LTM2881
1
2881fi
For more information www.linear.com/LTM2881
Typical applicaTion
DescripTion
Complete Isolated
RS485/RS422 µModule
Transceiver + Power
The LT M
®
2881 is a complete galvanically isolated full-du-
plex RS485/RS422 µModule
®
(micromodule) transceiver.
No external 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 2500VRMS 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, the Linear logo and µModule are registered trademarks of
Linear Technology Corporation. All other trademarks are the property of their respective owners.
Isolated Half-Duplex RS485 μModule Transceiver
FeaTures
applicaTions
n RS485/RS422 Transceiver: 2500VRMS for 1 Minute
n UL-CSA Recognized File #E151738
n CSA Component Acceptance Notice 5A
n Isolated DC Power: 5V at Up to 200mA
n No External Components Required
n 20Mbps or Low EMI 250kbps Data Rate
n High ESD: ±15kV HBM on Transceiver Interface
n High Common Mode Transient Immunity: 30kV/μs
n Integrated Selectable 120Ω Termination
n 3.3V (LTM2881-3) or 5.0V (LTM2881-5) Operation
n 1.62V to 5.5V Logic Supply Pin for Flexible Digital Interface
n Maximum Continuous Working Voltage: 560VPEAK
n High Input Impedance Failsafe RS485 Receiver
n Current Limited Drivers and Thermal Shutdown
n Compatible with TIA/EIA-485-A and PROFIBUS
n High Impedance Output During Internal Fault Condition
n Low Current Shutdown Mode (< 10µA)
n General Purpose CMOS Isolated Channel
n 15mm × 11.25mm BGA and LGA Packages
n Isolated RS485/RS422 Interface
n Industrial Networks
n Breaking RS485 Ground Loops
n Isolated PROFIBUS-DP Networks
LTM2881 Operating Through 35kV/μs CM Transients
2881 TA01
TWISTED-PAIR
CABLE
AVAILABLE CURRENT:
150mA (LTM2881-5)
100mA (LTM2881-3)
A
VCC2 5V
RO
VL
TE
RE
DE
DI
GND GND2
VCC
3.3V (LTM2881-3)
5V (LTM2881-5)
LTM2881
B
Y
Z
PWR
ISOLATION BARRIER
2881 TA01a
500V/DIV
50ns/DIV
1V/DIV
1V/DIV
DI
MULTIPLE SWEEPS
OF COMMON MODE
TRANSIENTS
RO
LTM2881
2
2881fi
For more information www.linear.com/LTM2881
pin conFiguraTionabsoluTe MaxiMuM raTings
VCC to GND ..................................................–0.3V to 6V
VCC2 to GND2 ...............................................–0.3V to 6V
VL to GND .................................................... –0.3V to 6V
Interface Voltages
(A, B, Y, Z) to GND2 ........................ VCC2 –15V to 15V
(A-B) with Terminator Enabled ..............................±6V
Signal Voltages ON, RO, DI, DE,
RE, TE, DOUT to GND ......................... –0.3V to VL +0.3V
Signal Voltages SLO,
DIN to GND2 ....................................–0.3V to VCC2 +0.3V
Operating Temperature Range
LTM2881C ............................................... 0°C to 70°C
LTM2881I .............................................–40°C to 85°C
LTM2881H ......................................... –40°C to 105°C
LTM2881MP ...................................... –55°C to 105°C
Maximum Internal Operating Temperature ....... 125°C
Storage Temperature Range ..................–55°C to 150°C
Peak Package Body Reflow Temperature .............. 245°C
(Note 1)
BGA PACKAGE
32-PIN (15mm × 11.25mm × 3.42mm)
TJMAX = 125°C,
θJA = 32.2°C/W,
θJCTOP = 27.2°C/W,
θJCBOTTOM = 20.9°C/W,
θJB = 26.4°C/W,
WEIGHT = 1g
LGA PACKAGE
32-PIN (15mm × 11.25mm × 2.8mm)
TJMAX = 125°C,
θJA = 31.1°C/W,
θJCTOP = 27.3°C/W,
θJCBOTTOM = 19.5°C/W,
θJB = 25.1°C/W,
WEIGHT = 1g
TOP VIEW
SLODIN
RO VLONREDEDITEDOUT
1
A
B
C
D
E
F
G
H
J
K
L
2345678
VCC2
Z
GND2
GND
B AY
VCC
LTM2881
3
2881fi
For more information www.linear.com/LTM2881
orDer inForMaTion
PART NUMBER
INPUT
VOLTAGE PAD OR BALL FINISH
PART MARKING PACKAGE
TYPE
MSL
RATING TEMPERATURE RANGEDEVICE FINISH CODE
LTM2881CY-3#PBF
3V to 3.6V
SAC305 (RoHS)
LTM2881Y-3
e1
BGA
3
0°C to 70°C
LTM2881IY-3#PBF –40°C to 85°C
LTM2881HY-3#PBF –40°C to 105°C
LTM2881HY-3 SnPb (63/37) e0 –40°C to 105°C
LTM2881MPY-3#PBF SAC305 (RoHS) e1 –55°C to 105°C
LTM2881MPY-3 SnPb (63/37) e0 –55°C to 105°C
LTM2881CY-5#PBF
4.5V to 5.5V
SAC305 (RoHS)
LTM2881Y-5
e1
0°C to 70°C
LTM2881IY-5#PBF –40°C to 85°C
LTM2881HY-5#PBF –40°C to 105°C
LTM2881HY-5 SnPb (63/37) e0 –40°C to 105°C
LTM2881MPY-5#PBF SAC305 (RoHS) e1 –55°C to 105°C
LTM2881MPY-5 SnPb (63/37) e0 –55°C to 105°C
LTM2881CV-3#PBF
3V to 3.6V
Au (RoHS)
LTM2881V-3
e4 LGA
0°C to 70°C
LTM2881IV-3#PBF –40°C to 85°C
LTM2881HV-3#PBF –40°C to 105°C
LTM2881CV-5#PBF
4.5V to 5.5V LTM2881V-5
0°C to 70°C
LTM2881IV-5#PBF –40°C to 85°C
LTM2881HV-5#PBF –40°C to 105°C
• Device temperature grade is indicated by a label on the shipping
container.
• Pad or ball finish code is per IPC/JEDEC J-STD-609.
• Terminal Finish Part Marking: www.linear.com/leadfree
• This product is not recommended for second side reflow. For more
information, go to: www.linear.com/BGA-assy
• Recommended BGA and LGA PCB Assembly and Manufacturing
Procedures: www.linear.com/umodule/pcbassembly
• LGA and BGA Package and Tray Drawings: www.linear.com/packaging
• This product is moisture sensitive. For more information, go to:
www.linear.com/umodule/pcbassembly
http://www.linear.com/product/LTM2881#orderinfo
LTM2881
4
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For more information www.linear.com/LTM2881
elecTrical characTerisTics
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Power Supply
VCC VCC Supply Voltage LTM2881-3
LTM2881-5
l
l
3.0
4.5
3.3
5.0
3.6
5.5
V
V
VLVL Supply Voltage l1.62 5.5 V
ICCPOFF VCC Supply Current in Off Mode ON = 0V l0 10 µA
ICCS VCC Supply Current in On Mode LTM2881-3 DE = 0V, RE = VL, No Load
LTM2881-5 DE = 0V, RE = VL, No Load
l
l
20
15
30
25
mA
mA
VCC2 Regulated VCC2 Output Voltage,
Loaded
LTM2881-3 DE = 0V, RE = VL, ILOAD = 100mA
LTM2881-5 DE = 0V, RE = VL, ILOAD = 150mA
LTM2881-3, H/MP-Grade, ILOAD = 90mA
l
l
l
4.75
4.75
4.75
5.0
5.0
V
V
V
VCC2NOLOAD Regulated VCC2 Output Voltage,
No Load
DE = 0V, RE = VL, No Load 4.8 5.0 5.35 V
Efficiency ICC2 = 100mA, LTM2881-5 (Note 2) 62 %
ICC2S VCC2 Short-Circuit Current DE = 0V, RE = VL, VCC2 = 0V 200 mA
Driver
|VOD| Differential Driver Output Voltage R = ∞ (Figure 1)
R = 27Ω (RS485) (Figure 1)
R = 50Ω (RS422) (Figure 1)
l
l
l
2.1
2.1
VCC2
VCC2
VCC2
V
V
V
∆|VOD| Difference in Magnitude of Driver
Differential Output Voltage for
Complementary Output States
R = 27Ω or R = 50Ω (Figure 1) l0.2 V
VOC Driver Common Mode Output
Voltage
R = 27Ω or R = 50Ω (Figure 1) l3 V
∆|VOC| Difference in Magnitude of Driver
Common Mode Output Voltage
for Complementary Output States
R = 27Ω or R = 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
DE = 0V, (Y or Z) = –7V, +12V, H/MP-Grade
l
l
±10
±50
µA
µA
IOSD Maximum Driver Short-Circuit
Current
–7V ≤ (Y or Z) ≤ 12V (Figure 2) l– 250 250 mA
Receiver
RIN Receiver Input Resistance RE = 0V or VL, VIN = –7V, –3V, 3V, 7V, 12V (Figure 3)
RE = 0V or VL, VIN = –7V, –3V, 3V, 7V, 12V (Figure 3),
H/MP-Grade
l
l
96
48
125
125
kΩ
kΩ
RTE Receiver Termination Resistance
Enabled
TE = VL, VAB = 2V, VB = –7V, 0V, 10V (Figure 8) l108 120 156 Ω
IIN Receiver Input Current (A, B) ON = 0V VCC2 = 0V or 5V, VIN = 12V (Figure 3)
ON = 0V VCC2 = 0V or 5V, VIN = 12V (Figure 3), H/MP-Grade
l
l
125
250
µA
ON = 0V VCC2 = 0V or 5V, VIN = –7V (Figure 3)
ON = 0V VCC2 = 0V or 5V, VIN = –7V (Figure 3), H/MP-Grade
l
l
–100
–145
µA
VTH Receiver Differential Input
Threshold Voltage (A-B)
–7V ≤ B ≤ 12V l–0.2 0.2 V
∆VTH Receiver Input Failsafe Hysteresis B = 0V 25 mV
Receiver Input Failsafe Threshold B = 0V –0.2 –0.05 0 V
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. LTM2881-3 VCC = 3.3V, LTM2881-5 VCC = 5.0V, VL = 3.3V, GND = GND2
= 0V, ON = VL unless otherwise noted.
LTM2881
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For more information www.linear.com/LTM2881
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Logic
VIL Logic Input Low Voltage 1.62V ≤ VL ≤ 5.5V l0.4 V
VIH
Logic Input High Voltage
DIN
SLO
DI, TE, DE, ON, RE:
VL ≥ 2.35V
1.62V ≤ VL < 2.35V
l
l
l
l
0.67•VCC2
2
0.67•VL
0.75•VL
V
V
V
V
IINL Logic Input Current l0 ±1 µA
VHYS Logic Input Hysteresis (Note 2) 150 mV
VOH Output High Voltage Output High, ILOAD = –4mA
(Sourcing), 5.5V ≥ VL ≥ 3V
Output High, ILOAD = –1mA
(Sourcing), 1.62V ≤ VL < 3V
l
l
VL –0.4
VL –0.4
V
V
VOL Output Low Voltage Output Low, ILOAD = 4mA
(Sinking), 5.5V ≥ VL ≥ 3V
Output High, ILOAD = 1mA
(Sinking), 1.62V ≤ VL < 3V
l
l
0.4
0.4
V
V
IOZR Three-State (High Impedance)
Output Current on RO
RE = VL, 0V ≤ RO ≤ VLl±1 µA
IOSR Short-Circuit Current 0V ≤ (RO or DOUT) ≤ VLl±85 mA
elecTrical characTerisTics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. LTM2881-3 VCC = 3.3V, LTM2881-5 VCC = 5.0V, VL = 3.3V, GND = GND2
= 0V, ON = VL unless otherwise noted.
swiTching characTerisTics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. LTM2881-3 VCC = 3.3V, LTM2881-5 VCC = 5.0V, VL = 3.3V, GND = GND2
= 0V, ON = VL unless otherwise noted.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Driver SLO = VCC2
fMAX Maximum Data Rate (Note 3) 20 Mbps
tPLHD
tPHLD
Driver Input to Output RDIFF = 54Ω, CL = 100pF
(Figure 4)
l60 85 ns
∆tPD Driver Input to Output Difference
|tPLHD – tPHLD|
RDIFF = 54Ω, CL = 100pF
(Figure 4)
l1 8 ns
tSKEWD Driver Output Y to Output Z RDIFF = 54Ω, CL = 100pF
(Figure 4)
l1 ±8 ns
tRD
tFD
Driver Rise or Fall Time RDIFF = 54Ω, CL = 100pF
(Figure 4)
l4 12.5 ns
tZLD, tZHD,
tLZD, tHZD
Driver Output Enable or Disable
Time
RL = 500Ω, CL = 50pF
(Figure 5)
l170 ns
Driver SLO = GND2
fMAX Maximum Data Rate (Note 3) 250 kbps
tPLHD
tPHLD
Driver Input to Output RDIFF = 54Ω, CL = 100pF
(Figure 4)
1 1.55 µs
∆tPD Driver Input to Output Difference
|tPLHD – tPHLD|
RDIFF = 54Ω, CL = 100pF
(Figure 4)
50 500 ns
tSKEWD Driver Output Y to Output Z RDIFF = 54Ω, CL = 100pF
(Figure 4)
±200 ±500 ns
tRD
tFD
Driver Rise or Fall Time RDIFF = 54Ω, CL = 100pF
(Figure 4)
l0.9 1.5 µs
LTM2881
6
2881fi
For more information www.linear.com/LTM2881
isolaTion characTerisTics
TA = 25°C, LTM2881-3 VCC = 3.3V, LTM2881-5 VCC = 5.0V, VL = 3.3V unless
otherwise noted.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
VISO Rated Dielectric Insulation Voltage 1 Minute (Derived from 1 Second Test) 2500 VRMS
1 Second (Notes 5, 6) ±4400 VDC
Common Mode Transient Immunity LTM2881-3 VCC = 3.3V, LTM2881-5 VCC = 5V,
VL = ON = 3.3V, VCM = 1kV, ∆t = 33ns (Note 2)
±30 kV/µs
VIORM Maximum Working Insulation Voltage (Notes 2, 5) 560
400
VPEAK
VRMS
Partial Discharge VPR = 1050 VPEAK (Note 2) 5 pC
CTI Comparative Tracking Index IEC 60112 (Note 2) 600 VRMS
Depth of Erosion IEC 60112 (Note 2) 0.017 mm
DTI Distance Through Insulation (Note 2) 0.06 mm
Input to Output Resistance (Notes 2, 5) 109Ω
Input to Output Capacitance (Notes 2, 5) 6 pF
Creepage Distance (Notes 2, 5) 9.48 mm
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 overtemperature protection that
is intended to protect the device during momentary overload conditions.
Junction temperature will exceed 125°C when overtemperature protection
is active. Continuous operation above specified maximum operating
junction temperature may result in device degradation or failure.
Note 5: Device considered a 2-terminal device. Pin group A1 through B8
shorted together and pin group K1 through L8 shorted together.
Note 6: The rated dielectric insulation voltage should not be interpreted as
a continuous voltage rating.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
tZLD, tZHD,
tLZD, tHZD
Driver Output Enable or Disable
Time
RL = 500Ω, CL = 50pF
(Figure 5)
l400 ns
Receiver
tPLHR
tPHLR
Receiver Input to Output CL = 15pF, VCM = 2.5V, |VAB| = 1.4V,
tR and tF < 4ns, (Figure 6)
l100 140 ns
tSKEWR Differential Receiver Skew
|tPLHR - tPHLR|
CL = 15pF
(Figure 6)
l1 8 ns
tRR
tFR
Receiver Output Rise or Fall Time CL = 15pF
(Figure 6)
l3 12.5 ns
tZLR, tZHR,
tLZR, tHZR
Receiver Output Enable Time RL =1kΩ, CL = 15pF
(Figure 7)
l50 ns
tRTEN, tRTZ Termination Enable or Disable
Time
RE = 0V, DE = 0V, VAB = 2V, VB = 0V (Figure 8) l100 µs
Generic Logic Input
tPLHL1
tPHLL1
DIN to DOUT Input to Output CL = 15pF,
tR and tF < 4ns
l60 100 ns
Power Supply Generator
VCC2–GND2 Supply Start-Up
Time
(0V to 4.5V)
ON VL, No Load l325 800 µs
swiTching characTerisTics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. LTM2881-3 VCC = 3.3V, LTM2881-5 VCC = 5.0V, VL = 3.3V, GND = GND2
= 0V, ON = VL unless otherwise noted.
LTM2881
7
2881fi
For more information www.linear.com/LTM2881
Receiver Skew vs Temperature Driver Skew vs Temperature
Driver Propagation Delay
vs Temperature
Typical perForMance characTerisTics
Receiver Output Voltage vs
Output Current (Source and Sink)
Receiver Propagation Delay
vs Temperature Supply Current vs Data Rate
RTERM vs Temperature
Driver Output Low/High Voltage
vs Output Current
Driver Differential Output Voltage
vs Temperature
OUTPUT CURRENT (mA)
OUTPUT VOLTAGE (V)
5.0
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
2881 G05
706050403020100
OUTPUT HIGH
OUTPUT LOW
TA = 25°C, LTM2881-3 VCC = 3.3V, LTM2881-5
VCC = 5.0V, VL = 3.3V unless otherwise noted.
OUTPUT CURRENT (mA)
OUTPUT VOLTAGE (V)
4
1
0
2
3
2881 G07
543210
SINK
SOURCE
DATA RATE (Mbps)
SUPPLY CURRENT (mA)
200
180
140
160
100
120
80
60
40
20
0
2881 G09
1010.1
R = 54Ω (LTM2881-3)
R = 100Ω (LTM2881-3)
R = 54Ω (LTM2881-5)
R = 100Ω (LTM2881-5)
R = ∞ (LTM2881-3)
R = ∞ (LTM2881-5)
TEMPERATURE (°C)
RECEIVER SKEW (ns)
2.0
0
0.5
1.5
1.0
–0.5
–1.0
2881 G01
1251007550250–25–50
TEMPERATURE (°C)
DRIVER SKEW (ns)
2.0
0
0.5
1.5
1.0
–0.5
–1.0
2881 G02
1251007550250–25–50
TEMPERATURE (°C)
DRIVER PROP DELAY (ns)
80
50
70
65
60
55
75
2881 G03
1251007550250–25–50
TEMPERATURE (°C)
RESISTANCE (Ω)
130
110
112
114
116
118
120
122
124
126
128
2881 G04
1251007550250–25–50
TEMPERATURE (°C)
OUTPUT VOLTAGE (V)
6
1
0
2
4
3
5
2881 G06
1251007550250–25–50
R = ∞
R = 100Ω
R = 54Ω
TEMPERATURE (°C)
RECEIVER PROP DELAY (ns)
120
115
110
105
100
95
90
2881 G08
1251007550250–25–50
LTM2881
8
2881fi
For more information www.linear.com/LTM2881
Typical perForMance characTerisTics
TA = 25°C, LTM2881-3 VCC = 3.3V, LTM2881-5
VCC = 5.0V, VL = 3.3V unless otherwise noted.
VCC2 vs Load Current
VCC Supply Current vs Temperature
at ILOAD = 100mA on VCC2
VCC2 Surplus Current
vs Temperature
VCC2 LOAD CURRENT (mA)
VOLTAGE (V)
6
4
5
3
2
2881 G12
18016010 20 40 60 80 100 120 140
LTM2881-5
LTM2881-3
ICC2 OUTPUT CURRENT (mA)
0
10
EFFICIENCY (%)
60
50
40
30
20
70
20050 100
2881 G13
150
LTM2881-5
LTM2881-3
100µs/DIV 2881 G14
VCC2
100mV/DIV
ILOAD
50mA/DIV
200µs/DIV 2881 G15
10mV/DIV
VCC2 Power Efficiency VCC2 Load Step (100mA) VCC2 Noise
TEMPERATURE (°C)
ICC CURRENT (mA)
350
250
300
200
150
100
50
0
2881 G10
125100755025–25 0–50
LTM2881-3, VCC = 3.3V
LTM2881-5, VCC = 5V
TEMPERATURE (°C)
SURPLUS CURRENT (mA)
250
200
150
100
50
0
2881 G11
125100755025–25 0–50
LTM2881-5 (RS485 60mA)
LTM2881-3 (RS485 60mA)
LTM2881-3 (RS485 90mA)
LTM2881-5 (RS485 90mA)
LTM2881
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For more information www.linear.com/LTM2881
LOGIC SIDE (VCC, VL, GND)
DOUT (Pin A1): General Purpose Logic Output. Logic
output connected through isolation path to DIN. Under
the condition of an isolation communication failure DOUT
is in a high impedance state.
TE (Pin A2): Terminator Enable. A logic high enables a
termination resistor (typically 120Ω) between pins A and B.
DI (Pin A3): Driver Input. If the driver outputs are enabled
(DE high), then a low on DI forces the driver noninverting
output (Y) low and the inverting output (Z) high. A high
on DI, with the driver outputs enabled, forces the driver
noninverting output (Y) high and inverting output (Z) low.
DE (Pin A4): Driver Enable. A logic low disables the driver
leaving the outputs Y and Z in a high impedance state. A
logic high enables the driver.
RE (Pin A5): Receiver Enable. A logic low enables the
receiver output. A logic high disables RO to a high imped-
ance state.
RO (Pin A6): Receiver Output. If the receiver output is
ena bled (RE low) and if A – B is > 200mV, RO is a logic
high, if A – B is < –200mV RO is a logic low. If the receiver
inputs are open, shorted, or terminated without a valid
signal, RO will be high. Under the condition of an isolation
communication failure RO is in a high impedance state.
VL (Pin A7): Logic Supply. Interface supply voltage for
pins RO, RE, TE, DI, DE, DOUT, and ON. Recommended
operating voltage is 1.62V to 5.5V. Internally bypassed
to GND with 2.2µF.
ON (Pin A8): Enable. Enables power and data communica-
tion through the isolation barrier. If ON is high the part is
enabled and power and communications are functional
to the isolated side. If ON is low the logic side is held in
reset and the isolated side is unpowered.
GND (Pins B1-B5): Circuit Ground.
VCC (Pins B6-B8): Supply Voltage. Recommended operat-
ing voltage is 3V to 3.6V for LTM2881-3 and 4.5V to 5.5V
for LTM2881-5. Internally bypassed to GND with 2.2µF.
pin FuncTions
ISOLATED SIDE (VCC2, GND2)
DIN (Pin L1): General Purpose Isolated Logic Input. Logic
input on the isolated side relative to VCC2 and GND2. A
logic high on DIN will generate a logic high on DOUT. A
logic low on DIN will generate a logic low on DOUT.
SLO (Pin L2): Driver Slew Rate Control. A low input, rela-
tive to GND2, will force the driver into a reduced slew rate
mode for reduced EMI. A high input, relative to GND2,
puts the driver into full speed mode to support maximum
data rates.
Y (Pin L3): Non Inverting Driver Output. High impedance
when the driver is disabled.
Z (Pin L4): Inverting Driver Output. High impedance when
the driver is disabled.
B (Pin L5): Inverting Receiver Input. Impedance is > 96kΩ
in receive mode with TE low or unpowered.
A (Pin L6): Non Inverting Receiver Input. Impedance is
> 96kΩ in receive mode with TE low or unpowered.
VCC2 (Pins L7-L8): Isolated Supply Voltage. Internally
generated from VCC by an isolated DC/DC converter and
regulated to 5V. Internally bypassed to GND2 with 2.2µF.
GND2 (Pins K1-K8): Isolated Side Circuit Ground. The
pads should be connected to the isolated ground and/or
cable shield.
LTM2881
10
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For more information www.linear.com/LTM2881
block DiagraM
120Ω
A
Y
TE
RE
RO
2.2µF
2.2µF
2.2µF
VCC
VL
GND
DOUT
Z
SLO
DIN
B
2881 BD
VCC2
ISOLATED
DC/DC
CONVERTER
ON
DI
DE
= LOGIC SIDE COMMON = ISOLATED SIDE COMMON
GND2
ISOLATED
COMM
INTERFACE
ISOLATED
COMM
INTERFACE
5V
REG
RX
DX
TesT circuiTs
–
+
DRIVER
DI
GND
OR
VL
R
2881 F01
Y
Z
R
VOC
–
+
VOD DRIVER
DI
GND
OR
VL
2881 F02
Y
Z
+
–
IOSD
–7V TO 12V
+
–RECEIVER
2881 F03
A OR B
VIN
I
IN
B OR A
VIN
IIN
RIN =
Figure 1. Driver DC Characteristics Figure 2. Driver Output Short-Circuit Current
Figure 3. Receiver Input Current and Input Resistance
LTM2881
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For more information www.linear.com/LTM2881
A
B
VCM
±VAB/2
±VAB/2
RO
CL
2881 F06a
RECEIVER tPLHR tPHLR
90%
0
90%
10%
tR
90%
10%
tF
90%
1/2 VL1/2 VL
tRR tFR
10%
2881 F06b
10%
VAB
VL
0
–VAB
RO
A-B
Figure 6. Receiver Propagation Delay Measurements
DRIVER
DI
VL
OR
GND
GND
OR
VCC2
VCC2
OR
GND
RL
RL
CL
2881 F05a
Y
Z
DE
CL
tZLD
tZHD tHZD
tLZD
1/2 VL
1/2 VCC2
1/2 VCC2
DE
Y OR Z
Z OR Y
V
L
VCC2
0V
0V
0.5V
0.5V
2881 F05b
Figure 5. Driver Enable and Disable Timing Measurements
TesT circuiTs
DRIVER
DI RDIFF
CL
CL
2881 F04a
Y
Z
1/2 VOD
90% 90%
0 0
10%
2881 F04b
10%
VOD
V
L
Y, Z
DI
(Y-Z)
0V
tSKEWD
tPLHD
tRD tFD
tPHLD
Figure 4. Driver Timing Measurement
LTM2881
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For more information www.linear.com/LTM2881
TesT circuiTs
A
B
0V OR VCC2
VCC2 OR 0V
RO
RE CL
RLVL
OR
GND
2881 F07a
RECEIVER
tZLR
tZHR tHZR
tLZR
1/2 VL
1/2 VL
1/2 VL
RE
RO
RO
V
L
VL
VOL
VOH
0V
0V
0.5V
0.5V
2881 F07b
Figure 7. Receiver Enable/Disable Time Measurements
tRTEN tRTZ
VL
B
A
IA
TE
2881 F08
RECEIVER
90%
10%
0V
TE
+
–
+
–
VAB
VB
RTE =IA
V
AB
1/2 VL
RO
IA
Figure 8. Termination Resistance and Timing Measurements
FuncTional Table
LOGIC INPUTS MODE A, B Y, Z RO
DC/DC
CONVERTER TERMINATOR
ON RE TE DE
1 0 0 0 Receive RIN Hi-Z Enabled On Off
1 0 0 1 Transceiver RIN Driven Enabled On Off
1 1 0 1 Transmit RIN Driven Hi-Z On Off
1 0 1 0 Receive + Term On RTE Hi-Z Enabled On On
0 X X X Off RIN Hi-Z Hi-Z Off Off
LTM2881
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For more information www.linear.com/LTM2881
Overview
The LTM2881 µModule transceiver provides a galvanically-
isolated robust RS485/RS422 interface, powered by an
integrated, regulated DC/DC converter, complete with
decoupling capacitors. A switchable termination resistor
is integrated at the receiver input to provide proper termi-
nation to the RS485 bus. The LTM2881 is ideal for use in
networks where grounds can take on different voltages.
Isolation in the LTM2881 blocks high voltage differences
and eliminates ground loops and is extremely tolerant of
common mode transients between ground potentials. Error
free operation is maintained through common mode events
greater than 30kV/μs providing excellent noise isolation.
µModule Technology
The LTM2881 utilizes isolator µModule technology to
translate signals and power across an isolation barrier.
Signals on either side of the barrier are encoded into
pulses and translated across the isolation boundary using
coreless transformers formed in the µModule substrate.
This system, complete with data refresh, error checking,
safe shutdown on fail, and extremely high common mode
immunity, provides a robust solution for bidirectional
signal isolation. The µModule technology provides the
means to combine the isolated signaling with our RS485
transceiver and powerful isolated DC/DC converter in one
small package.
DC/DC Converter
The LTM2881 contains a fully integrated isolated DC/DC
converter, including the transformer, so that no external
components are necessary. The logic side contains a full-
bridge driver, running about 2MHz, and is AC-coupled
to a single transformer primary. A series DC blocking
capacitor prevents transformer saturation due to driver
duty cycle imbalance. The transformer scales the primary
voltage, and is rectified by a full-wave voltage doubler.
This topology eliminates transformer saturation caused
by secondary imbalances.
The DC/DC converter is connected to a low dropout reg-
ulator (LDO) to provide a regulated low noise 5V output.
The internal power solution is sufficient to support the
transceiver interface at its maximum specified load and data
applicaTions inForMaTion
rate, and external pins are supplied for extra decoupling
(optional) and heat dissipation. The logic supplies, VCC and
VL have a 2.2µF decoupling capacitance to GND and the
isolated supply VCC2 has a 2.2µF decoupling capacitance
to GND2 within the µModule package.
VCC2 Output
The on-board DC/DC converter provides isolated 5V power
to output VCC2. VCC2 is capable of suppling up to 1W of
power at 5V in the LTM2881-5 option and up to 600mW
of power in the LTM2881-3 option. This surplus current is
available to external applications. The amount of surplus
current is dependent upon the implementation and current
delivered to the RS485 driver and line load. An example
of available surplus current is shown in the Typical Per-
formance Characteristics graph, VCC2 Surplus Current vs
Temperature. Figure 19 demonstrates a method of using
the VCC2 output directly and with a switched power path
that is controlled with the isolated RS485 data channel.
Driver
The driver provides full RS485 and RS422 compatibility.
When enabled, if DI is high, Y–Z is positive. When the
driver is disabled, both outputs are high impedance with
less than 10µA of leakage current over the entire common
mode range of –7V to 12V, with respect to GND2.
Driver Overvoltage and Overcurrent Protection
The driver outputs are protected from short circuits to
any voltage within the absolute maximum range of (VCC2
–15V) to (GND2 +15V) levels. The maximum VCC2 cur-
rent in this condition is 250mA. If the pin voltage exceeds
about ±10V, current limit folds back to about half of the
peak value to reduce overall power dissipation and avoid
damaging the part.
The device also features thermal shutdown protection
that disables the driver and receiver output in case of
excessive power dissipation (See Note 4 in the Electrical
Characteristics section).
SLO Mode
The LTM2881 features a logic-selectable reduced slew rate
mode (SLO mode) that softens the driver output edges to
LTM2881
14
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For more information www.linear.com/LTM2881
reduce EMI emissions from equipment and data cables.
The reduced slew rate mode is entered by taking the SLO
pin low to GND2, where the data rate is limited to about
250kbps. Slew limiting also mitigates the adverse effects
of imperfect transmission line termination caused by stubs
or mismatched cables.
Figures 9a and 9b show the frequency spectrums of the
LTM2881 driver outputs in normal and SLO mode operat-
ing at 250kbps. SLO mode significantly reduces the high
frequency harmonics.
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 polarity of (A-B).
During data communication the receiver detects the state
of the input with symmetric thresholds around 0V. The
symmetric thresholds preserve duty cycle for attenu-
ated signals with slow transition rates on high capacitive
busses, or long cable lengths. The receiver incorporates
a failsafe feature that guarantees the receiver output to
be a logic-high during an idle bus, when the inputs are
shorted, left open or terminated, but not driven. The failsafe
feature eliminates the need for system level integration of
network pre-biasing by guaranteeing a logic-high on RO
under the conditions of an idle bus. Further network bias-
ing constructed to condition transient noise during an idle
state is unnecessary due to the common mode transient
rejection of the LTM2881. The failsafe detector monitors
A and B in parallel with the receiver and detects the state
applicaTions inForMaTion
Figure 9a. Frequency Spectrum SLO Mode 125kHz Input Figure 9b. Normal Mode Frequency Spectrum 125kHz Input
FREQUENCY (MHz)
Y-Z 10dB/DIV
2881 F09a
12.56.250
FREQUENCY (MHz)
Y-Z 10dB/DIV
2881 F09b
12.56.250
of the bus when A-B is above the input failsafe threshold
for longer than about 3µs with a hysteresis of 25mV. 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 VL) or
low (to GND) 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 GND2 is
greater than 96k permitting up to a total of 256 receivers
per system without exceeding the RS485 receiver loading
specification. High temperature H-/MP-Grade operation
reduces the input resistance to 48k permitting 128 re-
ceivers on the bus. The input resistance of the receiver is
unaffected by enabling/disabling the receiver or by power-
ing/unpowering the part. The equivalent input resistance
looking into A and B is shown in Figure 10.
Figure 10. Equivalent Input Resistance into A and B
60Ω
60Ω
A
TE
B
2881 F10
>96k
>96k
LTM2881
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For more information www.linear.com/LTM2881
applicaTions inForMaTion
Switchable Termination
Proper cable termination is very important for signal fi-
delity. If the cable is not terminated with its characteristic
impedance, reflections will distort the signal waveforms.
The integrated switchable termination resistor provides
logic control of the line termination for optimal perfor-
mance when configuring transceiver networks.
When the TE pin is high, the termination resistor is enabled
and the differential resistance from A to B is 120Ω. Figure
11 shows the I/V characteristics between pins A and B
with the termination resistor enabled and disabled. The
resistance is maintained over the entire RS485 common
mode range of –7V to 12V as shown in Figure 12. The
integrated termination resistor has a high frequency re-
sponse which does not limit performance at the maximum
specified data rate. Figure 13 shows the magnitude and
Figure 13. Termination Magnitude and Phase vs Frequency
Figure 12. Termination Resistance vs Common Mode Voltage
Figure 11. Curve Trace Between A and B with Termination
Enabled and Disabled
2881 F11
COMMON MODE VOLTAGE (V)
RESISTANCE (Ω)
130
128
126
124
122
120
118
116
114
112
110
2881 G11
15105–5 0–10
FREQUENCY (MHz)
MAGNITUDE (Ω)
PHASE (DEGREES)
150
140
130
120
110
100
10
0
–10
–20
–30
–40
2881 F13
1010.1
PHASE
MAGNITUDE
Figure 14. Supply Current vs Data Rate
DATA RATE (Mbps)
2881 F14
1010.1
SUPPLY CURRENT (mA)
250
230
210
190
170
150
130
110
90
70
50
LTM2881-3
R=54 CL=1000p
R=54 CL=100p
R=54 CL=0
LTM2881-5
R=54 CL=1000p
R=54 CL=100p
R=54 CL=0
phase of the termination impedance versus frequency.
The termination resistor cannot be enabled by TE if the
device is unpowered, ON is low or the LTM2881 is in
thermal shutdown.
Supply Current
The static supply current is dominated by power delivered to
the termination resistance. Power supply current increases
with data rate due to capacitive loading. Figure 14 shows
supply current versus data rate for three different loads
for the circuit configuration of Figure 4. Supply current
increases with additional external applications drawing
current from VCC2.
LTM2881
16
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For more information www.linear.com/LTM2881
PROFIBUS Applications
The LTM2881 can be used in PROFIBUS-DP networks
where isolation is required. The standard PROFIBUS
termination differs from RS485 termination and is shown
in Figure15. If used in this way, the internal termination
should remain disabled (TE low). The 390Ω resistors in
Figure15 pre-bias the bus so that when the line is not
driven, the receiver delivers a high output. Since the
LTM2881 uses a fail-safe receiver, the pre-biasing resis-
tors are not necessary and standard RS485 termination
can be used with control from TE.
VCC2, provides an isolated source for the external termina-
tion resistor as shown in the Figure 15. When using the
LTM2881 in PROFIBUS applications, it is recommended
that no additional loads are connected to VCC2 in order to
maintain the specified driver output swing.
• Input and Output decoupling is not required, since
these components are integrated within the package.
An additional bulk capacitor with a value of 6.8µF to
22µF is recommended. The high ESR of this capaci-
tor reduces board resonances and minimizes voltage
spikes caused by hot plugging of the supply voltage.
For EMI sensitive applications, an additional low ESL
ceramic capacitor of 1µF to 4.7µF, placed as close to
the power and ground terminals as possible, is rec-
ommended. Alternatively, a number of smaller value
parallel capacitors may be used to reduce ESL and
achieve the same net capacitance.
• Do not place copper on the PCB between the inner
columns of pads. This area must remain open to
withstand the rated isolation voltage.
• The use of solid ground planes for GND and GND2
is recommended for non-EMI critical applications to
optimize signal fidelity, thermal performance, and to
minimize RF emissions due to uncoupled PCB trace
conduction. The drawback of using ground planes,
where EMI is of concern, is the creation of a dipole
antenna structure which can radiate differential volt-
ages formed between GND and GND2. If ground planes
are used it is recommended to minimize their area,
and use contiguous planes as any openings or splits
can exacerbate RF emissions.
• For large ground planes a small capacitance (≤ 330pF)
from GND to GND2, either discrete or embedded within
the substrate, provides a low impedance current return
path for the module parasitic capacitance, minimizing
any high frequency differential voltages and substan-
tially reducing radiated emissions. Discrete capacitance
will not be as effective due to parasitic ESL. In addi-
tion, voltage rating, leakage, and clearance must be
considered for component selection. Embedding the
capacitance within the PCB substrate provides a near
ideal capacitor and eliminates component selection
issues; however, the PCB must be 4 layers. Care must
be exercised in applying either technique to insure the
voltage rating of the barrier is not compromised.
applicaTions inForMaTion
PCB Layout Considerations
The high integration of the LTM2881 makes PCB layout
very simple. However, to optimize its electrical isolation
characteristics, EMI, and thermal performance, some
layout considerations are necessary.
• Under heavily loaded conditions VCC and GND current
can exceed 300mA. Sufficient copper must be used
on the PCB to insure resistive losses do not cause the
supply voltage to drop below the minimum allowed
level. Similarly, the VCC2 and GND2 conductors must
be sized to support any external load current. These
heavy copper traces will also help to reduce thermal
stress and improve the thermal conductivity.
Figure 15. PROFIBUS-DP Connections with Termination
A
390Ω
3.3V (LTM2881-3)
5V (LTM2881-5)
220Ω
390Ω
SHIELD
PROFIBUS CABLE
TYPE A
VL
DE
RO
DI
GND
VCC VCC2
2881 F15
B
Y
Z
TE
PWR
GND2 LTM2881
ISOLATION BARRIER
LTM2881
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For more information www.linear.com/LTM2881
applicaTions inForMaTion
Figure 16d. Low EMI Demo Board Layout (DC1746A), Inner Layer 2
Figure 16e. Low EMI Demo Board Layout (DC1746A), Bottom Layer
Figure 17. Low EMI Demo Board Emissions
FREQUENCY (MHz)
0
dBµV/m
60
50
40
30
20
–20
–10
0
–30 400200 600
2881 F17
1000300100 500 700 900800
10
DETECTOR = QuasiPeak
RBW = 120kHz, VBW = 300kHz
SWEEP TIME = 17sec
# OF POINTS = 501
DC1746A-B
CISPR 22 CLASS 8 LIMIT
LTM2881
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For more information www.linear.com/LTM2881
applicaTions inForMaTion
Figure 18. Cable Length vs Data Rate
The PCB layout in Figures 16a to 16e show the low EMI
demo board for the LTM2881. The demo board uses a
combination of EMI mitigation techniques, including both
embedded PCB bridge capacitance and discrete GND to
GND2 capacitors. Two safety rated type Y2 capacitors
are used in series, manufactured by Murata, part number
GA342QR7GF471KW01L. The embedded capacitor ef-
fectively suppresses emissions above 400MHz, whereas
the discrete capacitors are more effective below 400MHz.
EMI performance is shown in Figure 17, measured using
a Gigahertz Transverse Electromagnetic (GTEM) cell and
method detailed in IEC 61000-4-20, “Testing and Mea-
surement Techniques – Emission and Immunity Testing
in T
ransverse Electromagnetic Waveguides.”
Cable Length versus Data Rate
For a given data rate, the maximum transmission distance
is bounded by the cable properties. A typical curve of
cable length versus data rate compliant with the RS485
standard is shown in Figure 18. Three regions of this
curve reflect different performance limiting factors in data
transmission. In the flat region of the curve, maximum
distance is determined by resistive loss in the cable. The
downward sloping region represents limits in distance and
rate due to the AC losses in the cable. The solid vertical
line represents the specified maximum data rate in the
RS485 standard. The dashed line at 250kbps shows the
maximum data rate when SLO is low. The dashed line at
20Mbps shows the maximum data rate when SLO is high.
RF, Magnetic Field Immunity
The LTM2881 has been independently evaluated and has
successfully passed the RF and magnetic field immunity
testing requirements per European Standard EN 55024,
in accordance with the following test standards:
EN 61000-4-3 Radiated, Radio-Frequency,
Electromagnetic Field Immunity
EN 61000-4-8 Power Frequency Magnetic Field
Immunity
EN 61000-4-9 Pulsed Magnetic Field Immunity
Tests were performed using an unshielded test card de-
signed per the data sheet PCB layout recommendations.
Specific limits per test are detailed in Table 1.
Table 1
TEST FREQUENCY FIELD STRENGTH
EN 61000-4-3, Annex D 80MHz to 1GHz 10V/m
1.4MHz to 2GHz 3V/m
2GHz to 2.7GHz 1V/m
EN 61000-4-8, Level 4 50Hz and 60Hz 30A/m
EN 61000-4-8, Level 5 60Hz 100A/m*
EN 61000-4-9, Level 5 Pulse 1000A/m
*Non IEC Method
2881 F18
DATA RATE (bps)
CABLE LENGTH (FT)
10k 1M 10M100k 100M
100
1k
10
10k
LOW-EMI MODE
MAX DATA RATE
RS485 MAX
DATA RATE
NORMAL
MODE MAX
DATA RATE
LTM2881
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For more information www.linear.com/LTM2881
Typical applicaTions
Figure 21. Switched 5V Power with Isolated CMOS Logic Connection with Low Voltage Interface
Figure 22. 4-Wire Full Duplex Self Biasing for Unshielded CAT5 Connection
2881 F21
A
VCC2
RO
VL
TE
RE
DE
DI
DOUT
GND GND2
VCC
VCC
CMOS INPUTCMOS OUTPUT
B
Z
1.8V
DIN
PWR
ONOFF
REGULATED 5V
SWITCHED 5V
IRLML6402
330k
LTM2881
ISOLATION BARRIER
A
VL
RE
DE
RO
DI
GND
VCC
VCC
B
Y
Z
PWR
GND2
LTM2881
ISOLATION BARRIER
Y
VL
RE
RO
DE
DI
GND
VCC
VCCB
2881 F22
Z
A
B
PWR
GND2
BUS INHERITED
LTM2881
10nF
51Ω
51Ω
51Ω
51Ω 10nF
ISOLATION BARRIER
B
Figure 19. Isolated System Fault Detection
A
VL
RE
DE
TE
RO
DI
DOUT DIN
GND
FAULT
VCC
VCC
B
Y
Z
GND2
330k
2881 F19
LTM2881
ISOLATION BARRIER
Figure 20. Full-Duplex RS485 Connection
A
VL
RE
DE
TE
RO
DI
GND
VCC
VCC
2881 F20
B
Y
Z
PWR
GND2
LTM2881
ISOLATION BARRIER
LTM2881
21
2881fi
For more information www.linear.com/LTM2881
5. PRIMARY DATUM -Z- IS SEATING PLANE
6. SOLDER BALL COMPOSITION IS 96.5% Sn/3.0% Ag/0.5% Cu
7 PACKAGE ROW AND COLUMN LABELING MAY VARY
AMONG µModule PRODUCTS. REVIEW EACH PACKAGE
LAYOUT CAREFULLY
!
NOTES:
1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M-1994
2. ALL DIMENSIONS ARE IN MILLIMETERS
BALL DESIGNATION PER JESD MS-028 AND JEP95
4
3
DETAILS OF PIN #1 IDENTIFIER ARE OPTIONAL,
BUT MUST BE LOCATED WITHIN THE ZONE INDICATED.
THE PIN #1 IDENTIFIER MAY BE EITHER A MOLD OR
MARKED FEATURE
PACKAGE TOP VIEW
4
PIN “A1”
CORNER
X
Y
aaa Z
aaa Z
PACKAGE BOTTOM VIEW
3
SEE NOTES
SUGGESTED PCB LAYOUT
TOP VIEW BGA 32 1112 REV D
LTMXXXXXX
µModule
TRAY PIN 1
BEVEL PACKAGE IN TRAY LOADING ORIENTATION
COMPONENT
PIN “A1”
DETAIL A
PIN 1
0.000
0.635
0.635
1.905
1.905
3.175
3.175
4.445
4.445
6.350
6.350
5.080
5.080
0.000
DETAIL A
Øb (32 PLACES)
F
G
H
L
J
K
E
A
B
C
D
2 14 35678
DETAIL B
SUBSTRATE
0.27 – 0.37
2.45 – 2.55
// bbb Z
D
A
A1
b1
ccc Z
DETAIL B
PACKAGE SIDE VIEW
MOLD
CAP
Z
MX YZddd
MZeee
0.630 ±0.025 Ø 32x
SYMBOL
A
A1
A2
b
b1
D
E
e
F
G
aaa
bbb
ccc
ddd
eee
MIN
3.22
0.50
2.72
0.60
0.60
NOM
3.42
0.60
2.82
0.75
0.63
15.0
11.25
1.27
12.70
8.89
MAX
3.62
0.70
2.92
0.90
0.66
0.15
0.10
0.20
0.30
0.15
NOTES
DIMENSIONS
TOTAL NUMBER OF BALLS: 32
E
b
e
e
b
A2
F
G
BGA Package
32-Lead (15mm × 11.25mm × 3.42mm)
(Reference LTC DWG # 05-08-1851 Rev D)
7
SEE NOTES
package DescripTion
Please refer to http://www.linear.com/product/LTM2881#packaging for the most recent package drawings.
LTM2881
22
2881fi
For more information www.linear.com/LTM2881
package DescripTion
Please refer to http://www.linear.com/product/LTM2881#packaging for the most recent package drawings.
NOTES:
1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M-1994
2. ALL DIMENSIONS ARE IN MILLIMETERS
LAND DESIGNATION PER JESD MO-222
5. PRIMARY DATUM -Z- IS SEATING PLANE
6. THE TOTAL NUMBER OF PADS: 32
4
3
DETAILS OF PAD #1 IDENTIFIER ARE OPTIONAL,
BUT MUST BE LOCATED WITHIN THE ZONE INDICATED.
THE PAD #1 IDENTIFIER MAY BE EITHER A MOLD OR
MARKED FEATURE
DETAIL B
DETAIL B
SUBSTRATE
MOLD
CAP
0.290 – 0.350
2.400 – 2.600
bbb Z
Z
PACKAGE TOP VIEW
11.25
BSC
15.00
BSC
4
PAD “A1”
CORNER
X
Y
aaa Z
aaa Z
PACKAGE BOTTOM VIEW
3
PADS
SEE NOTES
SUGGESTED PCB LAYOUT
TOP VIEW
LGA 32 0113 REV A
LTMXXXXXX
µModule
TRAY PIN 1
BEVEL
PACKAGE IN TRAY LOADING ORIENTATION
COMPONENT
PIN “A1”
8.89
BSC
1.27
BSC
0.635
0.635
1.905
1.905
3.175
3.175
4.445
4.445
6.350
6.350
5.080
5.080
0.000
SYMBOL
aaa
bbb
eee
TOLERANCE
0.10
0.10
0.05
DETAIL A
0.630 ±0.025 Ø 32x
SYXeee
DETAIL C
0.630 ±0.025 Ø 32x
SYXeee
F
G
H
L
J
K
E
A
B
C
D
2 14 3567
2.69 – 2.95
DETAIL A
12.70
BSC
8
DETAIL c
LGA Package
32-Lead (15mm × 11.25mm × 2.82mm)
(Reference LTC DWG # 05-08-1773 Rev A)
PAD 1
7
SEE NOTES
7 PACKAGE ROW AND COLUMN LABELING MAY VARY
AMONG µModule PRODUCTS. REVIEW EACH PACKAGE
LAYOUT CAREFULLY
!
LTM2881
23
2881fi
For more information www.linear.com/LTM2881
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
A 3/10 Changes to Features, Description and Typical Application
Add BGA Package to Pin Configuration, Order Information and Package Description Sections
Changes to LGA Package in Pin Configuration Section
Changes to Electrical Characteristics Section
Changes to Graphs G09, G13, G14
Update to Pin Functions
Update to Applications Information
Change to X-Axis on Figures 9a and 9b
Update to Supply Current Section
“PCB Layout Isolation Considerations” Section Replaced
RF, Magnetic Field Immunity Section Added
Changes to Related Parts
1
2, 19
2
3
6, 7
8
12
13
14
15
16
22
B 8/10 H-Grade parts added. Reflected throughout the data sheet. 1-22
C 5/11 HV-Grade parts removed. Reflected throughout the data sheet.
Updated the PCB Layout section.
Updated the Related Parts.
1-24
15, 16, 17
24
D 1/12 HV and MPY parts added. Reflected throughout the data sheet. 1-24
E 4/12 Added H/MP-Grade condition for IOZD
Corrected Figure 15
3
15
F 2/13 Storage Temperature Range corrected 2
G 4/14 Added lead finish part numbers
Added CTI and DTI parameters
3
6
H 8/14 ICC2S, VCC2 Short-Circuit Current: Deleted max spec. Added typical spec. Removed temp dot. 4
I 4/16 Added CSA information
Changed ICCS limits
1
4
J 11/16 Corrected LGA Part Marking 3
LTM2881
24
2881fi
For more information www.linear.com/LTM2881
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
LINEAR TECHNOLOGY CORPORATION 2009
LT 1116 REV J • PRINTED IN USA
(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com/LTM2881
relaTeD parTs
Typical applicaTion
PART NUMBER DESCRIPTION COMMENTS
LTM2882 Dual Isolated RS232 µModule Transceiver + Power 1Mbps, ±10kV HBM ESD, 2500VRMS
LTC1535 Isolated RS485 Transceiver 2500VRMS Isolation in Surface Mount Package
LT1785 ±60V Fault-Protected Transceiver Half Duplex
LT1791 ±60V Fault-Protected Transceiver Full Duplex
LTC2861 20Mbps RS485 Transceivers with Integrated Switchable Termination Full Duplex 15kV ESD
LTC2870/LTC2871 RS232/RS485 Multiprotocol Transceivers with Integrated Termination 20Mbps RS485 and 500kbps RS232,
±26kV ESD, 3V to 5V Operation
LTC2862/LTC2863/
LTC2864/LTC2865
±60V Fault Protected 3V to 5.5V RS485/RS422 T
ransceivers 20Mbps or 250kbps, ±15kV HBM ESD,
±25V Common Mode Range
LTM2883 SPI/Digital or I2C Isolated µModule with Adjustable 5V and ±12V Rails 2500VRMS Isolation with Power in BGA Package
LTM2892 SPI/Digital or I2C Isolated µModule 3500VRMS Isolation, 6 Channels
Figure 23. Multi-Node Network with End Termination
and Single Ground Connection on Isolation Bus
A
VL
VCC1
RE
DE
TE
RO
DI
GND
VCC
VCCA
2881 F23
B
Y
Z
A
PWR
GND2
AVL
RE
DE
TE
RO
DI
GND
VCC
VCCC
B
Y
Z
PWR
GND2
A
VL
RE
DE
TE
RO
DI
GND
VCC
VCCB
B
Y
Z
PWR
GND2
LTM2881
LTM2881LTM2881
VCC2
C
B
CABLE SHIELD
OR GROUND RETURN
ISOLATION BARRIER
ISOLATION BARRIER
ISOLATION BARRIER
B
