2859_2861.indd
LTC2859/LTC2861
1
285961f
20Mbps RS485 Transceivers
with Integrated Switchable
Termination
The LTC
2859 and LTC2861 are low power, 20Mbps
RS485/422 transceivers operating on 5V supplies. The
receiver includes a logic-selectable 120 termination,
one-eighth unit load supporting up to 256 nodes per bus,
and a failsafe feature that guarantees a high output state
under conditions of fl oating or shorted inputs.
The driver features a logic-selectable low-EMI 250kbps
operating mode, and maintains a high output impedance
over the entire common mode range when disabled or
when the supply is removed. Excessive power dissipation
caused by bus contention or a fault is prevented by current
limiting all outputs and by a thermal shutdown.
Enhanced ESD protection allows the LTC2859 and LTC2861
to withstand 15kV (human body model) on the transceiver
interface pins without latchup or damage.
Low Power RS485/RS422 Transceiver
Level Translator
Backplane Transceiver
Integrated, Logic-Selectable 120 Termination
Resistor
20Mbps Max Data Rate
No Damage or Latchup to ESD: 15kV HBM
High Input Impedance Supports 256 Nodes
250kbps Low-EMI Mode
Guaranteed Failsafe Receiver Operation Over the
Entire Common Mode Range
Current Limited Drivers and Thermal Shutdown
Delayed Micropower Shutdown (5A Max)
Power Up/Down Glitch-Free Driver Outputs
Low Operating Current (900A Max in Receive
Mode)
Meets All TIA/EIA-485-A Specifi cations
Available in 10-Pin 3mm 3mm DFN, 12-Pin
4mm 3mm DFN and 16-Pin SSOP Packages
LTC2859 at 20Mbps
APPLICATIO S
U
FEATURES
DESCRIPTIO
U
TYPICAL APPLICATIO
U
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
PART NUMBER
DUPLEX
PACKAGE
LTC2859
HALF
DFN-10
LTC2861
FULL
SSOP-16, DFN-12
PRODUCT SELECTIO GUIDE
U
RE
TE
RO
DE
DI
SLO
R
D
2859/61 TA01
LTC2859
120
RE
RO
TE
DE
DI
SLO
R
D
LTC2859
120
RE
RO
TE DE
DI
SLO
R
D
LTC2859
120
2V/DIV
20nS/DIV
Y-Z
DI
Y
Z
LTC2859/LTC2861
2
285961f
Supply Voltage (V
CC
) ................................... 0.3V to 7V
Logic Input Voltages (RE, DE, DI, TE, SLO) ... 0.3V to 7V
Interface I/O:
A, B, Y, Z ...................................... (V
CC
15V) to +15V
(A-B) or (B-A) with Terminator Enabled ..................6V
Receiver Output Voltage (RO) ........ 0.3V to (V
CC
+0.3V)
(Note 1)
ABSOLUTE AXI U
RATI GS
W
W
W
U
Operating Temperature (Note 4)
LTC2859C, LTC2861C .............................. 0C to 70C
LTC2859I, LTC2861I ............................ 40C to 85C
Storage Temperature Range ................... 65C to 125C
Lead Temperature (Soldering, 10 sec)
GN
Package
...................................................... 300C
PACKAGE/ORDER I FOR ATIO
U
U
W
TOP VIEW
DD PACKAGE
10-LEAD (3mm
3mm) PLASTIC DFN
10
9
6
7
8
4
5
3
2
1
V
CC
B
A
SLO
GND
RO
RE
DE
DI
TE
11
GND
EXPOSED PAD (PIN 11) PCB GND CONNECTION
T
JMAX
= 125C,
JA
= 43C/W
JC
= 2.96C/W
12
11
10
9
8
7
1
2
3
4
5
6
V
CC
A
B
Z
Y
SLO
RO
RE
DE
DI
TE
GND
TOP VIEW
DE PACKAGE
12-LEAD (4mm
3mm) PLASTIC DFN
13
GND
EXPOSED PAD (PIN 13) PCB GND CONNECTION
T
JMAX
= 125C,
JA
= 44C/W
JC
= 43C/W
RO
RE
DE
DI
TE
GND
NC
NC
V
CC
B
Z
SLO
NC
NC
A
Y
GN PACKAGE
16-LEAD (NARROW 0.150) PLASTIC SSOP
1
2
3
4
5
6
7
8
TOP VIEW
16
15
14
13
12
11
10
9
T
JMAX
= 125C,
JA
= 110C/W
JC
= 40C/W
ORDER PART
NUMBER
DD PART*
MARKING
ORDER PART
NUMBER
DE PART*
MARKING
ORDER PART
NUMBER
GN PART
MARKING
LTC2859CDD
LTC2859IDD
LBNX
LBNX
LTC2861CDE
LTC2861IDE
2861
2861
LTC2861CGN
LTC2861IGN
2861
2861I
Order Options Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking:
http://www.linear.com/leadfree/
Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi ed by a label on the shipping container.
LTC2859/LTC2861
3
285961f
The
denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T
A
= 25C, V
CC
= 5V unless otherwise noted (Note 2).
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Driver
|V
OD
|
Differential Driver Output Voltage
R = , I
O
= 0mA, V
CC
= 4.5V (Figure 1)
R = 27 (RS485), V
CC
= 4.5V (Figure 1)
R = 50 (RS422), V
CC
= 4.5V (Figure 1)
1.5
2.0
V
CC
V
CC
V
CC
V
V
V
|V
OD
|
Change in Magnitude of Driver
Differential Output Voltage for
Complementary Output States
R = 27 or R = 50 (Figure 1)
0.2
V
V
OC
Driver Common Mode Output Voltage
R = 27 or R = 50 (Figure 1)
3.0
V
|V
OC
|
Change in Magnitude of Driver
Common Mode Output Voltage for
Complementary Output States
R = 27 or R = 50 (Figure 1)
0.2
V
I
OZD
Driver Three-State (High Impedance)
Output Current on Y and Z
DE = OV, V
O
= 7V, +12V
(LTC2861 Only)
10
A
I
OSD
Maximum Driver Short-Circuit Current
7V (Y or Z) 12 (Figure 2)
120
250
mA
Receiver
I
IN2
Receiver Input Current (A, B)
DE = TE = 0V, V
CC
= 0V or 5V, V
A
or V
B
=
12V, Other at 0V
125
A
DE = TE = 0V, V
CC
= 0V or 5V, V
A
or V
B
=
7V, Other at 0V
100
A
V
TH
Receiver Differential Input Threshold
Voltage
7V V
CM
12
0.2
V
V
TH
Receiver Input Hysteresis
V
CM
= 0V
25
mV
V
OH
Receiver Output HIGH Voltage
I
0
= 4mA, V
ID
= 200mV, V
CC
= 4.5V
2.4
V
V
OL
Receiver Output LOW Voltage
I
0
= 4mA, V
ID
= 200mV, V
CC
= 4.5V
0.4
V
I
OZR
Receiver Three-State (High Impedance)
Output Current on RO
RE = 5V, 0V V
O
V
CC
1
A
R
IN
Receiver Input Resistance
RE = 5V or 0V, DE = TE = 0V
7V V
A
= V
B
12V
96
125
k
R
TERM
Receiver Input Terminating Resistor
TE = 5V, V
AB
= 2V, V
B
= 7, 0, 10V
(Figure 7)
108
120
156
Logic
V
IH
Logic Input High Voltage
DE, DI, RE, TE, SLO, V
CC
= 4.5V
2
V
V
IL
Logic Input Low Voltage
DE, DI, RE, TE, SLO, V
CC
= 4.5V
0.8
V
I
IN1
Logic Input Current
DE, DI, RE, TE, SLO
0
10
A
Supplies
I
SHDN
Supply Current in Shutdown Mode
DE = 0V, RE = V
CC
, TE = 0V
0
5
A
I
CCR
Supply Current in Receive Mode
No Load, DE = 0V, RE = 0V, TE = 0V
540
900
A
I
CCT
Supply Current in Transmit Mode
No Load, DE = V
CC
, RE = V
CC
, SLO = V
CC
,
TE = 0V
630
1000
A
I
CCTS
Supply Current in Transmit SLO Mode
No Load, DE = V
CC
, RE = V
CC
, SLO = 0V,
TE = 0V
670
1100
A
I
CCL
Supply Current in Loopback Mode (Both
Driver and Receiver Enabled)
No Load, DE = V
CC
, RE = 0V, SLO = V
CC
,
TE = 0V
660
1100
A
I
CCRT
Supply Current in Termination Mode
DE = 0V, RE = V
CC
, TE = V
CC
, SLO = V
CC
640
1180
A
ELECTRICAL CHARACTERISTICS
LTC2859/LTC2861
4
285961f
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: All currents into device pins are positive; all currents out of device
pins are negative. All voltages are referenced to device ground unless
otherwise specifi ed.
Note 3: Maximum data rate is guaranteed by other measured parameters
and is not tested directly.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Driver in Normal Mode (SLO HIGH)
f
MAX
Maximum Data Rate
Note 3
20
Mbps
t
PLHD
, t
PHLD
Driver Input to Output
R
DIFF
= 54, C
L
= 100pF (Figure 3)
10
50
ns
t
PD
Driver Input to Output Difference
|t
PLHD
-t
PHLD
|
R
DIFF
= 54, C
L
= 100pF (Figure 3)
1
6
ns
t
SKEWD
Driver Output Y to Output Z
R
DIFF
= 54, C
L
= 100pF (Figure 3)
1
6
ns
t
RD
, t
FD
Driver Rise or Fall Time
R
DIFF
= 54, C
L
= 100pF (Figure 3)
4
12.5
ns
t
ZLD
, t
ZHD
, t
LZD
,
t
HZD
Driver Enable or Disable Time
R
L
= 500, C
L
= 50pF, RE = 0 (Figure 4)
70
ns
t
ZHSD
, t
ZLSD
Driver Enable from Shutdown
R
L
= 500, C
L
= 50pF, RE = V
CC
(Figure 4)
8
s
t
SHDN
Time to Shutdown
(DE = , RE = V
CC
) or (DE = 0, RE )
(Figure 4)
100
ns
Driver in SLO Mode (SLO LOW)
f
MAXS
Maximum Data Rate
Note 3
250
kbps
t
PLHDS,
t
PHLDS
Driver Input to Output
R
DIFF
= 54, C
L
= 100pF (Figure 3)
0.95
1.5
s
t
PDS
Driver Input to Output Difference
|t
PLHR
-t
PHLR
|
R
DIFF
= 54, C
L
= 100pF (Figure 3)
50
500
ns
t
SKEWDS
Driver Output A to Output B
R
DIFF
= 54, C
L
= 100pF (Figure 3)
200
500
ns
t
RDS,
t
FDS
Driver Rise or Fall Time
R
DIFF
= 54, C
L
= 100pF (Figure 3)
0.9
1.5
s
t
ZHDS,
t
ZLDS
Driver Enable Time
R
L
= 500, C
L
= 50pF, RE = 0 (Figure 4)
300
ns
t
LZDS,
t
HZDS
Driver Disable Time
R
L
= 500, C
L
= 50pF, RE = 0 (Figure 4)
70
ns
t
ZHSDS,
t
ZLSDS
Driver Enable from Shutdown
R
L
= 500, C
L
= 50pF, RE = V
CC
(Figure 4)
8
s
t
SHDNS
Time to Shutdown
(DE = 0, RE = ) or (DE = , RE = V
CC
)
(Figure 4)
500
ns
Receiver
t
PLHR
, t
PHLR
Receiver Input to Output
C
L
= 15pF, V
CM
= 1.5V, |V
AB
| = 1.5V, t
R
and
t
F
< 4ns (Figure 5)
50
70
ns
t
SKEWR
Differential Receiver Skew
|t
PLHR
-t
PHLR
|
C
L
= 15pF (Figure 5)
1
6
ns
t
RR
, t
FR
Receiver Output Rise or Fall Time
C
L
= 15pF (Figure 5)
3
12.5
ns
t
ZLR
, t
ZHR
, t
LZR
,
t
HZR
Receiver Enable/Disable
R
L
= 1k, C
L
=15pF, DE = V
CC
(Figure 6)
DI = 0 or V
CC
50
ns
t
ZHSR
, t
ZLSR
Receiver Enable from Shutdown
R
L
= 1k, C
L
= 15pF, DE = 0V (Figure 6)
DI = 0 or V
CC
8
s
t
RTEN
, t
RTZ
Termination Enable or Disable Time
V
B
= 0V, V
AB
= 2V, RE = V
CC
, DE = 0V
(Figure 7)
100
s
The
denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T
A
= 25C, V
CC
= 5V, T
E
= 0 unless otherwise noted (Note 2).
SWITCHI G CHARACTERISTICS
U
Note 4: This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 125C when overtemperature protection is active.
Continuous operation above the specifi ed maximum operating junction
temperature may result in device degradation or failure.
LTC2859/LTC2861
5
285961f
1/2 V
CC
1/2 V
CC
1/2 V
CC
t
ZLD
,
t
ZLDS
,
t
ZLSD
,
t
ZLSDS
t
ZHD
,
t
ZHDS
,
t
ZHSD
,
t
ZHSDS
t
LZD
,
t
LZDS
0.5V
0.5V
t
HZD
,
t
HZDS,
t
SHDN,
t
SHDNS
V
O
OV
V
CC
V
CC
GND
or
V
CC
V
CC
or
GND
R
L
R
L
C
L
C
L
Z
Y
DE
V
CC
or
GND
V
OL
V
OH
Y or Z
DE
Z or Y
OV
2859/61 F04
DI
DRIVER
TEST CIRCUITS
Figure 1. Driver DC Characteristics
Figure 2. Driver Output Short Circuit Current
Figure 4. Driver Enable and Disable Timing Measurement
GND
or
V
CC
+
V
OC
R
R
Z
Y
GND
or
V
CC
DI
DRIVER
+
V
OD
7V to +12V
Z
Y
DI
DRIVER
I
OSD
+
2859/61 F01-2
1/2 V
O
t
SKEWD
, t
SKEWDS
t
PLHD
,
t
PLHDS
t
PHLD
,
t
PHLDS
t
RD
,
t
RDS
t
FD
,
t
FDS
V
O
OV
V
CC
R
DIFF
C
L
C
L
Z
Y
Y, Z
DI
(Y-Z)
2859/61 F03
DRIVER
0
0
90%
10%
90%
10%
DI
Figure 3. Driver Timing Measurement
PDF 
ZIP