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Final Electrical Specifications
LTC2846 3.3V Software-Selectable Multiprotocol Transceiver with Termination
January 2002
FEATURES
s s s
DESCRIPTIO
s s s
Software-Selectable Transceiver Supports: RS232, RS449, EIA530, EIA530-A, V.35, V.36, X.21 Operates from Single 3.3V Supply 1.2MHz Boost Switching Regulator for 3.3V to 5V Conversion On-Chip Cable Termination Complete DTE or DCE Port with LTC2844 Small Footprint
APPLICATIO S
s s s
Data Networking CSU and DSU Data Routers
The LTC(R)2846 is a 3-driver/3-receiver multiprotocol transceiver with on-chip cable termination. When combined with the LTC2844, 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 LTC2846. The LTC2846 has a boost regulator that takes in a 3.3V input and switches at 1.2MHz, allowing the use of tiny, low cost capacitors and inductors 2mm or less in height. The 5V output drives an internal charge pump that requires only five space-saving surface mounted capacitors. The LTC2846 is available in a 36-lead SSOP surface mount package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
Complete DTE or DCE Multiprotocol Serial Interface with DB-25 Connector
LL CTS DSR DCD DTR RTS TXC SCTE TXD
RXD
RXC
LTC2844 D4 R4 R3 R2 R1 D3 D2 D1 R3 R2
LTC2846 D3 R1 D2 D1
T
T
18
13 5
10 8
22 6
23 20 19 4
1
7
16
3
9
17
DB-25 CONNECTOR
2846 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 15 11 24 14 2
U
U
DSR B
DSR A (109)
LL A (141)
CTS B
CTS A (106)
DTR B
DTR A (108)
RTS B
RTS A (105)
SHIELD (101)
SG (102)
DCD B
DCD A (107)
TXC B
TXC A (114)
SCTE B
SCTE A (113)
TXD B
TXD A (103)
RXD B
RXD A (104)
RXC B
RXC A (115)
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LTC2846
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW NC PGND VIN SHDN C1- C1
+
VCC Voltage.............................................. - 0.3V to 6.5V VIN Voltage .............................................. - 0.3V to 6.5V 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) VEE ........................................................ - 10V to 0.3V VDD ....................................................... - 0.3V to 10V Short-Circuit Duration Transmitter Output ..................................... Indefinite Receiver Output .......................................... Indefinite VEE .................................................................. 30 sec SW Voltage ............................................... - 0.4V to 36V FB Voltage ............................................... - 0.3V to 2.5V Current into FB Pin .............................................. 1mA SHDN Voltage ........................................... - 0.3V to 10V Operating Temperature Range LTC2846C ............................................... 0C to 70C LTC2846I ........................................... - 40C to 85C Storage Temperature Range ................ - 65C to 150C Lead Temperature (Soldering, 10 sec)................. 300C
ORDER PART NUMBER
36 SW 35 FB 34 SGND 33 C2 + 32 C2 - 31 VEE
1 2 3 4 5 6 7 8 9 D1 T T T CHARGE PUMP BOOST SWITCHING REGULATOR
LTC2846CG LTC2846IG
VDD VCC D1
30 GND 29 D1 A 28 D1 B 27 D2 A 26 D2 B 25 D3/R1 A 24 D3/R1 B
D2 10 D3 11 R1 12 R2 13 R3 14 M0 15 M1 16 VIN 17 M2 18 R2 R1 D2 D3
23 R2 A T 22 R2 B 21 R3 A T 20 R3 B 19 DCE/DTE
R3
G PACKAGE 36-LEAD PLASTIC SSOP
TJMAX = 125C, JA = 90C/W, JC = 35C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
SYMBOL Supplies ICC VIN Supply Current (DCE Mode, All Digital Pins = GND or VIN) PARAMETER
The q denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VCC = 5V, VIN = 3.3V, VSHDN = VIN, unless otherwise noted (Notes 2, 3)
CONDITIONS RS530, RS530-A, X.21 Modes, No Load RS530, RS530-A, X.21 Modes, Full Load V.35 Mode V.28 Mode, No Load V.28 Mode, Full Load No-Cable Mode RS530, RS530-A, X.21 Modes, Full Load V.35 Mode, Full Load V.28 Mode, Full Load V.11 or V.28 Mode, No Load V.35 Mode V.28 Mode, with Load V.28 Mode, with Load, IDD = 10mA
q q q
MIN
TYP 14 100 126 20 35 300 410 625 150
MAX
UNITS mA mA mA mA mA A mW mW mW V V V V
2846i
q q q q
130 170 75 900
PD
Internal Power Dissipation (DCE Mode)
V+
Positive Charge Pump Output Voltage
8 7 8
9.3 8.0 8.7 6.5
2
U
W
U
U
WW
W
LTC2846
ELECTRICAL CHARACTERISTICS
SYMBOL V- PARAMETER Negative Charge Pump Output Voltage
The q denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VCC = 5V, VIN = 3.3V, VSHDN = VIN, unless otherwise noted (Notes 2, 3)
CONDITIONS V.28 Mode, No Load V.28 Mode, Full Load V.35 Mode RS530, RS530-A, X.21 Modes, Full Load No-Cable Mode/Power-Off to Normal Operation D1, D2, D3, M0, M1, M2, DCE/DTE SHDN D1, D2, D3, M0, M1, M2, DCE/DTE SHDN D1, D2, D3 M0, M1, M2, DCE/DTE = GND M0, M1, M2, DCE/DTE = VIN SHDN = GND SHDN = 3V IO = - 3mA IO = 1.6mA 0V VO VIN M0 = M1 = M2 = VIN, VO = GND M0 = M1 = M2 = VIN, VO = VIN RL = 1.95k (Figure 1) RL = 50 (Figure 1) RL = 50 (Figure 1) RL = 50 (Figure 1) RL = 50 (Figure 1) RL = 50 (Figure 1) VOUT = GND
VA and VB 0.25V, Power Off or q q q q q q q q q q q q q
MIN - 7.5 - 5.5 - 4.5
TYP - 9.6 - 8.5 - 6.5 - 6.0 500 2
MAX
UNITS V V V V kHz ms V V
fOSC tr VIH VIL IIN
Charge Pump Oscillator Frequency Charge Pump Rise Time Logic Input High Voltage Logic Input Low Voltage Logic Input Current
Logic Inputs and Outputs 2.0 2.4 0.8 0.5 - 30 - 75 10 - 120 10 0.1 32 0.4 50 -30 -85 -160 10 5 0.5VODO 2 0.67VODO 0.2 3 0.2 150 1 2 15 15 0 15 40 40 3 3 100 25 65 65 12
V V A A A A A V V mA A A V V V V V V mA A ns ns ns ns ns
16
q q q q q
VOH VOL IOSR IOZR V.11 Driver VODO VODL VOD VOC VOC ISS IOZ t r, t f t PLH t PHL t t SKEW
Output High Voltage Output Low Voltage Output Short-Circuit Current Three-State Output Current
2.7
3 0.2
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 Rising Input to Output Falling Input to Output Difference, tPLH - tPHL Output to Output Skew
q q q q q
No-Cable Mode or Driver Disabled (Figures 2, 13) (Figures 2, 13) (Figures 2, 13) (Figures 2, 13) (Figures 2, 13)
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LTC2846
ELECTRICAL CHARACTERISTICS
SYMBOL VTH VTH RIN t r, t f t PLH t PHL t V.35 Driver VOD VOA, VOB VOC IOH IOL IOZ ROD ROC t r , tf t PLH t PHL t t SKEW VTH VTH RID RIC t r, t f tPLH tPHL t V.28 Driver VO ISS ROZ SR t PLH t PHL Output Voltage Short-Circuit Current Power-Off Resistance Slew Rate Input to Output Input to Output Differential Output Voltage Single-Ended Output Voltage Transmitter Output Offset Transmitter Output High Current Transmitter Output Low Current Transmitter Output Leakage Current Transmitter Differential Mode Impedance Transmitter Common Mode Impedance Rise or Fall Time Input to Output Input to Output Input to Output Difference, tPLH - tPHL Output to Output Skew Differential Receiver Input Threshold Voltage Receiver Input Hysteresis Receiver Differential Mode Impedance Receiver Common Mode Impedance Rise or Fall Time Input to Output Input to Output Input to Output Difference, tPLH - tPHL PARAMETER Input Threshold Voltage Input Hysteresis Input Impedance Rise or Fall Time Input to Output Rising Input to Output Falling Input to Output Difference, tPLH - tPHL V.11 Receiver
The q denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VCC = 5V, VIN = 3.3V, VSHDN = VIN, unless otherwise noted (Notes 2, 3)
CONDITIONS - 7V VCM 7V - 7V VCM 7V -7V VCM 7V (Figure 3) CL = 50pF (Figures 4, 14) CL = 50pF (Figures 4, 14) CL = 50pF (Figures 4, 14) CL = 50pF (Figures 4, 14) Open Circuit, RL = 1.95k (Figure 5) With Load, - 4V VCM 4V (Figure 6) Open Circuit, RL = 1.95k (Figure 5) RL = 50 (Figure 5) VA, VB = 0V VA, VB = 0V
VA and VB 0.25V q q q q q q
MIN - 0.2
TYP
MAX 0.2
UNITS V mV ns
15 100 103 15 50 50 0 4
40
90 90 25 1.2 0.66 1.2 0.6
ns ns ns V V V V mA mA A ns ns ns ns ns
q
0.44
q q q q q q
0.55
-9 9 50 135
- 11 11 1 100 150 5 35 35 0 4
- 13 13 100 150 165 65 65 16
- 2V VCM 2V (Figure 7) (Figures 8, 13) (Figures 8, 13) (Figures 8, 13) (Figures 8, 13) (Figures 8, 13) - 2V VCM 2V (Figure 9) - 2V VCM 2V (Figure 9) - 2V VCM 2V - 2V VCM 2V (Figure 10) CL = 50pF (Figures 4, 14) CL = 50pF (Figures 4, 14) CL = 50pF (Figures 4, 14) CL = 50pF (Figures 4, 14) Open Circuit RL = 3k (Figure 11) VOUT = GND - 2V < VO < 2V, Power Off or No-Cable Mode RL = 7k, CL = 0 (Figures 11, 15) RL = 3k, CL = 2500pF (Figures 11, 15) RL = 3k, CL = 2500pF (Figures 11, 15)
q q q q q q q q q
15 15
V.35 Receiver - 0.2 15 90 135 103 150 15 50 50 0 4 90 90 25 10 150 300 4 1.5 1.5 30 2.5 2.5 0.2 40 110 165 V mV ns ns ns ns V V mA V/s s s
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q q q q q q q
5
8.5
4
LTC2846
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER V.28 Receiver VTHL Input Low Threshold Voltage VTLH Input High Threshold Voltage VTH Receiver Input Hysteresis RIN Receiver Input Impedance t r , tf Rise or Fall Time tPLH Input to Output tPHL Input to Output Boost Switching Regulator (Notes 4) VIN Operating Voltage VFB Feedback Voltage IFB FB Pin Bias Current IQ Quiescent Current Quiescent Current in Shutdown VFB(LR) Reference Line Regulation f Switching Frequency DCMAX Maximum Duty Cycle ILIM Switch Current Limit VSAT Switch VCESAT ILEAK Switch Leakage Current
The q denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VCC = 5V, VIN = 3.3V, VSHDN = VIN, unless otherwise noted (Notes 2, 3)
CONDITIONS (Figure 12) (Figure 12) (Figure 12) - 15V VA 15V CL = 50pF (Figures 12, 16) CL = 50pF (Figures 12, 16) CL = 50pF (Figures 12, 16)
q q q q q q
MIN 0.8 0 3
TYP 1.2 1.2 0.05 5 15 60 160 3.3 1.255 120 4.2 0.01 0.01 1.2 90 1.2 350 0.01
MAX
UNITS V V V k ns ns ns V V nA mA A %/V MHz % A mV A
2 0.3 7 300 300 3.6 1.280 360 6 1 0.05 1.6 2 1
q
3 1.230
VFB = 1.255V VSHDN = 2.4V, Not Switching VSHDN = 0V, VIN = 3V 3V VIN 3.6V
q
q q
(Note 5) ISW = 900mA VSW = 5V
0.85 82 1
Note 1: Absolute Maximum Ratings are those values beyond which the life of the 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, CVCC = CVIN = 10F, CVDD = 1F, CVEE = 3.3F and TA = 25C. Note 4: The Boost Regulator is specified for VIN = 3V unless otherwise noted. Note 5: Current limit guaranteed by design and/or correlation to static test.
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LTC2846 TYPICAL PERFOR A CE CHARACTERISTICS
V.11 Mode ICC vs Data Rate
170 160 150 140
ICC (mA) ICC (mA) 140 ICC (mA) 135 130 125 120
TA = 25C
130 120 110 100 90 10 100 1000 10000
2846 G04
DATA RATE (kBd)
V.11 Mode ICC vs Temperature
110 105 100
ICC (mA)
ICC (mA)
95 90 85 80 -40 -20
125.5 125.0 124.5 124.0 123.5
ICC (mA)
40 20 60 0 TEMPERATURE (C)
Boost Switching Regulator SHDN Pin Current vs Voltage
40 35
SHDN PIN CURRENT (A)
30
CURRENT LIMIT (A)
25 TA = 25C 20 15 10 5 0 0 1 4 3 SHDN PIN VOLTAGE (V) 2 5 6
2846 G10
FREQUENCY (MHz)
TA = 100C
6
UW
80
2846 G07
V.35 Mode ICC vs Data Rate
150 145
V.28 Mode ICC vs Data Rate
60 TA = 25C
TA = 25C
55 50 45 40 35 30
10 100 1000 DATA RATE (kBd) 10000
2846 G05
10
20 40 DATA RATE (kBd)
60
80 100
2846 G06
V.35 Mode ICC vs Temperature
128.0 127.5 127.0 126.5 126.0
36.5 36.0 35.5 35.0 34.5 34.0 37.5 37.0
V.28 Mode ICC vs Temperature
100
123.0 -40 -20
40 20 0 60 TEMPERATURE (C)
80
100
33.5 -40 - 20
0
60 40 20 TEMPERATURE (C)
80
100
3846 G09
2846 G08
Boost Switching Regulator Current Limit vs Duty Cycle
1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 10 20 30 50 40 60 DUTY CYCLE (%) 70 80
1.30
Boost Switching Regulator Oscillator Frequency vs Temperature
TA = 25C
1.25
1.20
1.15
1.10
1.05 -40
-20
40 20 0 60 TEMPERATURE (C)
80
100
2846 G11
2846 G12
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LTC2846
PI FU CTIO S
NC (Pin 1): No Connect. PGND (Pin 2): Boost Switching Regulator Power Ground. Tie PGND to SGND. VIN (Pin 3): Input Supply Pin. Input supply to boost switching regulator. 3V VIN 3.6V. Bypass with a 10F capacitor to ground. SHDN (Pin 4): Boost Switching Regulator Shutdown Pin. Tie to 2.4V or more to enable regulator. Ground to shut down. C1 - (Pin 5): Capacitor C1 Negative Terminal. Connect a 1F capacitor between C1+ and C1-. C1 + (Pin 6): Capacitor C1 Positive Terminal. Connect a 1F capacitor between C1 + and C1 -. VDD (Pin 7): Generated Positive Supply Voltage for V.28. Connect a 1F capacitor to ground. VCC (Pin 8): Input Supply Pin. Input supply to transceiver. 4.75V VCC 5.25V. Connect to output of switching regulator. D1 (Pin 9): TTL Level Driver 1 Input. D2 (Pin 10): TTL Level Driver 2 Input. D3 (Pin 11): TTL Level Driver 3 Input. R1 (Pin 12): CMOS Level Receiver 1 Output with Pull-Up to VIN when Three-Stated. R2 (Pin 13): CMOS Level Receiver 2 Output with Pull-Up to VIN when Three-Stated. R3 (Pin 14): CMOS Level Receiver 3 Output with Pull-Up to VIN when Three-Stated. M0 (Pin 15): TTL Level Mode Select Input 0 with Pull-Up to VIN. See Table 1. M1 (Pin 16): TTL Level Mode Select Input 1 with Pull-Up to VIN. See Table 1. VIN (Pin 17): Input Supply Pin. Input supply to transceiver. 3V VIN 3.6V. Connect to Pin 3. M2 (Pin 18): TTL Level Mode Select Input 2 with Pull-Up to VIN. See Table 1. DCE/DTE (Pin 19): TTL Level Mode Select Input with Pull-Up to VIN. See Table 1. R3 B (Pin 20): Receiver 3 Noninverting Input. R3 A (Pin 21): Receiver 3 Inverting Input. R2 B (Pin 22): Receiver 2 Noninverting Input. R2 A (Pin 23): Receiver 2 Inverting Input. D3/R1 B (Pin 24): Receiver 1 Noninverting Input and Driver 3 Noninverting Output. D3/R1 A (Pin 25): Receiver 1 Inverting Input and Driver 3 Inverting Output. D2 B (Pin 26): Driver 2 Noninverting Output. D2 A (Pin 27): Driver 2 Inverting Output. D1 B (Pin 28): Driver 1 Noninverting Output. D1 A (Pin 29): Driver 1 Inverting Output. GND (Pin 30): Transceiver Ground. VEE (Pin 31): Generated Negative Supply Voltage. Connect a 3.3F capacitor to GND. C2 - (Pin 32): Capacitor C2 Negative Terminal. Connect a 1F capacitor between C2 + and C2 -. C2 + (Pin 33): Capacitor C2 Positive Terminal. Connect a 1F capacitor between C2 + and C2 - . SGND (Pin 34): Boost Switching Regulator Signal Ground. Tie PGND to SGND. FB (Pin 35): Boost Switching Regulator Feedback Pin. Reference voltage is 1.255V. Connect resistive divider tap here. Minimize trace area at FB. SW (Pin 36): Boost Switching Regulator Switch Pin. Connect inductor/diode here. Minimize trace area at this pin to reduce EMI.
U
U
U
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LTC2846
BLOCK DIAGRA
PGND VIN SHDN
DCE/DTE 19 10k R1 12 R1 20k
8
W
BOOST SWITCHING REGULATOR 2 3 4 GND VIN SW FB 36 SW 35 FB 34 SGND SHDN GND CHARGE PUMP C1- C1+ VDD VCC 5 6 7 8 C1- C1+ VDD VCC 50 S1 D1 9 D1 50 28 D1B 27 D2A 50 S1 D2 10 D2 50 26 D2B D3 11 D3 10k 20k 6k S3 S2 51.5 S1 125 51.5 24 D3/R1 B 23 R2A 20k 10k R2 13 R2 10k 20k 21 R3A 20k 10k R3 14 VIN 17 R3 10k 20k MODE SELECTION LOGIC S3 S2 125 51.5 20 R3B M0 15 M1 16 M2 18
2846 BD
C2+ C2- VEE GND
33 C2+ 32 C2- 31 VEE 30 GND 29 D1A
S2
125
S2
125
25 D3/R1 A
6k 51.5 S3 S2 125 51.5 22 R2B
6k 51.5
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LTC2846
TEST CIRCUITS
D B A VOD RL
2846 F01
RL
D
VOC
B A
RL 100
CL 100pF CL 100pF
2846 F02
Figure 1. V.11 Driver DC Test Circuit
IB B R IA VCM = 7V
Figure 2. V.11 Driver AC Test Circuit
B A
R CL
2846 F04
+ -
A 2(VB - VA) RIN = IB - IA 2846 F03
Figure 3. Input Impedance Test Circuit
VOB VOB
Figure 4. V.11, V.35 Receiver AC Test Circuit
125
50 VOD 50
RL
125 VOC
50
50
125 VCM
125
50
RL
50
50
50
+ -
2846 F07
VCM = 2V
2846 F05
2846 F06
VOA
VOA
Figure 5. V.35 Driver Open-Circuit Test
Figure 6. V.35 Driver Test Circuit
Figure 7. V.35 Driver Common Mode Impedance Test Circuit
51.5 125 50 50 125 125
50
50
VTH VCM
+ - + -
2846 F09
VCM = 2V
+ -
51.5
2846 F08
2846 F10
Figure 8. V.35 Driver AC Test Circuit
Figure 9. V.35 Receiver DC Test Circuit
Figure 10. Receiver Common Mode Impedance Test Circuit
R CL
2846 F12
D
A CL
2846 F11
A RL VA
Figure 11. V.28 Driver Test Circuit
Figure 12. V.28 Receiver Test Circuit
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LTC2846
ODE SELECTIO
Table 1
LTC2846 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 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.35 V.11 V.28 Z V.11 V.11 V.11 V.11 V.35 V.11 V.28 Z D2 V.11 V.11 V.11 V.11 V.35 V.11 V.28 Z V.11 V.11 V.11 V.11 V.35 V.11 V.28 Z D3 Z Z Z Z Z Z Z Z V.11 V.11 V.11 V.11 V.35 V.11 V.28 Z R1 V.11 V.11 V.11 V.11 V.35 V.11 V.28 Z Z Z Z Z Z Z Z Z R2 V.11 V.11 V.11 V.11 V.35 V.11 V.28 Z V.11 V.11 V.11 V.11 V.35 V.11 V.28 Z R3 V.11 V.11 V.11 V.11 V.35 V.11 V.28 Z V.11 V.11 V.11 V.11 V.35 V.11 V.28 Z
SWITCHI G TI E WAVEFOR S
3V D 0V VO B-A -VO A VO B t SKEW t SKEW
2846 F13
1.5V t PLH 50% tr 90% 10%
1/2 VO
Figure 13. V.11, V.35 Driver Propagation Delays
VOD2 B-A -VOD2 VOH R VOL
0V t PLH 1.65V
Figure 14. V.11, V.35 Receiver Propagation Delays
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W
U
f = 1MHz : t r 10ns : t f 10ns 1.5V t PHL 90% tf 50% 10%
f = 1MHz : t r 10ns : t f 10ns INPUT 0V t PHL OUTPUT 1.65V
2846 F14
W
U
W
LTC2846
SWITCHI G TI E WAVEFOR S
3V D 0V VO A -VO tf 1.5V t PHL 3V 0V SR = 6V tf -3V 1.5V t PLH 0V -3V tr 3V SR = 6V tr
2846 F15
Figure 15. V.28 Driver Propagation Delays
VIH A VIL VOH R VOL 1.5V t PHL 1.65V 1.5V t PLH 1.65V
2846 F16
Figure 16. V.28 Receiver Propagation Delays
APPLICATIO S I FOR ATIO
Overview
The LTC2846 consists of a boost switching regulator, a charge pump and a 3-driver/3-receiver transceiver. The boost switching regulator generates a 5V VCC from the 3.3V input at VIN to power the charge pump and transceiver. The charge pump generates the VDD and VEE supplies. The LTC2846's VCC, VDD and VEE supplies can be used to power a companion chip like the LTC2844 or LTC2845. The receiver outputs are driven between 0V and VIN to interface with 3.3V logic. The LTC2846 and LTC2844 form a complete softwareselectable DTE or DCE interface port that supports the RS232, RS449, EIA530, EIA530-A, V.35, V.36 and X.21 protocols. Cable termination is provided on-chip, eliminating the need for discrete termination designs. A complete DCE-to-DTE interface operating in EIA530 mode is shown in Figure 17. The LTC2846 half of each port is used to generate and appropriately terminate the clock and data signals. The LTC2844 is used to generate the control signals along with LL (Local Loopback).
W
U
W
UU
W
U
Mode Selection The interface protocol is selected using the mode select pins M0, M1 and M2 (see Table 1). 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 18. The internal pull-up current sources will ensure a binary 1 when a pin is left unconnected. The mode selection may also be accomplished by using jumpers to connect the mode pins to ground or VIN.
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LTC2846
APPLICATIO S I FOR ATIO
DTE
SERIAL CONTROLLER TXD D1 LTC2846
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 17. Complete Multiprotocol Interface in EIA530 Mode
When the cable is removed, leaving all mode pins unconnected, the LTC2846/LTC2844 will enter no-cable mode. In this mode the LTC2846/LTC2844 supply current drops to less than 900A and the LTC2846/LTC2844 driver outputs are forced into a high impedance state. At the same time, the R2 and R3 receivers of the LTC2846 are differentially terminated with 103 and the other receivers on
12
U
DCE
LTC2846 TXD 103 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 R4 D4
2846 F17
W
UU
D1
CTS
LL
the LTC2846 and LTC2844 are terminated with 30k to ground. Cable Termination Traditional implementations used expensive relays to switch resistors or required the user to change termination modules every time a new interface standard was
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LTC2846
APPLICATIO S I FOR ATIO
(DATA) M0 LTC2846 M1 M2 DCE/DTE 15 16 18 19
DCE/DTE M2 LTC2844 M1 M0 (DATA)
14 13 12 11
2846 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. The LTC2846/LTC2844 chip set solves the cable termination switching problem by automatically providing the appropriate termination and switching on-chip for the V.10 (RS423), V.11 (RS422), V.28 (RS232) and V.35 electrical protocols. V.10 (RS423) Interface All V.10 drivers and receivers necessary for the RS449, EIA530, EIA530-A, V.36 and X.21 protocols are implemented on the LTC2844. A typical V.10 unbalanced interface is shown in Figure 19. A V.10 single-ended generator with output A and ground C is connected to a differential receiver with input A' connected to A, and ground C' connected via the signal return to 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 20. The V.10 receiver configuration in the LTC2844 is shown in Figure 21. In V.10 mode, switch S3 inside the LTC2844 is turned off. The noninverting input is disconnected
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CONNECTOR NC NC CABLE
GENERATOR BALANCED INTERCONNECTING CABLE LOAD CABLE TERMINATION A A' RECEIVER C C'
2846 F19
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Figure 19. Typical V.10 Interface
IZ
3.25mA
-10V
-3V VZ 3V 10V
-3.25mA
2846 F20
Figure 20. V.10 Receiver Input Impedance
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LTC2846
APPLICATIO S I FOR ATIO
A' A R8 6k S3 R5 20k R6 10k RECEIVER LTC2844
B' C'
B GND
R4 20k
R7 10k
2846 F21
Figure 21. V.10 Receiver Configuration
BALANCED INTERCONNECTING CABLE
GENERATOR
LOAD CABLE TERMINATION RECEIVER
A
A' 100 MIN
B C
B' C'
Figure 22. Typical V.11 Interface
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. V.11 (RS422) Interface
A typical V.11 balanced interface is shown in Figure 22. A V.11 differential generator with outputs A and B and ground C is connected to a differential receiver with input A' connected to A, input B' connected to B, and ground C' connected via the signal return to ground C. 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 essential to prevent reflections from corrupting the data. The receiver inputs must also be compliant with the impedance curve shown in Figure 20. In V.11 mode, all switches are off except S1 of the LTC2846's receivers which connects a 103 differential
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.
1Actually,
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A' R1 51.5 S1 S2 R2 51.5 R8 6k S3 R5 20k R6 10k R3 124 RECEIVER LTC2846 B' C' R4 20k R7 10k GND
2846 F23
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Figure 23. V.11 Receiver Configuration
termination impedance to the cable as shown in Figure 231. The LTC2844 only handles control signals, so no termination other than its V.11 receivers' 30k input impedance is necessary. V.28 (RS232) Interface A typical V.28 unbalanced interface is shown in Figure 24. A V.28 single-ended generator with output A and ground C is connected to a single-ended receiver with input A' connected to A and ground C' connected via the signal return to ground C.
GENERATOR BALANCED INTERCONNECTING CABLE LOAD CABLE TERMINATION A A' RECEIVER
2846 F22
C
C'
2846 F24
Figure 24. Typical V.28 Interface
A' R1 51.5 S1 S2 R2 51.5 R8 6k S3 R5 20k R6 10k RECEIVER LTC2846
R3 124
B'
R4 20k
R7 10k
C'
GND
2846 F25
Figure 25. V.28 Receiver Configuration
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LTC2846
APPLICATIO S I FOR ATIO
In V.28 mode, S3 is closed 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 25. Proper termination is only provided when the B input of the receivers is floating, since S1 of the LTC2846's R2 and R3 receivers remains on in V.28 mode1. The noninverting input is disconnected inside the LTC2846/LTC2844 receiver and connected to a TTL level reference voltage to give a 1.4V receiver trip point. V.35 Interface A typical V.35 balanced interface is shown in Figure 26. A V.35 differential generator with outputs A and B and ground C is connected to a differential receiver with input A' connected to A, input B' connected to B, and ground C' connected via the signal return to ground C. 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
GENERATOR BALANCED INTERCONNECTING CABLE LOAD CABLE TERMINATION A 50 A' 50 RECEIVER
125
125
50 B C B' C'
50
Figure 26. Typical V.35 Interface
A' R1 51.5 S1 S2 R2 51.5 R8 6k S3 R5 20k R6 10k R3 124 RECEIVER LTC2846
B'
5V
2846 F27
8 C5 10F
VCC
GND
30
C'
GND
Figure 27. V.35 Receiver Configuration
Figure 28. Charge Pump
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R4 20k
R7 10k
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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 a T network impedance as shown in Figure 27. 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. 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 charge pump, bias circuitry, drivers and receivers are turned off, the driver outputs are forced into a high impedance state, and the VCC supply current to the transceiver drops to less than 900A while its VIN supply current drops to less than 10A. Note that the LTC2846's R2 and R3 receivers continue to be terminated by a 103 differential impedance. Charge Pump The LTC2846 uses an internal capacitive charge pump to generate VDD and VEE as shown in Figure 28. A voltage doubler generates about 8V on VDD and a voltage inverter generates about - 7.5V on 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.
2846 F26
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7 C3 1F 6 C1 1F 5
VDD C1+ LTC2846 C1-
C2 + C2 - VEE
33 32 31 C4 3.3F C2 1F
2846 F28
15
LTC2846
APPLICATIO S I FOR ATIO
Switching Regulator
The circuit as shown in Figure 29 can provide up to 480mA at 5V to drive the LTC2846's transceiver as well as its companion chip in the DTE-DCE interface. In its shut down mode with the SHDN pin at 0V, the boost switching regulator draws less than 10A. Ferrite core inductors should be used to obtain the best efficiency, as core losses at 1.2MHz are much lower for ferrite cores than for cheaper powdered-iron types. Choose an inductor that can handle at least 1A without saturating, and ensure that the inductor has a low DCR (copper wire resistance) to minimize I2R power losses. Use low ESR capacitors for the output to minimize output ripple voltage. Multilayer ceramic capacitors are an excellent choice, as they have extremely low ESR and are available in very small packages. Ceramic capacitors also make a good choice for the input decoupling capacitor, and should be placed as close as possible to the switching regulator. Solid tantalum or OS-CON capacitors can be used but they will occupy more board area than a ceramic and will have a higher ESR. A Schottky diode is recommended for use with the switching regulator. The ON Semiconductor MBR0520 is a very good choice. To set the output voltage, select the values of R1 and R2 according to the following equation. R1 = R2[(5V/1.255V) - 1] A good value for R2 is 4.3k which sets the current in the resistor divider chain to 1.255V/4.3k = 292A.
L1 5.6H 3 C6 10F VIN 36 R1 13k C5 10F R2 4.3k
D1
VIN 3.3V
SHDN
SW BOOST SWITCHING REGULATOR 35 4 SHDN FB GND 2, 34
+
C1,C2: TAIYO YUDEN X5R JMK316BJ106ML D1: ON SEMICONDUCTOR MBR0520 L1: SUMIDA CR43-5R6
2846 F29
Figure 29. Boost Switching Regulator
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The switching regulator has a switch current limit of 1A. This current limit protects the switch as well as the external components connected to the switching regulator. The high speed operation of the boost switching regulator demands careful attention to board layout. Figure 30 shows the recommended component placement. Receiver Fail-Safe All LTC2846/LTC2844 receivers feature fail-safe operation in all modes. If the receiver inputs are left floating or are 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 31. 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 32.
GND VCC
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VCC 5V 480mA
+
VIN C5 L1 C6
R1 D1 R2
SHUTDOWN
2846 F30
Figure 30. Suggested Layout
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LTC2846
TYPICAL APPLICATIO S
A port with one DB-25 connector, that can be configured for either DTE or DCE operation is shown in Figure 33. 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 the LTC2846's Driver 1. 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 34, 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 RL. Cable-Selectable Multiprotocol Interface A cable-selectable multiprotocol DTE/DCE interface is shown in Figure 35. 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.
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LTC2846
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
VCC 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 31. Controller-Selectable Multiprotocol DTE Port with DB-25 Connector
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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
2846 F31
LTC2846
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 C2 1F C4 3.3F 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
VCC 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 32. Controller-Selectable DCE Port with DB-25 Connector
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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
2846 F32
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LTC2846
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
VCC 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 33. Controller-Selectable Multiprotocol DTE/DCE Port with DB-25 Connector
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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
2846 F33
LTC2846
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 VCC 5V 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 34. Controller-Selectable Multiprotocol DTE/DCE Port with RL, LL, TM and DB-25 Connector
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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
2846 F34
21
LTC2846
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 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 VCC 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 PIN 18 PIN 21 V.35 PIN 7 PIN 7 RS449, V.36 NC PIN 7 RS232 PIN 7 NC CABLE WIRING FOR DTE/DCE SELECTION MODE DTE DCE PIN 25 PIN 7 NC
2846 F35
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 35. Cable-Selectable Multiprotocol DTE/DCE Port with DB-25 Connector
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2 14 24 11
CTS A CTS B DSR A DSR B
8 10 6 22 5 13
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
LTC2846
PACKAGE DESCRIPTIO
5.20 - 5.38** (.205 - .212)
.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
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G Package 36-Lead Plastic SSOP (0.209)
(LTC DWG # 05-08-1640)
12.67 - 12.93* (.499 - .509) 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 7.65 - 7.90 (.301 - .311) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 1.73 - 1.99 (.068 - .078) 0 - 8 .65 (.0256) BSC .25 - .38 (.010 - .015) .05 - .21 (.002 - .008)
G36 SSOP 0501
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LTC2846 RELATED PARTS
PART NUMBER
LTC1321 LTC1334 LTC1343 LTC1344A LTC1345 LTC1346A LTC1543 LTC1544 LTC1545 LTC1546 LTC2844 LTC2845
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 Companion to LTC2846 for Control Signals Including LL 5-Driver/5-Receiver Companion to LTC2846 for Control Signals Including LL, TM and R
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Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 q FAX: (408) 434-0507
q
LT/TP 0102 1.5K * PRINTED IN USA
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2002

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