LTC2844

LTC2844 3.3V Software-Selectable Multiprotocol Transceiver FEATURES s s s DESCRIPTIO s s Software-Selectable Transceiver Supports: RS232, RS449, EIA530, EIA530-A, V.35, V.36, X.21 Operates from Single 3.3V Supply with LTC2846 TUV Rheinland of North America Inc. Certified NET1, NET2 and TBR2 Compliant, Report No.: TBR2/051501/02 Complete DTE or DCE Port with LTC2846 28-Lead SSOP Surface Mount Package The LTC®2844 is a 4-driver/4-receiver multiprotocol transceiver. The LTC2844 and LTC2846 form the core of a complete software-selectable DTE or DCE interface port that supports the RS232, RS449, EIA530, EIA530-A, V.35, V.36 or X.21 protocols. The LTC2844 operates from a 3.3V supply and supplies provided by the LTC2846. The part is available in a 28-lead SSOP surface mount package. , LTC and LT are registered trademarks of Linear Technology Corporation. APPLICATIO S s s s Data Networking CSU and DSU Data Routers TYPICAL APPLICATIO DTE or DCE Multiprotocol Serial Interface with DB-25 Connector LL CTS DSR DCD DTR RTS RXD RXC TXC SCTE TXD LTC2844 D4 R4 R3 R2 R1 D3 D2 D1 R3 R2 LTC2846 D3 R1 D2 D1 T T 18 LL A (141) 13 5 DSR B CTS B CTS A (106) 22 6 DSR A (107) 10 8 DCD B DCD A (109) 23 20 19 4 DTR B DTR A (108) RTS B RTS A (105) SHIELD (101) 1 SG (102) 7 16 RXD B 3 RXD A (104) 9 RXC B 17 RXC A (115) DB-25 CONNECTOR 2844 TA01 U T T T 12 TXC B 15 11 TXC A (114) SCTE B 24 14 SCTE A (113) TXD B 2 TXD A (103) sn2844 2844fs U U 1 LTC2844 ABSOLUTE (Note 1) AXI U RATI GS PACKAGE/ORDER I FOR ATIO TOP VIEW VCC VDD D1 D2 D3 R1 R2 R3 D4 1 2 3 D1 4 5 6 7 8 9 R1 R2 R3 D4 R4 D2 D3 25 D1 B 24 D2 A 23 D2 B 22 D3/R1 A 21 D3/R1 B 20 R2 A 19 R2 B 18 R3 A 17 R3 B 16 D4/R4 A 15 VIN G PACKAGE 28-LEAD PLASTIC SSOP 28 VEE 27 GND 26 D1 A Supply Voltage VCC ....................................................... –0.3V to 6.5V VIN ..................................................................... – 0.3V to 6.5V VEE ...................................................................... –10V to 0.3V VDD ..................................................................... – 0.3V to 10V Input Voltage Transmitters ............................ – 0.3V to (VCC + 0.3V) Receivers ................................................– 18V to 18V Logic Pins ............................... – 0.3V to (VCC + 0.3V) Output Voltage Transmitters .................. (VEE – 0.3V) to (VDD + 0.3V) Receivers ................................. – 0.3V to (VIN + 0.3V) Short-Circuit Duration Transmitter Output ...................................... Indefinite Receiver Output ........................................... Indefinite VEE ................................................................... 30 sec Operating Temperature Range LTC2844CG ............................................. 0°C to 70°C LTC2844IG ......................................... – 40°C to 85°C Storage Temperature Range ................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec).................. 300°C ORDER PART NUMBER LTC2844CG LTC2844IG R4 10 M0 11 M1 12 M2 13 DCE/DTE 14 TJMAX = 125°C, θJA = 90°C/ W, θJC = 35°C/ W Consult LTC Marketing for parts specified with wider operating temperature ranges. The q denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 5V, VIN = 3.3V, VDD = 8V, VEE = – 7V for V.28, – 5.5V for V.10, V.11 (Notes 2, 3) SYMBOL Supplies ICC VCC Supply Current (DCE Mode, All Digital Pins = GND or VIN) RS530, RS530-A, X.21 Modes, No Load RS530, RS530-A, X.21 Modes, Full Load V.28 Mode, No Load V.28 Mode, Full Load No-Cable Mode q q q q ELECTRICAL CHARACTERISTICS PARAMETER CONDITIONS MIN TYP 2.7 95 1 1 600 1.6 14 25 1 7.5 10 0.2 0.2 1 8 10 490 MAX UNITS mA mA mA mA µA mA mA mA mA mA µA mA mA mA mA µA µA 120 2 2 1200 IEE VEE Supply Current (DCE Mode Unless RS530, RS530-A, X.21 Modes, No Load Otherwise Noted, All Digital Pins = GND or VIN) RS530, X.21 Modes, Full Load (DTE Mode) RS530-A, Full Load (DTE Mode) V.28 Mode, No Load V.28 Mode, Full Load No-Cable Mode VDD Supply Current (DCE Mode, All Digital Pins = GND or VIN) RS530, RS530-A, X.21 Modes, No Load RS530, RS530-A, X.21 Modes, Full Load V.28 Mode, No Load V.28 Mode, Full Load No-Cable Mode All Modes Except No-Cable Mode IDD IVIN VIN Supply Current (DCE Mode, All Digital Pins = GND or VIN) sn2844 2844fs 2 U W U U WW W LTC2844 The q denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 5V, VIN = 3.3V, VDD = 8V, VEE = – 7V for V.28, – 5.5V for V.10, V.11 (Notes 2, 3) SYMBOL PD PARAMETER Internal Power Dissipation (DCE Mode, All Digital Pins = GND or VIN) Logic Input High Voltage Logic Input Low Voltage Logic Input Current D1, D2, D3, D4 M0, M1, M2, DCE = GND M0, M1, M2, DCE = VIN IO = –3mA IO = 1.6mA 0V ≤ VO ≤ VIN M0 = M1 = M2 = VIN, VO = 0V M0 = M1 = M2 = VIN, VO = VIN RL = 1.95k (Figure 1) RL = 50Ω (Figure 1) q ELECTRICAL CHARACTERISTICS CONDITIONS RS530, RS530-A, X.21 Modes, Full Load V.28 Mode, Full Load q q q q q q q q q q MIN TYP 210 54 MAX UNITS mW mW V Logic Inputs and Outputs VIH VIL IIN 2 0.8 – 30 2.7 – 75 3 0.2 – 30 – 85 0.4 ± 50 – 160 ±10 ±5 0.5VODO ±2 0.67VODO 0.2 3 0.2 ±150 q q q q q q q q q V µA µA µA V V mA µA µA V V V V V V mA µA ns ns ns ns ns ns ns ns ns ±10 –120 ±10 VOH VOL IOSR IOZR V.11 Driver VODO VODL ∆VOD VOC ∆VOC ISS IOZ tr, tf tPLH tPHL ∆t tSKEW VTH ∆VTH IIN RIN tr, tf tPLH Output High Voltage Output Low Voltage Output Short-Circuit Current Three-State Output Current Open Circuit Differential Output Voltage Loaded Differential Output Voltage Change in Magnitude of Differential Output Voltage Common Mode Output Voltage Change in Magnitude of Common Mode Output Voltage Short-Circuit Current Output Leakage Current Rise or Fall Time Input to Output Input to Output Input to Output Difference, tPLH – tPHL Output to Output Skew Input Threshold Voltage Input Hysteresis Input Current (A, B) Input Impedance Rise or Fall Time Input to Output q RL = 50Ω (Figure 1) RL = 50Ω (Figure 1) RL = 50Ω (Figure 1) VOUT = GND –0.25V ≤ VO ≤ 0.25V, Power Off or No-Cable Mode or Driver Disabled LTC2844C (Figures 2, 5) LTC2844I (Figures 2, 5) LTC2844C (Figures 2, 5) LTC28441 (Figures 2, 5) LTC2844C (Figures 2, 5) LTC2844I (Figures 2, 5) LTC2844C (Figures 2, 5) LTC2844I (Figures 2, 5) (Figures 2, 5) –7V ≤ VCM ≤ 7V –7V ≤ VCM ≤ 7V –10V ≤ VA,B ≤ 10V –10V ≤ VA,B ≤ 10V (Figures 2, 6) LTC2844C CL = 50pF (Figures 2, 6) LTC2844I CL = 50pF (Figures 2, 6) q q q ±1 2 2 20 20 20 20 0 0 15 15 40 40 40 40 3 3 3 ±100 25 35 65 75 65 75 12 17 V.11 Receiver q q q q – 0.2 15 15 30 15 50 50 0.2 40 ± 0.66 V mV mA kΩ ns q q 80 90 ns ns sn2844 2844fs 3 LTC2844 The q denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 5V, VIN = 3.3V, VDD = 8V, VEE = – 7V for V.28, – 5.5V for V.10, V.11 (Notes 2, 3) SYMBOL tPHL ∆t V.10 Driver VO VT ISS IOZ tr, tf tPLH tPHL VTH ∆VTH IIN RIN tr, tf tPLH tPHL ∆t V.28 Driver VO ISS IOZ SR tPLH tPHL VTHL VTLH ∆VTH RIN tr, tf tPLH tPHL Output Voltage Short-Circuit Current Output Leakage Current Slew Rate Input to Output Input to Output Input Low Threshold Voltage Input High Threshold Voltage Receiver Input Hysterisis Receiver Input Impedance Rise or Fall Time Input to Output Input to Output –15V ≤ VA ≤ 15V CL = 50pF (Figures 4, 8) CL = 50pF (Figures 4, 8) CL = 50pF (Figures 4, 8) q q ELECTRICAL CHARACTERISTICS PARAMETER Input to Output Input to Output Difference, tPLH – tPHL CONDITIONS LTC2844C CL = 50pF (Figures 2, 6) LTC2844I CL = 50pF (Figures 2, 6) LTC2844C CL = 50pF (Figures 2, 6) LTC2844I CL = 50pF (Figures 2, 6) Open Circuit, RL = 3.9k RL = 450Ω (Figure 3) RL = 450Ω (Figure 3) VO = GND –0.25V ≤ VO ≤ 0.25V, Power Off or No-Cable Mode or Driver Disabled RL = 450Ω, CL = 100pF (Figures 3, 7) RL = 450Ω, CL = 100pF (Figures 3, 7) RL = 450Ω, CL = 100pF (Figures 3, 7) q q q q q q q MIN TYP 50 50 MAX 80 90 16 21 ±6 UNITS ns ns ns ns V V 0 0 ±4 ±3.6 0.9VO 4 4 Output Voltage Output Voltage Short-Circuit Current Output Leakage Current Rise or Fall Time Input to Output Input to Output Receiver Input Threshold Voltage Receiver Input Hysteresis Receiver Input Current Receiver Input Impedance Rise or Fall Time Input to Output Input to Output Input to Output Difference, tPLH – tPHL q q ±150 ±0.1 2 1 1 –0.25 25 15 30 15 55 109 60 q q q q q q q mA µA µs µs µs ±100 V.10 Receiver 0.25 50 ±0.66 V mV mA kΩ ns ns ns ns ±10 ±150 ±1 4 1.3 1.3 ±100 30 2.5 2.5 0.8 2 0.1 3 5 15 60 150 100 500 0.3 7 V V mA µA V/µs µs µs V V V kΩ ns ns ns –10V ≤ VA ≤ 10V –10V ≤ VA ≤ 10V CL = 50pF (Figures 4, 8) CL = 50pF (Figures 4, 8) CL = 50pF (Figures 4, 8) CL = 50pF (Figures 4, 8) Open Circuit RL = 3k (Figure 3) VO = GND –0.25V ≤ VO ≤ 0.25V, Power Off or No-Cable Mode or Driver Disabled RL = 3k, CL = 2500pF (Figures 3, 7) RL = 3k, CL = 2500pF (Figures 3, 7) RL = 3k, CL = 2500pF (Figures 3, 7) q q ±5 ±8.5 V.28 Receiver q q q q sn2844 2844fs 4 LTC2844 ELECTRICAL CHARACTERISTICS 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; all currents out of device are negative. All voltages are referenced to device ground unless otherwise specified. Note 3: All typicals are given for VCC = 5V, VIN = 3.3V, VDD = 8V, VEE = – 7V for V.28, – 5.5V for V.10, V.11 and TA = 25°C. TYPICAL PERFOR A CE CHARACTERISTICS RS530, X.21 in DCE Mode (Three V.11 Drivers with Full Load) ICC vs Data Rate 125 120 115 ICC (mA) IEE (mA) 110 105 100 95 90 10 100 1000 DATA RATE (kBd) 10000 2844 G01 TA = 25°C 20 18 16 14 10 20 30 40 50 60 70 80 100 DATA RATE (kBd) 2844 G02 IDD (mA) RS530, X.21 in DCE Mode (Three V.11 Drivers with Full Load) ICC vs Temperature 105 23.5 25.4 100 25.3 25.2 IDD (mA) ICC (mA) IEE (mA) 95 90 85 80 –40 –20 0 40 20 60 TEMPERATURE (°C) UW 80 2844 G04 RS530-A in DTE Mode (Two V.10 Drivers with Full Load) IEE vs Data Rate 26 24 22 TA = 25°C 10 9 8 7 6 5 4 V.28 in DCE Mode (Three V.28 Drivers with Full Load) IDD vs Data Rate TA = 25°C 10 20 30 40 50 60 70 80 100 DATA RATE (kBd) 2844 G03 RS530-A in DTE Mode (Two V.10 Drivers with Full Load) IEE vs Temperature 8.20 8.15 8.10 8.05 8.00 7.95 7.90 7.85 0 20 40 60 TEMPERATURE (°C) 80 100 V.28 in DCE Mode (Three V.28 Drivers with Full Load) IDD vs Temperature 25.1 25.0 24.9 24.8 24.7 24.6 100 24.5 –40 –20 7.80 –40 –20 0 20 40 60 TEMPERATURE (°C) 80 100 2844 G05 2844 G06 sn2844 2844fs 5 LTC2844 PI FU CTIO S VCC (Pin 1): Positive Supply for the Transceivers. Connect to VCC Pin 8 on LTC2846 or to 5V supply. Connect a 1µF capacitor to ground. VDD (Pin 2): Positive Supply Voltage for V.28. Connect to VDD Pin 7 on LTC2846 or 8V supply. Connect a 1µF capacitor to ground. D1 (Pin 3): TTL Level Driver 1 Input. D2 (Pin 4): TTL Level Driver 2 Input. D3 (Pin 5): TTL Level Driver 3 Input. R1 (Pin 6): CMOS Level Receiver 1 Output. Receiver outputs have a weak pull up to VIN when high impedance. R2 (Pin 7): CMOS Level Receiver 2 Output. R3 (Pin 8): CMOS Level Receiver 3 Output. D4 (Pin 9): TTL Level Driver 4 Input. R4 (Pin 10): CMOS Level Receiver 4 Output. M0 (Pin 11): TTL Level Mode Select Input 0. Mode select inputs pull up to VIN. M1 (Pin 12): TTL Level Mode Select Input 1. M2 (Pin 13): TTL Level Mode Select Input 2. DCE/DTE (Pin 14): TTL Level Mode Select Input. VIN (Pin 15): Positive Supply for the Receiver Outputs. 3V ≤ VIN ≤ 3.6V. Connect a 1µF capacitor to ground. D4/R4 A (Pin 16): Receiver 4 Inverting Input and Driver 4 Inverting Output. R3 B (Pin 17): Receiver 3 Noninverting Input. R3 A (Pin 18): Receiver 3 Inverting Input. R2 B (Pin 19): Receiver 2 Noninverting Input. R2 A (Pin 20): Receiver 2 Inverting Input. D3/R1 B (Pin 21): Receiver 1 Noninverting Input and Driver 3 Noninverting Output. D3/R1 A (Pin 22): Receiver 1 Inverting Input and Driver 3 Inverting Output. D2 B (Pin 23): Driver 2 Noninverting Output. D2 A (Pin 24): Driver 2 Inverting Output. D1 B (Pin 25): Driver 1 Noninverting Output. D1 A (Pin 26): Driver 1 Inverting Output. GND (Pin 27): Ground. VEE (Pin 28): Negative Supply Voltage. Connect to VEE Pin 31 on LTC2846 or to – 7V supply. Connect a 1µF capacitor to ground. 6 U U U sn2844 2844fs LTC2844 BLOCK DIAGRA VCC 1 VDD 2 D1 3 D1 25 D1B 24 D2A D2 4 D2 23 D2B 25 D3/R1 A D3 5 D3 10k 20k 6k B S3 A 10k 20k 21 D3/R1 B 2844 F02 R1 6 R1 20 R2A 20k 10k 6k S3 R2 7 R2 10k R3 8 R3 10k D4 9 D4 20k R4 10 R4 S3 2844 F04 M0 11 M1 12 M2 13 DCE/DTE 14 15 VIN 2844 BD MODE SELECTION LOGIC W 28 VEE 27 GND 26 D1A 19 R2B 20k 18 R3A 20k 10k S3 6k 17 R3B 20k 16 D4/R4 A 10k 6k TEST CIRCUITS A RL VOD RL B VOC 2844 F01 Figure 1. V.11 Driver Test Circuit RL 100Ω CL 100pF CL 100pF B A R CL Figure 2. V.11 Driver/Receiver AC Test Circuit D A CL RL 2844 F03 Figure 3. V.10/V.28 Driver Test Circuit D A A R CL Figure 4. V.10/V.28 Receiver Test Circuit sn2844 2844fs 7 LTC2844 ODE SELECTIO MODE NAME Not Used (Default V.11) RS530A RS530 X.21 V.35 RS449/V.36 V.28/RS232 No Cable Not Used (Default V.11) RS530A RS530 X.21 V.35 RS449/V.36 V.28/RS232 No Cable M2 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 Note 1: Driver inputs are TTL level compatible. (Note 2) R1 A V.11 V.11 V.11 V.11 V.28 V.11 V.28 30k 30k 30k 30k 30k 30k 30k 30k 30k B V.11 V.11 V.11 V.11 30k V.11 30k 30k 30k 30k 30k 30k 30k 30k 30k 30k A V.11 V.10 V.11 V.11 V.28 V.11 V.28 30k V.11 V.10 V.11 V.11 V.28 V.11 V.28 30k (Note 2) R2 B V.11 30k V.11 V.11 30k V.11 30k 30k V.11 30k V.11 V.11 30k V.11 30k 30k A V.11 V.11 V.11 V.11 V.28 V.11 V.28 30k V.11 V.11 V.11 V.11 V.28 V.11 V.28 30k (Note 2) R3 B V.11 V.11 V.11 V.11 30k V.11 30k 30k V.11 V.11 V.11 V.11 30k V.11 30k 30k (Note 2) (Note 3) (Note 3) (Note 3) R4A R1 R2 R4 R3 30k 30k 30k 30k 30k 30k 30k 30k V.10 V.10 V.10 V.10 V.28 V.10 V.28 30k CMOS CMOS CMOS CMOS CMOS CMOS CMOS Z Z Z Z Z Z Z Z Z CMOS CMOS CMOS CMOS CMOS CMOS CMOS Z CMOS CMOS CMOS CMOS CMOS CMOS CMOS Z Z Z Z Z Z Z Z Z CMOS CMOS CMOS CMOS CMOS CMOS CMOS Z MODE NAME Not Used (Default V.11) RS530A RS530 X.21 V.35 RS449/V.36 V.28/RS232 No Cable Not Used (Default V.11) RS530A RS530 X.21 V.35 RS449/V.36 V.28/RS232 No Cable M2 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 Note 2: Unused receiver inputs are terminated with 30k to ground. Note 3: Receiver outputs are CMOS level compatible and have a weak pull-up to VIN when Z. 8 U M1 M0 DCE /DTE 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 (Note 1) (Note 1) (Note 1) D1 D3 D4 D2 TTL TTL TTL TTL TTL TTL TTL X TTL TTL TTL TTL TTL TTL TTL X X X X X X X X X TTL TTL TTL TTL TTL TTL TTL X TTL TTL TTL TTL TTL TTL TTL X X X X X X X X X D1 A V.11 V.11 V.11 V.11 V.28 V.11 V.28 Z V.11 V.11 V.11 V.11 V.28 V.11 V.28 Z B V.11 V.11 V.11 V.11 Z V.11 Z Z V.11 V.11 V.11 V.11 Z V.11 Z Z A V.11 V.10 V.11 V.11 V.28 V.11 V.28 Z V.11 V.10 V.11 V.11 V.28 V.11 V.28 Z D2 B V.11 Z V.11 V.11 Z V.11 Z Z V.11 Z V.11 V.11 Z V.11 Z Z A Z Z Z Z Z Z Z Z V.11 V.11 V.11 V.11 V.28 V.11 V.28 Z D3 B Z Z Z Z Z Z Z Z V.11 V.11 V.11 V.11 Z V.11 Z Z V.10 V.10 V.10 V.10 V.28 V.10 V.28 Z Z Z Z Z Z Z Z Z D4A 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 M1 M0 DCE /DTE 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 sn2844 2844fs W LTC2844 SWITCHI G TI E WAVEFOR S 3V D 0V VO B–A –VO A VO B t SKEW t SKEW 2844 F05 1.5V t PLH 50% tr 90% 10% f = 1MHz : t r ≤ 10ns : t f ≤ 10ns 1/2 VO Figure 5. V.11, V.35 Driver Propagation Delays VOD2 B–A –VOD2 VOH R VOL 0V t PLH 1.65V f = 1MHz : t r ≤ 10ns : t f ≤ 10ns Figure 6. V.11, V.35 Receiver Propagation Delays 3V D 0V VO A –VO tf 1.5V t PHL 3V 0V –3V –3V tr 0V 1.5V t PLH 3V 2844 F07 Figure 7. V.10, V.28 Driver Propagation Delays VIH A VIL VOH R VOL RECEIVER THRESHOLD t PHL 1.65V RECEIVER THRESHOLD t PLH 1.65V 2844 F08 Figure 8. V.10, V.28 Receiver Propagation Delays W W U 1.5V t PHL VDIFF = V(A) – V(B) 90% tf 50% 10% INPUT 0V t PHL OUTPUT 1.65V 2844 F06 sn2844 2844fs 9 LTC2844 APPLICATIONS INFORMATION Overview The LTC2846/LTC2844 form the core of a complete software-selectable DTE or DCE interface port that supports the RS232, RS449, EIA530, EIA530-A, V.35, V.36 or X.21 protocols. A complete DCE-to-DTE interface operating in EIA530 mode is shown in Figure 9. The LTC2846 of each port is used to generate the clock and data signals. The LTC2844 is used to generate the control signals along with LL (local loop-back). Cable termination is used only for the clock and data signals. The control signals do not need any external resistors. DTE SERIAL CONTROLLER TXD D1 LTC2846 TXD 103Ω SCTE D2 D3 TXC R1 103Ω RXC R2 103Ω RXD R3 103Ω LTC2844 RTS D1 RTS DTR D2 D3 DCD R1 DSR R2 CTS R3 LL D4 R4 Figure 9. Complete Multiprotocol Interface in EIA530 Mode sn2844 2844fs 10 U W U U DCE LTC2846 R3 SERIAL CONTROLLER TXD SCTE 103Ω R2 SCTE R1 TXC D3 TXC RXC D2 RXC RXD D1 RXD LTC2844 R3 RTS DTR R2 DTR R1 DCD D3 DCD DSR D2 DSR CTS LL D1 CTS R4 D4 LL 2844 F09 LTC2844 APPLICATIONS INFORMATION Mode Selection The interface protocol is selected using the mode select pins M0, M1 and M2 (see the Mode Selection table). For example, if the port is configured as a V.35 interface, the mode selection pins should be M2 = 1, M1 = 0, M0 = 0. For the control signals, the drivers and receivers will operate in V.28 (RS232) electrical mode. For the clock and data signals, the drivers and receivers will operate in V.35 electrical mode. The DCE/DTE pin will configure the port for DCE mode when high, and DTE when low. The interface protocol may be selected simply by plugging the appropriate interface cable into the connector. The mode pins are routed to the connector and are left unconnected (1) or wired to ground (0) in the cable as shown in Figure 10. The internal pull-up current sources will ensure a binary 1 when a pin is left unconnected and that the LTC2846/ LTC2844 enter the no-cable mode when the cable is removed. In the no-cable mode the LTC2846/LTC2844 supply current drops to less than 900µA and all driver outputs are forced into a high impedance state. The mode selection may also be accomplished by using jumpers to connect the mode pins to ground or VIN. (DATA) M0 LTC2846 M1 M2 DCE/DTE 15 16 18 19 LTC2844 DCE/DTE M2 M1 M0 (DATA) 14 13 12 11 2844 F10 Figure 10. Single Port DCE V.35 Mode Selection in the Cable U W U U CONNECTOR NC NC CABLE sn2844 2844fs 11 LTC2844 APPLICATIONS INFORMATION Cable Termination Traditional implementations have included switching resistors with expensive relays, or required the user to change termination modules every time the interface standard has changed. Custom cables have been used with the termination in the cable head or separate terminations are built on the board and a custom cable routes the signals to the appropriate termination. Switching the termination with FETs is difficult because the FETs must remain off even though the signal voltage is beyond the supply voltage for the FET drivers or the power is off. Using the LTC2846/LTC2844 solves the cable termination switching problem. Via software control, appropriate termination for the V.10 (RS423), V.11 (RS422), V.28 (RS232) and V.35 electrical protocols is chosen. V.10 (RS423) Interface A typical V.10 unbalanced interface is shown in Figure 11. A V.10 single-ended generator output A with ground C is connected to a differential receiver with inputs A' connected to A, and input C' connected to the signal return ground C. Usually, no cable termination is required for V.10 interfaces, but the receiver inputs must be compliant with the impedance curve shown in Figure 12. 2844 F12 GENERATOR BALANCED INTERCONNECTING CABLE LOAD CABLE TERMINATION RECEIVER A A' B' C' C' R4 20k R7 10k C Figure 11. Typical V.10 Interface 12 U W U U The V.10 receiver configuration in the LTC2844 is shown in Figure 13. In V.10 mode switch S3 inside the LTC2844 is turned off.The noninverting input is disconnected inside the LTC2844 receiver and connected to ground. The cable termination is then the 30k input impedance to ground of the LTC2844 V.10 receiver. IZ 3.25mA –10V –3V VZ 3V 10V –3.25mA Figure 12. V.10 Receiver Input Impedance A' R8 6k S3 R5 20k R6 10k LTC2844 RECEIVER 2844 F11 GND 2844 F13 Figure 13. V.10 Receiver Configuration sn2844 2844fs LTC2844 APPLICATIONS INFORMATION V.11 (RS422) Interface A typical V.11 balanced interface is shown in Figure 14. A V.11 differential generator with outputs A and B with ground C is connected to a differential receiver with ground C', inputs A' connected to A, B' connected to B. The V.11 interface has a differential termination at the receiver end that has a minimum value of 100Ω. The termination resistor is optional in the V.11 specification, but for the high speed clock and data lines, the termination is required to prevent reflections from corrupting the data. The receiver inputs must also be compliant with the impedance curve shown in Figure 12. In V.11 mode, all switches are off except S1 of the LTC2846’s receivers which connects a 103Ω differential termination impedance to the cable as shown in Figure 151. The LTC2844 only handles control signals, so no termination other than its V.11 receivers’ 30k input impedance is necessary. GENERATOR BALANCED INTERCONNECTING CABLE LOAD CABLE TERMINATION A A' 100Ω MIN RECEIVER B C B' C' Figure 14. Typical V.11 Interface GENERATOR BALANCED INTERCONNECTING CABLE LOAD CABLE TERMINATION RECEIVER A A' C C' Figure 16. Typical V.28 Interface 1Actually, U W U U V.28 (RS232) Interface A typical V.28 unbalanced interface is shown in Figure 16. A V.28 single-ended generator output A with ground C is connected to a single-ended receiver with input A' connected to A, ground C' connected via the signal return ground C. In V.28 mode all switches are off except S3 inside the LTC2846/LTC2844 which connects a 6k (R8) impedance to ground in parallel with 20k (R5) plus 10k (R6) for a combined impedance of 5k as shown in Figure 17. The noninverting input is disconnected inside the LTC2846/ LTC2844 receiver and connected to a TTL level reference voltage for a 1.4V receiver trip point. A' R1 51.5Ω S1 S2 R2 51.5Ω R8 6k S3 R5 20k R6 10k R3 124Ω LTC2846 RECEIVER B' C' R4 20k R7 10k 2844 F14 GND 2844 F15 Figure 15. V.11 Receiver Configuration A' R8 6k S3 R5 20k R6 10k LTC2844 RECEIVER B' 2844 F16 R4 20k R7 10k C' GND 2844 F17 Figure 17. V.28 Receiver Configuration there is no switch S1 in receivers R2 and R3. However, for simplicity, all termination networks on the LTC2846 can be treated identically if it is assumed that an S1 switch exists and is always closed on the R2 and R3 receivers. sn2844 2844fs 13 LTC2844 APPLICATIONS INFORMATION V.35 Interface A typical V.35 balanced interface is shown in Figure 18. A V.35 differential generator with outputs A and B with ground C is connected to a differential receiver with ground C', inputs A' connected to A, B' connected to B. The V.35 interface requires a T or delta network termination at the receiver end and the generator end. The receiver differential impedance measured at the connector must be 100Ω ±10Ω, and the impedance between shorted terminals (A' and B') and ground C' must be 150Ω ±15Ω. In V.35 mode, both switches S1 and S2 inside the LTC2846 are on, connecting the T network impedance as shown in Figure 19. The 30k input impedance of the receiver is placed in parallel with the T network termination, but does not affect the overall input impedance significantly. The generator differential impedance must be 50Ω to 150Ω and the impedance between shorted terminals (A and B) and ground C must be 150Ω ±15Ω. For the generator termination, switches S1 and S2 are both on as shown in Figure 20. BALANCED INTERCONNECTING CABLE GENERATOR LOAD CABLE TERMINATION RECEIVER A 50Ω 125Ω A' 125Ω 50Ω 50Ω B C B' C' 50Ω Figure 18. Typical V.35 Interface A LTC2846 51.5Ω V.35 DRIVER 124Ω S2 51.5Ω B C 2844 F20 S1 5V C5 10µF 8 VCC GND 30 Figure 20. V.35 Driver Figure 21. Charge Pump sn2844 2844fs 14 + U W U U No-Cable Mode The no-cable mode (M0 = M1 = M2 = 1) is intended for the case when the cable is disconnected from the connector. The bias circuitry, drivers and receivers are turned off, the driver outputs are forced into a high impedance state, and the supply current drops to less than 600µA. LTC2846 Supplies The LTC2846 uses an internal capacitive charge pump to generate VDD and VEE as shown in Figure 21. A voltage doubler generates about 8V on VDD and a voltage inverter generates about – 7.5V for VEE. Three 1µF surface mounted tantalum or ceramic capacitors are required for C1, C2 and C3. The VEE capacitor C4 should be a minimum of 3.3µF. All capacitors are 16V and should be placed as close as possible to the LTC2846 to reduce EMI. The LTC2846 has an internal boost switching regulator which generates a 5V output from the 3.3V supply as shown in Figure 22. The 5V VCC supplies its internal charge pump and transceivers as well as its companion chip. A' R1 51.5Ω S1 S2 R2 51.5Ω R8 6k S3 R5 20k R6 10k R3 124Ω RECEIVER LTC2846 B' R4 20k R7 10k C' 2844 F18 GND 2844 F19 Figure 19. V.35 Receiver Configuration 7 C3 1µF 6 C1 1µF 5 VDD C1+ LTC2846 C1– C2 + C2 – VEE 33 32 31 C4 3.3µF C2 1µF 2844 F21 LTC2844 APPLICATIONS INFORMATION VIN 3.3V C6 10µF L1 5.6µH 3 VIN 36 SW R1 13k C5 10 µF R2 4.3k D1 VCC 5V 480mA SHDN BOOST SWITCHING REGULATOR 35 4 SHDN FB GND 2, 34 C1,C2: TAIYO YUDEN X5R JMK316BJ106ML D1: ON SEMICONDUCTOR MBR0520 L1: SUMIDA CR43-5R6 2844 F22 Figure 22. Boost Switching Regulator Receiver Fail-Safe All LTC2846/LTC2844 receivers feature fail-safe operation in all modes. If the receiver inputs are left floating or shorted together by a termination resistor, the receiver output will always be forced to a logic high. DTE vs DCE Operation The DCE/DTE pin acts as an enable for Driver 3/Receiver 1 in the LTC2846, and Driver 3/Receiver 1 and Receiver 4/ Driver 4 in the LTC2844. The LTC2846/LTC2844 can be configured for either DTE or DCE operation in one of two ways: a dedicated DTE or DCE port with a connector of appropriate gender or a port with one connector that can be configured for DTE or DCE operation by rerouting the signals to the LTC2846/LTC2844 using a dedicated DTE cable or dedicated DCE cable. A dedicated DTE port using a DB-25 male connector is shown in Figure 23. The interface mode is selected by logic outputs from the controller or from jumpers to either VIN or GND on the mode select pins. A port with one DB-25 connector, but can be configured for either DTE or DCE operation is shown in Figure 24. The configuration requires separate cables for proper signal routing in DTE or DCE operation. For example, in DTE U W U U mode, the TXD signal is routed to Pins 2 and 14 via Driver 1 in the LTC2846. In DCE mode, Driver 1 now routes the RXD signal to Pins 2 and 14. Multiprotocol Interface with RL, LL, TM and a DB-25 Connector If the RL, LL and TM signals are implemented, there are not enough drivers and receivers available in the LTC2846/ LTC2844. In Figure 25, the required control signals are handled by the LTC2845. The LTC2845 has an additional single-ended driver/receiver pair that can handle two more optional control signals such as TM and LL. Cable-Selectable Multiprotocol Interface A cable-selectable multiprotocol DTE/DCE interface is shown in Figure 26. The select lines M0, M1 and DCE/DTE are brought out to the connector. The mode is selected by the cable by wiring M0 (connector Pin 18) and M1 (connector Pin 21) and DCE/DTE (connector Pin 25) to ground (connector Pin 7) or letting them float. If M0, M1 or DCE/ DTE is floating, internal pull-up current sources will pull the signals to VIN. The select bit M2 is floating and therefore, internally pulled high. When the cable is pulled out, the interface will go into the no-cable mode. Compliance Testing The LTC2846/LTC2844 chipset has been tested by TUV Rheinland of North America Inc. and passed the NET1, NET2 and TBR2 requirements. Copies of the test report are available from LTC or TUV Rheinland of North America Inc. The title of the report is Test Report No. TBR2/051501/02 The address of TUV Rheinland of North America Inc. is: TUV Rheinland of North America Inc. 1775, Old Highway 8 NW, Suite 107 St. Paul, MN 55112 Tel. (651) 639-0775 Fax (651) 639-0873 sn2844 2844fs 15 LTC2844 TYPICAL APPLICATIO S VIN 3.3V L1 5.6µH C6 10µF SHDN 3 4 7 C3 1µF VCC 5V 5 C1 1µF 6 8 LTC2846 TXD 9 D1 T CHARGE PUMP BOOST SWITCHING REGULATOR 36 35 33 32 31 30 C4 3.3µF C2 1µF D1 MBR0520 R1 13k R2 4.3k C5 10µF VCC 5V 29 28 27 SCTE 10 D2 T 26 11 D3 12 T 25 TXC R1 24 23 RXC 13 R2 T 22 21 RXD 14 15 16 18 19 M0 M1 M2 DCE/DTE 17 VIN 3.3V 7 1 R3 T 20 15 12 17 9 3 16 TXC A (114) TXC B RXC A (115) RXC B RXD A (104) RXD B SG SHIELD C7 1µF C8 1µF 1 VCC 2 VDD 3 D1 VEE GND 28 27 26 C9 1µF 4 19 20 23 RTS 25 24 DTR 4 D2 23 5 D3 LTC2844 22 21 20 R2 19 18 R3 17 16 8 10 6 22 5 13 18 DCD 6 7 R1 DSR CTS 8 10 9 LL R4 D4 M0 M1 M2 DCE/DTE VIN M0 M1 M2 11 12 13 14 15 C10 1µF Figure 23. Controller-Selectable Multiprotocol DTE Port with DB-25 Connector sn2844 2844fs 16 + U 2 14 24 11 TXD A (103) TXD B SCTE A (113) SCTE B DB-25 MALE CONNECTOR RTS A (105) RTS B DTR A (108) DTR B DCD A (109) DCD B DSR A (107) DSR B CTS A (106) CTS B LL A (141) VIN 3.3V 2844 F23 LTC2844 TYPICAL APPLICATIO S VIN 3.3V L1 5.6µH C6 10µF SHDN 3 4 7 C3 1µF VCC 5V 5 C1 1µF 6 8 LTC2846 DTE_TXD/DCE_RXD 9 D1 T CHARGE PUMP BOOST SWITCHING REGULATOR 36 35 33 32 31 30 C2 1µF C4 3.3µF DTE TXD A TXD B SCTE A SCTE B DCE RXD A RXD B RXC A RXC B D1 MBR0520 VCC 5V C5 10µF R1 13k R2 4.3k 29 28 27 DTE_SCTE/DCE_RXC 10 D2 T 26 11 D3 DTE_TXC/DCE_TXC 12 T 25 R1 24 23 DTE_RXC/DCE_SCTE 13 R2 T 22 21 DTE_RXD/DCE_TXD 14 15 16 18 19 C7 1µF C8 1µF M0 M1 M2 DCE/DTE 17 VIN 3.3V VEE GND D1 28 27 26 DTE_RTS/DCE_CTS 3 25 24 D2 23 C9 1µF 4 19 20 23 7 1 R3 T 20 15 12 17 9 3 16 TXC A TXC B RXC A RXC B RXD A RXD B SG SHIELD DB-25 CONNECTOR TXC A TXC B SCTE A SCTE B TXD A TXD B 1 VCC 2 VDD DTE_DTR/DCE_DSR 4 5 D3 LTC2844 22 21 20 R2 19 18 R3 17 16 8 10 6 22 5 13 18 DTE_DCD/DCE_DCD 6 7 R1 DTE_DSR/DCE_DTR DTE_CTS/DCE_RTS 8 10 9 DTE_LL/DCE_LL R4 D4 M0 M1 M2 DCE/DTE VIN M0 M1 M2 DCE/DTE 11 12 13 14 15 C10 1µF Figure 24. Controller-Selectable Multiprotocol DTE/DCE Port with DB-25 Connector sn2844 2844fs + U 2 14 24 11 RTS A RTS B DTR A DTR B CTS A CTS B DSR A DSR B DCD A DCD B DSR A DSR B CTS A CTS B LL A DCD A DCD B DTR A DTR B RTS A RTS B LL A VIN 3.3V 2844 F25 17 LTC2844 TYPICAL APPLICATIO S VIN 3.3V L1 5.6µH C6 10µF SHDN 3 4 7 C3 1µF VCC 5V 5 C1 1µF 6 8 LTC2846 DTE_TXD/DCE_RXD 9 D1 T CHARGE PUMP BOOST SWITCHING REGULATOR 36 35 33 32 31 30 C2 1µF C4 3.3µF D1 MBR0520 R1 13k R2 4.3k C5 10µF VCC 5V 29 28 27 DTE_SCTE/DCE_RXC 10 D2 T 26 11 D3 12 T 25 DTE_TXC/DCE_TXC R1 24 23 DTE_RXC/DCE_SCTE 13 R2 T 22 21 DTE_RXD/DCE_TXD 14 15 16 18 19 C7 1µF C8 1µF M0 M1 M2 DCE/DTE 17 VIN 3.3V 36 35 34 DTE_RTS/DCE_CTS 3 D1 33 32 DTE_DTR/DCE_DSR 4 D2 31 C9 1µF 4 19 20 23 1 R3 T 20 15 12 17 9 3 16 7 TXC A TXC B RXC A RXC B RXD A RXD B SG SHIELD TXC A TXC B SCTE A SCTE B TXD A TXD B 1, 19 VCC 2 VDD VEE GND 5 D3 LTC2845 30 29 28 R2 27 26 R3 D4 R4 R5 D5 M0 M1 M2 DCE/DTE R4EN 25 24 23 22 21 20 VIN 15 D4ENB 16 NC VIN 3.3V 8 10 6 22 5 13 DTE_DCD/DCE_DCD 6 7 R1 DTE_DSR/DCE_DTR DTE_CTS/DCE_RTS DTE_LL/DCE_RI DTE_RI/DCE_LL DTE_TM/DCE_RL DTE_RL/DCE_TM M0 M1 M2 DCE/DTE 8 9 10 17 18 11 12 13 14 Figure 25. Controller-Selectable Multiprotocol DTE/DCE Port with RL, LL, TM and DB-25 Connector sn2844 2844fs 18 + U 2 14 24 11 DTE TXD A TXD B SCTE A SCTE B DCE RXD A RXD B RXC A RXC B DB-25 CONNECTOR RTS A RTS B DTR A DTR B CTS A CTS B DSR A DSR B DCD A DCD B DSR A DSR B CTS A DCD A DCD B DTR A DTR B RTS A RTS B RI LL RL TM CTS B 18 LL * 25 21 RI TM RL C10 1µF *OPTIONAL 2844 F26 LTC2844 TYPICAL APPLICATIO S VIN 3.3V L1 5.6µH C6 10µF SHDN 3 4 7 C3 1µF VCC 5V 5 C1 1µF 6 8 LTC2846 DTE_TXD/DCE_RXD 9 D1 T CHARGE PUMP BOOST SWITCHING REGULATOR 36 35 33 32 31 30 C4 3.3µF DTE TXD A TXD B SCTE A SCTE B DCE RXD A RXD B RXC A RXC B C2 1µF D1 MBR0520 R1 13k R2 4.3k C5 10µF VCC 5V 29 28 27 DTE_SCTE/DCE_RXC 10 D2 T 26 11 D3 12 T 25 DTE_TXC/DCE_TXC R1 24 23 DTE_RXC/DCE_SCTE 13 R2 T 22 21 DTE_RXD/DCE_TXD 14 15 16 NC 18 19 M0 M1 M2 DCE/DTE 17 VIN 3.3V R3 T 20 15 12 17 9 3 RXD A 16 7 1 RXD B SG SHIELD DB-25 CONNECTOR C7 1µF C8 1µF 1 VCC 2 VDD 3 D1 28 27 26 DTE_RTS/DCE_CTS 25 24 D2 23 C9 1µF 25 DCE/DTE 21 M1 18 M0 4 RTS A 19 RTS B 20 DTR A 23 DTR B TXC A TXC B RXC A RXC B TXC A TXC B SCTE A SCTE B TXD A TXD B VEE GND DTE_DTR/DCE_DSR 4 5 D3 LTC2844 22 21 20 R2 19 18 R3 17 16 CABLE WIRING FOR MODE SELECTION MODE V.35 RS449, V.36 RS232 PIN 18 PIN 7 NC PIN 7 PIN 21 PIN 7 PIN 7 NC 8 10 6 22 5 13 DTE_DCD/DCE_DCD 6 7 R1 DTE_DSR/DCE_DTR DTE_CTS/DCE_RTS 8 10 9 11 12 NC 13 14 M0 M1 M2 R4 D4 VIN 15 C10 1µF DCE/DTE Figure 26. Cable-Selectable Multiprotocol DTE/DCE Port with DB-25 Connector sn2844 2844fs 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 2 14 24 11 CTS A CTS B DSR A DSR B DCD A DCD B DSR A DSR B CTS A CTS B DCD A DCD B DTR A DTR B RTS A RTS B VIN 3.3V CABLE WIRING FOR DTE/DCE SELECTION MODE DTE DCE PIN 25 PIN 7 NC 2844 F27 19 LTC2844 PACKAGE DESCRIPTIO U G Package 28-Lead Plastic SSOP (5.3mm) (Reference LTC DWG # 05-08-1640) 9.90 – 10.50* (.390 – .413) 28 27 26 25 24 23 22 21 20 19 18 17 16 15 1.25 ± 0.12 5.3 – 5.7 7.40 – 8.20 (.291 – .323) 0.65 BSC 1 2 3 4 5 6 7 8 9 10 11 12 13 14 2.0 (.079) 0° – 8° 0.65 (.0256) BSC 0.22 – 0.38 (.009 – .015) 0.05 (.002) G28 SSOP 0802 7.8 – 8.2 0.42 ± 0.03 RECOMMENDED SOLDER PAD LAYOUT 5.00 – 5.60** (.197 – .221) 0.09 – 0.25 (.0035 – .010) 0.55 – 0.95 (.022 – .037) NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS MILLIMETERS 2. DIMENSIONS ARE IN (INCHES) 3. DRAWING NOT TO SCALE *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED .152mm (.006") PER SIDE **DIMENSIONS DO NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED .254mm (.010") PER SIDE RELATED PARTS PART NUMBER LTC1321 LTC1334 LTC1343 LTC1344A LTC1345 LTC1346A LTC1543 LTC1544 LTC1545 LTC1546 LTC2845 LTC2846 DESCRIPTION Dual RS232/RS485 Transceiver Single 5V RS232/RS485 Multiprotocol Transceiver Software-Selectable Multiprotocol Transceiver Software-Selectable Cable Terminator Single Supply V.35 Transceiver Dual Supply V.35 Transceiver Software-Selectable Multiprotocol Transceiver Software-Selectable Multiprotocol Transceiver Software-Selectable Multiprotocol Transceiver Software-Selectable Multiprotocol Transceiver 3.3V Software-Selectable Multiprotocol Transceiver 3.3V Software-Selectable Multiprotocol Transceiver COMMENTS Two RS232 Driver/Receiver Pairs or Two RS485 Driver/Receiver Pairs Two RS232 Driver/Receiver or Four RS232 Driver/Receiver Pairs 4-Driver/4-Receiver for Data and Clock Signals Perfect for Terminating the LTC1543 (Not Needed with LTC1546) 3-Driver/3-Receiver for Data and Clock Signals 3-Driver/3-Receiver for Data and Clock Signals Terminated with LTC1344A for Data and Clock Signals, Companion to LTC1544 or LTC1545 for Control Signals Companion to LTC1546 or LTC1543 for Control Signals Including LL 5-Driver/5-Receiver Companion to LTC1546 or LTC1543 for Control Signals Including LL, TM and RL 3-Driver/3-Receiver with Termination for Data and Clock Signals 3.3V Supply, 5-Driver/5-Receiver Companion to LTC2846 for Control Signals Including LL, TM and RL 3.3V Supply, 3-Driver/3-Receiver with Termination for Data and Clock Signals, Generates the Required 5V and ±8V Supplies for LTC2846 and Companion Parts sn2844 2844fs LT/TP 0503 1K • PRINTED IN USA 20 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 q FAX: (408) 434-0507 q www.linear.com © LINEAR TECHNOLOGY CORPORATION 2002