Datasheet

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LTC2847

sn2847 2847fs

APPLICATIO S

DESCRIPTIO

FEATURES

TYPICAL APPLICATIO

, LTC and LT are registered trademarks of Linear Technology Corporation.

Complete DTE or DCE Multiprotocol Serial Interface with DB-25 Connector

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Data Networking

■

CSU and DSU

■

Data Routers

■

Software-Selectable Transceiver Supports:

RS232, RS449, EIA530, EIA530-A, V.35, V.36, X.21

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Operates from Single 5V Supply

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Separate Supply Pin for Digital Interface Works

down to 3V

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On-Chip Cable Termination

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Complete DTE or DCE Port with LTC2845

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Available in 38-Pin 5mm × 7mm QFN Package

The LTC

2847 is a 3-driver/3-receiver multiprotocol trans-

ceiver with on-chip cable termination. When combined with

the LTC2845, this chip set forms a complete software-

selectable DTE or DCE interface port that supports the

RS232, RS449, EIA530, EIA530-A, V.35, V.36 and X.21

protocols. All necessary cable termination is provided inside

the LTC2847.

The V

supplies the drivers, the receivers and an internal

charge pump that requires only five space-saving surface

mounted capacitors. The V

supply drives the digital inter-

face circuitry including the receiver output drivers. It can be

tied to V

or be powered off a lower supply (down to 3V) to

interface with low voltage ASICs. The LTC2847 is available in

a 0.8mm tall, 5mm × 7mm QFN package.

Software-Selectable

Multiprotocol Transceiver with

Termination and 3.3V Digital Interface

D2 D1

LTC2845

RTS

DTRDSR DCDCTS

R2 R1R4

LTC2847

RILLTMRL

TXDSCTETXC

RXCRXD

21424111512179314192082310513 622182521 716

2847 TA01

SCTE B

SCTE A (113)

TXD B

TXD A (103)

RXC A (115)

RXC B

RXD A (104)

RXD B

RTS A (105)

RTS B

DTR A (108)

DTR B

LL A (141)

TM (142)

RL (140)

SG (102)

SHIELD (101)

DB-25 CONNECTOR

TXC A (114)

DCD A (109)

DCD B

DSR A (107)

DSR B

D2D3

R1R2R3

TXC B

TTTTT

CTS A (106)

CTS B

RI (125)

*OPTIONAL

Summary of content (20 pages)

PAGE 1
LTC2847 Software-Selectable Multiprotocol Transceiver with Termination and 3.3V Digital Interface U FEATURES ■ ■ ■ ■ ■ ■ DESCRIPTIO The LTC®2847 is a 3-driver/3-receiver multiprotocol transceiver with on-chip cable termination. When combined with the LTC2845, this chip set forms a complete softwareselectable DTE or DCE interface port that supports the RS232, RS449, EIA530, EIA530-A, V.35, V.36 and X.21 protocols. All necessary cable termination is provided inside the LTC2847.
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LTC2847 W W W AXI U U ABSOLUTE RATI GS U U W PACKAGE/ORDER I FOR ATIO (Note 1) ORDER PART NUMBER VEE VEE C2 – C2 + VEE C1– C1+ TOP VIEW 38 37 36 35 34 33 32 NC 1 31 GND VDD 2 30 GND NC 3 29 D1 A VCC 4 28 D1 B D1 5 27 D2 A D2 6 26 D2 B D3 7 25 D3/R1 A R1 8 24 D3/R1 B R2 9 23 NC R3 10 22 NC M0 11 21 R2 A M1 12 LTC2847CUHF LTC2847IUHF UHF PART MARKING 2847 2847I 20 R2 B NC NC R3 A R3 B DCE/DTE M2 13 14 15 16 17 18 19 VIN VCC Voltage..............................
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LTC2847 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, unless otherwise noted (Notes 2, 3) SYMBOL PARAMETER CONDITIONS V– Negative Charge Pump Output Voltage V.28 Mode, No Load V.28 Mode, Full Load V.35 Mode RS530, RS530-A, X.21 Modes, Full Load fOSC Charge Pump Oscillator Frequency tr Charge Pump Rise Time ● ● ● MIN TYP – 7.5 – 5.5 – 4.5 – 9.6 – 8.5 – 6.5 – 6.
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LTC2847 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, unless otherwise noted (Notes 2, 3) SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS 0.2 V 40 mV V.
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LTC2847 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, unless otherwise noted (Notes 2, 3) SYMBOL PARAMETER V.
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LTC2847 U U U PI FU CTIO S NC (Pins 1,3,18,19,22,23): No Connect. R3 B (Pin 16): Receiver 3 Noninverting Input. VDD (Pin 2): Generated Positive Supply Voltage for V.28. Connect a 1µF capacitor to ground. R3 A (Pin 17): Receiver 3 Inverting Input. VCC (Pin 4): Input Supply Pin. Input supply to charge pump and transceiver. 4.75V ≤ VCC ≤ 5.25V. Connect a 1µF capacitor to GND. D1 (Pin 5): TTL Level Driver 1 Input. D2 (Pin 6): TTL Level Driver 2 Input. D3 (Pin 7): TTL Level Driver 3 Input.
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LTC2847 W BLOCK DIAGRA CHARGE PUMP C1– 37 C1– C2+ 35 C2+ C1+ 38 C1+ C2– 34 C2– VDD 2 VDD VEE VCC GND VCC 4 32 33 36 VEE 30 31 GND 29 D1 A 50Ω S1 D1 5 D1 S2 125Ω 50Ω 28 D1 B 27 D2 A 50Ω S1 D2 6 D2 S2 125Ω 50Ω 26 D2 B D3 7 D3 25 D3/R1 A 10k 20k 6k S3 DCE/DTE 15 10k 51.5Ω S2 S1 125Ω 51.5Ω 20k 24 D3/R1 B R1 8 R1 21 R2 A 20k 6k 10k R2 9 51.5Ω S3 R2 S2 125Ω 10k 51.
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LTC2847 TEST CIRCUITS D RL B D VOD A RL B A VOC CL 100pF RL 100Ω CL 100pF 2847 F02 2847 F01 Figure 1. V.11 Driver DC Test Circuit IB Figure 2. V.11 Driver AC Test Circuit B R B IA VCM = ±7V A + – CL A 2(VB – VA) RIN = IB – IA 2847 F03 2847 F04 Figure 3. Input Impedance Test Circuit VOB 125Ω R Figure 4. V.11, V.
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LTC2847 U W ODE SELECTIO Table 1 Not Used (Default V.11) 0 0 0 0 (Note 1) M2 M1 M0 DCE/ D1,2 D3 DTE (Note 1) Mode Name TTL X D1 A D2 B A D3 B V.11 V.11 V.11 V.11 A B Z Z R1 R2 R3 R1 R2,R3 (Note 2) (Note 2) (Note 2) (Note 3) (Note 3) VDD (Note 4) VEE (Note 5) V.11 V.11 V.11 V.11 V.11 V.11 CMOS CMOS 9.3V –6V A B A B A B RS530A 0 0 1 0 TTL X V.11 V.11 V.11 V.11 Z Z V.11 V.11 V.11 V.11 V.11 V.11 CMOS CMOS 9.3V –6V RS530 0 1 0 0 TTL X V.11 V.11 V.
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LTC2847 U W W SWITCHI G TI E WAVEFOR S 3V 1.5V 1.5V D 0V t PHL VO t PLH 3V 0V A –VO SR = 6V tf –3V 3V SR = 6V tr 0V –3V tf 2847 F15 tr Figure 15. V.28 Driver Propagation Delays VIH 1.5V 1.5V A VIL t PHL VOH R VOL t PLH 1.65V 1.65V 2847 F16 Figure 16. V.28 Receiver Propagation Delays U W U U APPLICATIO S I FOR ATIO Overview The LTC2847 consists of a charge pump and a 3-driver/ 3-receiver transceiver. The 5V VCC input powers the charge pump and transceiver.
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LTC2847 U W U U APPLICATIO S I FOR ATIO SERIAL CONTROLLER DTE DCE LTC2847 LTC2847 TXD D1 TXD 103Ω R3 SERIAL CONTROLLER TXD SCTE D2 SCTE 103Ω R2 SCTE R1 D3 TXC R1 103Ω TXC D3 TXC RXC R2 103Ω RXC D2 RXC RXD R3 103Ω RXD D1 RXD LTC2845 LTC2845 RTS D1 RTS R3 RTS DTR D2 DTR R2 DTR D3 R1 DCD R1 DCD D3 DCD DSR R2 DSR D2 DSR CTS R3 CTS D1 CTS LL TM RI RL LL D4 R4 TM R4 R5 D5 D4 RI D5 RL R5 LL TM RI RL 2847 F17 Figure 17.
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LTC2847 U W U U APPLICATIO S I FOR ATIO (DATA) CONNECTOR M0 LTC2847 M1 M2 NC DCE/DTE NC CABLE DCE/DTE M2 LTC2845 M1 M0 (DATA) 2847 F18 Figure 18. Single Port DCE V.35 Mode Selection in the Cable selected. Switching the terminations with FETs is difficult because the FETs must remain off when the signal voltage is beyond the supply voltage. Alternatively, custom cables may contain termination in the cable head or route signals to various terminations on the board.
PAGE 13
LTC2847 U W U U APPLICATIO S I FOR ATIO A' A A' LTC2845 R8 6k R5 20k R1 51.5Ω R6 10k S3 LTC2847 R8 6k R6 10k RECEIVER S1 R3 124Ω S2 R4 20k B B' C' R7 10k B' GND Figure 21. V.10 Receiver Configuration GENERATOR A RECEIVER A' B B' C C' R7 10k R4 20k GND 2847 F23 Figure 23. V.11 Receiver Configuration LOAD CABLE TERMINATION RECEIVER S3 R2 51.5Ω C' 2847 F21 BALANCED INTERCONNECTING CABLE R5 20k termination impedance to the cable as shown in Figure 231.
PAGE 14
LTC2847 U W U U APPLICATIO S I FOR ATIO In V.28 mode, S3 is closed inside the LTC2847/LTC2845 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 25. Proper termination is only provided when the B input of the receivers is floating, since S1 of the LTC2847’s R2 and R3 receivers remains on in V.28 mode1.
PAGE 15
LTC2847 U TYPICAL APPLICATIO S DTE vs DCE Operation The DCE/DTE pin acts as an enable for Driver 3/Receiver␣ 1 in the LTC2847, and Driver 3/Receiver 1 in the LTC2845. The LTC2847/LTC2845 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 LTC2847/LTC2845 using a dedicated DTE cable or dedicated DCE cable.
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LTC2847 U TYPICAL APPLICATIO S C3 1µF C2 1µF C1 1µF CHARGE PUMP VCC 5V + C5 1µF C4 3.3µF LTC2847 TXD D1 2 T 14 24 SCTE D2 T D3 11 R1 12 17 T R2 RXC 9 3 RXD T R3 16 M0 7 M1 M2 C8 1µF 1 VIN 3.
PAGE 17
LTC2847 U TYPICAL APPLICATIO S C3 1µF C2 1µF C1 1µF CHARGE PUMP VCC 5V + C5 1µF C4 3.3µF LTC2847 RXD D1 2 T 14 24 RXC D2 T D3 11 R1 12 24 T R2 SCTE 11 2 TXD T R3 14 M0 7 M1 M2 NC C7 1µF C8 1µF VIN 3.
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LTC2847 U TYPICAL APPLICATIO S C3 1µF C2 1µF C1 1µF CHARGE PUMP VCC 5V + C5 1µF C4 3.3µF LTC2847 DTE_TXD/DCE_RXD D1 2 T 14 24 DTE_SCTE/DCE_RXC D2 T D3 11 R1 12 17 DTE_RXC/DCE_SCTE T R2 9 3 DTE_RXD/DCE_TXD T R3 16 M0 7 M1 M2 VIN 3.
PAGE 19
LTC2847 U PACKAGE DESCRIPTIO UHF Package 38-Lead Plastic QFN (5mm × 7mm) (Reference LTC DWG # 05-08-1701) 0.70 ± 0.05 5.50 ± 0.05 (2 SIDES) 4.10 ± 0.05 (2 SIDES) 3.20 ± 0.05 (2 SIDES) PACKAGE OUTLINE 0.25 ± 0.05 0.50 BSC 5.20 ± 0.05 (2 SIDES) 6.10 ± 0.05 (2 SIDES) 7.50 ± 0.05 (2 SIDES) RECOMMENDED SOLDER PAD LAYOUT 5.00 ± 0.10 (2 SIDES) 3.15 ± 0.10 (2 SIDES) 0.75 ± 0.05 0.00 – 0.05 0.435 0.18 0.18 37 38 PIN 1 TOP MARK (SEE NOTE 6) 1 0.23 2 5.15 ± 0.10 (2 SIDES) 7.00 ± 0.10 (2 SIDES) 0.
PAGE 20
LTC2847 U TYPICAL APPLICATIO S The V.11 drivers are driven between VCC and GND while the V.10 drivers are driven between VCC and VEE. Assume that the V.11 driver outputs are high and V.10 driver outputs low. Current going into each 100Ω V.11 receiver termination = (110mA – 2.7mA) – 23mA/3 = 28.1mA. Current going into each 450Ω V.10 receiver termination = 23mA – 2mA/2 = 10.5mA. From Equation (2), V.11 PRT = 79mW and V.10 PRT = 49.6mW. From Equation (3), PDISS(2845) = 5V • (110mA – 23mA) + (8V • 0.3mA) + 5.