LTC2856-1/LTC2856-2
LTC2857-1/LTC2857-2
LTC2858-1/LTC2858-2
20Mbps and Slew Rate
Limited 15kV RS485/RS422
Transceivers
DESCRIPTION
The LTC
®
2856-1, LTC2856-2, LTC2857-1, LTC2857-2,
LTC2858-1 and LTC2858-2 are low power, RS485/RS422
transceivers operating on 5V supplies at maximum data
rates of 20Mbps or 250kbps for low EMI. 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
±15kV (human body model) on the transceiver interface
pins without latchup or damage.
PART
NUMBER
LTC2856-1
LTC2856-2
LTC2857-1
LTC2857-2
LTC2858-1
LTC2858-2
MAX DATA
RATE (Mbps)
20
0.25
20
0.25
20
0.25
DUPLEX
Half
Half
Full
Full
Full
Full
PACKAGE
MSOP-8, DFN-8
MSOP-8, DFN-8
MSOP-8, DFN-8
MSOP-8, DFN-8
MSOP-10, DFN-10
MSOP-10, DFN-10
FEATURES
■
■
■
■
■
■
■
■
■
■
■
20Mbps or Low EMI 250kbps Maximum Data Rate
No Damage or Latchup to ESD: ±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: 900μA Maximum in Receive
Mode
Compatible with TIA/EIA-485-A Specifications
Available in 8-Lead and 10-Lead 3mm
×
3mm DFN
and 8-Lead and 10-Lead MSOP Packages
APPLICATIONS
■
■
■
Low Power RS485/RS422 Transceiver
Level Translator
Backplane Transceiver
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
LTC2856-1
RO1
RE1
DE1
DI1
D
GND1
2V/DIV
R
V
CC1
R
T
LTC2858-1 at 20Mbps
DI
Y
Z
LTC2856-1
RO2
RE2
DE2
DI2
D
GND2
285678 TA01a
R
V
CC2
R
T
Y-Z
20ns/DIV
2856 TA01b
285678fe
1
LTC2856-1/LTC2856-2
LTC2857-1/LTC2857-2
LTC2858-1/LTC2858-2
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 Range (Note 4)
LTC285xC ................................................ 0°C to 70°C
LTC285xI.............................................. –40°C to 85°C
LTC285xH .......................................... –40°C to 125°C
Storage Temperature Range
MSOP ................................................ –65°C to 150°C
DFN.................................................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
MSOP ............................................................... 300°C
PACKAGE INFORMATION
LTC2856
TOP VIEW
RO 1
RE 2
DE 3
DI 4
9
8
7
6
5
V
CC
B
A
GND
TOP VIEW
RO
RE
DE
DI
1
2
3
4
8
7
6
5
V
CC
B
A
GND
MS8 PACKAGE
8-LEAD PLASTIC MSOP
DD PACKAGE
8-LEAD (3mm 3mm) PLASTIC DFN
T
JMAX
= 150°C,
θ
JA
= 200°C/W,
θ
JC
= 40°C/W
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
T
JMAX
= 150°C,
θ
JA
= 43°C/W,
θ
JC
= 3°C/W
LTC2857
TOP VIEW
V
CC
1
RO 2
DI 3
GND 4
9
8
7
6
5
A
B
Z
Y
TOP VIEW
V
CC
RO
DI
GND
1
2
3
4
8
7
6
5
A
B
Z
Y
MS8 PACKAGE
8-LEAD PLASTIC MSOP
DD PACKAGE
8-LEAD (3mm 3mm) PLASTIC DFN
T
JMAX
= 150°C,
θ
JA
= 200°C/W,
θ
JC
= 40°C/W
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
T
JMAX
= 150°C,
θ
JA
= 43°C/W,
θ
JC
= 3°C/W
LTC2858
TOP VIEW
RO
RE
DE
DI
GND
1
2
3
4
5
11
10 V
CC
9 A
8 B
7 Z
6 Y
TOP VIEW
RO
RE
DE
DI
GND
1
2
3
4
5
10
9
8
7
6
V
CC
A
B
Z
Y
DD PACKAGE
10-LEAD (3mm 3mm) PLASTIC DFN
MS PACKAGE
10-LEAD PLASTIC MSOP
T
JMAX
= 150°C,
θ
JA
= 120°C/W,
θ
JC
= 45°C/W
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
T
JMAX
= 150°C,
θ
JA
= 43°C/W,
θ
JC
= 3°C/W
285678fe
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LTC2856-1/LTC2856-2
LTC2857-1/LTC2857-2
LTC2858-1/LTC2858-2
ORDER INFORMATION
LTC2856 C
DD
-1
#TR PBF
LEAD FREE DESIGNATOR
TAPE AND REEL
TR = Tape and Reel
SPEED
-1 = 20Mbps Max. Data Rate
-2 = 250kbps Max. Data Rate
PACKAGE TYPE
DD = 8-Lead Plastic DFN (LTC2856, LTC2858)
MS8 = 8-Lead Plastic MSOP (LTC2856, LTC2857)
MS = 10-Lead Plastic MSOP (LTC2858)
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
LTC2856 = Half Duplex, with Enables
LTC2857 = Full Duplex, no Enables
LTC2858 = 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
LTC2856-1
LTC2856-2
LTC2857-1
LTC2857-2
LTC2858-1
LTC2858-2
PART MARKING
LTCMF, LCMG
LTCMH, LCMJ
LTCMC, LCMD
LTCMK, LCMM
LTCGQ, LCGR
LTCMQ, LCMR
MAX DATA RATE (Mbps)
20
0.25
20
0.25
20
0.25
DUPLEX
Half
Half
Full
Full
Full
Full
LOW POWER
SHUTDOWN MODE
Yes
Yes
No
No
Yes
Yes
PACKAGE
MSOP-8, DFN-8
MSOP-8, DFN-8
MSOP-8, DFN-8
MSOP-8, DFN-8
MSOP-10, DFN-10
MSOP-10, DFN-10
285678fe
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LTC2856-1/LTC2856-2
LTC2857-1/LTC2857-2
LTC2858-1/LTC2858-2
ELECTRICAL CHARACTERISTICS
SYMBOL
Driver
|V
OD
|
Differential Driver Output Voltage
R = ∞, V
CC
= 4.5V (Figure 1)
R = 27Ω (RS485), V
CC
= 4.5V (Figure 1)
R = 50Ω (RS422), V
CC
= 4.5V (Figure 1)
Δ|V
OD
|
Change in Magnitude of Driver Differential
Output Voltage for Complementary Output
States
Driver Common Mode Output Voltage
Change 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
Receiver Input Current (A, B)
R = 27Ω or R = 50Ω (Figure 1)
●
●
●
●
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 5V unless otherwise noted. (Note 2)
PARAMETER
CONDITIONS
MIN
TYP
MAX
V
CC
1.5
2
V
CC
V
CC
0.2
UNITS
V
V
V
V
V
OC
Δ|V
OC
|
R = 27Ω or R = 50Ω (Figure 1)
R = 27Ω or R = 50Ω (Figure 1)
●
●
3
0.2
V
V
I
OZD
I
OSD
Receiver
I
IN
DE = 0V, (Y or Z) = –7V, 12V, LTC2858-1,
LTC2858-2
–7V ≤ (Y or Z) ≤ 12V (Figure 2)
DE = TE = 0V, V
CC
= 0V or 5V, V
IN
= 12V
(Figure 3) (C, I-Grade)
DE = TE = 0V, V
CC
= 0V or 5V, V
IN
= –7V,
(Figure 3) (C, I-Grade)
DE = TE = 0V, V
CC
= 0V or 5V, V
IN
= 12V
(Figure 3) (H-Grade)
DE = TE = 0V, V
CC
= 0V or 5V, V
IN
= –7V,
(Figure 3) (H-Grade)
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)
–7V ≤ B ≤ 12V
B = 0V
I(RO) = –4mA, A-B = 200mV, V
CC
= 4.5V
I(RO) = 4mA, A-B = –200mV, V
CC
= 4.5V
RE
= 5V, 0V ≤ RO ≤ V
CC
, LTC2856-1,
LTC2856-2, LTC2858-1, LTC2858-2
DE, DI,
RE,
V
CC
= 5.5V
DE, DI,
RE,
V
CC
= 4.5V
DE, DI,
RE
DE = 0V,
RE
= V
CC
,
LTC2856, LTC2858 (C and I-Grade)
LTC2856, LTC2858 (H-Grade)
No Load, DE = 0V,
RE
= 0V, LTC2856-1,
LTC2856-2, LTC2858-1, LTC2858-2
●
●
±10
±120
±250
125
–100
250
–145
96
125
μA
mA
μA
μA
μA
μA
kΩ
●
●
●
●
●
R
IN
Receiver Input Resistance
●
48
125
kΩ
V
TH
ΔV
TH
V
OH
V
OL
I
OZR
Logic
V
IH
V
IL
I
INL
Supplies
I
CCS
Receiver Differential Input Threshold Voltage
Receiver Input Hysteresis
Receiver Output High Voltage
Receiver Output Low Voltage
Receiver Three-State (High Impedance) Output
Current on RO
Logic Input High Voltage
Logic Input Low Voltage
Logic Input Current
Supply Current in Shutdown Mode
●
±0.2
25
2.4
0.4
±1
V
mV
V
V
μA
●
●
●
●
●
●
2
0.8
0
0
0
540
±10
5
15
900
V
V
μA
μA
μA
μA
●
●
●
I
CCR
Supply Current in Receive Mode
285678fe
4
LTC2856-1/LTC2856-2
LTC2857-1/LTC2857-2
LTC2858-1/LTC2858-2
SWITCHING CHARACTERISTICS
SYMBOL
I
CCT
PARAMETER
Supply Current in Transmit Mode
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 5V unless otherwise noted. (Note 2)
CONDITIONS
No Load, DE = V
CC
,
RE
= V
CC
LTC2856-1
LTC2858-1
LTC2856-2
LTC2858-2
LTC2856-1
LTC2857-1
LTC2858-1
LTC2856-2
LTC2857-2
LTC2858-2
●
●
●
MIN
TYP
630
670
660
MAX
1000
1100
1100
UNITS
μA
μA
μA
I
CCTR
Supply Current with Both Driver and Receiver
Enabled
No Load, DE = V
CC
,
RE
= 0V
●
700
1200
μA
Driver in LTC2856-1, LTC2857-1, LTC2858-1
f
MAX
t
PLHD
, t
PHLD
Δt
PD
t
SKEWD
t
RD
, t
FD
t
ZLD
, t
ZHD
,
t
LZD
, t
HZD
t
ZHSD
, t
ZLSD
t
SHDN
Maximum Data Rate
Driver Input to Output
Driver Output Y to Output Z
Driver Rise or Fall Time
Driver Enable or Disable Time
Driver Enable from Shutdown
Time to Shutdown
(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
L
= 500Ω, C
L
= 50pF,
RE
= 0V,
LTC2856-1, LTC2858-1 (Figure 5)
R
L
= 500Ω, C
L
= 50pF,
RE
= V
CC
,
LTC2856-1, LTC2858-1 (Figure 5)
(DE =
↓,
RE
= V
CC
) or (DE = 0V,
RE
=
↑),
LTC2856-1, LTC2858-1 (Figure 5)
(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
L
= 500Ω, C
L
= 50pF,
RE
= 0V,
LTC2856-2, LTC2858-2 (Figure 5)
R
L
= 500Ω, C
L
= 50pF,
RE
= 0V,
LTC2856-2, LTC2858-2 (Figure 5)
R
L
= 500Ω, C
L
50pF,
RE
= V
CC
,
LTC2856-2, LTC2858-2 (Figure 5)
(DE = 0V,
RE↑)
or (DE =
↓,
RE
= V
CC
),
LTC2856-2, LTC2858-2 (Figure 5)
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
,
LTC2856-1, LTC2856-2, LTC2858-1,
LTC2858-2 (Figure 7)
R
L
= 1k, C
L
= 15pF, DE = 0V,
LTC2856-1, LTC2856-2, LTC2858-1,
LTC2858-2 (Figure 7)
●
●
●
●
●
●
●
●
20
10
1
1
4
50
6
±6
12.5
70
8
100
Mbps
ns
ns
ns
ns
ns
μs
ns
Driver Input to Output Difference |t
PLHD
– t
PHLD
| R
DIFF
= 54Ω, C
L
= 100pF (Figure 4)
Driver in LTC2856-2, LTC2857-2, LTC2858-2
f
MAXS
Δt
PDS
t
SKEWDS
t
RDS
, t
FDS
t
ZHDS
, t
ZLDS
t
LZDS
, t
HZDS
Maximum Data Rate
●
●
●
●
●
●
●
●
●
250
0.95
50
200
0.90
1.5
500
±500
1.5
300
70
8
500
kbps
μs
ns
ns
μs
ns
ns
μs
ns
t
PLHDS
, t
PHLDS
Driver Input to Output
Driver Output A to Output B
Driver Rise or Fall Time
Driver Enable Time
Driver Disable Time
Driver Input to Output Difference |t
PLHD
– t
PHLD
| R
DIFF
= 54Ω, C
L
= 100pF (Figure 4)
t
ZHSDS
, t
ZLSDS
Driver Enable from Shutdown
t
SHDNS
Receiver
t
PLHR
, t
PHLR
t
SKEWR
t
RR
, t
FR
t
ZLR
, t
ZHR
,
t
LZR
, t
HZR
t
ZHSR
, t
ZLSR
Receiver Input to Output
Differential Receiver Skew, |t
PLHR
– t
PHLR
|
Receiver Output Rise or Fall Time
Receiver Enable/Disable
Time to Shutdown
●
●
●
●
50
1
3
70
6
12.5
50
ns
ns
ns
ns
Receiver Enable from Shutdown
●
8
μs
285678fe
5
测试/测量
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