICC = 300A LTC1480 3.3V Ultralow Power RS485 Transceiver 3.3V Operation LTC1483 Ultralow Power RS485 Low EMI Transceiver Controlled Driver Slew Rate LTC1485 Differential Bus Transceiver 10Mbps Operation LTC1487 Ultralow Power RS485 with Low EMI, Shutdown and High Input Impedance Up to 256 Transceiver on the Bus LTC1520 50Mbps Precision Quad Line Receiver Channel-to-Channel Skew 400ps (Typ) LTC1535 Isolated RS485 Full-Duplex Transceiver 2500VRMS Isolation in Surface Mount Package LTC1685 52Mbps RS485 Transceiver with Precision Delay Propagation Delay Skew 500ps (Typ) LT1785 60V Fault Protected RS485 Transceiver 60V Tolerant, 15kV ESD LTC2854/LTC2855 3.3V 20Mbps RS485/RS422 Transceivers with Integrated Switchable 3.3V Operation, Integrated, Switchable, 120 Termination Termination Resistor, 25kV ESD (LTC2854), 15kV ESD (LTC2855) LTC2856-1 20Mbps and Slew Rate-Limited, 15kV RS485/RS422 Transceiver 15kV ESD LTC2859/LTC2861 20Mbps RS485/RS422 Transceiver with Integrated Switchable Termination Integrated, Switchable, 120 Termination Resistor, 15kV ESD 285012fd 18 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 www.linear.com LT 0510 REV D * PRINTED IN USA LINEAR TECHNOLOGY CORPORATION 2007