LTC2844 3.3V Software-Selectable Multiprotocol Transceiver U FEATURES ■ ■ ■ ■ ■ DESCRIPTIO 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.
LTC2844 W W W AXI U U ABSOLUTE RATI GS U U W PACKAGE/ORDER I FOR ATIO (Note 1) 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.
LTC2844 ELECTRICAL CHARACTERISTICS The ● 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 PARAMETER CONDITIONS PD Internal Power Dissipation (DCE Mode, All Digital Pins = GND or VIN) RS530, RS530-A, X.21 Modes, Full Load V.
LTC2844 ELECTRICAL CHARACTERISTICS The ● 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.
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.
LTC2844 U U U 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.
LTC2844 W BLOCK DIAGRA TEST CIRCUITS VCC 1 28 VEE VDD 2 27 GND A RL 26 D1A D1 3 VOD D1 B 24 D2A D2 4 VOC RL 25 D1B 2844 F01 Figure 1. V.11 Driver Test Circuit D2 23 D2B 25 D3/R1 A D3 5 D3 10k 20k 6k B RL 100Ω S3 A 10k CL 100pF B CL 100pF A R CL 20k 21 D3/R1 B R1 6 R1 2844 F02 20 R2A 20k Figure 2. V.11 Driver/Receiver AC Test Circuit 6k 10k R2 7 S3 R2 10k D A 19 R2B 20k RL CL 18 R3A 20k 6k 2844 F03 10k R3 8 S3 R3 Figure 3. V.10/V.
LTC2844 U W 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 M1 M0 DCE /DTE (Note 1) (Note 1) (Note 1) D1 D3 D4 D2 D1 D2 D3 D4A A B A B A B 0 0 0 0 1 1 1 1 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 0 0 0 0 0 0 0 0 TTL TTL TTL TTL TTL TTL TTL X X X X X X X X X TTL TTL TTL TTL TTL TTL TTL X V.11 V.11 V.11 V.11 V.28 V.11 V.28 Z V.11 V.11 V.11 V.11 Z V.11 Z Z V.
LTC2844 U W W SWITCHI G TI E WAVEFOR S 3V f = 1MHz : t r ≤ 10ns : t f ≤ 10ns 1.5V D 0V 1.5V t PHL t PLH VO B–A –VO 90% 50% 10% tr 90% VDIFF = V(A) – V(B) 1/2 VO 50% 10% tf A VO B t SKEW t SKEW 2844 F05 Figure 5. V.11, V.35 Driver Propagation Delays VOD2 B–A –VOD2 f = 1MHz : t r ≤ 10ns : t f ≤ 10ns 0V INPUT t PLH 0V t PHL VOH R VOL 1.65V OUTPUT 1.65V 2844 F06 Figure 6. V.11, V.35 Receiver Propagation Delays 3V 1.5V 1.
LTC2844 U U W U APPLICATIONS INFORMATION Overview 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.
LTC2844 U U W U 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.
LTC2844 U U W U 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.
LTC2844 U U W U APPLICATIONS INFORMATION V.11 (RS422) Interface V.28 (RS232) 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.
LTC2844 U U W U APPLICATIONS INFORMATION V.35 Interface No-Cable Mode 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.
LTC2844 U U W U APPLICATIONS INFORMATION L1 5.6µH VIN 3.3V D1 3 C6 10µF SHDN VIN VCC 5V 480mA 36 SW BOOST SWITCHING REGULATOR 35 4 SHDN FB GND 2, 34 R1 13k C5 10µF R2 4.3k 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.
LTC2844 U TYPICAL APPLICATIO S D1 MBR0520 L1 5.6µH 3 C6 10µF SHDN 4 7 C3 1µF 36 BOOST SWITCHING REGULATOR 5 C1 1µF VCC 5V 33 30 LTC2846 9 D1 10 SCTE R2 4.3k T D2 C5 10µF C2 1µF 31 CHARGE PUMP 8 TXD 35 32 6 VCC 5V R1 13k T + VIN 3.3V C4 3.3µF 29 2 28 14 27 24 26 11 25 15 24 12 23 17 22 9 21 3 20 16 TXD A (103) TXD B SCTE A (113) SCTE B 11 D3 12 TXC 15 16 18 19 C8 1µF RTS DTR R2 14 RXD C7 1µF R1 13 RXC T R3 T T M0 7 M1 M2 17 VIN 3.
LTC2844 U TYPICAL APPLICATIO S D1 MBR0520 L1 5.6µH 3 C6 10µF SHDN 4 7 C3 1µF 36 BOOST SWITCHING REGULATOR 5 C1 1µF VCC 5V 6 8 9 D1 10 DTE_SCTE/DCE_RXC T D2 R2 4.3k 33 30 LTC2846 DTE_TXD/DCE_RXD 35 T C5 10µF C2 1µF 32 31 CHARGE PUMP VCC 5V R1 13k + VIN 3.3V C4 3.
LTC2844 U TYPICAL APPLICATIO S D1 MBR0520 L1 5.6µH 36 3 C6 10µF SHDN 4 7 C3 1µF BOOST SWITCHING REGULATOR 5 C1 1µF VCC 5V 8 LTC2846 D1 10 DTE_SCTE/DCE_RXC T D2 R2 4.3k 33 30 9 DTE_TXD/DCE_RXD 35 T C5 10µF C2 1µF 32 31 CHARGE PUMP 6 VCC 5V R1 13k + VIN 3.3V C4 3.
LTC2844 U TYPICAL APPLICATIO S D1 MBR0520 L1 5.6µH 3 C6 10µF SHDN 4 7 C3 1µF 36 BOOST SWITCHING REGULATOR 5 C1 1µF 33 30 LTC2846 9 D1 10 DTE_SCTE/DCE_RXC R2 4.3k T D2 C5 10µF C2 1µF 31 CHARGE PUMP 8 DTE_TXD/DCE_RXD 35 32 6 VCC 5V VCC 5V R1 13k T + VIN 3.3V C4 3.
LTC2844 U PACKAGE DESCRIPTIO 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 7.8 – 8.2 5.3 – 5.7 0.42 ±0.03 7.40 – 8.20 (.291 – .323) 0.65 BSC 1 2 3 4 5 6 7 8 9 10 11 12 13 14 RECOMMENDED SOLDER PAD LAYOUT 5.00 – 5.60** (.197 – .221) 2.0 (.079) 0° – 8° 0.09 – 0.25 (.0035 – .010) 0.55 – 0.95 (.022 – .037) NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS MILLIMETERS 2.
