LTC2847
Software-Selectable
Multiprotocol Transceiver with
Termination and 3.3V Digital Interface
U
FEATURES
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■
■
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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.
The VCC supplies the drivers, the receivers and an internal
charge pump that requires only five space-saving surface
mounted capacitors. The VIN supply drives the digital interface circuitry including the receiver output drivers. It can be
tied to VCC 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 Transceiver Supports:
RS232, RS449, EIA530, EIA530-A, V.35, V.36, X.21
Operates from Single 5V Supply
Separate Supply Pin for Digital Interface Works
down to 3V
On-Chip Cable Termination
Complete DTE or DCE Port with LTC2845
Available in 38-Pin 5mm × 7mm QFN Package
U
APPLICATIO S
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Data Networking
CSU and DSU
Data Routers
, LTC and LT are registered trademarks of Linear Technology Corporation.
U
TYPICAL APPLICATIO
Complete DTE or DCE Multiprotocol Serial Interface with DB-25 Connector
RL
TM
LL
RI
CTS
DSR
DCD
DTR
RTS
RXD
TXC
D4
R5
21
25
D3
R3
R4
18
*
13 5
R2
22 6
TXD
D3
D2
D1
T
T
T
12
15 11
24 14
LTC2847
LTC2845
D5
SCTE
RXC
D2
D1
R1
10 8
23 20 19 4
1
7
R3
R2
T
T
16
3
9
R1
17
2
TXD A (103)
TXD B
SCTE A (113)
SCTE B
TXC A (114)
TXC B
RXC A (115)
RXC B
RXD A (104)
RXD B
SG (102)
SHIELD (101)
RTS A (105)
RTS B
DTR A (108)
DCD A (109)
DTR B
DCD B
DSR A (107)
DSR B
CTS A (106)
CTS B
RI (125)
LL A (141)
TM (142)
RL (140)
DB-25 CONNECTOR
2847 TA01
*OPTIONAL
sn2847 2847fs
1
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.............................................. – 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
Operating Temperature Range
LTC2847C ............................................... 0°C to 70°C
LTC2847I ........................................... – 40°C to 85°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
UHF PACKAGE
38-LEAD (7mm × 5mm) PLASTIC QFN
UNDERSIDE METAL INTERNALLY CONNECTED TO VEE
(PCB CONNECTION OPTIONAL)
TJMAX = 125°C, θJA = 34°C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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
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.35 Mode
V.28 Mode, No Load
V.28 Mode, Full Load
No-Cable Mode
MIN
TYP
MAX
UNITS
Supplies
ICC
14
100
126
20
35
300
●
●
●
●
130
170
75
900
mA
mA
mA
mA
mA
µA
IVIN
VIN Supply Current
(DCE Mode, All Digital Pins = GND or VIN)
All Modes Except No-Cable Mode
405
µA
PD
Internal Power Dissipation (DCE Mode)
RS530, RS530-A, X.21 Modes, Full Load
V.35 Mode, Full Load
V.28 Mode, Full Load
410
625
150
mW
mW
mW
V+
Positive Charge Pump Output Voltage
V.11 or V.28 Mode, No Load
V.35 Mode
V.28 Mode, with Load
V.28 Mode, with Load, IDD = 10mA
9.3
8.0
8.7
6.5
V
V
V
V
●
●
●
8
7
8
sn2847 2847fs
2
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
– 6.0
V
V
V
V
500
kHz
2
ms
No-Cable Mode/Power-Off to Normal Operation
MAX
UNITS
Logic Inputs and Outputs
VIH
Logic Input High Voltage
D1, D2, D3, M0, M1, M2, DCE/DTE
●
VIL
Logic Input Low Voltage
D1, D2, D3, M0, M1, M2, DCE/DTE
●
IIN
Logic Input Current
D1, D2, D3
M0, M1, M2, DCE/DTE = GND
M0, M1, M2, DCE/DTE = VIN
●
●
●
– 30
– 75
2.7
3
VOH
Output High Voltage
IO = – 3mA
●
VOL
Output Low Voltage
IO = 1.6mA
●
IOSR
Output Short-Circuit Current
0V ≤ VO ≤ VIN
●
IOZR
Three-State Output Current
M0 = M1 = M2 = VIN, VO = GND
M0 = M1 = M2 = VIN, VO = VIN
●
●
VODO
Open Circuit Differential Output Voltage
RL = 1.95k (Figure 1)
●
VODL
Loaded Differential Output Voltage
RL = 50Ω (Figure 1)
RL = 50Ω (Figure 1)
●
2.0
V
0.2
–30
–85
0.8
V
±10
– 120
±10
µA
µA
µA
V
0.4
V
±50
mA
–160
±10
µA
µA
±5
V
0.67VODO
V
V
0.2
V
V.11 Driver
0.5VODO
±2
∆VOD
Change in Magnitude of Differential
Output Voltage
RL = 50Ω (Figure 1)
●
VOC
Common Mode Output Voltage
RL = 50Ω (Figure 1)
●
3
V
∆VOC
Change in Magnitude of Common Mode
Output Voltage
RL = 50Ω (Figure 1)
●
0.2
V
ISS
Short-Circuit Current
VOUT = GND
IOZ
Output Leakage Current
VA and VB ≤ 0.25V, Power Off or
±1
●
±150
mA
±100
µA
No-Cable Mode or Driver Disabled
t r, t f
Rise or Fall Time
(Figures 2, 13)
●
2
15
25
ns
t PLH
Input to Output Rising
(Figures 2, 13)
●
15
40
65
ns
t PHL
Input to Output Falling
(Figures 2, 13)
●
15
40
65
ns
∆t
Input to Output Difference, tPLH – tPHL
(Figures 2, 13)
●
0
3
12
ns
t SKEW
Output to Output Skew
(Figures 2, 13)
3
ns
sn2847 2847fs
3
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.11 Receiver
VTH
Input Threshold Voltage
– 7V ≤ VCM ≤ 7V
●
∆VTH
Input Hysteresis
– 7V ≤ VCM ≤ 7V
●
RIN
Input Impedance
–7V ≤ VCM ≤ 7V (Figure 3)
●
t r, t f
Rise or Fall Time
CL = 50pF (Figures 4, 14)
t PLH
Input to Output Rising
CL = 50pF (Figures 4, 14)
●
50
90
ns
t PHL
Input to Output Falling
CL = 50pF (Figures 4, 14)
●
50
90
ns
∆t
Input to Output Difference, tPLH – tPHL
CL = 50pF (Figures 4, 14)
●
0
4
25
ns
VOD
Differential Output Voltage
Open Circuit, RL = 1.95k (Figure 5)
With Load, – 4V ≤ VCM ≤ 4V (Figure 6)
●
±0.44
±0.55
±1.2
±0.66
V
V
VOA, VOB
Single-Ended Output Voltage
Open Circuit, RL = 1.95k (Figure 5)
●
±1.2
V
VOC
Transmitter Output Offset
RL = 50Ω (Figure 5)
●
±0.6
V
IOH
Transmitter Output High Current
VA, VB = 0V
●
–9
– 13
mA
IOL
Transmitter Output Low Current
VA, VB = 0V
●
9
IOZ
Transmitter Output Leakage Current
VA and VB ≤ 0.25V
●
ROD
Transmitter Differential Mode Impedance
ROC
Transmitter Common Mode Impedance
– 2V ≤ VCM ≤ 2V (Figure 7)
t r , tf
t PLH
Rise or Fall Time
(Figures 8, 13)
Input to Output
(Figures 8, 13)
●
15
35
65
ns
15
35
65
ns
0
16
ns
– 0.2
15
100
103
Ω
15
ns
V.35 Driver
●
– 11
11
13
mA
±1
±100
µA
50
100
150
Ω
135
150
165
5
t PHL
Input to Output
(Figures 8, 13)
●
∆t
Input to Output Difference, tPLH – tPHL
(Figures 8, 13)
●
t SKEW
Output to Output Skew
(Figures 8, 13)
Ω
ns
4
ns
V.35 Receiver
VTH
Differential Receiver Input Threshold Voltage
– 2V ≤ VCM ≤ 2V (Figure 9)
●
∆VTH
Receiver Input Hysteresis
– 2V ≤ VCM ≤ 2V (Figure 9)
●
RID
Receiver Differential Mode Impedance
– 2V ≤ VCM ≤ 2V
●
RIC
Receiver Common Mode Impedance
– 2V ≤ VCM ≤ 2V (Figure 10)
t r, t f
Rise or Fall Time
CL = 50pF (Figures 4, 14)
tPLH
Input to Output
CL = 50pF (Figures 4, 14)
●
50
90
ns
tPHL
Input to Output
CL = 50pF (Figures 4, 14)
●
50
90
ns
∆t
Input to Output Difference, tPLH – tPHL
CL = 50pF (Figures 4, 14)
●
0
4
25
ns
VO
Output Voltage
Open Circuit
RL = 3k (Figure 11)
●
●
±5
±8.5
±10
V
V
ISS
Short-Circuit Current
VOUT = GND
●
±150
mA
ROZ
Power-Off Resistance
– 2V < VO < 2V, Power Off
or No-Cable Mode
●
300
SR
Slew Rate
RL = 7k, CL = 0 (Figures 11, 15)
●
4
30
V/µs
t PLH
Input to Output
RL = 3k, CL = 2500pF (Figures 11, 15)
●
1.5
2.5
µs
t PHL
Input to Output
RL = 3k, CL = 2500pF (Figures 11, 15)
●
1.5
2.5
µs
– 0.2
0.2
V
15
40
mV
90
103
110
Ω
135
150
165
Ω
15
ns
V.28 Driver
Ω
sn2847 2847fs
4
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.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
CONDITIONS
MIN
(Figure 12)
(Figure 12)
(Figure 12)
– 15V ≤ VA ≤ 15V
CL = 50pF (Figures 12, 16)
CL = 50pF (Figures 12, 16)
CL = 50pF (Figures 12, 16)
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.
TYP
●
2
0
3
●
●
●
0.05
5
15
60
160
●
●
MAX
UNITS
0.8
V
V
V
kΩ
ns
ns
ns
0.3
7
300
300
Note 3: All typicals are given for VCC = 5V, VIN = 3.3V, CVCC = CVIN = 10µF,
CVDD = 1µF, CVEE = 3.3µF and TA = 25°C.
U W
TYPICAL PERFOR A CE CHARACTERISTICS
V.11 Mode ICC vs Data Rate
170
V.35 Mode ICC vs Data Rate
TA = 25°C
160
V.28 Mode ICC vs Data Rate
60
150
TA = 25°C
TA = 25°C
145
55
140
50
ICC (mA)
ICC (mA)
140
130
120
ICC (mA)
150
135
45
130
40
125
35
110
100
90
10
100
120
1000
10000
30
10
DATA RATE (kBd)
10
10000
100
1000
DATA RATE (kBd)
V.11 Mode ICC vs Temperature
V.35 Mode ICC vs Temperature
37.5
127.5
105
37.0
127.0
36.5
126.5
95
90
36.0
126.0
ICC (mA)
ICC (mA)
100
ICC (mA)
80 100
V.28 Mode ICC vs Temperature
128.0
110
60
2846 G06
2846 G05
2846 G04
125.5
125.0
35.5
35.0
124.5
34.5
124.0
85
34.0
123.5
80
–40 –20
20
40
DATA RATE (kBd)
40
20
60
0
TEMPERATURE (°C)
80
100
2846 G07
123.0
–40 –20
40
20
0
60
TEMPERATURE (°C)
80
100
2846 G08
33.5
–40 – 20
60
40
20
TEMPERATURE (°C)
0
80
100
3846 G09
sn2847 2847fs
5
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.
R2 B (Pin 20): Receiver 2 Noninverting Input.
R2 A (Pin 21): 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.
R1 (Pin 8): CMOS Level Receiver 1 Output with Pull-Up to
VIN when Three-Stated.
D2 A (Pin 27): Driver 2 Inverting Output.
R2 (Pin 9): CMOS Level Receiver 2 Output with Pull-Up to
VIN when Three-Stated.
D1 A (Pin 29): Driver 1 Inverting Output.
R3 (Pin 10): CMOS Level Receiver 3 Output with Pull-Up
to VIN when Three-Stated.
D1 B (Pin 28): Driver 1 Noninverting Output.
GND (Pins 30,31): Transceiver Ground.
M0 (Pin 11): TTL Level Mode Select Input 0 with Pull-Up
to VIN. See Table 1.
VEE (Pins 32,33,36): Generated Negative Supply Voltage.
Connect a 3.3µF capacitor to GND. Exposed pad can also
be connected to VEE.
M1 (Pin 12): TTL Level Mode Select Input 1 with Pull-Up
to VIN. See Table 1.
C2 – (Pin 34): Capacitor C2 Negative Terminal. Connect a
1µF capacitor between C2 + and C2 –.
VIN (Pin 13): Input Supply Pin. Input supply to digital
interface including receiver output drivers. 3V ≤ VIN ≤
5.25V. Connect to VCC (Pin 4) or to separate supply for
lower receiver output swing. Connect a 1µF capacitor to
GND.
C2 + (Pin 35): Capacitor C2 Positive Terminal. Connect a
1µF capacitor between C2 + and C2 – .
M2 (Pin 14): TTL Level Mode Select Input 2 with Pull-Up
to VIN. See Table 1.
C1– (Pin 37): Capacitor C1 Negative Terminal. Connect a
1µF capacitor between C1+ and C1–.
C1+ (Pin 38): Capacitor C1 Positive Terminal. Connect a
1µF capacitor between C1+ and C1–.
DCE/DTE (Pin 15): TTL Level Mode Select Input with
Pull-Up to VIN. See Table 1.
sn2847 2847fs
6
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
51.5Ω
20 R2 B
20k
17 R3 A
20k
6k
10k
R3 10
VIN 13
10k
M0 11
M1 12
M2 14
MODE
SELECTION
LOGIC
51.5Ω
S3
R3
S2
125Ω
51.5Ω
16 R3 B
20k
2847 BD
sn2847 2847fs
7
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.35 Receiver AC Test Circuit
VOB
50Ω
RL
125Ω
50Ω
50Ω
50Ω
50Ω
125Ω
125Ω
50Ω
VOD
50Ω
VOC
RL
2847 F05
2847 F06
VOA
+
–
50Ω
VCM
VCM = ±2V
2847 F07
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
51.5Ω
125Ω
50Ω
50Ω
50Ω
50Ω
VTH
+
–
2847 F08
VCM
+
–
125Ω
125Ω
VCM = ± 2V
+
–
2847 F10
2847 F09
Figure 8. V.35 Driver AC Test Circuit
D
Figure 9. V.35 Receiver DC Test Circuit
A
A
CL
RL
2847 F11
Figure 11. V.28 Driver Test Circuit
51.5Ω
VA
Figure 10. Receiver Common Mode
Impedance Test Circuit
R
CL
2847 F12
Figure 12. V.28 Receiver Test Circuit
sn2847 2847fs
8
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.11 V.11
Z
Z
V.11 V.11 V.11 V.11 V.11 V.11 CMOS
CMOS
9.3V
–6V
X.21
0
1
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
V.35
1
0
0
0
TTL
X
V.35 V.35 V.35 V.35
Z
Z
V.35 V.35 V.35 V.35 V.35 V.35 CMOS
CMOS
8V
–6.5V
RS449/V.36
1
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
V.28/RS232
1
1
0
0
TTL
X
V.28
Z
V.28
Z
Z
Z
V.28 30k V.28 30k V.28 30k CMOS
CMOS
8.7V
–8.5V
No Cable
1
1
1
0
X
X
Z
Z
Z
Z
Z
Z
30k 30k 30k 30k
Not Used
(Default V.11) 0
0
0
1
30k 30k
Z
Z
4.7V
0.3V
TTL TTL V.11 V.11 V.11 V.11 V.11 V.11 30k 30k V.11 V.11 V.11 V.11
Z
CMOS
9.3V
–6V
RS530A
0
0
1
1
TTL TTL V.11 V.11 V.11 V.11 V.11 V.11 30k 30k V.11 V.11 V.11 V.11
Z
CMOS
9.3V
–6V
RS530
0
1
0
1
TTL TTL V.11 V.11 V.11 V.11 V.11 V.11 30k 30k V.11 V.11 V.11 V.11
Z
CMOS
9.3V
–6V
X.21
0
1
1
1
TTL TTL V.11 V.11 V.11 V.11 V.11 V.11 30k 30k V.11 V.11 V.11 V.11
Z
CMOS
9.3V
–6V
V.35
1
0
0
1
TTL TTL V.35 V.35 V.35 V.35 V.35 V.35 30k 30k V.35 V.35 V.35 V.35
Z
CMOS
8V
–6.5V
RS449/V.36
1
0
1
1
TTL TTL V.11 V.11 V.11 V.11 V.11 V.11 30k 30k V.11 V.11 V.11 V.11
Z
CMOS
9.3V
–6V
V.28/RS232
1
1
0
1
TTL TTL V.28
30k 30k V.28 30k V.28 30k
Z
CMOS
8.7V
–8.5V
No Cable
1
1
1
1
30k 30k 30k 30k
Z
Z
4.7V
0.3V
X
X
Z
Z
V.28
Z
V.28
Z
Z
Z
Z
Z
Z
Note 1: Driver inputs are TTL level compatible.
Note 2: Unused receiver inputs are terminated with 30k to ground. In addition, R2 and R3 are always
terminated by a 103Ω differential impedence (see Block Diagram on page 7).
Note 3: Receiver Outputs are CMOS level compatible and have a weak pull up to VIN when Z.
30k 30k
Note 4: VDD values shown are typical values for VCC = 5V, VIN = 3.3V and TA = 25°C with LTC2847
under full load for each mode.
Note 5: VEE values shown are typical values for VCC = 5V, VIN = 3.3V and TA = 25°C with LTC2847
under full load for each mode.
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%
90%
50%
10%
tr
1/2 VO
50%
10%
tf
A
VO
B
t SKEW
t SKEW
2847 F13
Figure 13. V.11, V.35 Driver Propagation Delays
VOD2
B–A
–VOD2
VOH
R
VOL
f = 1MHz : t r ≤ 10ns : t f ≤ 10ns
0V
INPUT
0V
t PHL
t PLH
1.65V
OUTPUT
1.65V
2847 F14
Figure 14. V.11, V.35 Receiver Propagation Delays
sn2847 2847fs
9
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
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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. The charge pump generates the
VDD and VEE supplies. The LTC2847’s VDD and VEE
supplies can be used to power a companion chip like the
LTC2845. The VIN input powers the digital interface including the receiver output drivers. Having a separate pin
to power the digital interface allows the flexibility of
controlling the receiver output swing to interface with 5V
or 3.3V logic.
The LTC2847 and LTC2845 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 LTC2847 half of each port
is used to generate and appropriately terminate the
clock and data signals. The LTC2845 is used to generate
the control signals along with LL (local loopback),
RL (Remote Loop-Back), TM (Test Mode) and RI (Ring
Indicate).
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.
sn2847 2847fs
10
LTC2847
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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. Complete Multiprotocol Interface in EIA530 Mode
When the cable is removed, leaving all mode pins unconnected, the LTC2847/LTC2845 will enter no-cable mode.
In this mode the LTC2847/LTC2845 supply current drops
to less than 1000µA and the LTC2847/LTC2845 driver
outputs are forced into a high impedance state. At the
same time, the R2 and R3 receivers of the LTC2847 are
differentially terminated with 103Ω and the other receiv-
ers on the LTC2847 and LTC2845 are terminated with
30kΩ 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
sn2847 2847fs
11
LTC2847
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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.
BALANCED
INTERCONNECTING
CABLE
GENERATOR
LOAD
CABLE
TERMINATION
The LTC2847/LTC2845 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.
A
A'
C
C'
RECEIVER
2847 F19
Figure 19. Typical V.10 Interface
V.10 (RS423) Interface
IZ
All V.10 drivers and receivers necessary for the RS449,
EIA530, EIA530-A, V.36 and X.21 protocols are implemented on the LTC2845.
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 LTC2845 is shown
in Figure 21. In V.10 mode, switch S3 inside the LTC2845
is turned off. The noninverting input is disconnected
inside the LTC2845 receivers and connected to ground.
–10V
3.25mA
–3V
VZ
3V
–3.25mA
10V
2847 F20
Figure 20. V.10 Receiver Input Impedance
sn2847 2847fs
12
LTC2847
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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. The LTC2845 only handles control signals, so no
termination other than its V.11 receivers’ 30k input impedance is necessary.
V.28 (RS232) Interface
100Ω
MIN
2847 F22
Figure 22. Typical V.11 Interface
The cable termination is then the 30k input impedance to
ground of the LTC2845 V.10 receiver.
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.
BALANCED
INTERCONNECTING
CABLE
GENERATOR
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 100Ω. 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
LTC2847’s receivers which connects a 103Ω differential
LOAD
CABLE
TERMINATION
A
A'
C
C'
RECEIVER
2847 F24
Figure 24. Typical V.28 Interface
A'
LTC2847
R1
51.5Ω
S1
S2
B'
C'
R8
6k
R3
124Ω
R5
20k
R6
10k
S3
R2
51.5Ω
R4
20k
GND
RECEIVER
R7
10k
2847 F25
1Actually,
there is no switch S1 in receivers R2 and R3. However, for simplicity, all termination
networks on the LTC2847 can be treated identically if it is assumed that an S1 switch exists and is
always closed on the R2 and R3 receivers.
Figure 25. V.28 Receiver Configuration
sn2847 2847fs
13
LTC2847
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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. The noninverting input is disconnected inside the
LTC2847/LTC2845 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
100Ω␣ ±10Ω, and the impedance between shorted terminals (A' and B') and ground (C') must be 150Ω ±15Ω.
BALANCED
INTERCONNECTING
CABLE
GENERATOR
LOAD
CABLE
TERMINATION
A'
A
50Ω
RECEIVER
125Ω
50Ω
125Ω
50Ω
50Ω
B
B'
C
C'
2847 F26
Figure 26. Typical V.35 Interface
A'
LTC2847
R1
51.5Ω
R8
6k
S2
B'
C'
R3
124Ω
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 300µA while its VIN supply
current drops to less than 10µA. Note that the LTC2847’s
R2 and R3 receivers continue to be terminated by a 103Ω
differential impedance.
Charge Pump
The LTC2847 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. Four 1µF surface mounted
tantalum or ceramic capacitors are required for C1, C2, C3
and C5. The VEE capacitor C4 should be a minimum of
3.3µF. All capacitors are 16V and should be placed as close
as possible to the LTC2847 to reduce EMI.
Receiver Fail-Safe
All LTC2847/LTC2845 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.
R5
20k
R6
10k
S1
In V.35 mode, both switches S1 and S2 inside the LTC2847
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 50Ω to
150Ω and the impedance between shorted terminals (A
and B) and ground (C) must be 150Ω ±15Ω.
RECEIVER
C3
1µF
S3
C1
1µF
R2
51.5Ω
R4
20k
R7
10k
C2 +
C1+
C2 –
C2
1µF
LTC2847
C1–
VEE
+
VCC
5V
GND
VDD
2847 F27
C4
3.3µF
GND
C5
1µF
2847 F28
Figure 27. V.35 Receiver Configuration
Figure 28. Charge Pump
sn2847 2847fs
14
LTC2847
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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.
A dedicated DTE port using a DB-25 male connector is
shown in Figure 29. 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 30.
A port with one DB-25 connector, that can be configured
for either DTE or DCE operation is shown in Figure 31. 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
LTC2847’s Driver 1. In DCE mode, Driver 1 now routes the
RXD signal to Pins 2 and 14.
Power Dissipation Calculations
The LTC2847 takes in 5V VCC. VDD and VEE are in turn
produced from VCC with an internal charge pump at
approximately 80% and 70% efficiency respectively. Current drawn internally from VDD or VEE translates directly
into a higher ICC. The LTC2847 dissipates power according to the equation:
PDISS(2847) = VCC • ICC – ND • PRT + NR • PRT
(1)
PRT refers to the power dissipated by each driver in a
receiver termination on the far end of the cable while ND
is the number of drivers. Conversely, current from the
far end drivers dissipate power NR • PRT in the internal
receiver termination where NR is the number of receivers.
LTC2847 Power Dissipation
Consider an LTC2847 in X.21, DCE mode (three V.11
drivers and two V.11 receivers). From the Electrical Characteristics Table, ICC at no load = 14mA, ICC at full load =
100mA. Each receiver termination is 100Ω (RRT) and
current going into each receiver termination = (100mA –
14mA)/3 = 28.7mA (IRT).
PRT = (IRT)2 • RRT
(2)
From Equation (2), PRT = 82.4mW and from Equation (1),
DC power dissipation PDISS(2847) = 5V • 100mA – 3 •
82.4mW + 2 • 82.4mW = 418mW.
Consider the above example running at a baud rate of
10MBd. From the Typical Characteristic for “V.11 Mode
ICC vs Data Rate,” the ICC at 10MBd is 160mA. ICC
increases with baud rate due to driver transient dissipation. From Equation (1), AC power dissipation PDISS(2847)
= 5V • 160mA –3 • 82.4mW + 2 • 82.4mW = 718mW.
LTC2845 Power Dissipation
If a LTC2845 is used to form a complete DCE port with the
LTC2847, it will be running in the X.21 mode (three V.11
drivers and two V.10 drivers, two V.11 receivers and two
V.10 receivers, all with internal 30k termination). In addition to VCC, it uses the VDD and VEE outputs from the
LTC2847. Negligible power is dissipated in the large
internal receiver termination of the LTC2845 so the NR •
PRT term of Equation (1) can be omitted. Thus Equation (1)
is modified as follows:
PDISS(2845) = (VCC • ICC) + (VDD • IDD)
+ (VEE • IEE) – ND • PRT
(3)
Since power is drawn from the supplies of the LTC2847
(VDD and VEE) at less than 100% efficiency, the LTC2847
dissipates extra power to source PDISS(2845) and PRT :
PDISS1(2847) = 125% • (VDD • IDD) + 143% •
(4)
(VEE • IEE) – PDISS(2845) – ND • PRT
= 25% • (VDD • IDD) + 43% • (VEE • IEE)
From the LTC2845 Electrical Characteristics Table, for
VCC = 5V, VDD = 8V and VEE = – 5.5V:
ICC at no load
2.7mA
ICC at full load with all drivers high
110mA
IEE at no load
2mA
IEE at full load with both V.10 drivers low
23mA
IDD at no load
0.3mA
IDD at full load
0.3mA
sn2847 2847fs
15
LTC2847
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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
3.3V
C6
1µF
DCE/DTE
C7
1µF
VCC
VEE
VDD
GND
D1
19
20
D2
DTR
SCTE A (113)
SCTE B
TXC A (114)
TXC B
RXC A (115)
RXC B
RXD A (104)
RXD B
SG
SHIELD
DB-25 MALE
CONNECTOR
C9
1µF
4
RTS
TXD B
T
15
TXC
TXD A (103)
23
RTS A (105)
RTS B
DTR A (108)
DTR B
D3
LTC2845
8
R1
DCD
10
6
R2
DSR
22
5
R3
CTS
13
18
R4
LL
RI
D4
TM
R5
RL
*
25
21
D5
M0
M0
VIN
M1
M1
D4ENB
M2
M2
DCE/DTE
R4EN
VIN
3.3V
C10
1µF
DCD A (109)
DCD B
DSR A (107)
DSR B
CTS A (106)
CTS B
LL (141)
RI (125)
TM (142)
RL (140)
*OPTIONAL
2847 F29
NC
Figure 29. Controller-Selectable Multiprotocol DTE Port with DB-25 Connector
sn2847 2847fs
16
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
3.3V
C6
1µF
DCE/DTE
VCC
VEE
VDD
GND
1
D1
13
6
D2
DSR
RXC A (115)
RXC B
TXC A (114)
TXC B
SCTE A (113)
SCTE B
TXD A (103)
TXD B
SGND (102)
SHIELD (101)
DB-25 FEMALE
CONNECTOR
C9
1µF
5
CTS
RXD B
T
15
TXC
RXD A (104)
22
CTS A (106)
CTS B
DSR A (107)
DSR B
D3
LTC2845
8
R1
DCD
10
20
R2
DTR
23
4
R3
RTS
19
*
R4
RI
LL
D4
RL
R5
18
21
25
D5
TM
M0
M0
VIN
M1
M1
D4ENB
M2
M2
NC
DCE/DTE
R4EN
C10
1µF
VIN
3.3V
DCD A (109)
DCD B
DTR A (108)
DTR B
RTS A (105)
RTS B
RI (125)
LL (141)
RL (140)
TM 9142)
*OPTIONAL
2847 F30
NC
Figure 30. Controller-Selectable DCE Port with DB-25 Connector
sn2847 2847fs
17
LTC2847
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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
3.3V
C6
1µF
DCE/DTE
C7
1µF
C8
1µF
DTE_RTS/DCE_CTS
VCC
VEE
VDD
GND
1
TXD B
RXD B
SCTE A
RXC A
SCTE B
RXC B
TXC A
TXC A
TXC B
TXC B
RXC A
SCTE A
RXC B
SCTE B
RXD A
TXD A
RXD B
TXD B
SG
SHIELD
DB-25
CONNECTOR
C9
1µF
4
D1
19
20
DTE_DTR/DCE_DSR
DCE
RXD A
T
15
DTE_TXC/DCE_TXC
DTE
TXD A
D2
23
RTS A
CTS A
RTS B
CTS B
DTR A
DSR A
DTR B
DSR B
DCD A
DCD A
D3
LTC2845
DTE_DCD/DCE_DCD
8
R1
10
6
R2
DTE_DSR/DCE_DTR
22
5
DTE_CTS/DCE_RTS
R3
DTE_LL/DCE_RI
13
18
D4
DTE_RI/DCE_LL
R4
DTE_TM/DCE_RL
R5
DTE_RL/DCE_TM
*
25
21
D5
M0
M0
VIN
M1
M1
D4ENB
M2
M2
DCE/DTE
DCE/DTE
R4EN
15
C10
1µF
VIN
3.3V
DCD B
DCD B
DSR A
DTR A
DSR B
DTR B
CTS A
RTS A
CTS B
RTS B
LL
LL
RI
RI
TM
TM
RL
RL
*OPTIONAL
2847 F31
NC
Figure 31. Controller-Selectable Multiprotocol DTE/DCE Port with DB-25 Connector
sn2847 2847fs
18
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)
0.40 ± 0.10
0.200 REF 0.25 ± 0.05
0.200 REF
0.00 – 0.05
0.75 ± 0.05
NOTE:
1. DRAWING CONFORMS TO JEDEC PACKAGE
OUTLINE M0-220 VARIATION WHKD
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
0.50 BSC
R = 0.115
TYP
(UH) QFN 0303
BOTTOM VIEW—EXPOSED PAD
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.20mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION
ON THE TOP AND BOTTOM OF PACKAGE
sn2847 2847fs
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.
19
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) + 5.5V • 23mA – 3 • 79mW – 2 • 49.6mW =
228mW. Since the LTC2845 runs slow control signals, the
AC power dissipation can be assumed to be equal to the DC
power dissipation.
The extra power dissipated in the LTC2847 due to LTC2845
is given by Equation(4), PDISS1(2847) = 25% • (8V • 0.3mA)
+ 43% • (5.5V • 23mA) = 55mW. So for an X.21 DCE port
running at 10MBd, the LTC2847 dissipates approximately
718mW + 55mW = 773mW while the LTC2845 dissipates
228mW.
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC1321
Dual RS232/RS485 Transceiver
Two RS232 Driver/Receiver Pairs or Two RS485 Driver/Receiver Pairs
LTC1334
Single 5V RS232/RS485 Multiprotocol Transceiver
Two RS232 Driver/Receiver or Four RS232 Driver/Receiver Pairs
LTC1343
Software-Selectable Multiprotocol Transceiver
4-Driver/4-Receiver for Data and Clock Signals
LTC1344A
Software-Selectable Cable Terminator
Perfect for Terminating the LTC1543 (Not Needed with LTC1546)
LTC1345
Single Supply V.35 Transceiver
3-Driver/3-Receiver for Data and Clock Signals
LTC1346A
Dual Supply V.35 Transceiver
3-Driver/3-Receiver for Data and Clock Signals
LTC1543
Software-Selectable Multiprotocol Transceiver
Terminated with LTC1344A for Data and Clock Signals, Companion to
LTC1544 or LTC1545 for Control Signals
LTC1544
Software-Selectable Multiprotocol Transceiver
Companion to LTC1546 or LTC1543 for Control Signals Including LL
LTC1545
Software-Selectable Multiprotocol Transceiver
5-Driver/5-Receiver Companion to LTC1546 or LTC1543
for Control Signals Including LL, TM and RL
LTC1546
Software-Selectable Multiprotocol Transceiver
3-Driver/3-Receiver with Termination for Data and Clock Signals
LTC2844
3.3V Software-Selectable Multiprotocol Transceiver
Companion to LTC2846 for Control Signals Including LL
LTC2845
3.3V Software-Selectable Multiprotocol Transceiver
5-Driver/5-Receiver Companion to LTC2846 or LTC2847 for Control
Signals Including LL, TM and RL
LTC2846
3.3V Software-Selectable Multiprotocol Transceiver
3.3V Supply, 3-Driver/3-Receiver with Termination for Data and Clock
Signals, Generates the Required 5V and ±8V Supplies for LTC2846
Companion Parts
sn2847 2847fs
20
Linear Technology Corporation
LT/TP 0603 1K • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
LINEAR TECHNOLOGY CORPORATION 2003
工商网监
湘ICP备2023018690号
