LINER LTM2882CV-3

Electrical Specifications Subject to Change
LTM2882
Dual Isolated RS232
µModule Transceiver + Power
FEATURES
DESCRIPTION
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The LTM®2882 is a complete galvanically isolated dual
RS232 μModule® transceiver. No external components are
required. A single 3.3V or 5V supply powers both sides
of the interface through an integrated, isolated DC/DC
converter. A logic supply pin allows easy interfacing with
different logic levels from 1.62V to 5.5V, independent of
the main supply.
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Isolator μModule Technology
Isolated Dual RS232 Transceiver: 2500VRMS
Integrated Isolated DC/DC Converter:
1W, 65% Efficiency
No External Components Required
1.62V to 5.5V Logic Supply for Flexible Digital
Interface
High Speed Operation
1Mbps for 250pF/3kΩ Load
250kbps for 1nF/3kΩ Load
100kbps for 2.5nF/3kΩ TIA/EIA-232-F Load
3.3V (LTM2882-3) or 5V (LTM2882-5) Operation
No Damage or Latchup to ±10kV ESD HBM on
Isolated RS232 Interface or Across Isolation Barrier
High Common Mode Transient Immunity: 30kV/μs
Common Mode Working Voltage: 560VPEAK
True RS232 Compliant Output Levels
Small Low Profile (15mm × 11.25mm × 2.8mm)
Surface Mount LGA Package
APPLICATIONS
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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
with different grounds, allowing for large common mode
voltages. Uninterrupted communication is guaranteed for
common mode transients greater than 30kV/μs.
This part is compatible with the TIA/EIA-232-F standard.
Driver outputs are protected from overload and can be
shorted to ground or up to ±15V without damage. An
auxiliary isolated digital channel is available. This channel
allows configuration for half-duplex operation by controlling the DE pin.
Enhanced ESD protection allows this part to withstand up
to ±10kV (human body model) on the transceiver interface
pins to isolated supplies and across the isolation barrier
to logic supplies without latchup or damage.
Isolated RS232 Interface
Industrial Communication
Test and Measurement Equipment
Breaking RS232 Ground Loops
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.
TYPICAL APPLICATION
Isolated Dual RS232 μModule Transceiver
1Mbps Operation
3.3V (LTM2882-3)
5V (LTM2882-5)
VL
VCC
LTM2882
VCC2
ON
DE
DIN
DOUT
T1IN
R1OUT
T2IN
ISOLATION BARRIER
OFF ON
TIN
5V/DIV
T1OUT/R1IN
10V/DIV
T2OUT/R2IN
T1OUT
R1OUT
5V/DIV
R2OUT
R1IN
T2OUT
R2OUT
GND
5V
AVAILABLE CURRENT:
150mA (LTM2882-5)
100mA (LTM2882-3)
R2IN
GND2
2882 TA01b
400ns/DIV
DRIVER OUTPUTS TIED TO RECEIVER INPUTS
TOUT LOAD = 250pF + RIN
ROUT LOAD = 150pF
2882 TA01a
2882p
1
LTM2882
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Note 1)
VCC to GND .................................................. –0.3V to 6V
VL to GND .................................................... –0.3V to 6V
VCC2 to GND2............................................... –0.3V to 6V
Logic Inputs
T1IN, T2IN, ON, DIN to GND .......–0.3V to (VL + 0.3V)
DE to GND2 ............................–0.3V to (VCC2 + 0.3V)
Logic Outputs
R1OUT, R2OUT to GND ...............–0.3V to (VL + 0.3V)
DOUT to GND2........................–0.3V to (VCC2 + 0.3V)
Driver Output Voltage
T1OUT, T2OUT to GND2...........................–15V to 15V
Receiver Input Voltage
R1IN, R2IN to GND2 ............................... –25V to 25V
Operating Temperature Range (Note 4)
LTM2882C .........................................0°C ≤ TA ≤ 70°C
LTM2882I ..................................... –40°C ≤ TA ≤ 85°C
Storage Temperature Range .................. –55°C to 125°C
Peak Reflow Temperature (Soldering, 10 sec)....... 245°C
TOP VIEW
1
2
3
4
R2OUT T2IN R1OUT T1IN
5
6
7
8
DIN
ON
VL
VCC
A
B
GND
C
D
E
F
G
H
I
J
GND2
K
L
R2IN T2OUT R1IN T1OUT DOUT
DE
VCC2
LGA PACKAGE
32-PIN (15mm s 11.25mm s 2.8mm)
TJMAX = 125°C, ΘJA = 29°C/W, ΘJC(TOP) = 27.9°C/W,
ΘJC(BOT) = 18°C/W, ΘJBOARD = 22.7°C/W, WEIGHT = 1.1g
ORDER INFORMATION
LEAD FREE FINISH
TRAY
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTM2882CV-3#PBF
LTM2882CV-3#PBF
LTM2882V-3
32-Pin (15mm × 11.25mm × 2.8mm) LGA
0°C to 70°C
LTM2882IV-3#PBF
LTM2882IV-3#PBF
LTM2882V-3
32-Pin (15mm × 11.25mm × 2.8mm) LGA
–40°C to 85°C
LTM2882CV-5#PBF
LTM2882CV-5#PBF
LTM2882V-5
32-Pin (15mm × 11.25mm × 2.8mm) LGA
0°C to 70°C
LTM2882IV-5#PBF
LTM2882IV-5#PBF
LTM2882V-5
32-Pin (15mm × 11.25mm × 2.8mm) LGA
–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.
Consult LTC Marketing for information on lead based finish parts.
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/
2882p
2
LTM2882
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. LTM2882-3 VCC = 3.3V, LTM2882-5 VCC = 5.0V, VL = VCC, and GND =
GND2 = 0V, ON = VL unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Supplies
VCC
Input Supply Range
VL
Logic Supply Range
ICC
Input Supply Current
VCC2
Regulated Output Voltage, Loaded
VCC2(NOLOAD) Regulated Output Voltage, No Load
Efficiency
ICC2
LTM2882-3
l
3.0
3.3
3.6
V
LTM2882-5
l
4.5
5.0
5.5
V
l
1.62
5.5
V
ON = 0V
l
0
10
μA
LTM2882-3, No Load
l
24
30
mA
LTM2882-5, No Load
l
17
21
mA
LTM2882-3 DE = 0V, ILOAD = 100mA
l
4.7
5.0
LTM2882-5 DE = 0V, ILOAD = 150mA
l
4.7
5.0
4.8
5.0
DE = 0, No Load
ICC2 = 100mA, LTM2882-5 (Note 2)
V
5.35
V
250
mA
65
l
Output Supply Short-Circuit Current
V
%
Driver
VOLD
Driver Output Voltage Low
RL = 3kΩ
l
–5
–5.7
V
VOHD
Driver Output Voltage High
RL = 3kΩ
l
5
6.2
V
±35
±70
mA
±0.1
±10
μA
IOSD
Driver Short-Circuit Current
VT1OUT, VT2OUT = 0V, VCC2 = 5.5V
l
IOZD
Driver Three-State (High Impedance)
Output Current
DE = 0V, VT1OUT, VT2OUT = ±15V
l
VIR
Receiver Input Threshold
Input Low
l
Input High
l
VHYSR
Receiver Input Hysteresis
RIN
Receiver Input Resistance
Receiver
0.8
1.3
V
1.7
2.5
V
l
0.1
0.4
1.0
V
–15V ≤ (VR1IN, VR2IN) ≤ 15V
l
3
5
7
kΩ
Logic
VITH
Logic Input Threshold Voltage
ON, T1IN, T2IN, DIN = 1.62V ≤ VL < 2.35V
l
0.25•VL
0.75•VL
V
ON, T1IN, T2IN, DIN = 2.35V ≤ VL ≤ 5.5V
l
0.4
0.67•VL
V
DE
l
0.4
0.67•VCC2
V
l
IINL
Logic Input Current
VHYS
Logic Input Hysteresis
T1IN, T2IN, DIN (Note 2)
VOH
Logic Output High Voltage
R1OUT, R2OUT
ILOAD = –1mA (Sourcing), 1.62V ≤ VL < 3.0V
ILOAD = –4mA (Sourcing), 3.0V ≤ VL ≤ 5.5V
l
l
VL – 0.4
VL – 0.4
V
V
DOUT, ILOAD = –4mA (Sourcing)
l
VCC2 – 0.4
V
R1OUT, R2OUT
ILOAD = 1mA (Sinking), 1.62V ≤ VL < 3.0V
ILOAD = 4mA (Sinking), 3.0V ≤ VL ≤ 5.5V
l
l
0.4
0.4
V
V
DOUT, ILOAD = 4mA (Sinking)
l
0.4
V
VOL
Logic Output Low Voltage
±1
150
μA
mV
ESD (HBM) (Note 2)
RS232 Driver and Receiver Protection
Isolation Boundary
(T1OUT, T2OUT, R1IN, R2IN) to (VCC2, GND2)
±10
kV
(T1OUT, T2OUT, R1IN, R2IN) to (VCC, VL, GND)
±10
kV
(VCC2, GND2) to (VCC, VL, GND)
±10
kV
2882p
3
LTM2882
SWITCHING CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. LTM2882-3 VCC = 3.3V, LTM2882-5 VCC = 5.0V, VL = VCC, and GND =
GND2 = 0V, ON = VL unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Maximum Data Rate
(T1IN to T1OUT, T2IN to T2OUT)
RL = 3kΩ, CL = 2.5nF (Note 3)
l
100
kbps
RL = 3kΩ, CL = 1nF (Note 3)
l
250
kbps
RL = 3kΩ, CL = 250pF (Note 3)
l
1000
kbps
Maximum Data Rate (DIN to DOUT)
CL = 15pF
l
10
Mbps
Driver Slew Rate (6V/tTHL or tTLH)
RL = 3kΩ, CL = 50pF (Figure 1)
l
tPHLD, tPLHD
Driver Propagation Delay
RL = 3kΩ, CL = 50pF (Figure 1)
l
0.2
RL = 3kΩ, CL = 50pF (Figure 1)
Driver
150
V/μs
0.5
μs
0.6
2
μs
tSKEWD
Driver Skew |tPHLD – tPLHD|
tPZHD, tPZLD
Driver Output Enable Time
DE = ↑ , RL = 3kΩ, CL = 50pF (Figure 2)
l
40
ns
tPHZD, tPLZD
Driver Output Disable Time
DE = ↓ , RL = 3kΩ, CL = 50pF (Figure 2)
l
0.3
2
μs
tPHLR, tPLHR
Receiver Propagation Delay
CL = 150pF (Figure 3)
l
0.2
0.4
μs
tSKEWR
Receiver Skew |tPHLR – tPLHR|
CL = 150pF (Figure 3)
tRR, tFR
Receiver Rise or Fall Time
CL = 150pF (Figure 3)
l
60
200
ns
tPHLL, tPLHL
Propagation Delay
CL = 15pF, tR and tF < 4ns (Figure 4)
l
60
100
ns
tRL, tFL
Rise or Fall Time
CL = 150pF (Figure 4)
l
60
200
ns
Power-Up Time
ON = ↑ to VCC2(MIN)
l
0.2
2
ms
Receiver
40
ns
Auxiliary Channel
Power Supply
ISOLATION CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. LTM2882-3 VCC = 3.3V, LTM2882-5 VCC = 5.0V, VL = VCC, and GND =
GND2 = 0V, ON = VL unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
VISO
Rated Dielectric Insulation Voltage
1 Minute, Derived from 1 Second Test
2500
VIORM
TYP
MAX
UNITS
VRMS
1 Second
±4400
Common Mode Transient Immunity
(Note 2)
30
kV/μs
V
Maximum Working Insulation Voltage
(Note 2)
560
VPEAK
Partial Discharge
VPR = 1050 VPEAK (Note 2)
<5
>109
pC
Ω
Input to Output Resistance
(Note 2)
Input to Output Capacitance
(Note 2)
6
pF
Creepage Distance
(Note 2)
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 device includes over-temperature 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.
2882p
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LTM2882
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25°C, LTM2882-3 VCC = 3.3V, LTM2882-5
VCC = 5V, VL = 3.3V, and GND = GND2 = 0V, ON = VL unless otherwise noted.
VCC Supply Current
vs Temperature
VCC = 3.3V
LTM2882-3
20
100
65
90
VCC = 3.3V
LTM2882-3
60
VCC CURRENT (mA)
VCC CURRENT (mA)
25
70
VCC = 5.0V
LTM2882-5
15
55
50
45
VCC = 5.0V
LTM2882-5
40
10
–50
0
50
25
75
TEMPERATURE (°C)
–25
100
T1OUT AND T2OUT
35 BAUD = 100kbps
RL = 3k, CL = 2.5nF
30
–50 –25
25
75
0
50
TEMPERATURE (°C)
125
VCC CURRENT (mA)
3.3V CL = 250pF
5.0V CL = 1nF
40
20
THRESHOLD VOLTAGE (V)
120
100
200
400
600
DATA RATE (kbps)
800
100
60
INPUT HIGH
2.0
1.5
INPUT LOW
1.0
45
SOURCING
20
–25
0
50
25
75
TEMPERATURE (°C)
100
–25
0
50
75
25
TEMPERATURE (°C)
50
40
30
FALLING
20
0
125
100
125
2882 G07
0
1
3
2
4
LOAD CAPACITANCE (nF)
2882 G06
6
VTOUT = ±15V
5
10
1
0.1
0.001
–50
5
Receiver Output Voltage
vs Load Current
0.01
15
2.5
RISING
OUTPUT VOLTAGE (V)
LEAKAGE CURRENT (nA)
30
0.5
1.5
1
2
LOAD CAPACITANCE (nF)
10
100
SINKING
0
2882 G05
1000
35
19.2kbps, LTM2882-5
Driver Slew Rate
vs Load Capacitance
Driver Disabled Leakage Current
vs Temperature at ±15V
40
100kbps, LTM2882-5
2882 G03
2.5
0
–50
1000
50
SHORT-CIRCUIT CURRENT (mA)
125
70
Driver Short-Circuit Current
vs Temperature
10
–50
20
3.0
2882 G04
25
250kbps, LTM2882-5
40
0.5
5.0V CL = 250pF
0
19.2kbps, LTM2882-3
50
Receiver Input Threshold
vs Temperature
140
60
100kbps, LTM2882-3
60
2882 G02
VCC Supply Current vs Data Rate
(Dual Transceiver)
80
70
30
2882 G01
3.3V CL = 1nF
250kbps, LTM2882-3
80
VCC CURRENT (mA)
NO LOAD
SLEW RATE (V/μs)
30
VCC Supply Current vs Load
Capacitance (Dual Transceiver)
VCC Supply Current
vs Temperature
VL = 5.5V
VL = 3.3V
VL = 1.62V
4
3
2
1
–25
25
0
50
75
TEMPERATURE (°C)
100
125
2882 G08
0
0
2
6
4
LOAD CURRENT(mA)
8
10
2882 G09
2882p
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LTM2882
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25°C, LTM2882-3 VCC = 3.3V, LTM2882-5
VCC = 5V, VL = 3.3V, and GND = GND2 = 0V, ON = VL unless otherwise noted.
VCC2 Output Voltage
vs Load Current
3.5
5.2
3.0
5.1
2.5
VCC2 VOLTAGE (V)
THRESHOLD VOLTAGE (V)
Logic Input Threshold
vs VL Supply Voltage
INPUT HIGH
2.0
INPUT LOW
1.5
4.9
3.0V
0.5
4.6
1
3
2
4
VL SUPPLY VOLTAGE (V)
4.5
6
5
5.0V
3.3V
4.8
4.7
0
5.5V
5.0
1.0
0
VCC = 3.0V TO 3.6V, LTM2882-3
VCC = 4.5V TO 5.5V, LTM2882-5
3.6V
4.5V
50
0
150
100
200
LOAD CURRENT (mA)
250
2882 G10
300
2882 G11
Driver Outputs Exiting Shutdown
Driver Outputs Enable/Disable
ON
T1OUT
5V/DIV
DE = DOUT,
DIN = VL
2V/DIV
T2OUT
T1OUT
5V/DIV
DE
T1OUT
DE = VCC2
T2OUT
T2OUT
2882 G12
100μs/DIV
2μs/DIV
2882 G13
Operating Through 35kV/μs
Common Mode Transients
T1IN
2V/DIV
2V/DIV
T1OUT = R1IN
R1OUT
*
500V/DIV
50ns/DIV
* MULTIPLE SWEEPS OF
COMMON MODE TRANSIENTS
2882 G14
2882p
6
LTM2882
TYPICAL PERFORMANCE CHARACTERISTICS
VCC = 5V, VL = 3.3V, and GND = GND2 = 0V, ON = VL unless otherwise noted.
VCC2 Surplus Current
vs Temperature
VCC2 Power Efficiency
300
70
1.2
60
VCC = 5.0V
LTM2882-5
EFFICIENCY (%)
200
VCC = 3.3V
LTM2882-3
100
T1OUT AND T2OUT
50 BAUD = 100kbps
RL = 3k, CL = 2.5nF
VCC2 = 4.8V
0
0
50
–50 –25
25
75
TEMPERATURE (°C)
1.0
LTM2882-5
100
125
50
0.8
LTM2882-3
40
0.6
30
0.4
20
0.2
10
POWER LOSS (W)
VCC2 CURRENT (mA)
250
150
TA = 25°C, LTM2882-3 VCC = 3.3V, LTM2882-5
TA = 25°C
0
50
150
100
200
LOAD CURRENT (mA)
2882 G15
250
0
300
2882 G16
VCC2 Load Step Response
VCC2 Ripple and Noise
200mV/DIV
100mV/DIV
50mA/DIV
T1IN = 250kbps
T1OUT, T2OUT, RL = 3k
10μs/DIV
2882 G17
100μs/DIV
2882 G18
2882p
7
LTM2882
TEST CIRCUITS
VL
TIN
½VL
0V
TOUT
TIN
CL
RL
tPLHD
VOHD
TOUT
0V
–3V
VOLD
tr, tf ≤ 40ns
tPHLD
3V
tTHL
tTLH
2882 F01
Figure 1. Driver Slew Rate and Timing Measurement
VCC2
DE
½VCC2
0V
TOUT
0 OR VL
CL
RL
tPZHD
VOHD
VOHD – 0.5V
0V
0V
DE
tPHZD
5V
TOUT
tPZLD
tPLZD
TOUT
tr, tf ≤ 40ns
VOLD – 0.5V
–5V
VOLD
2882 F02
Figure 2. Driver Enable/Disable Times
3V
RIN
ROUT
1.5V
–3V
CL
RIN
tPHLR
VOH
tr, tf ≤ 40ns
tPLHR
10%
ROUT
90%
90%
VOL
½VL
10%
tFR
tRR
2882 F03
Figure 3. Receiver Timing Measurement
VL
DIN
DIN
½VL
0V
DOUT
CL
VOH
DOUT
VOL
tPLHL
90%
10%
tPHLL
10%
½VCC2
tRL
90%
tFL
2882 F04
Figure 4. Auxiliary Channel Timing Measurement
2882p
8
LTM2882
PIN FUNCTIONS
LOGIC SIDE
ISOLATED SIDE
R2OUT (Pin A1): Channel 2 RS232 Inverting Receiver
Output. Controlled through isolation barrier from receiver
input R2IN. Under the condition of an isolation communication failure R2OUT is in a high impedance state.
GND2 (Pins K1-K7): Isolated Side Circuit Ground. These
pads should be connected to the isolated ground and/or
cable shield.
T2IN (Pin A2): Channel 2 RS232 Inverting Driver Input.
A logic low on this input generates a high on isolated
output T2OUT. A logic high on this input generates a low
on isolated output T2OUT. Do not float.
VCC2 (Pins K8, L7-L8): Isolated Supply Voltage Output.
Internally generated from VCC by an isolated DC/DC converter and regulated to 5V. Supply voltage for pins R1IN,
R2IN, DE, and DOUT.
R1OUT (Pin A3): Channel 1 RS232 Inverting Receiver
Output. Controlled through isolation barrier from receiver
input R1IN. Under the condition of an isolation communication failure R1OUT is in a high impedance state.
R2IN (Pin L1): Channel 2 RS232 Inverting Receiver Input.
A low on isolated input R2IN generates a logic high on
R2OUT. A high on isolated input R2IN generates a logic
low on R2OUT. Impedance is nominally 5kΩ in receive
mode or unpowered.
T1IN (Pin A4): Channel 1 RS232 Inverting Driver Input.
A logic low on this input generates a high on isolated
output T1OUT. A logic high on this input generates a low
on isolated output T1OUT. Do not float.
T2OUT (Pin L2): Channel 2 RS232 Inverting Driver
Output. Controlled through isolation barrier from driver
input T2IN. High impedance when the driver is disabled
(DE pin is low).
DIN (Pin A5): General Purpose Non-Inverting Logic Input.
A logic high on DIN generates a logic high on isolated
output DOUT. A logic low on DIN generates a logic low
on isolated output DOUT. Do not float.
R1IN (Pin L3): Channel 1 RS232 Inverting Receiver Input.
A low on isolated input R1IN generates a logic high on
R1OUT. A high on isolated input R1IN generates a logic
low on R1OUT. Impedance is nominally 5kΩ in receive
mode or unpowered.
ON (Pin A6): Enable. Enables power and data communication 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. Do not float.
T1OUT (Pin L4): Channel 1 RS232 Inverting Driver
Output. Controlled through isolation barrier from driver
input T1IN. High impedance when the driver is disabled
(DE pin is low).
VL (Pin A7): Logic Supply. Interface supply voltage for
pins DIN, R2OUT, T2IN, R1OUT, T1IN, and ON. Operating
voltage is 1.62V to 5.5V.
DOUT (Pin L5): General Purpose Non-Inverting Logic
Output. Logic output connected through isolation barrier
to DIN.
VCC (Pins A8, B7-B8): Supply Voltage. Operating voltage is 3.0V to 3.6V for LTM2882-3, and 4.5V to 5.5V for
LTM2882-5.
DE (Pin L6): Driver Output Enable. A low input forces
both RS232 driver outputs, T1OUT and T2OUT, into a high
impedance state. A high input enables both RS232 driver
outputs. Do not float.
GND (Pins B1-B6): Circuit Ground.
2882p
9
LTM2882
BLOCK DIAGRAM
5V
REG
VCC
VCC2
2.2μF
2.2μF
VL
GND2
2.2μF
DE
GND
DOUT
VDD
DC/DC
CONVERTER
VEE
ON
DIN
VDD
T1OUT
T1IN
R1OUT
ISOLATED
COMMUNICATIONS
INTERFACE
ISOLATED
COMMUNICATIONS
INTERFACE
VEE
R1IN
5k
VDD
T2IN
T2OUT
VEE
R2OUT
R2IN
5k
2882 BD
2882p
10
LTM2882
APPLICATIONS INFORMATION
Overview
ANY VOLTAGE FROM
1.62V TO 5.5V
VL
ON
DC/DC Converter
The LTM2882 contains a fully integrated isolated DC/DC
converter, including the transformer, so that no external
components are necessary. The logic side contains a fullbridge driver, running at 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 regulator
(LDO) to provide a regulated low noise 5V output, VCC2.
An integrated boost converter generates a 7V VDD supply
and a charge pumped –6.3V VEE supply. VDD and VEE power
the output stage of the RS232 drivers and are regulated to
levels that guarantee greater than ±5V output swing.
VCC
DIN
EXTERNAL
DEVICE
T1IN
R1OUT
T2IN
LTM2882
GND
VCC2
DE
DOUT
T1OUT
R1IN
T2OUT
R2IN
R2OUT
μModule Technology
The LTM2882 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 advanced dual
RS232 transceiver and powerful isolated DC/DC converter
in one small package.
3.0V TO 3.6V LTM2882-3
4.5V TO 5.5V LTM2882-5
ISOLATION BARRIER
The LTM2882 μModule transceiver provides a galvanically-isolated robust RS232 interface, powered by an
integrated, regulated DC/DC converter, complete with
decoupling capacitors. The LTM2882 is ideal for use in
networks where grounds can take on different voltages.
Isolation in the LTM2882 blocks high voltage differences,
eliminates ground loops and is extremely tolerant of common mode transients between grounds. Error-free operation is maintained through common mode events greater
than 30kV/μs providing excellent noise isolation.
GND2
2882 F05
Figure 5. VCC and VL Are Independent
The internal power solution is sufficient to support the
transceiver interface at its maximum specified load and
data rate, and has the capacity to provide additional 5V
power on the isolated side VCC2 and GND2 pins. VCC and
VCC2 are each bypassed internally with 2.2μF ceramic
capacitors.
VL Logic Supply
A separate logic supply pin VL allows the LTM2882 to interface with any logic signal from 1.62V to 5.5V as shown in
Figure 5. Simply connect the desired logic supply to VL.
There is no interdependency between VCC and VL; they
may simultaneously operate at any voltage within their
specified operating ranges and sequence in any order. VL
is bypassed internally by a 2.2μF capacitor.
Hot Plugging Safely
Caution must be exercised in applications where power
is plugged into the LTM2882’s power supplies, VCC or VL,
due to the integrated ceramic decoupling capacitors. The
parasitic cable inductance along with the high Q characteristics of ceramic capacitors can cause substantial
ringing which could exceed the maximum voltage ratings
and damage the LTM2882. Refer to Linear Technology Application Note 88, entitled “Ceramic Input Capacitors Can
Cause Overvoltage Transients” for a detailed discussion
and mitigation of this phenomenon.
2882p
11
LTM2882
APPLICATIONS INFORMATION
Channel Timing Uncertainty
Driver Overvoltage and Overcurrent Protection
Multiple channels are supported across the isolation boundary by encoding and decoding of the inputs and outputs.
The technique used assigns T1IN/R1IN the highest priority
such that there is no jitter on the associated output channels T1OUT/R1OUT, only delay. This preemptive scheme
will produce a certain amount of uncertainty on T2IN/R2IN
to T2OUT/R2OUT and DIN to DOUT. The resulting pulse
width uncertainty on these low priority channels is typically
±6ns, but may vary up to about 40ns.
The driver outputs are protected from short-circuits to
any voltage within the absolute maximum range of ±15V
relative to GND2. The maximum current is limited to no
more than 70mA to maintain a safe power dissipation and
prevent damaging the LTM2882.
Half-Duplex Operation
Each receiver input has a nominal input impedance of 5kΩ
relative to GND2. An open circuit condition will generate a
logic high on each receiver’s respective output pin.
The DE pin serves as a low-latency driver enable for halfduplex operation. The DE pin can be easily driven from
the logic side by using the uncommitted auxiliary digital
channel, DIN to DOUT. Each driver is enabled and disabled
in less than 2μs, while each receiver remains continuously
active. This mode of operation is illustrated in Figure 6.
3.3V (LTM2882-3)
5V (LTM2882-5)
RX TX
VCC
DIN
T1IN
R1OUT
T2IN
LTM2882
T1OUT
RF, Magnetic Field Immunity
The LTM2882 has been independently evaluated and has
successfully passed the RF and magnetic field immunity
testing requirements per European Standard EN 550024,
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
R1IN
T2OUT
R2IN
R2OUT
GND
VCC2
DE
The receiver inputs are protected from common mode
voltages of ±25V relative to GND2.
DOUT
ISOLATION BARRIER
VL
ON
Receiver Overvoltage and Open Circuit
GND2
2882 F06
Tests were performed using an unshielded test card designed per the data sheet PCB layout recommendations.
Specific limits per test are detailed in Table 1.
Table 1
Figure 6. Half-Duplex Configuration Using DOUT to Drive DE
TEST
EN 61000-4-3, Annex D
FREQUENCY
FIELD STRENGTH
80MHz to 1GHz
10V/m
1.4MHz to 2GHz
3V/m
2GHz to 2.7GHz
1V/m
50Hz and 60Hz
30A/m
EN61000-4-8, Level 5
60Hz
100A/m*
EN61000-4-9, Level 5
Pulse
1000A/m
EN61000-4-8, Level 4
*Non IEC Method
2882p
12
LTM2882
APPLICATIONS INFORMATION
PCB Layout
• 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 PCB may also be slotted
in this area to facilitate cleaning and ensure contamination does not compromise the isolation voltage.
The high integration of the LTM2882 makes PCB layout
very simple. However, to optimize its electrical isolation
characteristics, EMI, and thermal performance, some layout considerations are necessary. Figure 7 is a suggested
layout for good thermal performance and to optimize
isolation characteristics.
• The recommended layout of Figure 7 shows copper
planes for GND and GND2, which is good practice to
optimize signal fidelity and minimize emissions on either
side of the isolation boundary. However, this creates a
dipole antenna which can radiate differential voltages
formed between GND and GND2. A small capacitance
(<200pF) from GND to GND2, either discrete or embedded within the substrate, provides a low impedance
path minimizing the high frequency differential voltages
and substantially reducing radiated emissions. Care
should be exercised in applying these techniques to
insure the voltage rating of the isolation barrier is not
compromised.
• Under heavily loaded conditions, the current in VCC and
GND can exceed 300mA. PCB copper must be made
wide enough in these paths to ensure resistive losses
do not cause the supply voltage at the LTM2882 to drop
below the minimum allowed levels. Similarly, the metal
in the VCC2 and GND2 must be wide enough to support
any external load connected.
• Input and output decoupling is not required, since
these components are integrated within the package.
If additional capacitance is used, place as close to the
power and ground terminals as possible to minimize
high frequency noise. For EMI sensitive applications,
an additional low ESR capacitance of 6.8μF to 22μF is
recommended from VCC to GND.
TOP COPPER
VCC
VCC2
VL
ON
DE
DIN
DOUT
T1IN
SLOT
T1OUT
R1IN
R1OUT
T2IN
T2OUT
R2OUT
R2IN
GND
GND2
SLOT
BOTTOM COPPER
Figure 7. Recommended PCB Layout
2882p
13
LTM2882
TYPICAL APPLICATIONS
3.3V (LTM2882-3)
5V (LTM2882-5)
3.3V (LTM2882-3)
5V (LTM2882-5)
DIN
T1IN
3.3k
R1OUT
T2IN
3.3k
VL
LTM2882
DE
DOUT
DIN
DOUT
T1OUT
T1IN
R1OUT
T2IN
T2OUT
T1OUT
R1IN
μP
OFF ON
DE
DIN
T1IN
R1OUT
T2IN
DOUT
DIN
T1OUT
T1IN
R1IN
VCC
R1OUT
T2OUT
T2IN
R2IN
R2OUT
GND
VL
ON
LTM2882
LTM2882
GND
2882 F10
R1IN
T2OUT
R2IN
GND2
2882 F11
Figure 10. 1.8V Microprocessor Interface
Figure 11. Isolated 5V Power Supply
5V
REGULATED
3.0V TO 3.6V (LTM2882-3)
4.5V TO 5.5V (LTM2882-5)
VL
VCC
LTM2882
VCC2
ON
DE
DIN
DOUT
T1IN
R1OUT
T2IN
R2OUT
GND
ISOLATION BARRIER
OFF ON
T1OUT
R2OUT
GND2
VCC2
DE
5V
REGULATED
150mA (LTM2882-5)
100mA (LTM2882-3)
DOUT
ISOLATION BARRIER
VCC
5
2
0.5
Figure 9. Driving Larger Capacitive Loads
3.3V (LTM2882-3)
5V (LTM2882-5)
ISOLATION BARRIER
VL
ON
100
250
1000
2882 F09
3.3V (LTM2882-3)
5V (LTM2882-5)
1.8V
DATA RATE
CL (nF)
(kbps)
GND2
2882 F08
Figure 8. Single Line Dual Half-Duplex
Isolated Transceiver
CL
R2IN
GND
GND2
3k
T2OUT
R2OUT
R2IN
GND
LTM2882
ON
R1IN
R2OUT
VCC
DE
ISOLATION BARRIER
RX TX
VCC
ISOLATION BARRIER
VL
ON
T1OUT
7V
SWITCHED
R1IN
T2OUT
–6.3V
SWITCHED
R2IN
GND2
2882 F12
RETURN
Figure 12. Isolated Multirail Power Supply
with Switched Outputs
2882p
14
4
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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
3.175
0.635
1.905
SUGGESTED PCB LAYOUT
TOP VIEW
0.635
PACKAGE TOP VIEW
11.25
BSC
1.905
PAD “A1”
CORNER
4.445
3.175
4.445
aaa Z
Y
X
6.350
5.080
0.000
5.080
6.350
DETAIL c
15.00
BSC
aaa Z
bbb Z
DETAIL C
0.630 ±0.025 Ø 32x
DETAIL B
2.69 – 2.95
eee S X Y
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
4
SYMBOL TOLERANCE
aaa
0.10
bbb
0.10
eee
0.05
6. THE TOTAL NUMBER OF PADS: 32
5. PRIMARY DATUM -Z- IS SEATING PLANE
LAND DESIGNATION PER JESD MO-222
3
2. ALL DIMENSIONS ARE IN MILLIMETERS
NOTES:
1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M-1994
DETAIL A
0.290 – 0.350
SUBSTRATE
eee S X Y
DETAIL B
0.630 ±0.025 Ø 32x
2.400 – 2.600
MOLD
CAP
Z
(Reference LTC DWG # 05-08-1773 Rev Ø)
LGA Package
32-Lead (15mm × 11.25mm × 2.82mm)
TRAY PIN 1
BEVEL
COMPONENT
PIN “A1”
12.70
BSC
8
DETAIL A
7
8.89
BSC
5
4
3
1.27
BSC
2
1
L
K
J
H
G
F
E
D
C
B
A
LGA 32 0308 REV Ø
3
PADS
SEE NOTES
PAD 1
PACKAGE IN TRAY LOADING ORIENTATION
LTMXXXXXX
μModule
PACKAGE BOTTOM VIEW
6
LTM2882
PACKAGE DESCRIPTION
2882p
15
LINEAR TECHNOLOGY CONFIDENTIAL
LTM2882
TYPICAL APPLICATIONS
3.3V (LTM2882-3)
5V (LTM2882-5)
1.62V TO 5.5V
VL
ON
μC
VCC
TXD
RXD
PY
PZ
T1IN
R2OUT
T2IN
VL
ON
PERIPHERAL
OFF ON
DOUT
ISOLATION BARRIER
DIN
VCC2
DE
LTM2882
VL
TX
T2OUT
R1OUT
0V
T2IN
RTS
R2IN
GND
T1IN
RX
R1IN
VL
CTS
LTM2882
DE
DIN
T1OUT
R2OUT
VCC
DOUT
ISOLATION BARRIER
3.3V (LTM2882-3)
5V (LTM2882-5)
T1OUT
R1IN
–25V TO 0V
T2OUT
R2IN
R2OUT
–25V TO 0V
GND
GND2
2882 F12
2882 F13
Figure 13. Isolated RS232 Interface with Handshaking
Figure 14. Isolated Dual Inverting Level Translator
3.3V (LTM2882-3)
5V (LTM2882-5)
VCC
T1IN
PWMA
R1OUT
FAULT
PWMB
T2IN
LTM2882
ISOLATION BARRIER
DIN
RESET
3V TO 25V
0V
GND2
VL
ON
3V TO 25V
R2OUT
GND
+VS
1k
VCC2
DE
DOUT
T1OUT
LOGIC
LEVEL
FETS
R1IN
T2OUT
R2IN
IRLML6402
GND2
CMPT2369-LTV
1k
3k
470pF
IRLML2402
3k
47pF
RILIM = 0.6/MAX CURRENT
2882 F14
Figure 15. Isolated Gate Drive with Overcurrent Detection
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTM2881
Isolated RS485/RS422 μModule Transceiver with
Integrated DC/DC Converter
20Mbps, 15kV HBM ESD, 2500VRMS Isolation with Power
LTC2804
1Mbps RS232 Transceiver
Dual Channel, Full-Duplex, 10kV HBM ESD
LTC1535
Isolated RS485 Transceiver
2500 VRMS Isolation with External Transformer Driver
2882p
16 Linear Technology Corporation
LT 1209 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2009