View LTC2844_286202.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

Final Electrical Specifications
LTC2844 3.3V Software-Selectable Multiprotocol Transceiver
April 2002
FEATURES
s s s
DESCRIPTIO
Software-Selectable Transceiver Supports: RS232, RS449, EIA530, EIA530-A, V.35, V.36, X.21 Operates from Single 3.3V Supply with LTC2846 Complete DTE or DCE Port with LTC2846
APPLICATIO S
s s s
Data Networking CSU and DSU Data Routers
The LTC(R)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.
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 CTS B CTS A (106)
10 8 DSR B DSR A (109)
22 6 DCD B DCD A (107)
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
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
T T T 12 TXC B 15 11 TXC A (114) SCTE B 24 14 SCTE A (113) TXD B 2 TXD A (103)
2844i
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 ............................................. 0C to 70C LTC2844IG ......................................... - 40C to 85C Storage Temperature Range ................. - 65C to 150C Lead Temperature (Soldering, 10 sec).................. 300C
ORDER PART NUMBER LTC2844CG LTC2844IG
R4 10 M0 11 M1 12 M2 13 DCE/DTE 14
TJMAX = 125C, JA = 90C/ W, JC = 35C/ 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 = 25C. 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 A mA mA mA mA mA A mA mA mA mA A A
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)
2
U
2844i
W
U
U
WW
W
LTC2844
The q denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. 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 = 50 (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 300 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 A A A V V mA A A V V V V V V mA A 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 = 50 (Figure 1) RL = 50 (Figure 1) RL = 50 (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 k ns
q q
80 90
ns ns
2844i
3
LTC2844
The q denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. 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 = 450 (Figure 3) RL = 450 (Figure 3) VO = GND -0.25V VO 0.25V, Power Off or No-Cable Mode or Driver Disabled RL = 450, CL = 100pF (Figures 3, 7) RL = 450, CL = 100pF (Figures 3, 7) RL = 450, 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 A s s s
100
V.10 Receiver 0.25 50 0.66 V mV mA k 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 A V/s s s V V V k 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
2844i
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 = 25C.
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 1F capacitor to ground. VDD (Pin 2): Positive Supply Voltage for V.28. Connect to VDD Pin 7 on LTC2846 or 8V supply. Connect a 1F 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 1F capacitor to ground. D4/R4 A (Pin 16): Receiver 4 Inverting Input and Driver 4 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 1F capacitor to ground.
U
U
U
2844i
5
LTC2844
BLOCK DIAGRA
6
W
VCC 1 VDD 2 28 VEE 27 GND 26 D1A D1 3 D1 25 D1B 24 D2A D2 4 D2 23 D2B 25 D3/R1 A D3 5 D3 10k 20k 6k S3 10k R1 6 R1 20 R2A 20k 10k R2 7 R2 10k 19 R2B 20k 18 R3A 20k 10k R3 8 R3 10k 17 R3B 20k D4 9 D4 20k 16 D4/R4 A S3 6k S3 6k 20k 21 D3/R1 B 10k R4 10 R4 S3 6k M0 11 M1 12 M2 13 DCE/DTE 14 15 VIN
2844 BD
MODE SELECTION LOGIC
2844i
LTC2844
TEST CIRCUITS
A RL VOD RL B VOC
CL 100pF CL 100pF
B A
RL 100
B A
R
CL
2844 F01
2844 F02
Figure 1. V.11 Driver Test Circuit
Figure 2. V.11 Driver/Receiver AC Test Circuit
D
A CL RL
D
A
A
R CL
2844 F04
2844 F03
Figure 3. V.10/V.28 Driver Test Circuit
Figure 4. V.10/V.28 Receiver Test Circuit
ODE SELECTIO
M2 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1
LTC2844 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
U
M1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 M0 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 DCE/DTE 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 D1 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 D2 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 D3 Z Z Z Z Z Z Z Z V.11 V.11 V.11 V.11 V.28 V.11 V.28 Z R1 V.11 V.11 V.11 V.11 V.28 V.11 V.28 Z Z Z Z Z Z Z Z Z R2 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 R3 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 D4 V.10 V.10 V.10 V.10 V.28 V.10 V.28 Z Z Z Z Z Z Z Z Z R4 Z Z Z Z Z Z Z Z V.10 V.10 V.10 V.10 V.28 V.10 V.28 Z
2844i
W
7
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
8
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
2844i
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 103
SCTE
D2
D3
TXC
R1
103
RXC
R2
103
RXD
R3
103
LTC2844 RTS D1 RTS
DTR
D2
D3
DCD
R1
DSR
R2
CTS
R3
LL
D4 R4
Figure 9. Complete Multiprotocol Interface in EIA530 Mode
2844i
U
W
U
U
DCE
LTC2846 R3 SERIAL CONTROLLER TXD
SCTE
103
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
9
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 1200A 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
10
U
W
U
U
CONNECTOR
NC NC CABLE
2844i
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' R4 20k R7 10k
C
C'
Figure 11. Typical V.10 Interface
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
C'
GND
2844 F13
Figure 13. V.10 Receiver Configuration
2844i
11
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 100. 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 103 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' 100 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,
12
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 51.5 S1 S2 R2 51.5 R8 6k S3 R5 20k R6 10k R3 124
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.
2844i
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 100 10, and the impedance between shorted terminals (A' and B') and ground C' must be 150 15. 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 50 to 150 and the impedance between shorted terminals (A and B) and ground C must be 150 15. For the generator termination, switches S1 and S2 are both on as shown in Figure 20. 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 1200A.
GENERATOR
BALANCED INTERCONNECTING CABLE
LOAD CABLE TERMINATION RECEIVER
A 50
A' 50
125
125
50 B C B' C'
50
Figure 18. Typical V.35 Interface
LTC2846 51.5 S1 124 S2 51.5 B C
2844 F20
V.35 DRIVER
U
W
U
U
A' R1 51.5 S1 S2 R2 51.5 R8 6k S3 R5 20k R6 10k R3 124
LTC2846
RECEIVER
B'
R4 20k
R7 10k
C'
2844 F18
GND
2844 F19
Figure 19. V.35 Receiver Configuration
A
Figure 20. V.35 Driver
2844i
13
LTC2844
APPLICATIONS INFORMATION
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 1F surface mounted tantalum or ceramic capacitors are required for C1, C2 and C3. The VEE capacitor C4 should be a minimum of 3.3F. All capacitors are 16V and should be placed as close as possible to the LTC2846 to reduce EMI.
7 C3 1F 6 C1 1F 5 8 C5 10F
2844 F21
VDD C1+ LTC2846 C1- VCC
C2 +
33 C2 1F
32 C2 - VEE GND 31 30
C4 3.3F
5V
Figure 21. Charge Pump
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.
VIN 3.3V C6 10F L1 5.6H 3 VIN 36 SW R1 13k C5 10F 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.
14
U
+
W
U
U
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 dedicated DCE port using a DB-25 female connector is shown in Figure 24. A port with one DB-25 connector, but can be configured for either DTE or DCE operation is shown in Figure 25. The configuration requires separate cables for proper signal routing in DTE or DCE operation. For example, in DTE 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 26, 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 27. 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. 2844i
LTC2844
TYPICAL APPLICATIO S
L1 5.6H VIN 3.3V C6 10F SHDN 3 4 7 C3 1F VCC 5V 5 C1 1F 6 8 LTC2846 TXD 9 D1 T CHARGE PUMP BOOST SWITCHING REGULATOR 36 35 33 32 31 30 C4 3.3F C2 1F D1 MBR0520 R1 13k R2 4.3k C5 10F 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 1F
C8 1F
1 VCC 2 VDD 3 D1
VEE GND
28 27 26 C9 1F 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 1F
Figure 23. Controller-Selectable Multiprotocol DTE Port with DB-25 Connector
2844i
+
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
15
LTC2844
TYPICAL APPLICATIO S
L1 5.6H VIN 3.3V C6 10F SHDN 3 4 7 C3 1F VCC 5V 5 C1 1F 6 8 LTC2846 RXD 9 D1 T CHARGE PUMP BOOST SWITCHING REGULATOR 36 35 33 32 31 30 C4 3.3F C2 1F D1 MBR0520 R1 13k R2 4.3k C5 10F VCC 5V
29 28 27
RXC
10
D2
T
26
11 D3 12 T 25 TXC R1 24 23 SCTE 13 R2 T 22 21 TXD 14 15 16 18 NC C7 1F C8 1F 19 M0 M1 M2 DCE/DTE 17 VIN 3.3V VEE GND D1 28 27 26 CTS 3 25 24 D2 23 C9 1F 5 13 6 22 7 1 R3 T 20 15 12 24 11 2 14 TXC B SCTE A (113) SCTE B TXD A (103) TXD B SGND (102) SHIELD (101) DB-25 FEMALE CONNECTOR
1 VCC 2 VDD
DSR
4
5
D3 LTC2844 22 21 20 R2 19 18 R3 17 16 8 10 20 23 4 19 18
DCD
6 7
R1
DTR
RTS
8 10 9
LL
R4 D4 M0 M1 M2 DCE/DTE VIN
M0 M1 M2 NC
11 12 13 14
15 C10 1F
Figure 24. Controller-Selectable DCE Port with DB-25 Connector
2844i
16
+
U
3 16 17 9
RXD A (104) RXD B RXC A (115) RXC B
CTS A (106) CTS B DSR A (107) DSR B
DCD A (109) DCD B DTR A (108) DTR B RTS A (105) RTS B LL A (141)
VIN 3.3V
2844 F24
LTC2844
TYPICAL APPLICATIO S
L1 5.6H VIN 3.3V C6 10F SHDN 3 4 7 C3 1F VCC 5V 5 C1 1F 6 8 LTC2846 DTE_TXD/DCE_RXD 9 D1 T CHARGE PUMP BOOST SWITCHING REGULATOR 36 35 33 32 31 30 C2 1F C4 3.3F DTE TXD A TXD B SCTE A SCTE B DCE RXD A RXD B RXC A RXC B D1 MBR0520 VCC 5V C5 10F 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 1F C8 1F 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 1F 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 1F
Figure 25. Controller-Selectable Multiprotocol DTE/DCE Port with DB-25 Connector
2844i
+
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
L1 5.6H VIN 3.3V C6 10F SHDN 3 4 7 C3 1F VCC 5V 5 C1 1F 6 8 LTC2846 DTE_TXD/DCE_RXD 9 D1 T CHARGE PUMP BOOST SWITCHING REGULATOR 36 35 33 32 31 30 C2 1F C4 3.3F D1 MBR0520 R1 13k R2 4.3k C5 10F 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 1F C8 1F 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 1F 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 26. Controller-Selectable Multiprotocol DTE/DCE Port with RL, LL, TM and DB-25 Connector
2844i
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 1F
*OPTIONAL
2844 F26
LTC2844
TYPICAL APPLICATIO S
L1 5.6H VIN 3.3V C6 10F SHDN 3 4 7 C3 1F VCC 5V 5 C1 1F 6 8 LTC2846 DTE_TXD/DCE_RXD 9 D1 T CHARGE PUMP BOOST SWITCHING REGULATOR 36 35 33 32 31 30 C4 3.3F DTE TXD A TXD B SCTE A SCTE B DCE RXD A RXD B RXC A RXC B C2 1F D1 MBR0520 R1 13k R2 4.3k C5 10F 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 1F C8 1F 1 VCC 2 VDD 3 D1 28 27 26 DTE_RTS/DCE_CTS 25 24 D2 23 C9 1F 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 1F
DCE/DTE
Figure 27. Cable-Selectable Multiprotocol DTE/DCE Port with DB-25 Connector
2844i
+
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)
10.07 - 10.33* (.397 - .407) 28 27 26 25 24 23 22 21 20 19 18 17 16 15 7.65 - 7.90 (.301 - .311) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 5.20 - 5.38** (.205 - .212) 1.73 - 1.99 (.068 - .078) 0 - 8 .65 (.0256) BSC .25 - .38 (.010 - .015) .05 - .21 (.002 - .008)
G28 SSOP 0501
.13 - .22 (.005 - .009)
.55 - .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 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
2844i LT/TP 0402 1.5K * 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
(c) LINEAR TECHNOLOGY CORPORATION 2002

▲Up To Search▲

Price & Availability of LTC2844

	To Download LTC2844 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .