LTC2850/LTC2851/LTC2852
3.3V 20Mbps RS485/RS422
Transceivers
FEATURES
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DESCRIPTION
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.
PART NUMBER
LTC2850
LTC2851
LTC2852
DUPLEX
Half
Full
Full
PACKAGE
SO-8, MSOP-8, DFN-8
SO-8, MSOP-8, DFN-8
SO-14, MSOP-10, DFN-10
3.3V Supply Voltage
20Mbps Maximum Data Rate
No Damage or Latchup Up to ±15kV HBM
High Input Impedance Supports 256 Nodes
(C, I-Grade)
Operation Up to 125°C (H-Grade)
Guaranteed Failsafe Receiver Operation Over the
Entire Common Mode Range
Current Limited Drivers and Thermal Shutdown
Delayed Micropower Shutdown: 5μA Maximum
(C, I-Grade)
Power Up/Down Glitch-Free Driver Outputs
Low Operating Current: 370μA Typical in Receive
Mode
Compatible with TIA/EIA-485-A Specifications
Available in 8-Pin and 10-Pin 3mm
×
3mm DFN,
8-Pin and 10-Pin MSOP and 8-Pin and 14-Pin SO
,
Packages
APPLICATIONS
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Low Power RS485/RS422 Transceiver
Level Translator
Backplane Transceiver
L,
LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
TYPICAL APPLICATION
LTC2850
RO1
RE1
DE1
DI1
D
GND1
2V/DIV
LTC2850
RO2
RE2
DE2
DI2
D
GND2
285012 TA01a
LTC2850 at 20Mbps Into 54Ω
V
CC1
DI
R
T
A
R
B
A-B
R
V
CC2
R
T
20ns/DIV
285012 TA01b
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1
LTC2850/LTC2851/LTC2852
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Supply Voltage (V
CC
) ................................... –0.3V to 7V
Logic Input Voltages (RE, DE, DI) ................ –0.3V to 7V
Interface I/O:
A, B, Y, Z .......................................(V
CC
– 15V) to 15V
Receiver Output Voltage (RO) .......–0.3V to (V
CC
+ 0.3V)
Operating Temperature (Note 4)
LTC285xC................................................. 0°C to 70°C
LTC285xI .............................................. –40°C to 85°C
LTC285xH .......................................... –40°C to 125°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
MSOP ............................................................... 300°C
PIN CONFIGURATION
LTC2850
TOP VIEW
TOP VIEW
RO
RE
DE
DI
1
2
3
4
9
8
7
6
5
V
CC
B
A
GND
RO
RE
DE
DI
1
2
3
4
TOP VIEW
8
7
6
5
V
CC
B
A
GND
RO
RE
DE
DI
1
2
3
4
8
7
6
5
V
CC
B
A
GND
DD PACKAGE
8-LEAD (3mm × 3mm) PLASTIC DFN
T
JMAX
= 150°C,
θ
JA
= 43°C/W,
θ
JC
= 3°C/W
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
LTC2851
TOP VIEW
MS8 PACKAGE
8-LEAD PLASTIC MSOP
T
JMAX
= 150°C,
θ
JA
= 200°C/W,
θ
JC
= 40°C/W
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 150°C,
θ
JA
= 150°C/W,
θ
JC
= 39°C/W
TOP VIEW
V
CC
RO
DI
GND
1
2
3
4
9
8
7
6
5
A
B
Z
Y
V
CC
RO
DI
GND
1
2
3
4
TOP VIEW
8
7
6
5
A
B
Z
Y
V
CC
RO
DI
GND
1
2
3
4
8
7
6
5
A
B
Z
Y
DD PACKAGE
8-LEAD (3mm × 3mm) PLASTIC DFN
T
JMAX
= 150°C,
θ
JA
= 43°C/W,
θ
JC
= 3°C/W
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
MS8 PACKAGE
8-LEAD PLASTIC MSOP
T
JMAX
= 150°C,
θ
JA
= 200°C/W,
θ
JC
= 40°C/W
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 150°C,
θ
JA
= 150°C/W,
θ
JC
= 39°C/W
LTC2852
TOP VIEW
TOP VIEW
RO
RE
DE
DI
GND
1
2
3
4
5
11
10 V
CC
9 A
8 B
7 Z
6 Y
RO
RE
DE
DI
GND
1
2
3
4
5
10
9
8
7
6
V
CC
A
B
Z
Y
NC 1
RO 2
RE 3
DE 4
DI 5
GND 6
GND 7
TOP VIEW
14 V
CC
13 NC
12 A
11 B
10 Z
9
8
Y
NC
MS PACKAGE
10-LEAD PLASTIC MSOP
T
JMAX
= 150°C,
θ
JA
= 120°C/W,
θ
JC
= 45°C/W
DD PACKAGE
10-LEAD (3mm × 3mm) PLASTIC DFN
T
JMAX
= 150°C,
θ
JA
= 43°C/W,
θ
JC
= 3°C/W
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
S PACKAGE
14-LEAD PLASTIC SO
T
JMAX
= 150°C,
θ
JA
= 88°C/W,
θ
JC
= 37°C/W
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LTC2850/LTC2851/LTC2852
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)
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/
PRODUCT SELECTION GUIDE
PART NUMBER
LTC2850
LTC2851
LTC2852
PART MARKING
2850/I/H, LTCQD, LCQC
2851/I/H, LTCWF, LCWD
2852CS/IS/HS, LTCRX, LCRY
DUPLEX
Half
Full
Full
LOW POWER SHUTDOWN MODE
Yes
No
Yes
PACKAGE
SO-8, MSOP-8, DFN-8
SO-8, MSOP-8, DFN-8
SO-14, MSOP-10, DFN-10
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3
LTC2850/LTC2851/LTC2852
ELECTRICAL CHARACTERISTICS
SYMBOL
Driver
|V
OD
|
Differential Driver Output Voltage
R = ∞, V
CC
= 3V (Figure 1)
R = 27Ω, V
CC
= 3V (Figure 1)
R = 50Ω, V
CC
= 3.13V (Figure 1)
l
l
l
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 3.3V unless otherwise noted. (Note 2)
PARAMETER
CONDITIONS
MIN
TYP
MAX
V
CC
V
CC
V
CC
0.2
UNITS
V
V
V
V
1.5
2
Δ|V
OD
|
Difference in Magnitude of Driver Differential R = 27Ω or 50Ω (Figure 1)
Output Voltage for Complementary Output
States
Driver Common Mode Output Voltage
Difference in Magnitude of Driver Common
Mode Output Voltage for Complementary
Output States
Driver Three-State (High Impedance) Output
Current on Y and Z
Maximum Driver Short-Circuit Current
R = 27Ω or 50Ω (Figure 1)
R = 27Ω or 50Ω (Figure 1)
V
OC
Δ|V
OC
|
l
l
3
0.2
V
V
I
OZD
I
OSD
Receiver
I
IN
DE = 0V, (Y or Z) = –7V, 12V (LTC2852)
–7V ≤ (Y or Z) ≤ 12V (Figure 2)
l
±10
±180
–250
±250
300
125
–100
250
–145
96
125
μA
mA
mA
μA
μA
μA
μA
kΩ
l
l
l
l
l
l
Receiver Input Current (A, B)
DE = TE = 0V, V
CC
= 0V or 3.3V, V
IN
= 12V
(Figure 3) (C, I-Grade)
DE = TE = 0V, V
CC
= 0V or 3.3V, V
IN
= –7V,
(Figure 3) (C, I-Grade)
DE = TE = 0V, V
CC
= 0V or 3.3V, V
IN
= 12V
(Figure 3) (H-Grade)
DE = TE = 0V, V
CC
= 0V or 3.3V, V
IN
= –7V,
(Figure 3) (H-Grade)
R
IN
Receiver Input Resistance
RE
= V
CC
or 0V, DE = TE = 0V,
V
IN
= –7V, –3V, 3V, 7V, 12V (Figure 3)
(C, I-Grade)
RE
= V
CC
or 0V, DE = TE = 0V,
V
IN
= –7V, –3V, 3V, 7V, 12V (Figure 3)
(H-Grade)
l
48
125
kΩ
V
TH
ΔV
TH
V
OH
V
OL
I
OZR
I
OSR
Logic
V
IH
V
IL
I
INL
Receiver Differential Input Threshold Voltage –7V ≤ B ≤ 12V
Receiver Input Hysteresis
Receiver Output High Voltage
Receiver Output Low Voltage
Receiver Three-State (High Impedance)
Output Current on RO
Receiver Short-Circuit Current
Logic Input High Voltage
Logic Input Low Voltage
Logic Input Current
B = 0V
I(RO) = –4mA, A-B = 200mV, V
CC
= 3V
I(RO) = 4mA, A-B = –200mV, V
CC
= 3V
RE
= V
CC
, 0V ≤ RO ≤ V
CC
(LTC2850, LTC2852)
0V ≤ RO ≤ V
CC
V
CC
= 3.6V
V
CC
= 3V
l
±0.2
25
2.4
0.4
±1
±85
2
0.8
0
±10
V
mV
V
V
μA
mA
V
V
μA
l
l
l
l
l
l
l
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4
LTC2850/LTC2851/LTC2852
ELECTRICAL CHARACTERISTICS
SYMBOL
Supplies
I
CCS
Supply Current in Shutdown Mode
DE = 0V,
RE
= V
CC
,
LTC2850, LTC2852 (C and I-Grade)
LTC2850, LTC2852 (H-Grade)
DE = 0V,
RE
= 0V (LTC2850, LTC2852)
No Load, DE = V
CC
,
RE
= V
CC
(LTC2850,
LTC2852)
No Load, DE = V
CC
,
RE
= 0V
l
l
l
l
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 3.3V unless otherwise noted. (Note 2)
PARAMETER
CONDITIONS
MIN
TYP
0
0
370
450
450
MAX
5
15
900
1000
1000
UNITS
μA
μA
μA
μA
μA
I
CCR
I
CCT
I
CCTR
Supply Current in Receive Mode
Supply Current in Transmit Mode
Supply Current with Both Driver and
Receiver Enabled
SWITCHING CHARACTERISTICS
SYMBOL
Driver
f
MAX
Δt
PD
t
SKEWD
t
RD
, t
FD
t
ZLD
, t
ZHD
,
t
LZD
, t
HZD
Maximum Data Rate
Driver Input to Output Difference
|t
PLHD
– t
PHLD
|
Driver Output Y to Output Z
Driver Rise or Fall Time
Driver Enable or Disable Time
PARAMETER
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 3.3V, unless otherwise noted. (Note 2)
CONDITIONS
(Note 3)
R
DIFF
= 54Ω, C
L
= 100pF (Figure 4)
R
DIFF
= 54Ω, C
L
= 100pF (Figure 4)
R
DIFF
= 54Ω, C
L
= 100pF (Figure 4)
R
DIFF
= 54Ω, C
L
= 100pF (Figure 4)
R
L
= 500Ω, C
L
= 50pF
RE
= 0V (Figure 5)
,
(LTC2850, LTC2852)
R
L
= 500Ω, C
L
= 50pF
RE
= V
CC
(Figure 5)
,
(LTC2850, LTC2852)
R
L
= 500Ω, C
L
= 50pF (DE =
↓,
RE
= V
CC
)
,
or (DE = 0V,
RE
=
↑)
(Figure 5) (LTC2850,
LTC2852)
C
L
= 15pF V
CM
= 1.5V, |V
AB
| = 1.5V,
,
t
R
and t
F
< 4ns (Figure 6)
C
L
= 15pF (Figure 6)
C
L
= 15pF (Figure 6)
R
L
=1k, C
L
=15pF DE = V
CC
(Figure 7)
,
(LTC2850, LTC2852)
R
L
= 1k, C
L
= 15pF DE = 0V (Figure 7)
,
(LTC2850, LTC2852)
l
l
l
l
l
l
l
l
MIN
20
TYP
MAX
UNITS
Mbps
t
PLHD
, t
PHLD
Driver Input to Output
10
1
1
4
50
6
±6
12.5
70
8
100
ns
ns
ns
ns
ns
μs
ns
t
ZHSD
, t
ZLSD
Driver Enable from Shutdown
t
SHDN
Time to Shutdown
Receiver
t
PLHR
, t
PHLR
Receiver Input to Output
t
SKEWR
t
RR
, t
FR
t
ZLR
, t
ZHR
,
t
LZR
, t
HZR
Differential Receiver Skew
|t
PLHR
– t
PHLR
|
Receiver Output Rise or Fall Time
Receiver Enable/Disable
l
l
l
l
l
50
1
3
70
6
12.5
50
8
ns
ns
ns
ns
μs
t
ZHSR
, t
ZLSR
Receiver Enable from Shutdown
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.
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.
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模拟电子
