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LTC2846
sn2846 2846fs
APPLICATIO S
U
DESCRIPTIO
U
FEATURES
TYPICAL APPLICATIO
U
, LTC and LT are registered trademarks of Linear Technology Corporation.
Complete DTE or DCE Multiprotocol Serial Interface with DB-25 Connector
s
Data Networking
s
CSU and DSU
s
Data Routers
s
Software-Selectable Transceiver Supports:
RS232, RS449, EIA530, EIA530-A, V.35, V.36, X.21
s
Operates from Single 3.3V Supply
s
TUV Rheinland of North America Inc. Certified NET1,
NET2 and TBR2 Compliant, Report No.:
TBR2/050101/02, TBR2/051501/02
s
1.2MHz Boost Switching Regulator for 3.3V to 5V
Conversion
s
On-Chip Cable Termination
s
Complete DTE or DCE Port with LTC2844 or LTC2845
s
Small Footprint
s
Available in 36-Lead SSOP (0.209 Wide) Package
The LTC
2846 is a 3-driver/3-receiver multiprotocol trans-
ceiver with on-chip cable termination. When combined with
the LTC2844 or LTC2845, this chip set forms a complete
software-selectable DTE or DCE interface port that supports
the RS232, RS449, EIA530, EIA530-A, V.35, V.36 and X.21
protocols. All necessary cable termination is provided inside
the 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.
3.3V Software-Selectable
Multiprotocol Transceiver
with Termination
D2
D1
LTC2844
RTS
DTR
DSR
DCD
CTS
D3
R2
R1
R4
R3
LTC2846
LL
TXD
SCTE
TXC
RXC
RXD
2
14
24
11
15
12
17
9
3
1
4
19
20
6
23
22
5
13
8
10
18
7
16
2846 TA01
D1
SCTE B
SCTE A (113)
TXD B
TXD A (103)
RXC A (115)
RXC B
RXD A (104)
RXD B
RTS A (105)
RTS B
DTR A (108)
DTR B
CTS A (106)
CTS B
LL A (141)
SG (102)
SHIELD (101)
DB-25 CONNECTOR
TXC A (114)
DCD A (109)
DCD B
DSR A (107)
DSR B
D4
D2
D3
R1
R2
R3
TXC B
T
T
T
T
T
2
LTC2846
sn2846 2846fs
ORDER PART
NUMBER
(Note 1)
V
CC
Voltage .............................................. 0.3V to 6.5V
V
IN
Voltage .............................................. 0.3V to 6.5V
Input Voltage
Transmitters ........................... 0.3V to (V
CC
+ 0.3V)
Receivers ............................................... 18V to 18V
Logic Pins .............................. 0.3V to (V
CC
+ 0.3V)
Output Voltage
Transmitters ................. (V
EE
0.3V) to (V
DD
+ 0.3V)
Receivers ................................. 0.3V to (V
IN
+ 0.3V)
V
EE
........................................................ 10V to 0.3V
V
DD
....................................................... 0.3V to 10V
Short-Circuit Duration
Transmitter Output ..................................... Indefinite
Receiver Output .......................................... Indefinite
V
EE
.................................................................. 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 ............................................... 0
C to 70
C
LTC2846I ........................................... 40
C to 85
C
Storage Temperature Range ................ 65
C to 150
C
Lead Temperature (Soldering, 10 sec)................. 300
C
LTC2846CG
LTC2846IG
T
JMAX
= 125
C,
JA
= 90
C/W,
JC
= 35
C/W
ABSOLUTE AXI U RATI GS
W
W
W
U
PACKAGE/ORDER I FOR ATIO
U
U
W
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
TOP VIEW
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
20
19
NC
PGND
V
IN
SHDN
C1
C1
+
V
DD
V
CC
D1
D2
D3
R1
R2
R3
M0
M1
V
IN
M2
SW
FB
SGND
C2
+
C2
V
EE
GND
D1 A
D1 B
D2 A
D2 B
D3/R1 A
D3/R1 B
R2 A
R2 B
R3 A
R3 B
DCE/DTE
R3
CHARGE PUMP
R1
D2
D1
R2
D3
G PACKAGE
36-LEAD PLASTIC SSOP
T
T
T
T
T
BOOST
SWITCHING
REGULATOR
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25
C. V
CC
= 5V, V
IN
= 3.3V, V
SHDN
= V
IN
, unless otherwise noted. (Notes 2, 3)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Supplies
I
CC
V
CC
Supply Current (DCE Mode,
RS530, RS530-A, X.21 Modes, No Load
14
mA
All Digital Pins = GND or V
IN
)
RS530, RS530-A, X.21 Modes, Full Load
q
100
130
mA
V.35 Mode
q
126
170
mA
V.28 Mode, No Load
20
mA
V.28 Mode, Full Load
q
35
75
mA
No-Cable Mode
q
300
900
A
P
D
Internal Power Dissipation (DCE Mode)
RS530, RS530-A, X.21 Modes, Full Load
550
mW
V.35 Mode, Full Load
775
mW
V.28 Mode, Full Load
200
mW
V
+
Positive Charge Pump Output Voltage
V.11 or V.28 Mode, No Load
q
8
9.3
V
V.35 Mode
q
7
8.0
V
V.28 Mode, with Load
q
8
8.7
V
V.28 Mode, with Load, I
DD
= 10mA
6.5
V
ELECTRICAL CHARACTERISTICS
Consult LTC Marketing for parts specified with wider operating temperature ranges.
*
JA
SOLDERED TO A CIRCUIT BOARD IS TYPICALLY 60
C/W
3
LTC2846
sn2846 2846fs
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25
C. V
CC
= 5V, V
IN
= 3.3V, V
SHDN
= V
IN
, unless otherwise noted. (Notes 2, 3)
ELECTRICAL CHARACTERISTICS
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
Negative Charge Pump Output Voltage
V.28 Mode, No Load
9.6
V
V.28 Mode, Full Load
q
7.5
8.5
V
V.35 Mode
q
5.5
6.5
V
RS530, RS530-A, X.21 Modes, Full Load
q
4.5
6.0
V
f
OSC
Charge Pump Oscillator Frequency
500
kHz
t
r
Charge Pump Rise Time
No-Cable Mode/Power-Off to Normal Operation
2
ms
Logic Inputs and Outputs
V
IH
Logic Input High Voltage
D1, D2, D3, M0, M1, M2, DCE/DTE
q
2.0
V
SHDN
2.4
V
V
IL
Logic Input Low Voltage
D1, D2, D3, M0, M1, M2, DCE/DTE
q
0.8
V
SHDN
0.5
V
I
IN
Logic Input Current
D1, D2, D3
q
10
A
M0, M1, M2, DCE/DTE = GND
q
30
75
120
A
M0, M1, M2, DCE/DTE = V
IN
q
10
A
SHDN = GND
0.1
A
SHDN = 3V
16
32
A
V
OH
Output High Voltage
I
O
= 3mA
q
2.7
3
V
V
OL
Output Low Voltage
I
O
= 1.6mA
q
0.2
0.4
V
I
OSR
Output Short-Circuit Current
0V
V
O
V
IN
q
50
mA
I
OZR
Three-State Output Current
M0 = M1 = M2 = V
IN
, V
O
= GND
q
30
85
160
A
M0 = M1 = M2 = V
IN
, V
O
= V
IN
q
10
A
V.11 Driver
V
ODO
Open Circuit Differential Output Voltage
R
L
= 1.95k (Figure 1)
q
5
V
V
ODL
Loaded Differential Output Voltage
R
L
= 50
(Figure 1)
0.5V
ODO
0.67V
ODO
V
R
L
= 50
(Figure 1)
q
2
V
V
OD
Change in Magnitude of Differential
R
L
= 50
(Figure 1)
q
0.2
V
Output Voltage
V
OC
Common Mode Output Voltage
R
L
= 50
(Figure 1)
q
3
V
V
OC
Change in Magnitude of Common Mode
R
L
= 50
(Figure 1)
q
0.2
V
Output Voltage
I
SS
Short-Circuit Current
V
OUT
= GND
150
mA
I
OZ
Output Leakage Current
V
A
and
V
B
0.25V, Power Off or
q
1
100
A
No-Cable Mode or Driver Disabled
t
r
, t
f
Rise or Fall Time
(Figures 2, 13)
q
2
15
25
ns
t
PLH
Input to Output Rising
(Figures 2, 13)
q
15
40
65
ns
t
PHL
Input to Output Falling
(Figures 2, 13)
q
15
40
65
ns
t
Input to Output Difference,
t
PLH
t
PHL
(Figures 2, 13)
q
0
3
12
ns
t
SKEW
Output to Output Skew
(Figures 2, 13)
3
ns
4
LTC2846
sn2846 2846fs
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25
C. V
CC
= 5V, V
IN
= 3.3V, V
SHDN
= V
IN
, unless otherwise noted. (Notes 2, 3)
ELECTRICAL CHARACTERISTICS
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V.11 Receiver
V
TH
Input Threshold Voltage
7V
V
CM
7V
q
0.2
0.2
V
V
TH
Input Hysteresis
7V
V
CM
7V
q
15
40
mV
R
IN
Input Impedance
7V
V
CM
7V (Figure 3)
q
100
103
t
r
, t
f
Rise or Fall Time
C
L
= 50pF (Figures 4, 14)
15
ns
t
PLH
Input to Output Rising
C
L
= 50pF (Figures 4, 14)
q
50
90
ns
t
PHL
Input to Output Falling
C
L
= 50pF (Figures 4, 14)
q
50
90
ns
t
Input to Output Difference,
t
PLH
t
PHL
C
L
= 50pF (Figures 4, 14)
q
0
4
25
ns
V.35 Driver
V
OD
Differential Output Voltage
Open Circuit, R
L
= 1.95k (Figure 5)
q
1.2
V
With Load, 4V
V
CM
4V (Figure 6)
0.44
0.55
0.66
V
V
OA
, V
OB
Single-Ended Output Voltage
Open Circuit, R
L
= 1.95k (Figure 5)
q
1.2
V
V
OC
Transmitter Output Offset
R
L
= 50
(Figure 5)
q
0.6
V
I
OH
Transmitter Output High Current
V
A
,
V
B
= 0V
q
9
11
13
mA
I
OL
Transmitter Output Low Current
V
A
,
V
B
= 0V
q
9
11
13
mA
I
OZ
Transmitter Output Leakage Current
V
A
and
V
B
0.25V
q
1
100
A
R
OD
Transmitter Differential Mode Impedance
q
50
100
150
R
OC
Transmitter Common Mode Impedance
2V
V
CM
2V (Figure 7)
135
150
165
t
r
, t
f
Rise or Fall Time
(Figures 8, 13)
5
ns
t
PLH
Input to Output
(Figures 8, 13)
q
15
35
65
ns
t
PHL
Input to Output
(Figures 8, 13)
q
15
35
65
ns
t
Input to Output Difference,
t
PLH
t
PHL
(Figures 8, 13)
q
0
16
ns
t
SKEW
Output to Output Skew
(Figures 8, 13)
4
ns
V.35 Receiver
V
TH
Differential Receiver Input Threshold Voltage
2V
V
CM
2V (Figure 9)
q
0.2
0.2
V
V
TH
Receiver Input Hysteresis
2V
V
CM
2V (Figure 9)
q
15
40
mV
R
ID
Receiver Differential Mode Impedance
2V
V
CM
2V
q
90
103
110
R
IC
Receiver Common Mode Impedance
2V
V
CM
2V (Figure 10)
135
150
165
t
r
, t
f
Rise or Fall Time
C
L
= 50pF (Figures 4, 14)
15
ns
t
PLH
Input to Output
C
L
= 50pF (Figures 4, 14)
q
50
90
ns
t
PHL
Input to Output
C
L
= 50pF (Figures 4, 14)
q
50
90
ns
t
Input to Output Difference,
t
PLH
t
PHL
C
L
= 50pF (Figures 4, 14)
q
0
4
25
ns
V.28 Driver
V
O
Output Voltage
Open Circuit
q
10
V
R
L
= 3k (Figure 11)
q
5
8.5
V
I
SS
Short-Circuit Current
V
OUT
= GND
q
150
mA
R
OZ
Power-Off Resistance
2V < V
O
< 2V, Power Off
q
300
or No-Cable Mode
SR
Slew Rate
R
L
= 7k, C
L
= 0 (Figures 11, 15)
q
4
30
V/
s
t
PLH
Input to Output
R
L
= 3k, C
L
= 2500pF (Figures 11, 15)
q
1.5
2.5
s
t
PHL
Input to Output
R
L
= 3k, C
L
= 2500pF (Figures 11, 15)
q
1.5
2.5
s
5
LTC2846
sn2846 2846fs
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25
C. V
CC
= 5V, V
IN
= 3.3V, V
SHDN
= V
IN
, unless otherwise noted. (Notes 2, 3)
ELECTRICAL CHARACTERISTICS
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 V
CC
= 5V, V
IN
= 3.3V, C
VCC
= C
VIN
= 10
F,
C
VDD
= 1
F, C
VEE
= 3.3
F and T
A
= 25
C.
Note 4: The Boost Regulator is specified for V
IN
= 3V unless otherwise
noted.
Note 5: Current limit guaranteed by design and/or correlation to static test.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V.28 Receiver
V
THL
Input Low Threshold Voltage
(Figure 12)
q
0.8
V
V
TLH
Input High Threshold Voltage
(Figure 12)
q
2
V
V
TH
Receiver Input Hysteresis
(Figure 12)
q
0
0.05
0.3
V
R
IN
Receiver Input Impedance
15V
V
A
15V
q
3
5
7
k
t
r
, t
f
Rise or Fall Time
C
L
= 50pF (Figures 12, 16)
15
ns
t
PLH
Input to Output
C
L
= 50pF (Figures 12, 16)
q
60
300
ns
t
PHL
Input to Output
C
L
= 50pF (Figures 12, 16)
q
160
300
ns
Boost Switching Regulator (Note 4)
V
IN
Operating Voltage
3
3.3
3.6
V
V
FB
Feedback Voltage
q
1.230
1.255
1.280
V
I
FB
FB Pin Bias Current
V
FB
= 1.255V
q
120
360
nA
I
Q
Quiescent Current
V
SHDN
= 2.4V, Not Switching
4.2
6
mA
Quiescent Current in Shutdown
V
SHDN
= 0V, V
IN
= 3V
0.01
1
A
V
FB(LR)
Reference Line Regulation
3V
V
IN
3.6V
0.01
0.05
%/V
f
Switching Frequency
q
0.85
1.2
1.6
MHz
DC
MAX
Maximum Duty Cycle
q
82
90
%
I
LIM
Switch Current Limit
(Note 5)
1
1.2
2
A
V
SAT
Switch V
CESAT
I
SW
= 900mA
350
mV
I
LEAK
Switch Leakage Current
V
SW
= 5V
0.01
1
A
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
V.11 Mode I
CC
vs Data Rate
DATA RATE (kBd)
10
I
CC
(mA)
120
130
140
2846 G04
110
100
90
100
1000
150
160
170
10000
T
A
= 25
C
DATA RATE (kBd)
10
120
I
CC
(mA)
125
130
135
140
150
100
1000
2846 G05
10000
145
T
A
= 25
C
DATA RATE (kBd)
10
30
I
CC
(mA)
35
40
45
50
60
20
40
60
80 100
2846 G06
55
T
A
= 25
C
V.35 Mode I
CC
vs Data Rate
V.28 Mode I
CC
vs Data Rate
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