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Electrical Specifications Subject to Change
LTM2882 Dual Isolated RS232 Module Transceiver + Power FEATURES
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DESCRIPTION
The LTM(R)2882 is a complete galvanically isolated dual RS232 Module(R) 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. 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/s. 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.
L, LT, LTC, LTM, Linear Technology, the Linear logo and Module are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
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Isolator Module 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/3k Load 250kbps for 1nF/3k Load 100kbps for 2.5nF/3k 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/s Common Mode Working Voltage: 560VPEAK True RS232 Compliant Output Levels Small Low Profile (15mm x 11.25mm x 2.8mm) Surface Mount LGA Package
APPLICATIONS
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Isolated RS232 Interface Industrial Communication Test and Measurement Equipment Breaking RS232 Ground Loops
TYPICAL APPLICATION
Isolated Dual RS232 Module Transceiver
3.3V (LTM2882-3) 5V (LTM2882-5) VL OFF ON ON ISOLATION BARRIER DIN T1IN R1OUT T2IN R2OUT GND GND2
2882 TA01a
1Mbps Operation
5V/DIV TIN
VCC
LTM2882
VCC2 DE DOUT T1OUT
5V AVAILABLE CURRENT: 150mA (LTM2882-5) 100mA (LTM2882-3)
T1OUT/R1IN 10V/DIV T2OUT/R2IN R1OUT 5V/DIV R2OUT
R1IN T2OUT R2IN
2882 TA01b 400ns/DIV DRIVER OUTPUTS TIED TO RECEIVER INPUTS TOUT LOAD = 250pF + RIN ROUT LOAD = 150pF
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LTM2882 ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW 1 A B C D E F G H I J GND2 K L R2IN T2OUT R1IN T1OUT DOUT LGA PACKAGE 32-PIN (15mm 11.25mm DE VCC2 GND 2 3 4 5 DIN 6 ON 7 VL 8 VCC R2OUT T2IN R1OUT T1IN
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 .........................................0C TA 70C LTM2882I ..................................... -40C TA 85C Storage Temperature Range .................. -55C to 125C Peak Reflow Temperature (Soldering, 10 sec)....... 245C
2.8mm)
TJMAX = 125C, JA = 29C/W, JC(TOP) = 27.9C/W, JC(BOT) = 18C/W, JBOARD = 22.7C/W, WEIGHT = 1.1g
ORDER INFORMATION
LEAD FREE FINISH LTM2882CV-3#PBF LTM2882IV-3#PBF LTM2882CV-5#PBF LTM2882IV-5#PBF TRAY LTM2882CV-3#PBF LTM2882IV-3#PBF LTM2882CV-5#PBF LTM2882IV-5#PBF PART MARKING* LTM2882V-3 LTM2882V-3 LTM2882V-5 LTM2882V-5 PACKAGE DESCRIPTION 32-Pin (15mm x 11.25mm x 2.8mm) LGA 32-Pin (15mm x 11.25mm x 2.8mm) LGA 32-Pin (15mm x 11.25mm x 2.8mm) LGA 32-Pin (15mm x 11.25mm x 2.8mm) LGA TEMPERATURE RANGE 0C to 70C -40C to 85C 0C to 70C -40C to 85C
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/
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LTM2882 ELECTRICAL CHARACTERISTICS
SYMBOL Supplies VCC VL ICC Input Supply Range Logic Supply Range Input Supply Current ON = 0V LTM2882-3, No Load LTM2882-5, No Load VCC2 Regulated Output Voltage, Loaded LTM2882-3 DE = 0V, ILOAD = 100mA LTM2882-5 DE = 0V, ILOAD = 150mA VCC2(NOLOAD) Regulated Output Voltage, No Load Efficiency ICC2 Driver VOLD VOHD IOSD IOZD Receiver VIR VHYSR RIN Logic VITH Logic Input Threshold Voltage ON, T1IN, T2IN, DIN = 1.62V VL < 2.35V ON, T1IN, T2IN, DIN = 2.35V VL 5.5V DE IINL VHYS VOH Logic Input Current Logic Input Hysteresis Logic Output High Voltage T1IN, T2IN, DIN (Note 2) R1OUT, R2OUT ILOAD = -1mA (Sourcing), 1.62V VL < 3.0V ILOAD = -4mA (Sourcing), 3.0V VL 5.5V DOUT, ILOAD = -4mA (Sourcing) VOL Logic Output Low Voltage R1OUT, R2OUT ILOAD = 1mA (Sinking), 1.62V VL < 3.0V ILOAD = 4mA (Sinking), 3.0V VL 5.5V DOUT, ILOAD = 4mA (Sinking) ESD (HBM) (Note 2) RS232 Driver and Receiver Protection Isolation Boundary (T1OUT, T2OUT, R1IN, R2IN) to (VCC2, GND2) (T1OUT, T2OUT, R1IN, R2IN) to (VCC, VL, GND) (VCC2, GND2) to (VCC, VL, GND) 10 10 10 kV kV kV
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The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. LTM2882-3 VCC = 3.3V, LTM2882-5 VCC = 5.0V, VL = VCC, and GND = GND2 = 0V, ON = VL unless otherwise noted.
PARAMETER CONDITIONS LTM2882-3 LTM2882-5
l l l l l l l l
MIN 3.0 4.5 1.62
TYP 3.3 5.0 0 24 17
MAX 3.6 5.5 5.5 10 30 21
UNITS V V V A mA mA V V
4.7 4.7 4.8
5.0 5.0 5.0 65 5.35 250
DE = 0, No Load ICC2 = 100mA, LTM2882-5 (Note 2)
l l l l l
V % mA V V
Output Supply Short-Circuit Current Driver Output Voltage Low Driver Output Voltage High Driver Short-Circuit Current Driver Three-State (High Impedance) Output Current Receiver Input Threshold Receiver Input Hysteresis Receiver Input Resistance -15V (VR1IN, VR2IN) 15V RL = 3k RL = 3k VT1OUT, VT2OUT = 0V, VCC2 = 5.5V DE = 0V, VT1OUT, VT2OUT = 15V
-5 5
-5.7 6.2 35 0.1 70 10
mA A
Input Low Input High
l l l l l l l l
0.8 0.1 3 0.25*VL 0.4 0.4
1.3 1.7 0.4 5 2.5 1.0 7 0.75*VL 0.67*VL 0.67*VCC2 1 150
V V V k V V V A mV V V V 0.4 0.4 0.4 V V V
l l l l l l
VL - 0.4 VL - 0.4 VCC2 - 0.4
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LTM2882 SWITCHING CHARACTERISTICS
SYMBOL PARAMETER Maximum Data Rate (T1IN to T1OUT, T2IN to T2OUT)
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. LTM2882-3 VCC = 3.3V, LTM2882-5 VCC = 5.0V, VL = VCC, and GND = GND2 = 0V, ON = VL unless otherwise noted.
CONDITIONS RL = 3k, CL = 2.5nF (Note 3) RL = 3k, CL = 1nF (Note 3) RL = 3k, CL = 250pF (Note 3) Maximum Data Rate (DIN to DOUT) CL = 15pF RL = 3k, CL = 50pF (Figure 1) RL = 3k, CL = 50pF (Figure 1) RL = 3k, CL = 50pF (Figure 1) DE = , RL = 3k, CL = 50pF (Figure 2) DE = , RL = 3k, CL = 50pF (Figure 2) CL = 150pF (Figure 3) CL = 150pF (Figure 3) CL = 150pF (Figure 3) CL = 15pF tR and tF < 4ns (Figure 4) , CL = 150pF (Figure 4) ON = to VCC2(MIN)
l l l l l l l l l l l
MIN 100 250 1000 10
TYP
MAX
UNITS kbps kbps kbps Mbps
Driver Driver Slew Rate (6V/tTHL or tTLH) tPHLD, tPLHD tSKEWD tPZHD, tPZLD tPHZD, tPLZD Receiver tPHLR, tPLHR tSKEWR tRR, tFR Auxiliary Channel tPHLL, tPLHL tRL, tFL Power Supply Power-Up Time 0.2 2 ms Propagation Delay Rise or Fall Time 60 60 100 200 ns ns Receiver Propagation Delay Receiver Skew |tPHLR - tPLHR| Receiver Rise or Fall Time 0.2 40 60 200 0.4 s ns ns Driver Propagation Delay Driver Skew |tPHLD - tPLHD| Driver Output Enable Time Driver Output Disable Time
l l
150 0.2 40 0.6 0.3 2 2 0.5
V/s s ns s s
ISOLATION CHARACTERISTICS
SYMBOL VISO PARAMETER Rated Dielectric Insulation Voltage Common Mode Transient Immunity VIORM Maximum Working Insulation Voltage Partial Discharge Input to Output Resistance Input to Output Capacitance Creepage Distance
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. LTM2882-3 VCC = 3.3V, LTM2882-5 VCC = 5.0V, VL = VCC, and GND = GND2 = 0V, ON = VL unless otherwise noted.
CONDITIONS 1 Minute, Derived from 1 Second Test 1 Second (Note 2) (Note 2) VPR = 1050 VPEAK (Note 2) (Note 2) (Note 2) (Note 2) >109 6 9.48 MIN 2500 4400 30 560 <5 TYP MAX UNITS VRMS V kV/s VPEAK pC pF 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 125C when overtemperature protection is active. Continuous operation above specified maximum operating junction temperature may result in device degradation or failure.
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LTM2882 TYPICAL PERFORMANCE CHARACTERISTICS
VCC = 5V, VL = 3.3V, and GND = GND2 = 0V, ON = VL unless otherwise noted. VCC Supply Current vs Temperature
30 NO LOAD VCC = 3.3V LTM2882-3 VCC CURRENT (mA) 70 65 60 55 50 45 40 VCC = 5.0V LTM2882-5 VCC CURRENT (mA) VCC = 3.3V LTM2882-3
TA = 25C, LTM2882-3 VCC = 3.3V, LTM2882-5 VCC Supply Current vs Load Capacitance (Dual Transceiver)
100 90 80 70 100kbps, LTM2882-3 60 50 40 30 100 125 20 0 19.2kbps, LTM2882-3 250kbps, LTM2882-5 100kbps, LTM2882-5 19.2kbps, LTM2882-5 0.5 1.5 1 2 LOAD CAPACITANCE (nF) 2.5
2882 G03
VCC Supply Current vs Temperature
25 VCC CURRENT (mA)
250kbps, LTM2882-3
20
VCC = 5.0V LTM2882-5
15
10 -50
-25
0 50 25 75 TEMPERATURE (C)
100
125
T1OUT AND T2OUT 35 BAUD = 100kbps RL = 3k, CL = 2.5nF 30 -50 -25 25 75 0 50 TEMPERATURE (C)
2882 G01
2882 G02
VCC Supply Current vs Data Rate (Dual Transceiver)
140 120 THRESHOLD VOLTAGE (V) 3.3V CL = 1nF VCC CURRENT (mA) 100 80 60 40 20 3.3V CL = 250pF 3.0 2.5 2.0 1.5 1.0 0.5
Receiver Input Threshold vs Temperature
70 60 SLEW RATE (V/s) INPUT HIGH 50 40 30
Driver Slew Rate vs Load Capacitance
INPUT LOW
FALLING 20 RISING 10 0
5.0V CL = 1nF 5.0V CL = 250pF
0
200
400 600 DATA RATE (kbps)
800
1000
2882 G04
0 -50
-25
0 50 25 75 TEMPERATURE (C)
100
125
0
1
3 2 4 LOAD CAPACITANCE (nF)
5
2882 G06
2882 G05
Driver Short-Circuit Current vs Temperature
50 SHORT-CIRCUIT CURRENT (mA) 45 LEAKAGE CURRENT (nA) 40 35 SINKING 30 25 20 15 10 -50 -25 0 50 75 25 TEMPERATURE (C) 100 125 SOURCING 1000 100 10 1 0.1 0.01
Driver Disabled Leakage Current vs Temperature at 15V
VTOUT = 15V 6 5 OUTPUT VOLTAGE (V) 4 3 2 1 0
Receiver Output Voltage vs Load Current
VL = 5.5V VL = 3.3V VL = 1.62V
0.001 -50
-25
25 0 50 75 TEMPERATURE (C)
100
125
0
2
6 4 LOAD CURRENT(mA)
8
10
2882 G09
2882 G07
2882 G08
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LTM2882 TYPICAL PERFORMANCE CHARACTERISTICS
VCC = 5V, VL = 3.3V, and GND = GND2 = 0V, ON = VL unless otherwise noted. Logic Input Threshold vs VL Supply Voltage
3.5 3.0 THRESHOLD VOLTAGE (V) VCC2 VOLTAGE (V) 2.5 INPUT HIGH 2.0 INPUT LOW 1.5 1.0 0.5 0 5.2 5.1 5.0 4.9 3.3V 4.8 3.0V 4.7 4.6 4.5 4.5V 3.6V 5.0V
TA = 25C, LTM2882-3 VCC = 3.3V, LTM2882-5
VCC2 Output Voltage vs Load Current
VCC = 3.0V TO 3.6V, LTM2882-3 VCC = 4.5V TO 5.5V, LTM2882-5 5.5V
0
1
3 2 4 VL SUPPLY VOLTAGE (V)
5
6
2882 G10
0
50
150 100 200 LOAD CURRENT (mA)
250
300
2882 G11
Driver Outputs Exiting Shutdown
ON T1OUT DE = DOUT, DIN = VL 5V/DIV T2OUT T1OUT DE = VCC2 T2OUT 100s/DIV
2882 G12
Driver Outputs Enable/Disable
2V/DIV
DE T1OUT
5V/DIV T2OUT
2s/DIV
2882 G13
Operating Through 35kV/s Common Mode Transients
T1IN 2V/DIV 2V/DIV T1OUT = R1IN R1OUT
* 500V/DIV 50ns/DIV * MULTIPLE SWEEPS OF COMMON MODE TRANSIENTS
2882 G14
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LTM2882 TYPICAL PERFORMANCE CHARACTERISTICS
VCC = 5V, VL = 3.3V, and GND = GND2 = 0V, ON = VL unless otherwise noted. VCC2 Surplus Current vs Temperature
300 250 VCC2 CURRENT (mA) 200 150 100 T1OUT AND T2OUT 50 BAUD = 100kbps RL = 3k, CL = 2.5nF VCC2 = 4.8V 0 0 50 -50 -25 25 75 TEMPERATURE (C) VCC = 5.0V LTM2882-5 EFFICIENCY (%) 70 60 LTM2882-5 POWER LOSS (W) 50 LTM2882-3 40 30 20 10 TA = 25C 0 50 150 100 200 LOAD CURRENT (mA) 250 0.6 0.4 0.2 0 300 0.8
TA = 25C, LTM2882-3 VCC = 3.3V, LTM2882-5
VCC2 Power Efficiency
1.2 1.0
VCC = 3.3V LTM2882-3
100
125
2882 G15
2882 G16
VCC2 Ripple and Noise
VCC2 Load Step Response
200mV/DIV 100mV/DIV 50mA/DIV
T1IN = 250kbps T1OUT, T2OUT, RL = 3k 10s/DIV
2882 G17
100s/DIV
2882 G18
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LTM2882 TEST CIRCUITS
VL TIN TOUT TIN RL CL TOUT tr, tf 40ns VOLD 0V VOHD tPLHD 3V -3V tTHL 0V tTLH
2882 F01
1/2VL tPHLD
Figure 1. Driver Slew Rate and Timing Measurement
VCC2 DE 0V 0 OR VL RL DE tr, tf 40ns TOUT VOLD -5V CL TOUT VOHD TOUT 0V 0V 5V tPZLD tPLZD VOLD - 0.5V
2882 F02
1/2VCC2 tPZHD tPHZD VOHD - 0.5V
Figure 2. Driver Enable/Disable Times
3V RIN ROUT CL RIN tr, tf 40ns ROUT VOL -3V VOH tPHLR 10% 90% tFR tRR
2882 F03
1.5V tPLHR 90% 10% 1/2VL
Figure 3. Receiver Timing Measurement
VL DIN DOUT DIN CL DOUT VOL 0V VOH tPLHL 90% 10% 1/2VCC2 tRL tPHLL 10% 90% tFL
2882 F04
1/2VL
Figure 4. Auxiliary Channel Timing Measurement
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LTM2882 PIN FUNCTIONS
LOGIC 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. 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. 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. 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. 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. 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. 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. 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. GND (Pins B1-B6): Circuit Ground. ISOLATED SIDE GND2 (Pins K1-K7): Isolated Side Circuit Ground. These pads should be connected to the isolated ground and/or cable shield. 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. 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 5k in receive mode or unpowered. 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). 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 5k in receive mode or unpowered. 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). DOUT (Pin L5): General Purpose Non-Inverting Logic Output. Logic output connected through isolation barrier to DIN. 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.
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LTM2882 BLOCK DIAGRAM
5V REG 2.2F 2.2F GND DC/DC CONVERTER ON DIN VDD T1IN ISOLATED COMMUNICATIONS INTERFACE ISOLATED COMMUNICATIONS INTERFACE VEE 5k VDD T2IN VEE R2OUT 5k R2IN T2OUT R1IN T1OUT VDD VEE DOUT 2.2F GND2 DE
VCC VL
VCC2
R1OUT
2882 BD
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LTM2882 APPLICATIONS INFORMATION
Overview The LTM2882 Module 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/s providing excellent noise isolation. Module Technology The LTM2882 utilizes isolator Module 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 Module 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 Module 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. 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.
ANY VOLTAGE FROM 1.62V TO 5.5V 3.0V TO 3.6V LTM2882-3 4.5V TO 5.5V LTM2882-5
VL ON DIN EXTERNAL DEVICE T1IN
VCC
LTM2882
VCC2 DE DOUT T1OUT R1IN T2OUT R2IN
R1OUT T2IN R2OUT GND
ISOLATION BARRIER 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 2.2F 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 2.2F 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.
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LTM2882 APPLICATIONS INFORMATION
Channel Timing Uncertainty 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. Half-Duplex Operation 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 2s, while each receiver remains continuously active. This mode of operation is illustrated in Figure 6.
3.3V (LTM2882-3) 5V (LTM2882-5) VL ON RX TX DIN T1IN R1OUT T2IN R2OUT GND GND2
2882 F06
Driver Overvoltage and Overcurrent Protection 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. Receiver Overvoltage and Open Circuit The receiver inputs are protected from common mode voltages of 25V relative to GND2. Each receiver input has a nominal input impedance of 5k relative to GND2. An open circuit condition will generate a logic high on each receiver's respective output pin. 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 EN 61000-4-8 EN 61000-4-9 Radiated, Radio-Frequency, Electromagnetic Field Immunity Power Frequency Magnetic Field Immunity Pulsed Magnetic Field Immunity
VCC
LTM2882
VCC2 DE DOUT T1OUT R1IN T2OUT R2IN
ISOLATION BARRIER
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
TEST EN 61000-4-3, Annex D FREQUENCY 80MHz to 1GHz 1.4MHz to 2GHz 2GHz to 2.7GHz EN61000-4-8, Level 4 EN61000-4-8, Level 5 EN61000-4-9, Level 5 *Non IEC Method 50Hz and 60Hz 60Hz Pulse FIELD STRENGTH 10V/m 3V/m 1V/m 30A/m 100A/m* 1000A/m
Figure 6. Half-Duplex Configuration Using DOUT to Drive DE
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LTM2882 APPLICATIONS INFORMATION
PCB Layout 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. * 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 6.8F to 22F is recommended from VCC to GND.
VCC VL ON DIN T1IN R1OUT T2IN R2OUT SLOT DE DOUT T1OUT R1IN T2OUT R2IN
* 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 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.
TOP COPPER
VCC2
GND
GND2
SLOT
BOTTOM COPPER
Figure 7. Recommended PCB Layout
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LTM2882 TYPICAL APPLICATIONS
3.3V (LTM2882-3) 5V (LTM2882-5) VL ON RX TX DIN T1IN 3.3k R1OUT T2IN 3.3k R2OUT GND GND2
2882 F08
3.3V (LTM2882-3) 5V (LTM2882-5) VCC LTM2882 DE ISOLATION BARRIER DOUT T1OUT R1IN T2OUT R2IN
VL ON DIN T1IN
VCC
LTM2882 DE ISOLATION BARRIER DOUT T1OUT R1IN T2OUT R2IN GND2
2882 F09
R1OUT T2IN R2OUT GND
3k
CL
DATA RATE CL (nF) (kbps) 100 250 1000 5 2 0.5
Figure 8. Single Line Dual Half-Duplex Isolated Transceiver
3.3V (LTM2882-3) 5V (LTM2882-5) VL ON DIN P T1IN R1OUT T2IN R2OUT GND GND2
2882 F10
Figure 9. Driving Larger Capacitive Loads
1.8V
3.3V (LTM2882-3) 5V (LTM2882-5) DE OFF ON VL ON DIN T1IN R1OUT T2IN R2OUT GND GND2
2882 F11
VCC
LTM2882 DOUT T1OUT R1IN T2OUT R2IN
VCC
LTM2882
VCC2 DE DOUT T1OUT R1IN T2OUT R2IN
5V REGULATED 150mA (LTM2882-5) 100mA (LTM2882-3)
ISOLATION BARRIER
Figure 10. 1.8V Microprocessor Interface
3.0V TO 3.6V (LTM2882-3) 4.5V TO 5.5V (LTM2882-5) VL ON OFF ON ISOLATION BARRIER DIN T1IN R1OUT T2IN R2OUT GND VCC LTM2882 VCC2 DE DOUT T1OUT R1IN T2OUT R2IN GND2
2882 F12
Figure 11. Isolated 5V Power Supply
5V REGULATED
7V SWITCHED
-6.3V SWITCHED
RETURN
Figure 12. Isolated Multirail Power Supply with Switched Outputs
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ISOLATION BARRIER
LGA Package 32-Lead (15mm x 11.25mm x 2.82mm)
(Reference LTC DWG # 05-08-1773 Rev O)
DETAIL A 2.69 - 2.95 aaa Z
8
PAD 1
7
6
5
4
3
2
1
A B C D E
15.00 BSC MOLD CAP SUBSTRATE 0.290 - 0.350 2.400 - 2.600 DETAIL B bbb Z Z 12.70 BSC
PAD "A1" CORNER
4
F G H J K L
PACKAGE DESCRIPTION
X Y DETAIL B 0.630 0.025 O 32x eee S X Y eee S X Y 0.630 0.025 O 32x 8.89 BSC
11.25 BSC
1.27 BSC
PADS SEE NOTES 3
aaa Z
PACKAGE TOP VIEW
PACKAGE BOTTOM VIEW
4.445
3.175
1.905
0.635
0.635
1.905
3.175
4.445
DETAIL c
6.350 5.080
DETAIL A
DETAIL C
NOTES: 1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M-1994 2. ALL DIMENSIONS ARE IN MILLIMETERS 3 4 LAND DESIGNATION PER JESD MO-222
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.
0.000
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
5. PRIMARY DATUM -Z- IS SEATING PLANE 6. THE TOTAL NUMBER OF PADS: 32
5.080 6.350
COMPONENT PIN "A1"
LTMXXXXXX Module
TRAY PIN 1 BEVEL PACKAGE IN TRAY LOADING ORIENTATION
LGA 32 0308 REV O
SYMBOL TOLERANCE aaa 0.10 bbb 0.10 eee 0.05
LTM2882
15
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SUGGESTED PCB LAYOUT TOP VIEW
LINEAR TECHNOLOGY CONFIDENTIAL LTM2882 TYPICAL APPLICATIONS
3.3V (LTM2882-3) 5V (LTM2882-5) C VL ON DIN T1IN R2OUT T2IN R2OUT GND VCC LTM2882 VCC2 DE DOUT T1OUT R1IN T2OUT R2IN GND2
2882 F12
1.62V TO 5.5V PERIPHERAL OFF ON
3.3V (LTM2882-3) 5V (LTM2882-5) VL ON DIN VCC LTM2882 DE ISOLATION BARRIER DOUT T1OUT R1IN T2OUT R2IN GND2
2882 F13
ISOLATION BARRIER
TXD RXD PY PZ
RX TX RTS CTS VL 0V VL 0V
T1IN R1OUT T2IN R2OUT GND
3V TO 25V -25V TO 0V
3V TO 25V -25V TO 0V
Figure 13. Isolated RS232 Interface with Handshaking
Figure 14. Isolated Dual Inverting Level Translator
3.3V (LTM2882-3) 5V (LTM2882-5) VL ON RESET PWMA FAULT PWMB DIN T1IN R1OUT T2IN R2OUT GND VCC LTM2882 VCC2 DE DOUT T1OUT R1IN T2OUT R2IN GND2 IRLML6402
1k
+VS
ISOLATION BARRIER
LOGIC LEVEL FETS
CMPT2369-LTV 1k 3k 470pF IRLML2402 3k 47pF
2882 F14
RILIM = 0.6/MAX CURRENT
Figure 15. Isolated Gate Drive with Overcurrent Detection
RELATED PARTS
PART NUMBER LTM2881 LTC2804 LTC1535 DESCRIPTION Isolated RS485/RS422 Module Transceiver with Integrated DC/DC Converter 1Mbps RS232 Transceiver Isolated RS485 Transceiver COMMENTS 20Mbps, 15kV HBM ESD, 2500VRMS Isolation with Power Dual Channel, Full-Duplex, 10kV HBM ESD 2500 VRMS Isolation with External Transformer Driver
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16 Linear Technology Corporation
(408) 432-1900 FAX: (408) 434-0507
LT 1209 * PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2009

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