components are required. A single supply powers both
sides of the interface through an integrated, isolated, low
noise, efficient 5V output DC/DC converter.
Coupled inductors and an isolation power transformer
provide 2500V
RMS
of isolation between the line transceiver
and the logic interface. This device is ideal for systems
where the ground loop is broken allowing for large com-
mon mode voltage variation. Uninterrupted communica-
tion is guaranteed for common mode transients greater
than 30kV/μs.
Maximum data rates are 20Mbps or 250kbps in slew
limited mode. Transmit data, DI and receive data, RO, are
implemented with event driven low jitter processing. The
receiver has a one-eighth unit load supporting up to 256
nodes per bus. A logic supply pin allows easy interfacing
with different logic levels from 1.62V to 5.5V, independent
of the main supply.
Enhanced ESD protection allows this part to withstand up
to ±15kV (human body model) on the transceiver interface
pins to isolated supplies and ±10kV through the isolation
barrier to logic supplies without latch-up or damage.
L,
LT, LTC, LTM, Linear Technology, µModule and the Linear logo are registered trademarks of
Linear Technology Corporation. All other trademarks are the property of their respective owners.
Isolated RS485/RS422 Transceiver: 2500V
RMS
Isolated DC Power: 5V at Up to 200mA
No External Components Required
20Mbps or Low EMI 250kbps Data Rate
High ESD: ±15kV HBM on Transceiver Interface
High Common Mode Transient Immunity: 30kV/μs
Integrated Selectable 120Ω Termination
3.3V (LTM2881-3) or 5.0V (LTM2881-5) Operation
1.62V to 5.5V Logic Supply Pin for Flexible Digital Interface
Common Mode Working Voltage: 560V
PEAK
High Input Impedance Failsafe RS485 Receiver
Current Limited Drivers and Thermal Shutdown
Compatible with TIA/EIA-485-A Specification
High Impedance Output During Internal Fault Condition
Low Current Shutdown Mode (< 10µA)
General Purpose CMOS Isolated Channel
Small, Low Profile (15mm
×
11.25mm
×
2.8mm)
Surface Mount BGA and LGA Packages
applicaTions
n
n
n
Isolated RS485/RS422 Interface
Industrial Networks
Breaking RS485 Ground Loops
Typical applicaTion
Isolated Half-Duplex RS485 μModule Transceiver
3.3V
V
CC
ISOLATION BARRIER
V
L
RO
RE
TE
DE
DI
GND
LTM2881
V
CC2
A
B
TWISTED-PAIR
CABLE
Y
Z
GND2
2881 TA01
LTM2881 Operating Through 35kV/μs CM Transients
MULTIPLE SWEEPS
OF COMMON MODE
TRANSIENTS
500V/DIV
PWR
5V
AVAILABLE CURRENT:
150mA (LTM2881-5)
100mA (LTM2881-3)
DI
1V/DIV
1V/DIV
RO
50ns/DIV
2881 TA01a
2881fa
LTM2881
absoluTe MaxiMuM raTings
(Note 1)
pin conFiguraTion
TOP VIEW
1
A
B
C
D
E
F
G
H
J
K
L
D
IN
SLO
Y
Z
B
A
V
CC2
BGA PACKAGE
32-PIN (15mm 11.25mm 3.42mm)
T
JMAX
= 125°C,
JA
= 32.2°C/W,
JCTOP
= 27.2°C/W,
JCBOTTOM
= 20.9°C/W,
JB
= 26.4°C/W,
WEIGHT = 1g
LGA PACKAGE
32-PIN (15mm 11.25mm 2.8mm)
T
JMAX
= 125°C,
JA
= 31.1°C/W,
JCTOP
= 27.3°C/W,
JCBOTTOM
= 19.5°C/W,
JB
= 25.1°C/W,
WEIGHT = 1g
GND2
GND
V
CC
2
3
4
5
6
7
8
D
OUT
TE
DI DE
RE
RO V
L
ON
V
CC
to GND .................................................. –0.3V to 6V
V
CC2
to GND2............................................... –0.3V to 6V
V
L
to GND .................................................... –0.3V to 6V
Interface Voltages
(A, B, Y, Z) to GND2 ........................ V
CC2
–15V to 15V
Signal Voltages ON, RO, DI, DE,
RE,
TE, D
OUT
to GND......................... –0.3V to V
L
+0.3V
Signal Voltages
SLO,
D
IN
to GND2 ....................................–0.3V to V
CC2
+0.3V
Operating Temperature Range
LTM2881C ............................................... 0°C to 70°C
LTM2881I.............................................–40°C to 85°C
Storage Temperature Range .................. –55°C to 125°C
Peak Reflow Temperature (Soldering, 10 sec)....... 245°C
orDer inForMaTion
LEAD FREE FINISH
LTM2881CY-3#PBF
LTM2881IY-3#PBF
LTM2881CY-5#PBF
LTM2881IY-5#PBF
LTM2881CV-3#PBF
LTM2881IV-3#PBF
LTM2881CV-5#PBF
LTM2881IV-5#PBF
TRAY
LTM2881CY-3#PBF
LTM2881IY-3#PBF
LTM2881CY-5#PBF
LTM2881IY-5#PBF
LTM2881CV-3#PBF
LTM2881IV-3#PBF
LTM2881CV-5#PBF
LTM2881IV-5#PBF
PART MARKING*
LTM2881Y-3
LTM2881Y-3
LTM2881Y-5
LTM2881Y-5
LTM2881V-3
LTM2881V-3
LTM2881V-5
LTM2881V-5
PACKAGE DESCRIPTION
32-Pin (15mm
×
11.25mm
×
3.42mm) BGA
32-Pin (15mm
×
11.25mm
×
3.42mm) BGA
32-Pin (15mm
×
11.25mm
×
3.42mm) BGA
32-Pin (15mm
×
11.25mm
×
3.42mm) BGA
32-Pin (15mm
×
11.25mm
×
2.8mm) LGA
32-Pin (15mm
×
11.25mm
×
2.8mm) LGA
32-Pin (15mm
×
11.25mm
×
2.8mm) LGA
32-Pin (15mm
×
11.25mm
×
2.8mm) LGA
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
0°C to 70°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
This product is only offered in trays. For more information go to:
http://www.linear.com/packaging/
2881fa
LTM2881
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. LTM2881-3 V
CC
= 3.3V, LTM2881-5 V
CC
= 5.0V, V
L
= 3.3V, GND = GND2 =
0V, ON = V
L
unless otherwise noted.
SYMBOL
Power Supply
V
CC
V
L
I
CCPOFF
I
CCS
V
CC2
V
CC2NOLOAD
I
CC2S
Driver
|V
OD
|
∆|V
OD
|
V
OC
∆|V
OC
|
I
OZD
I
OSD
Receiver
R
IN
R
TE
I
IN
Receiver Input Resistance
Receiver Termination Resistance Enabled
Receiver Input Current (A, B)
RE
= 0V or V
L
, V
IN
= –7V, –3V, 3V, 7V,
12V (Figure 3)
TE = V
L
, V
AB
= 2V, V
B
= – 7V, 0V, 10V
(Figure 8)
ON = 0V V
CC2
= 0V or 5V, V
IN
= 12V
(Figure 3)
ON = 0V V
CC2
= 0V or 5V, V
IN
= –7V
(Figure 3)
V
TH
∆V
TH
Logic
V
IL
V
IH
Logic Input High Voltage
Logic Input Low Voltage
1.62V ≤ V
L
≤ 5.5V
D
IN
SLO
DI, TE, DE, ON,
RE:
V
L
≥ 2.35V
1.62V ≤ V
L
< 2.35V
l
l
l
l
l
l
l
l
l
l
elecTrical characTerisTics
PARAMETER
V
CC
Supply Voltage
V
L
Supply Voltage
V
CC
Supply Current in Off Mode
V
CC
Supply Current in On Mode
Regulated V
CC2
Output Voltage, Loaded
Regulated V
CC2
Output Voltage, No Load
Efficiency
V
CC2
Short-Circuit Current
Differential Driver Output Voltage
CONDITIONS
LTM2881-3
LTM2881-5
ON = 0V
LTM2881-3 DE = 0V,
RE
= V
L
, No Load
LTM2881-5 DE = 0V,
RE
= V
L
, No Load
LTM2881-3 DE = 0V,
RE
= V
L
, I
LOAD
= 100mA
LTM2881-5 DE = 0V,
RE
= V
L
, I
LOAD
= 150mA
DE = 0V,
RE
= V
L
, No Load
I
CC2
= 100mA, LTM2881-5 (Note 2)
DE = 0V,
RE
= V
L
, V
CC2
= 0V
R = ∞ (Figure 1)
R = 27Ω (RS485) (Figure 1)
R = 50Ω (RS422) (Figure 1)
R = 27Ω or R = 50Ω (Figure 1)
l
l
l
l
l
l
l
l
MIN
3.0
4.5
1.62
TYP
3.3
5.0
0
20
15
MAX
3.6
5.5
5.5
10
25
19
UNITS
V
V
V
µA
mA
mA
V
V
4.7
4.7
4.8
5.0
5.0
5.0
62
250
V
CC2
V
CC2
V
CC2
0.2
5.35
V
%
mA
V
V
V
V
l
l
l
l
1.5
2
Difference in Magnitude of Driver Differential
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 R = 50Ω (Figure 1)
R = 27Ω or R = 50Ω (Figure 1)
l
l
3
0.2
V
V
DE = 0V, (Y or Z) = –7V, +12V
– 7V ≤ (Y or Z) ≤ 12V (Figure 2)
l
l
±10
– 250
96
108
125
120
156
125
–100
–0.2
25
–0.2
–0.05
0
0.4
0.67•V
CC2
2
0.67•V
L
0.75•V
L
0.2
250
µA
mA
kΩ
Ω
µA
µA
V
mV
V
V
V
V
V
V
2881fa
Receiver Differential Input Threshold Voltage
(A-B)
Receiver Input Failsafe Hysteresis
Receiver Input Failsafe Threshold
–7V ≤ B ≤ 12V
B = 0V
B = 0V
LTM2881
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. LTM2881-3 V
CC
= 3.3V, LTM2881-5 V
CC
= 5.0V, V
L
= 3.3V, GND = GND2 =
0V, ON = V
L
unless otherwise noted.
SYMBOL
I
INL
V
HYS
V
OH
PARAMETER
Logic Input Current
Logic Input Hysteresis
Output High Voltage
(Note 2)
Output High, I
LOAD
= –4mA
(Sourcing), 5.5V ≥ V
L
≥ 3V
Output High, I
LOAD
= –1mA
(Sourcing), 1.62V ≤ V
L
< 3V
Output Low, I
LO AD
= 4mA
(Sinking), 5.5V ≥ V
L
≥ 3V
Output High, I
LOAD
= 1mA
(Sinking), 1.62V ≤ V
L
< 3V
l
l
l
l
l
l
elecTrical characTerisTics
CONDITIONS
l
MIN
TYP
0
150
MAX
±1
UNITS
µA
mV
V
V
V
L
–0.4
V
L
–0.4
0.4
0.4
±1
±85
V
OL
Output Low Voltage
V
V
µA
mA
I
OZR
I
OSR
Three-State (High Impedance) Output Current
RE
= V
L
, 0V ≤ RO ≤ V
L
on RO
Short-Circuit Current
0V ≤ (RO or D
OUT
) ≤ V
L
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. LTM2881-3 V
CC
= 3.3V, LTM2881-5 V
CC
= 5.0V, V
L
= 3.3V, GND = GND2 =
0V, ON = V
L
unless otherwise noted.
SYMBOL
f
MAX
t
PLHD
t
PHLD
∆t
PD
t
SKEWD
t
RD
t
FD
t
ZLD
, t
ZHD
,
t
LZD
, t
HZD
f
MAX
t
PLHD
t
PHLD
∆t
PD
t
SKEWD
t
RD
t
FD
t
ZLD
, t
ZHD
,
t
LZD
, t
HZD
PARAMETER
Maximum Data Rate
Driver Input to Output
Driver Input to Output Difference
|t
PLHD
– t
PHLD
|
Driver Output Y to Output Z
Driver Rise or Fall Time
Driver Output Enable or Disable Time
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
(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
DIFF
= 54Ω, C
L
= 100pF
(Figure 4)
R
L
= 500Ω, C
L
= 50pF
(Figure 5)
l
l
l
l
l
l
l
swiTching characTerisTics
Driver
SLO
= V
CC2
MIN
20
TYP
MAX
UNITS
Mbps
60
1
1
4
85
8
±8
12.5
170
ns
ns
ns
ns
ns
Driver
SLO
= GND2
Maximum Data Rate
Driver Input to Output
Driver Input to Output Difference
|t
PLHD
– t
PHLD
|
Driver Output Y to Output Z
Driver Rise or Fall Time
Driver Output Enable or Disable Time
250
1
50
±200
0.9
1.55
500
±500
1.5
400
kbps
µs
ns
ns
µs
ns
2881fa
LTM2881
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. LTM2881-3 V
CC
= 3.3V, LTM2881-5 V
CC
= 5.0V, V
L
= 3.3V, GND = GND2 =
0V, ON = V
L
unless otherwise noted.
SYMBOL
Receiver
t
PLHR
t
PHLR
t
SKEWR
t
RR
t
FR
t
ZLR
, t
ZHR
,
t
LZR
, t
HZR
t
RTEN
, t
RTZ
Receiver Input to Output
Differential Receiver Skew
|t
PLHR
- t
PHLR
|
Receiver Output Rise or Fall Time
Receiver Output Enable Time
Termination Enable or Disable Time
C
L
= 15pF, V
CM
= 2.5V, |V
AB
| = 1.4V,
t
R
and t
F
< 4ns, (Figure 6)
C
L
= 15pF
(Figure 6)
C
L
= 15pF
(Figure 6)
R
L
=1kΩ, C
L
= 15pF
(Figure 7)
RE
= 0V, DE = 0V, V
AB
= 2V, V
B
= 0V
(Figure 8)
C
L
= 15pF,
t
R
and t
F
< 4ns
ON
V
L
, No Load
l
l
l
l
l
swiTching characTerisTics
PARAMETER
CONDITIONS
MIN
TYP
100
1
3
MAX
140
8
12.5
50
100
UNITS
ns
ns
ns
ns
µs
Generic Logic Input
t
PLHL1
t
PHLL1
D
IN
to D
OUT
Input to Output
l
60
100
ns
Power Supply Generator
V
CC2
–GND2 Supply Start-Up Time
(0V to 4.5V)
l
325
800
µs
otherwise noted.
SYMBOL
V
ISO
isolaTion characTerisTics
PARAMETER
Rated Dielectric Insulation Voltage
Common Mode Transient Immunity
V
IORM
Maximum Working Insulation Voltage
Partial Discharge
Input to Output Resistance
Input to Output Capacitance
Creepage Distance
T
A
= 25°C, LTM2881-3 V
CC
= 3.3V, LTM2881-5 V
CC
= 5.0V, V
L
= 3.3V unless
MIN
2500
±4400
30
560
<5
>10
9
6
9.48
TYP
MAX
UNITS
V
RMS
V
DC
kV/µs
V
PEAK
pC
Ω
pF
mm
CONDITIONS
1 Minute (Derived from 1 Second Test)
1 Second
(Note 2)
(Note 2)
V
PR
= 1050 V
PEAK
(Note 2)
(Note 2)
(Note 2)
(Note 2)
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.
Note 2:
Guaranteed by design and not subject to production test.
Note 3:
Maximum Data rate is guaranteed by other measured parameters
and is not tested directly.
Note 4:
This µModule transceiver includes over temperature protection
that is intended to protect the device during momentary overload
conditions. Junction temperature will exceed 125°C when over
temperature protection is active. Continuous operation above specified
maximum operating junction temperature may result in device degradation
随着阅读器与标签价格的降低和全球市场的扩大，射频标识 RFID(以下简称RFID)的应用与日俱增。标签既可由阅读器供电(无源标签)，也可以由标签的板上电源供电(半有源标签和有源标签)。由于亚微型无源 CMOS 标签的成本降低，库存和其他应用迅速增加。一些评估表明，随着无源标签的价格持续下降，几乎每一个售出产品的内部都将有一个 RFID 标签。由于无源 RFID 标签的重要性及其独特的工程实现...[详细]
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