LTC2850/LTC2851/LTC2852
1
285012fd
Typical applicaTion
FeaTures
applicaTions
DescripTion
3.3V 20Mbps RS485/RS422
Transceivers
The LTC
®
2850, LTC2851 and LTC2852 are low power,
20Mbps RS485/RS422 transceivers operating on 3.3V
supplies. The receiver has a one-eighth unit load supporting
up to 256 nodes per bus (C, I-grade), and a failsafe feature
that guarantees a high output state under conditions of
floating or shorted inputs.
The driver 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 thermal shutdown.
Enhanced ESD protection allows these parts to withstand
up to ±15kV (human body model) on the transceiver
interface pins without latchup or damage.
LTC2850 at 20Mbps Into 54Ω
n 3.3V Supply Voltage
n 20Mbps Maximum Data Rate
n No Damage or Latchup Up to ±15kV HBM
n High Input Impedance Supports 256 Nodes
(C, I‑Grade)
n Operation Up to 125°C (H‑Grade)
n Guaranteed Failsafe Receiver Operation Over the
Entire Common Mode Range
n Current Limited Drivers and Thermal Shutdown
n Delayed Micropower Shutdown: 5µA Maximum
(C, I-Grade)
n Power Up/Down Glitch-Free Driver Outputs
n Low Operating Current: 370µA Typical in
Receive Mode
n Compatible with TIA/EIA-485-A Specifications
n Available in 8-Pin and 10-Pin 3mm × 3mm DFN,
8-Pin and 10-Pin MSOP, and 8-Pin and 14-Pin
SO Packages
n Low Power RS485/RS422 Transceiver
n Level Translator
n Backplane Transceiver
VCC1
GND1
R
RO1
RE1
DE1
DI1 D
RT
LTC2850
LTC2850
RT
285012 TA01a
VCC2
GND2
R
RO2
RE2
DE2
DI2 D
PART NUMBER DUPLEX PACKAGE
LTC2850 Half SO-8, MSOP-8, DFN-8
LTC2851 Full SO-8, MSOP-8, DFN-8
LTC2852 Full SO-14, MSOP-10, DFN-10
20ns/DIV
2V/DIV
285012 TA01b
DI
A
B
A-B
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
LTC2850/LTC2851/LTC2852
2
285012fd
absoluTe MaxiMuM raTings
Supply Voltage (VCC) ................................... –0.3V to 7V
Logic Input Voltages (RE, DE, DI) ................ –0.3V to 7V
Interface I/O:
A, B, Y, Z .......................................(VCC – 15V) to 15V
Receiver Output Voltage (RO) .......–0.3V to (VCC + 0.3V)
(Note 1)
pin conFiguraTion
Operating Temperature (Note 4)
LTC285xC ................................................ 0°C to 70°C
LTC285xI .............................................–40°C to 85°C
LTC285xH .......................................... –40°C to 125°C
LTC285xMP ....................................... –55°C to 125°C
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
MSOP ............................................................... 300°C
LTC2850
TOP VIEW
DD PACKAGE
8-LEAD (3mm × 3mm) PLASTIC DFN
5
96
7
8
4
3
2
1RO
RE
DE
DI
VCC
B
A
GND
TJMAX = 150°C, θJA = 43°C/W, θJC = 3°C/W
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
1
2
3
4
RO
RE
DE
DI
8
7
6
5
VCC
B
A
GND
TOP VIEW
MS8 PACKAGE
8-LEAD PLASTIC MSOP
TJMAX = 150°C, θJA = 200°C/W, θJC = 40°C/W
1
2
3
4
8
7
6
5
TOP VIEW
VCC
B
A
GND
RO
RE
DE
DI
S8 PACKAGE
8-LEAD PLASTIC SO
TJMAX = 150°C, θJA = 150°C/W, θJC = 39°C/W
LTC2851
TOP VIEW
DD PACKAGE
8-LEAD (3mm × 3mm) PLASTIC DFN
5
6
7
8
4
3
2
1VCC
RO
DI
GND
A
B
Z
Y
9
TJMAX = 150°C, θJA = 43°C/W, θJC = 3°C/W
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
1
2
3
4
VCC
RO
DI
GND
8
7
6
5
A
B
Z
Y
TOP VIEW
MS8 PACKAGE
8-LEAD PLASTIC MSOP
TJMAX = 150°C, θJA = 200°C/W, θJC = 40°C/W
1
2
3
4
8
7
6
5
TOP VIEW
A
B
Z
Y
VCC
RO
DI
GND
S8 PACKAGE
8-LEAD PLASTIC SO
TJMAX = 150°C, θJA = 150°C/W, θJC = 39°C/W
LTC2852
TJMAX = 150°C, θJA = 43°C/W, θJC = 3°C/W
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
1
2
3
4
5
RO
RE
DE
DI
GND
10
9
8
7
6
VCC
A
B
Z
Y
TOP VIEW
MS PACKAGE
10-LEAD PLASTIC MSOP
TJMAX = 150°C, θJA = 120°C/W, θJC = 45°C/W
TOP VIEW
S PACKAGE
14-LEAD PLASTIC SO
1
2
3
4
5
6
7
14
13
12
11
10
9
8
NC
RO
RE
DE
DI
GND
GND
VCC
NC
A
B
Z
Y
NC
TJMAX = 150°C, θJA = 88°C/W, θJC = 37°C/W
LTC2850/LTC2851/LTC2852
3
285012fd
proDucT selecTion guiDe
orDer inForMaTion
LTC2850 C DD #TR PBF
LEAD FREE DESIGNATOR
PBF = Lead Free
TAPE AND REEL
TR = Tape and Reel
PACKAGE TYPE
DD = 8-Lead Plastic DFN
DD = 10-Lead Plastic DFN
MS8 = 8-Lead Plastic MSOP
MS = 10-Lead Plastic MSOP
S8 = 8-Lead Plastic SO
S = 14-Lead Plastic SO
TEMPERATURE GRADE
C = Commercial Temperature Range (0°C to 70°C)
I = Industrial Temperature Range (–40°C to 85°C)
H = Automotive Temperature Range (–40°C to 125°C)
MP = Military Temperature Range (–55°C to 125°C)
PRODUCT PART NUMBER
LTC2850 = Half Duplex, with Enables
LTC2851 = Full Duplex, No Enables
LTC2852 = Full Duplex, with Enables
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
PART NUMBER PART MARKING DUPLEX LOW POWER SHUTDOWN MODE PACKAGE
LTC2850
2850/I/H, LTCQD, LCQC Half
Yes SO-8, MSOP-8, DFN-8
LTC2851
2851/I/H, LTCWF, LCWD
Full No SO-8, MSOP-8, DFN-8
LTC2852
2852CS/IS/HS, LTCRX, LCRY
Full Yes SO-14, MSOP-10, DFN-10
LTC2850MP
2850MP, LTFYD, LFYC Half
Yes SO-8, MSOP-8, DFN-8
LTC2851MP
2851MP, LTFYG, LFYF
Full No SO-8, MSOP-8, DFN-8
LTC2852MP
2852MPS, LTFYH, LFYJ
Full Yes SO-14, MSOP-10, DFN-10
LTC2850/LTC2851/LTC2852
4
285012fd
elecTrical characTerisTics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 3.3V, unless otherwise noted. (Note 2)
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Driver
|VOD| Differential Driver Output Voltage R = ∞, VCC = 3V (Figure 1)
R = 27Ω, VCC = 3V (Figure 1)
R = 50Ω, VCC = 3.13V (Figure 1)
l
l
l
1.5
2
VCC
VCC
VCC
V
V
V
Δ|VOD|Difference in Magnitude of Driver Differential
Output Voltage for Complementary Output
States
R = 27Ω or 50Ω (Figure 1) l0.2 V
VOC Driver Common Mode Output Voltage R = 27Ω or 50Ω (Figure 1) l3 V
Δ|VOC|Difference in Magnitude of Driver Common
Mode Output Voltage for Complementary
Output States
R = 27Ω or 50Ω (Figure 1) l0.2 V
IOZD Driver Three-State (High Impedance) Output
Current on Y and Z
DE = 0V, (Y or Z) = –7V, 12V (LTC2852) l±10 µA
IOSD Maximum Driver Short-Circuit Current –7V ≤ (Y or Z) ≤ 12V (Figure 2)
l
–250
±180 ±250
300
mA
mA
Receiver
IIN Receiver Input Current (A, B) DE = TE = 0V, VCC = 0V or 3.3V, VIN = 12V
(Figure 3) (C, I-Grade)
DE = TE = 0V, VCC = 0V or 3.3V, VIN = –7V,
(Figure 3) (C, I-Grade)
l
l
–100
125 µA
µA
DE = TE = 0V, VCC = 0V or 3.3V, VIN = 12V
(Figure 3) (H-Grade)
DE = TE = 0V, VCC = 0V or 3.3V, VIN = –7V,
(Figure 3) (H-Grade)
l
l
–145
250 µA
µA
RIN Receiver Input Resistance RE = VCC or 0V, DE = TE = 0V,
VIN = –7V, –3V, 3V, 7V, 12V (Figure 3)
(C, I-Grade)
l96 125 kΩ
RE = VCC or 0V, DE = TE = 0V,
VIN = –7V, –3V, 3V, 7V, 12V (Figure 3)
(H-Grade)
l48 125 kΩ
VTH Receiver Differential Input Threshold Voltage –7V ≤ B ≤ 12V l±0.2 V
ΔVTH Receiver Input Hysteresis B = 0V 25 mV
VOH Receiver Output High Voltage I(RO) = –4mA, A-B = 200mV, VCC = 3V l2.4 V
VOL Receiver Output Low Voltage I(RO) = 4mA, A-B = –200mV, VCC = 3V l0.4 V
IOZR Receiver Three-State (High Impedance)
Output Current on RO
RE = VCC, 0V ≤ RO ≤ VCC (LTC2850, LTC2852) l±1 µA
IOSR Receiver Short-Circuit Current 0V ≤ RO ≤ VCC l±85 mA
Logic
VIH Logic Input High Voltage VCC = 3.6V l2 V
VIL Logic Input Low Voltage VCC = 3V l0.8 V
IINL Logic Input Current l0 ±10 µA
LTC2850/LTC2851/LTC2852
5
285012fd
swiTching characTerisTics
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime. High temperatures degrade operating lifetimes.
Operating lifetime is derated at temperatures greater than 105°C.
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 specified.
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 3.3V, unless otherwise noted. (Note 2)
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Driver
fMAX Maximum Data Rate (Note 3) l20 Mbps
tPLHD, tPHLD Driver Input to Output RDIFF = 54Ω, CL = 100pF (Figure 4) l10 50 ns
ΔtPD Driver Input to Output Difference
|tPLHD – tPHLD|
RDIFF = 54Ω, CL = 100pF (Figure 4) l1 6 ns
tSKEWD Driver Output Y to Output Z RDIFF = 54Ω, CL = 100pF (Figure 4) l1 ±6 ns
tRD, tFD Driver Rise or Fall Time RDIFF = 54Ω, CL = 100pF (Figure 4) l4 12.5 ns
tZLD, tZHD,
tLZD, tHZD
Driver Enable or Disable Time RL = 500Ω, CL = 50pF, RE = 0V (Figure 5)
(LTC2850, LTC2852)
l70 ns
tZHSD, tZLSD Driver Enable from Shutdown RL = 500Ω, CL = 50pF, RE = VCC (Figure 5)
(LTC2850, LTC2852)
l8 µs
tSHDN Time to Shutdown RL = 500Ω, CL = 50pF, (DE = ↓, RE = VCC)
or (DE = 0V, RE = ↑) (Figure 5) (LTC2850,
LTC2852)
l100 ns
Receiver
tPLHR, tPHLR Receiver Input to Output CL = 15pF, VCM = 1.5V, |VAB| = 1.5V,
tR and tF < 4ns (Figure 6)
l50 70 ns
tSKEWR Differential Receiver Skew
|tPLHR – tPHLR|
CL = 15pF (Figure 6) l1 6 ns
tRR, tFR Receiver Output Rise or Fall Time CL = 15pF (Figure 6) l3 12.5 ns
tZLR, tZHR,
tLZR, tHZR
Receiver Enable/Disable RL =1k, CL =15pF, DE = VCC (Figure 7)
(LTC2850, LTC2852)
l50 ns
tZHSR, tZLSR Receiver Enable from Shutdown RL = 1k, CL = 15pF, DE = 0V (Figure 7)
(LTC2850, LTC2852)
l8 µs
Note 3: Maximum data rate is guaranteed by other measured parameters
and is not tested directly.
Note 4: This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions.
Overtemperature protection activates at a junction temperature exceeding
150°C. Continuous operation above the specified maximum operating
junction temperature may result in device degradation or failure.
elecTrical characTerisTics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 3.3V, unless otherwise noted. (Note 2)
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Supplies
ICCS Supply Current in Shutdown Mode DE = 0V, RE = VCC,
LTC2850, LTC2852 (C and I-Grade)
LTC2850, LTC2852 (H-Grade)
l
l
0
0
5
15
µA
µA
ICCR Supply Current in Receive Mode DE = 0V, RE = 0V (LTC2850, LTC2852) l370 900 µA
ICCT Supply Current in Transmit Mode No Load, DE = VCC, RE = VCC (LTC2850,
LTC2852)
l450 1000 µA
ICCTR Supply Current with Both Driver and
Receiver Enabled
No Load, DE = VCC, RE = 0V l450 1000 µA
LTC2850/LTC2851/LTC2852
6
285012fd
TesT circuiTs
–
+
DRIVER
DI
GND
OR
VCC
R
285012 F01
Y
Z
R
VOC
–
+
VOD
Figure 1. Driver DC Characteristics Figure 2. Driver Output Short‑Circuit Current
Figure 3. Receiver Input Current and Input Resistance
Figure 4. Driver Timing Measurement
DRIVER
DI
GND
OR
VCC
285012 F02
Y
Z
+
–
IOSD
–7V TO 12V
+
–RECEIVER
285012 F03
A OR B
VIN
IIN
B OR A
VIN
IIN
RIN =
DRIVER
DI RDIFF
CL
CL
285012 F04a
Y
Z
1/2 VO
90% 90%
0 0
10%
285012 F04b
10%
VO
VCC
Y, Z
DI
(Y-Z)
0V
tSKEWD
tPLHD
tRD tFD
tPHLD
LTC2850/LTC2851/LTC2852
7
285012fd
Figure 5. Driver Enable and Disable Timing Measurements
DRIVER
DI
VCC
OR
GND
GND
OR
VCC
VCC
OR
GND
RL
RL
CL
285012 F05a
Y
Z
DE
CL
tZLD,
tZLSD
tZHD,
tZHSD
tHZD,
tSHDN
tLZD
1/2 VCC
1/2 VCC
1/2 VCC
DE
Y OR Z
Z OR Y
VCC
VCC
VOL
VO
VOH
0V
0V
0.5V
0.5V
285012 F05b
Figure 6. Receiver Propagation Delay Measurements
TesT circuiTs
A
B
VCM
±VAB/2
±VAB/2
RO
CL
285012 F06a
RECEIVER
tPLHR tPHLR
90%
0
90%
10%
tR
90%
10%
tF
tSKEWR =
|
tPLHR – tPHLR
|
90%
1/2 VCC 1/2 VCC
tRR tFR
10%
285012 F06b
10%
VAB
VCC
VO
0
–VAB
RO
A-B
A
B
0V OR VCC
VCC OR 0V
RO
RE CL
DI = 0V OR VCC
RLVCC
OR
GND
285012 F07a
RECEIVER
tZLR,
tZLSR
tZHR,
tZHSR tHZR
tLZR
1/2 VCC
1/2 VCC
1/2 VCC
RE
RO
RO
VCC
VCC
VOL
VO
VOH
0V
0V
0.5V
0.5V
285012 F07b
Figure 7. Receiver Enable/Disable Time Measurements
LTC2850/LTC2851/LTC2852
8
285012fd
OUTPUT CURRENT (mA)
0
0
OUTPUT VOLTAGE (V)
2.0
3.0
3 4 5 6
285012 G07
3.5
2.5
1.0
1.5
0.5
1 2
SINK
SOURCE
TEMPERATURE (°C)
–40
35
PROP DELAY (ns)
55
65
0 40 80 120
285012 G08
70
60
40
45
50
–20 20 60 100
DATA RATE (Mbps)
0.1
0
SUPPLY CURRENT (mA)
30
50
1 100
285012 G09
60
40
10
20
10
CL = 100pF
RDIFF = 54Ω
RDIFF = 100Ω
RDIFF = ∞
TEMPERATURE (°C)
–40
80
OUTPUT SHORT-CIRCUIT CURRENT (mA)
120
140
0 40 80 120
285012 G04
150
130
90
100
110
–20 20 60 100
SINK
VOUT = 3.3V
SOURCE
VOUT = 0V
OUTPUT CURRENT (mA)
0
0
OUTPUT VOLTAGE (V)
2.0
3.0
30 40 50 70
285012 G05
3.5
2.5
1.0
1.5
0.5
10 20 60
VOH
VOL
TEMPERATURE (°C)
–40
–1
RECEIVER SKEW (ns)
0
1
0 40 80 120
285012 G01
2
–20 20 60 100
VAB = 1.5V
CL = 15pF
TEMPERATURE (°C)
–40
–1.5
DRIVER SKEW (ns)
0
1.0
0 40 80 120
285012 G02
1.5
0.5
–1.0
–0.5
–20 20 60 100
RDIFF = 54Ω
CL = 100pF
TEMPERATURE (°C)
–40
4
PROP DELAY (ns)
12
16
0 40 80 120
285012 G03
18
14
6
8
10
–20 20 60 100
RDIFF = 54Ω
CL = 100pF
Typical perForMance characTerisTics
Receiver Skew vs Temperature Driver Skew vs Temperature
Driver Propagation Delay
vs Temperature
Driver Output Short‑Circuit
Current vs Temperature
Driver Output Low/High Voltage
vs Output Current
Driver Differential Output Voltage
vs Temperature
Receiver Output Voltage vs
Output Current (Source and Sink)
Receiver Propagation Delay
vs Temperature Supply Current vs Data Rate
TEMPERATURE (°C)
–40
OUTPUT VOLTAGE (V)
0 40 80 120
285012 G06
–20 20 60 100
RDIFF = 54Ω
RDIFF = 100Ω
RDIFF = ∞
0
2.0
3.0
3.5
2.5
1.0
1.5
0.5
TA = 25°C. VCC = 3.3V, unless otherwise noted.
LTC2850/LTC2851/LTC2852
9
285012fd
FuncTion Tables
pin FuncTions
RO: Receiver Output. If the receiver output is enabled (RE
low) and A > B by 200mV, then RO will be high. If A < B
by 200mV, then RO will be low. If the receiver inputs are
open, shorted, or terminated without a valid signal, RO
will be high.
RE: Receiver Enable. A low enables the receiver. A high input
forces the receiver output into a high impedance state.
DE: Driver Enable. A high on DE enables the driver. A low
input will force the driver outputs into a high impedance.
If RE is high with DE low, the part will enter a low power
shutdown state.
DI: Driver Input. If the driver outputs are enabled (DE
high), then a low on DI forces the driver positive output
low and negative output high. A high on DI, with the driver
outputs enabled, forces the driver positive output high and
negative output low.
GND: Ground.
Y: Noninverting Driver Output for LTC2851 and LTC2852.
High impedance when driver disabled or unpowered.
Z: Inverting Driver Output for LTC2851 and LTC2852. High
impedance when driver disabled or unpowered.
A: Noninverting Receiver Input (and Noninverting Driver
Output for LTC2850). Impedance is >96kΩ in receive
mode or unpowered.
B: Inverting Receiver Input (and Inverting Driver Output
for LTC2850). Impedance is >96kΩ in receive mode or
unpowered.
VCC: Positive Supply. 3V < VCC < 3.6V. Bypass with 0.1µF
ceramic capacitor.
Exposed Pad: Ground. The exposed pads on the DFN
packages must be soldered to ground.
LTC2850
Logic Inputs Mode A, B RO
DE RE
0 0 Receive RIN Driven
0 1 Shutdown RIN Hi-Z
1 0 Transceive Driven Driven
1 1 Transmit Driven Hi-Z
LTC2852
Logic Inputs Mode A, B Y, Z RO
DE RE
0 0 Receive RIN Hi-Z Driven
0 1 Shutdown RIN Hi-Z Hi-Z
1 0 Transceive RIN Driven Driven
1 1 Transmit RIN Driven Hi-Z
LTC2850/LTC2851/LTC2852
10
285012fd
block DiagraM
LTC2850 LTC2851
LTC2852
SLEEP/SHUTDOWN
LOGIC AND DELAY
RECEIVER
DRIVER
RO
RE
DE
DI
A
(15kV)
VCC
GND
B
(15kV)
285012 BDa
RECEIVER
DRIVER
RO
DI
285012 BDb
A
(15kV)
Z
(15kV)
Y
(15kV)
B
(15kV)
VCC
GND
SLEEP/SHUTDOWN
LOGIC AND DELAY
RECEIVER
DRIVER
RO
RE
DE
DI
285012 BDc
A
(15kV)
Z
(15kV)
Y
(15kV)
B
(15kV)
VCC
GND
LTC2850/LTC2851/LTC2852
11
285012fd
applicaTions inForMaTion
Driver
The driver provides full RS485/RS422 compatibility. When
enabled, if DI is high, Y-Z is positive for the full-duplex
devices (LTC2851, LTC2852) and A-B is positive for the
half-duplex device (LTC2850).
When the driver is disabled, both outputs are high im-
pedance. For the full-duplex devices, the leakage on the
driver output pins is guaranteed to be less than 10µA
over the entire common mode range of –7V to 12V. On
the half-duplex LTC2850, the impedance is dominated by
the receiver input resistance, RIN.
Driver Overvoltage and Overcurrent Protection
The driver outputs are protected from short-circuits
to any voltage within the Absolute Maximum range of
(VCC – 15V) to 15V. The typical peak current in this condi-
tion does not exceed 180mA.
If a high driver output is shorted to a voltage just above
VCC, a reverse current will flow into the supply. When
this voltage exceeds VCC by about 1.4V, the reverse
current turns off. Preventing the driver from turning off
with outputs shorted to output voltages just above VCC
keeps the driver active even for receiver loads that have
a positive common mode with respect to the driver—
a valid condition.
The worst-case peak reverse short-circuit current can
be as high as 300mA in extreme cold conditions. If this
current can not be absorbed by the supply, a 3.6V Zener
diode can be added in parallel with the supply to sink this
current.
All devices also feature thermal shutdown protection that
disables the driver and receiver in case of excessive power
dissipation (see Note 4 in the Electrical Characteristics
section).
Receiver and Failsafe
With the receiver enabled, when the absolute value of
the differential voltage between the A and B pins is
greater than 200mV, the state of RO will reflect the polar-
ity of (A-B)
These parts have a failsafe feature that guarantees the
receiver output to be in a logic-high state when the
inputs are either shorted, left open, or terminated but
not driven. This failsafe feature is guaranteed to work
for inputs spanning the entire common mode range of
–7V to 12V.
The receiver output is internally driven high (to VCC) or
low (to ground) with no external pull-up needed. When
the receiver is disabled the RO pin becomes Hi-Z with
leakage of less than ±1µA for voltages within the supply
range.
Receiver Input Resistance
The receiver input resistance from A or B to ground is
guaranteed to be greater than 96k (C, I-grade). This is 8x
higher than the requirements for the RS485 standard and
thus this receiver represents a one-eighth unit load. This,
in turn, means that 8x the standard number of receivers,
or 256 total, can be connected to a line without loading
it beyond what is specified in the RS485 standard. The
receiver input resistance from A or B to ground on high
temperature H-grade parts is greater than 48k providing
a one-quarter unit load. The high input resistance of the
receiver is maintained whether it is enabled or disabled,
powered or unpowered.
Supply Current
The unloaded static supply currents in these devices are
very low, typically under 500µA for all modes of opera-
tion. In applications with resistively terminated cables,
the supply current is dominated by the driver load. For
example, when using two 120Ω terminators with a dif-
ferential driver output voltage of 2V, the DC load current
is 33mA, which is sourced by the positive voltage supply.
Power supply current increases with toggling data due to
capacitive loading and this term can increase significantly
at high data rates. Figure 13 shows supply current vs
data rate for two different capacitive loads for the circuit
configuration of Figure 4.
LTC2850/LTC2851/LTC2852
12
285012fd
applicaTions inForMaTion
High Speed Considerations
A ground plane layout is recommended. A 0.1µF bypass
capacitor less than one-quarter inch away from the VCC pin
is also recommended. The PC board traces connected to
signals A/B and Z/Y should be symmetrical and as short
as possible to maintain good differential signal integrity.
To minimize capacitive effects, the differential signals
should be separated by more than the width of a trace
and should not be routed on top of each other if they are
on different signal planes.
Care should be taken to route outputs away from any
sensitive inputs to reduce feedback effects that might
cause noise, jitter, or even oscillations. For example, in
the full-duplex devices, DI and A/B should not be routed
near the driver or receiver outputs.
The logic inputs have 150mV of hysteresis to provide noise
immunity. Fast edges on the outputs can cause glitches in
the ground and power supplies which are exacerbated by
capacitive loading. If a logic input is held near its threshold
(typically 1.5V), a noise glitch from a driver transition may
exceed the hysteresis levels on the logic and data input
285012 F14
DATA RATE (bps)
CABLE LENGTH (FT)
10k 1M 10M100k 100M
100
1k
10
10k
RS485/RS422
MAX DATA RATE
LTC2850/
LTC2851/LTC2852
MAX DATA RATE
Figure 14. Cable Length vs Data Rate
(RS485/RS422 Standard Shown in Solid Line)
pins causing an unintended state change. This can be
avoided by maintaining normal logic levels on the pins
and by slewing inputs through their thresholds by faster
than 1V/µs when transitioning. Good supply decoupling
and proper driver termination also reduce glitches caused
by driver transitions.
Cable Length vs Data Rate
For a given data rate, the maximum transmission distance
is bounded by the cable properties. A curve of cable length
vs data rate compliant with the RS485/RS422 standards
is shown in Figure 14. Three regions of this curve reflect
different performance limiting factors in data transmis-
sion. In the flat region of the curve, maximum distance
is determined by resistive losses in the cable. The down-
ward sloping region represents limits in distance and
data rate due to AC losses in the cable. The solid vertical
line represents the specified maximum data rate in the
RS485/RS422 standards. The dashed lines at 20Mbps
show the maximum data rates of the LTC2850, LTC2851
and LTC2852.
Figure 13. Supply Current vs Data Rate
DATA RATE (Mbps)
0.1
20
SUPPLY CURRENT (mA)
60
70
80
1 10 100
285012 F13
50
40
30
RDIFF = 54Ω
CL = 1000pF
CL = 100pF
LTC2850/LTC2851/LTC2852
13
285012fd
Typical applicaTions
RD
LTC2850
RD
LTC2850
D
TE = 3.3V
R
D
TE = 3.3V
285012 TA03
R
LTC2854LTC2854
D
VCC
I1
I2
100k
B
A
“A”
“B”
RO
DI
LTC2850 285012 TA02
R
Failsafe “0” Application (Idle State = Logic “0”)
Multinode Network with End Termination Using the LTC2850 and LTC2854
LTC2850/LTC2851/LTC2852
14
285012fd
package DescripTion
3.00 p0.10
(4 SIDES)
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2).
CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm 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
0.40 p 0.10
BOTTOM VIEW—EXPOSED PAD
1.65 p 0.10
(2 SIDES)
0.75 p0.05
R = 0.125
TYP
2.38 p0.10
(2 SIDES)
15
106
PIN 1
TOP MARK
(SEE NOTE 6)
0.200 REF
0.00 – 0.05
(DD) DFN REV C 0310
0.25 p 0.05
2.38 p0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
1.65 p0.05
(2 SIDES)
2.15 p0.05
0.50
BSC
0.70 p0.05
3.55 p0.05
PACKAGE
OUTLINE
0.25 p 0.05
0.50 BSC
PIN 1 NOTCH
R = 0.20 OR
0.35 s 45o
CHAMFER
3.00 p0.10
(4 SIDES)
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-1)
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION
ON TOP AND BOTTOM OF PACKAGE
0.40 p 0.10
BOTTOM VIEW—EXPOSED PAD
1.65 p 0.10
(2 SIDES)
0.75 p0.05
R = 0.125
TYP
2.38 p0.10
14
85
PIN 1
TOP MARK
(NOTE 6)
0.200 REF
0.00 – 0.05
(DD8) DFN 0509 REV C
0.25 p 0.05
2.38 p0.05
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
1.65 p0.05
(2 SIDES)
2.10 p0.05
0.50
BSC
0.70 p0.05
3.5 p0.05
PACKAGE
OUTLINE
0.25 p 0.05
0.50 BSC
DD Package
8‑Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1698 Rev C)
DD Package
10‑Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1699 Rev B)
LTC2850/LTC2851/LTC2852
15
285012fd
package DescripTion
MS8 Package
8‑Lead Plastic MSOP
(Reference LTC DWG # 05-08-1660 Rev F)
MS Package
10‑Lead Plastic MSOP
(Reference LTC DWG # 05-08-1661 Rev E)
MSOP (MS8) 0307 REV F
0.53 p 0.152
(.021 p .006)
SEATING
PLANE
NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
0.18
(.007)
0.254
(.010)
1.10
(.043)
MAX
0.22 – 0.38
(.009 – .015)
TYP
0.1016 p 0.0508
(.004 p .002)
0.86
(.034)
REF
0.65
(.0256)
BSC
0o – 6o TYP
DETAIL “A”
DETAIL “A”
GAUGE PLANE
1 2 34
4.90 p 0.152
(.193 p .006)
8765
3.00 p 0.102
(.118 p .004)
(NOTE 3)
3.00 p 0.102
(.118 p .004)
(NOTE 4)
0.52
(.0205)
REF
5.23
(.206)
MIN
3.20 – 3.45
(.126 – .136)
0.889 p 0.127
(.035 p .005)
RECOMMENDED SOLDER PAD LAYOUT
0.42 p 0.038
(.0165 p .0015)
TYP
0.65
(.0256)
BSC
MSOP (MS) 0307 REV E
0.53 ± 0.152
(.021 ± .006)
SEATING
PLANE
0.18
(.007)
1.10
(.043)
MAX
0.17 –0.27
(.007 – .011)
TYP
0.86
(.034)
REF
0.50
(.0197)
BSC
1 2 34 5
4.90 ± 0.152
(.193 ± .006)
0.497 ± 0.076
(.0196 ± .003)
REF
8910 76
3.00 ± 0.102
(.118 ± .004)
(NOTE 3)
3.00 ± 0.102
(.118 ± .004)
(NOTE 4)
NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
0.254
(.010) 0° – 6° TYP
DETAIL “A”
DETAIL “A”
GAUGE PLANE
5.23
(.206)
MIN
3.20 – 3.45
(.126 – .136)
0.889 ± 0.127
(.035 ± .005)
RECOMMENDED SOLDER PAD LAYOUT
0.305 ± 0.038
(.0120 ± .0015)
TYP
0.50
(.0197)
BSC
0.1016 ± 0.0508
(.004 ± .002)
LTC2850/LTC2851/LTC2852
16
285012fd
package DescripTion
.016 – .050
(0.406 – 1.270)
.010 – .020
(0.254 – 0.508)× 45°
0°– 8° TYP
.008 – .010
(0.203 – 0.254)
SO8 0303
.053 – .069
(1.346 – 1.752)
.014 – .019
(0.355 – 0.483)
TYP
.004 – .010
(0.101 – 0.254)
.050
(1.270)
BSC
1234
.150 – .157
(3.810 – 3.988)
NOTE 3
8765
.189 – .197
(4.801 – 5.004)
NOTE 3
.228 – .244
(5.791 – 6.197)
.245
MIN .160 ±.005
RECOMMENDED SOLDER PAD LAYOUT
.045 ±.005
.050 BSC
.030 ±.005
TYP
INCHES
(MILLIMETERS)
NOTE:
1. DIMENSIONS IN
2. DRAWING NOT TO SCALE
3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)
1
N
234
.150 – .157
(3.810 – 3.988)
NOTE 3
14 13
.337 – .344
(8.560 – 8.738)
NOTE 3
.228 – .244
(5.791 – 6.197)
12 11 10 9
567
N/2
8
.016 – .050
(0.406 – 1.270)
.010 – .020
(0.254 – 0.508)× 45°
0° – 8° TYP
.008 – .010
(0.203 – 0.254)
S14 0502
.053 – .069
(1.346 – 1.752)
.014 – .019
(0.355 – 0.483)
TYP
.004 – .010
(0.101 – 0.254)
.050
(1.270)
BSC
.245
MIN
N
1 2 3 N/2
.160 ±.005
RECOMMENDED SOLDER PAD LAYOUT
.045 ±.005
.050 BSC
.030 ±.005
TYP
INCHES
(MILLIMETERS)
NOTE:
1. DIMENSIONS IN
2. DRAWING NOT TO SCALE
3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)
S8 Package
8‑Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610)
S Package
14‑Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610)
LTC2850/LTC2851/LTC2852
17
285012fd
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 representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
revision hisTory
REV DATE DESCRIPTION PAGE NUMBER
D 05/10 Added military grade parts. 2, 3
(Revision history begins at Rev D)
LTC2850/LTC2851/LTC2852
18
285012fd
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com
LINEAR TECHNOLOGY CORPORATION 2007
LT 0510 REV D • PRINTED IN USA
relaTeD parTs
Typical applicaTion
PART NUMBER DESCRIPTION COMMENTS
LTC485 Low Power RS485 Interface Transceiver ICC = 300µA (Typ)
LTC491 Differential Driver and Receiver Pair ICC = 300µA
LTC1480 3.3V Ultralow Power RS485 Transceiver 3.3V Operation
LTC1483 Ultralow Power RS485 Low EMI Transceiver Controlled Driver Slew Rate
LTC1485 Differential Bus Transceiver 10Mbps Operation
LTC1487 Ultralow Power RS485 with Low EMI, Shutdown and High Input
Impedance
Up to 256 Transceiver on the Bus
LTC1520 50Mbps Precision Quad Line Receiver Channel-to-Channel Skew 400ps (Typ)
LTC1535 Isolated RS485 Full-Duplex Transceiver 2500VRMS Isolation in Surface Mount Package
LTC1685 52Mbps RS485 Transceiver with Precision Delay Propagation Delay Skew 500ps (Typ)
LT1785 60V Fault Protected RS485 Transceiver 60V Tolerant, 15kV ESD
LTC2854/LTC2855 3.3V 20Mbps RS485/RS422 Transceivers with Integrated Switchable
Termination
3.3V Operation, Integrated, Switchable, 120Ω Termination
Resistor, 25kV ESD (LTC2854), 15kV ESD (LTC2855)
LTC2856-1 20Mbps and Slew Rate-Limited, 15kV RS485/RS422 Transceiver 15kV ESD
LTC2859/LTC2861 20Mbps RS485/RS422 Transceiver with Integrated Switchable
Termination
Integrated, Switchable, 120Ω Termination Resistor, 15kV ESD
Full Duplex Network Using the LTC2852 and LTC2855
D
TE = 3.3V
120Ω
R
LTC2855
MASTER
RD
LTC2852
SLAVE
TE = 3.3V
285012 TA04
D
R
LTC2855
SLAVE
RD
LTC2852
SLAVE