IL3185/IL3122
IsoLoop® is a registered trademark of NVE Corporation.
*U.S. Patent numbers 5,831,426; 6,300,617 and others.
REV. P
NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344-3617 Phone: (952) 829-9217 www.isoloop.com iso-info@nve.com ©NVE Corporation
Low Cost Passive Input RS-485 and RS-422 Isolated Transceivers
Functional Diagrams
R
RE
A
B
Z
R
RE
Y
IL3122
IL3185
A
B
VCOIL2
VCOIL1
VCOIL1
VCOIL2
DE
D
DE
D
IL3185 Truth Table
V(A-B) DE D R RE Mode
≥ 200 mV H H H L Drive
≤−200 mV H L L L Drive
≥ 200 mV L X H L Receive
≤−200 mV L X L L Receive
X X X Z H X
Open L X H L Receive
Z = High Impedance X = Irrelevant
IL3122 Receiver
RE R V
(
A-B
)
H Z X
L H ≥ 200 mV
L L ≤−200 mV
L H Open
IL3122 Driver
DE D V
(
Y-Z
)
L X Z
H H ≥ 200 mV
H L ≤−200 mV
Features
• 5 Mbps data rate
• 3 V to 5 V power supplies
• Supports up to 32 nodes
• 15 kV bus ESD protection
• 2500 VRMS isolation per UL 1577
• 20 kV/µs typical common mode rejection
• No carrier or clock for low EMI emissions and susceptibility
• −40°C to +85°C temperature range
• Thermal shutdown protection
• UL 1577 recognized; IEC 60747-5-5 (VDE 0884) certified
• 0.15", 0.3" or True 8™ mm 16-pin SOIC packages
Applications
• P.O.S. systems
• Security networks
• Building environmental controls
• Industrial control networks
• Gaming systems
• Factory automation
Description
The IL3185 and IL3122 are galvanically isolated, differential
bus transceivers designed for bidirectional data
communication over balanced transmission lines. The
devices use NVE’s patented* IsoLoop spintronic Giant
Magnetoresistance (GMR) technology. The IL3185 delivers
at least 1.5 V into a 54 Ω load, and the IL3122 at least 2 V
into a 100 Ω load for excellent data integrity over long
cables. These devices are also compatible with 3 V input
supplies, allowing interface to standard microcontrollers
without additional level shifting.
Both the IL3185 and IL3122 have current limiting and
thermal shutdown features to protect against output short
circuits and bus contentions that may cause excessive power
dissipation. The receivers also incorporate a “fail-safe if
open” design, ensuring a logic high on R if the bus lines are
disconnected or “floating.”
Selection Table
Model
Full/Half
Duplex
No. of Devices
Allowed on Bus
Data
Rate
Mbps Fail-Safe
IL3185 half 32 5 yes
IL3122 full 32 5 yes
IL3185/IL3122
2
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Absolute Maximum Ratings
Operating at absolute maximum ratings will not damage the device. However, extended periods of operation at the absolute maximum ratings may affect
performance and reliability.
Parameters Symbol Min. Typ. Max. Units Test Conditions
Storage Temperature TS −55 150 °C
Ambient Operating Temperature TA −40 85 °C
Voltage Range at A or B Bus Pins −7 12 V
Supply Voltage
(
1
)
V
DD1, VDD2 −0.5 7 V
Digital Input Voltage −0.5 VDD+0.5 V
Digital Output Voltage −0.5 VDD+1 V
ESD Protection ±15 kV
Input Current IIN −25 +25 mA
ESD (all bus nodes) 15 kV HBM
Note 1. All voltage values are with respect to network ground except differential I/O bus voltages.
Recommended Operating Conditions
Parameters Symbol Min. Typ. Max. Units Test Conditions
Supply Voltage VDD1
VDD2
3.0
4.5 5.5
5.5 V
Ambient Operating Temperature TA −40 85 °C
Input Voltage at any Bus Terminal
(separately or common mode)
VI
VIC 12
−7 V
Input Threshold for Output Logic High IINH 1.5 0.8 mA
Input Threshold for Output Logic Low IINL 5 3.5 mA
Differential Input Voltage VID +12/−7 V
High-Level Output Current (Driver) IOH −60 60 mA
High-Level Digital Output Current
(Receiver) IOH −8 8 mA
Low-Level Output Current (Driver) IOL −60 60 mA
Low-Level Digital Output Current
(Receiver) IOL −8 8 mA
Ambient Operating Temperature TA −40 85 °C
Digital Input Signal Rise, Fall Times tIR,tIF 1 µs
Insulation Specifications
Parameters Symbol Min. Typ. Max. Units Test Conditions
Comparative Tracking Index CTI ≥175 V Per IEC 60112
Endurance Voltage
(Maximum Working Voltage
for Indefinite Life)
AC
DC
VIO
1000
1500
VRMS
VDC
At maximum
operating temperature
Creepage Distance
(external)
0.15" SOIC
0.3" SOIC 4.03
8.03
8.3 mm Per IEC 60601
Total Barrier Thickness (internal) 0.012 0.013 mm
Barrier Resistance
(
5
)
R
IO >1014 Ω 500 V
Barrier Capacitance
(
5
)
C
IO 7 pF f = 1 MHz
Leakage Current 0.2 μA 240 VRMS, 60 Hz
IL3185/IL3122
3
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Safety Approvals
IEC 60747-5-5 (VDE 0884) (File Number 5016933-4880-0001)
• Working Voltage (VIORM) 600 VRMS (848 VPK); basic insulation; pollution degree 2
• Transient overvoltage (VIOTM) and surge voltage (VIOSM) 4000 VPK
• Each part tested at 1590 VPK for 1 second, 5 pC partial discharge limit
• Samples tested at 4000 VPK for 60 sec.; then 1358 VPK for 10 sec. with 5 pC partial discharge limit
IEC 61010-1 (Edition 2; TUV Certificate Numbers N1502812; N1502812-101)
Reinforced Insulation; Pollution Degree II; Material Group III
Part No. Suffix Package Working Voltage
-3 SOIC 150 VRMS
None Wide-body SOIC/True 8™ 300 VRMS
UL 1577 (Component Recognition Program File Number E207481)
Each part tested at 3000 VRMS (4240 VPK) for 1 second; each lot sample tested at 2500 VRMS (3530 VPK) for 1 minute
Soldering Profile
Per JEDEC J-STD-020C, MSL 1
Electrostatic Discharge Sensitivity
This product has been tested for electrostatic sensitivity to the limits stated in the specifications. However, NVE recommends that all integrated
circuits be handled with appropriate care to avoid damage. Damage caused by inappropriate handling or storage could range from performance
degradation to complete failure.
IL3185/IL3122
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IL3185-3 Pin Connections (0.15" SOIC Package)
1 VDD1 Input power supply
2 GND1 Ground return for VDD1
3 R Output data from bus
4
RE Read enable
(if RE is high, R is high impedance)
5 DE Drive enable
6 VCOIL1 Coils for DE and D (connect to VDD1)
7 D Data input to bus
8 NC No internal connection
9 GND2 Ground return for VDD2
(internally connected to pin 15)
10 NC No internal connection
11 VDD2 Output power supply
12 A Non-inverting bus line
13 B Inverting bus line
14 NC No internal connection
15 GND2 Ground return for VDD2
(internally connected to pin 9)
16 VCOIL2 Coil for R
V
DD1
V
COIL2
GND
1
V
COIL1
GND
2
RNC
RE B
DE A
D
V
DD2
NC
NC GND
2
IL3185-3
IL3122-3 Pin Connections (0.15" SOIC Package)
1 VDD1 Input power supply
2 GND1 Ground return for VDD1
3 R Output data from bus
4
RE Read enable
(if RE is high, R is high impedance)
5 DE Drive enable
6 VCOIL1 Coils for DE and D (connect to VDD1)
7 D Data input to bus
8 NC No internal connection
9 GND2 Ground return for VDD2
(internally connected to pin 15)
10 Y Non-inverting driver bus line
11 VDD2 Output power supply
12 Z Inverting driver bus line
13 B Inverting receiver bus line
14 A Non-inverting receiver bus line
15 GND2 Ground return for VDD2
(internally connected to pin 9)
16 VCOIL2 Coil for R
V
DD1
V
COIL2
GND
1
V
COIL1
GND
2
RA
RE B
DE Z
D
V
DD2
Y
NC GND
2
IL3122-3
IL3185/IL3122
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IL3185 Pin Connections (0.3" SOIC Package)
1 VDD1 Input power supply
2 GND1 Ground return for VDD1
3 R Output data from bus
4
RE Read enable
(if RE is high, R is high impedance)
5 DE Drive enable
6 VCOIL1 Coils for DE and D (connect to VDD1)
7 D Data input to bus
8 GND1 Internally connected to pin 2 for 0.3" package;
no internal connection on 0.15" IL3285-3
9 GND2 Ground return for VDD2
(internally connected to pin 15)
10 NC No internal connection
11 VDD2 Output power supply
12 A Non-inverting bus line
13 B Inverting bus line
14 NC No internal connection
15 GND2 Ground return for VDD2
(internally connected to pin 9)
16 VCOIL2 Coil for R
VDD1 VCOIL2
GND1
VCOIL1
GND2
RNC
RE B
DE A
D
VDD2
NC
GND1GND2
IL3185
IL3122 Pin Connections (0.3" SOIC Package)
1 VDD1 Input power supply
2 GND1 Ground return for VDD1
3 R Output data from bus
4
RE Read enable
(if RE is high, R is high impedance)
5 DE Drive enable
6 VCOIL1 Coils for DE and D (connect to VDD1)
7 D Data input to bus
8 GND1 Internally connected to pin 2 for 0.3" package;
no internal connection on 0.15" IL3122-3
9 GND2 Ground return for VDD2
(internally connected to pin 15)
10 Y Non-inverting driver bus line
11 VDD2 Output power supply
12 Z Inverting driver bus line
13 B Inverting receiver bus line
14 A Non-inverting receiver bus line
15 GND2 Ground return for VDD2
(internally connected to pin 9)
16 VCOIL2 Coil for R
VDD1 VCOIL2
GND1
VCOIL1
GND2
RA
RE B
DE Z
D
VDD2
Y
GND1GND2
IL3122
IL3185/IL3122
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Driver Section
Electrical Specifications (VDD1 = 3 V − 5.5 V; VDD2 = 4.5 V − 5.5 V; T = −40°C − 85°C unless otherwise stated)
Parameters Symbol Min. Typ. Max. Units Test Conditions
Coil Input Resistance RCOIL 47 85 112 Ω T = 25°C
Coil Input Resistance RCOIL 31 85 128 Ω T = −40°C − 85°C
Coil Resistance Temperature Coefficient TC RCOIL 0.2 0.25 Ω/°C
Coil Inductance LCOIL 9 nH
High Level Input Current IINH 0.5 1 mA
tIR = tIF = 3 ns;
CBOOST = 16 pF
Low Level Input Current IINL 3.5 5 mA
Output voltage VDD V IO = 0
Differential Output Voltage |VOD1| VDD V IO = 0
Differential Output Voltage |VOD2| 2 3 V RL = 100 Ω, VDD = 5 V
Differential Output Voltage
(
6
)
VOD3 1.5 2.3 V RL = 54 Ω, VDD = 5 V
Change in Magnitude
(
7
)
of Differential
Output Voltage Δ|VOD| ±0.2 V RL = 54 Ω or 100 Ω
Common Mode Output Voltage VOC 3 V RL = 54 Ω or 100 Ω
Change in Magnitude
(
7
)
of Common
Mode Output Voltage Δ|VOC| 0.2 V RL = 54 Ω or 100 Ω
Output Current(4)
1
−0.8
mA
mA
Output disabled,
VO = 12 V
VO = −7 V
|Short-circuit Output Current| IOS 60 250 mA −7 V < VO < 12 V
Supply Current (VDD2 = +5 V)
(VDD1 = +5 V)
IDD2
IDD1 6
2.5
7
3 mA No Load
(Outputs Enabled)
Supply Current (VDD1 = +3.3 V) IDD2 1.3 2 mA
No Load
(Outputs Enabled)
Common Mode Rejection |CMH|,|CML| 15 20 kV/μs VT = 300 V
p
ea
k
Switching Specifications (VDD1 = 5 V; VDD2 = 5 V; T = −40°C − 85°C)
Parameters Symbol Min. Typ. Max. Units Test Conditions
Data Rate 5 Mbps
RL = 54 Ω;
CL = 50 pF;
Cboost = 16pF
Differential Output Prop Delay tD(OD) 40 65 ns
Pulse Skew
(
10
)
t
S
K
(P) 6 15 ns
Differential Output Rise and Fall Time tT(OD) 3 12 25 ns
Drive Enable Time to High Level tPZH 25 40 ns
Drive Enable Time to Low Level tPZL 25 40 ns
Drive Disable Time from High Level tPHZ 25 40 ns
Drive Disable Time from Low Level tPLZ 25 40 ns
Skew Limit
(
3
)
t
S
K
(LIM) 8 ns
Switching Specifications (VDD1 = 3.3 V; VDD2 = 5 V; T = −40°C − 85°C)
Parameters Symbol Min. Typ. Max. Units Test Conditions
Data Rate 5 Mbps
RL = 54 Ω;
CL = 50 pF;
Cboost = 16pF
Differential Output Prop Delay tD(OD) 40 65 ns
Pulse Skew
(
10
)
t
S
K
(P) 6 20 ns
Differential Output Rise and Fall Time tT(OD) 3 12 25 ns
Drive Enable Time to High Level tPZH 25 40 ns
Drive Enable Time to Low Level tPZL 25 40 ns
Drive Disable Time from High Level tPHZ 25 40 ns
Drive Disable Time from Low Level tPLZ 25 40 ns
Skew Limit
(
3
)
t
S
K
(LIM) 8 ns
IL3185/IL3122
7
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Receiver Section
Electrical Specifications (VDD1 = 3 V − 5.5 V; VDD2 = 4.5 V − 5.5 V; T = −40°C − 85°C unless otherwise stated)
Parameters Symbol Min. Typ. Max. Units Test Conditions
Coil Resistance RCOIL 47 85 112 Ω T = 25°C
31 85 128 Ω T = −40°C − 85°C
Coil Resistance Temperature Coefficient TC RCOIL 0.2 0.25 Ω/°C
Positive-going Input Threshold VIT+ 0.2 V −7 V < VCM < 12 V
Negative-going Input Threshold VIT− −0.2 V −7 V < VCM < 12 V
Hysteresis Voltage (Vit+ − Vit−) VHYS 70 mV VCM = 0V, T = 25°C
High Level Digital Output Voltage VOH VDD − 0.2 VDD − 0.2 V VID = 200 mV
I
OH = 4 mA
Low Level Digital Output Voltage VOL 0.8 V VID = −200 mV
I
OL = 4 mA
High impedance state output current IOZ 10 µA
0.4≤VO
(VDD2 − 0.5) V
Line Input Current
(
8
)
I
I 1 mA VI = 12 V
−0.8 VI = −7 V
Input Resistance rI 12 25 kΩ
Switching Specifications (VDD1 = 5 V; VDD2 = 5 V; C
b
oost = 16pF; T = −40°C − 85°C)
Parameters Symbol Min. Typ. Max. Units Test Conditions
Data Rate 5 Mbps RL = 54
Ω
, CL = 50 pF
Propagation Delay(9) tPD 50 85 ns
−1.5
≤
VO
1.5 V,
CL = 15 pF
Pulse Skew(10) t
SK(P) 10 17 ns
−1.5
≤
VO
1.5 V,
CL = 15 pF
Skew Limit(3) t
S
K
(LIM) 2 8 ns
RL = 54
Ω
, CL = 50 pF
Read Enable Time to High Level tPZH 4 40 ns
CL = 15 pF
Read Enable Time to Low Level tPZL 4 40 ns
Read Disable Time from High Level tPHZ 4 40 ns
Read Disable Time from Low Level tPLZ 4 40 ns
Switching Specifications (VDD1 = 3.3 V; VDD2 = 5 V; C
b
oost = 16pF; T = −40°C − 85°C)
Parameters Symbol Min. Typ. Max. Units Test Conditions
Data Rate 5 Mbps RL = 54
Ω
, CL = 50 pF
Propagation Delay(9) tPD 55 85 ns
−1.5
≤
VO
1.5 V,
CL = 15 pF
Pulse Skew(10) t
SK(P) 12 20 ns
−1.5
≤
VO
1.5 V,
CL = 15 pF
Skew Limit(3) t
S
K
(LIM) 4 10 ns
RL = 54
Ω
, CL = 50 pF
Read Enable Time to High Level tPZH 5 10 ns
CL = 15 pF
Read Enable Time to Low Level tPZL 5 10 ns
Read Disable Time from High Level tPHZ 5 10 ns
Read Disable Time from Low Level tPLZ 17 10 ns
Notes (apply to both driver and receiver sections):
1. All voltages are with respect to network ground except differential I/O bus voltages.
2. Differential input/output voltage is measured at the non-inverting terminal A with respect to the inverting terminal B.
3. Skew limit is the maximum difference in any two channels in one device.
4. The power-off measurement in ANSI Standard EIA/TIA-422-B applies to disabled outputs only and is not applied to combined inputs and outputs.
5. All typical values are at VDD1, VDD2 = 5 V or VDD1= 3.3 V and TA = 25°C.
6. While −7 V < VCM < 12 V, the minimum VOD2 with a 54 Ω load is either ½ VOD1 or 1.5 V, whichever is greater.
7. Δ|VOD| and Δ|VOC| are the changes in magnitude of VOD and VOC, respectively, that occur when the input is changed from one logic state to the other.
8. This applies for both power on and power off; refer to ANSI standard RS-485 for exact condition. The EIA/TIA-422-B limit does not apply for a combined
driver and receiver terminal.
9. Includes 10 ns read enable time. Maximum propagation delay is 25 ns after read assertion.
10. Pulse skew is defined as the |tPLH − tPHL| of each channel.
IL3185/IL3122
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2500 16 5000
3
500
1000
Signal
Rise/Fall Time (ns)
C
Boost
( pF )
16 5000
3
1000
Signal
Rise/Fall Time (ns)
C
Boost
( pF )
20
50
100 210
Applications Information
Input Resistor Values
The IL3122 and IL3185 are current-mode devices. Changes in input coil current switch internal spintronic GMR sensors. Inputs
are logically high when the coil voltage is high, that is when there is no coil current.
A single resistor is required to limit the input coil current to the 5 mA threshold current. The absolute maximum current through
any coil is 25 mA.
Typical Input Resistor Values
The table shows typical values for the external resistor in 5 V and 3 V logic systems.
As always, these values as approximate and should be adjusted for temperature or
other application specifics. If the expected temperature range is large, 1% tolerance
resistors may provide additional design margin.
Boost Capacitor
The boost capacitor in parallel with the current-limiting resistor boosts
the instantaneous coil current at the signal transition. This ensures
switching and reduces propagation delay and reduces pulse-width
distortion.
Select the value of the boost capacitor based on the rise and fall times
of the signal driving the inputs. The instantaneous boost capacitor
current is proportional to input edge speeds ( ). Select a capacitor
value based on the rise and fall times of the input signal to be isolated
that provides approximately 20 mA of additional “boost” current.
Figure 2 is a guide to boost capacitor selection. For high-speed logic
signals (tr,tf < 10 ns), a 16 pF capacitor is recommended. The capacitor
value is generally not critical; if in doubt, choose a higher value up to a
maximum of 470 pF.
RS-485 and RS-422 Busses
RS-485 and RS-422 are differential (balanced) data transmission standards for use over long distances or in noisy environments.
RS-422 is an RS-485 subset, so RS-485 transceivers are also RS-422-compliant. RS-422 is a multi-drop standard allowing only
one driver and up to 10 receivers on each bus (assuming unit load receivers). RS-485 is a true multipoint standard which allows up
to 32 unit load devices (any combination of drivers and receivers) on each bus. To allow for multipoint operation, RS-485 requires
drivers to handle bus contention without damage. Another important advantage of RS-485 is the extended common-mode range
(CMR), which requires driver outputs and receiver inputs withstand +12 V to −7 V. RS-422 and RS-485 are intended for runs as
long as 4,000 feet (1,200 m), so the wide CMR is necessary for ground potential differences, as well as voltages induced in the
cable by external fields.
Receiver Features
IL3000 transceivers have differential input receivers for maximum noise immunity and common-mode rejection. Input sensitivity
is ±200 mV as required by the RS-422 and RS-485 specifications. The receivers include a “fail-safe if open” function that
guarantees a high level receiver output if the receiver inputs are unconnected (floating). Receivers easily meet the data rates
supported by the corresponding driver. IL3000-Series receiver outputs have tri-state capabilities with active low RE inputs.
Driver Features
The RS485/422 driver is a differential output device that delivers at least 1.5 V across a 54 Ω load (RS-485), and at least 2 V
across a 100 Ω load (RS-422). The driver features low propagation delay skew to maximize bit width and minimize EMI. IL3222
and IL3285 drivers have tri-state capability with an active high DE input.
VCOIL 0.125W, 5% Resistor
3.3 V 510 Ω
5 V 820 Ω
Figure 2. Cboost Selector
dV
dt
C
IL3185/IL3122
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Cabling, Data Rate and Terminations
Cabling
Use twisted-pair cable. The cable can be unshielded if it is short (less than 10 meters) and the data rate is slow (less than
100 Kbps). Otherwise, use screened cable with the shield tied to earth ground at one end only. Do not tie the shield to digital
ground. The other end of the shield may be tied to earth ground through an RC network. This prevents a DC ground loop in the
shield. Shielded cable minimizes EMI emissions and external noise coupling to the bus.
Data Rate
The longer the cable, the slower the data rate. The RS-485 bus can transmit ground over 4,000 feet (1,200 meters) or at 10 Mbps,
but not both at the same time. Transducer and cable characteristics combine to act as a filter with the general response shown in
Figure 3. Other parameters such as acceptable jitter affect the final cable length versus data rate tradeoff. Less jitter means better
signal quality but shorter cable lengths or slower data rates. Figure 4 shows a generally accepted 30% jitter and a corresponding
data rate versus cable length.
Figure 3. Cable Length vs. Data Rate (30% jitter).
Terminations
Transmission lines should be terminated to avoid reflections that cause data errors. In RS-485 systems both ends of the bus, not
every node, should be terminated. In RS-422 systems only the receiver end should be terminated.
100 Ω
Unterminated Parallel
Proper termination is imperative when using IL3185 and IL3122 to minimize reflections. Unterminated lines are only suitable for
very low data rates and very short cable runs, otherwise line reflections cause problems. Parallel terminations are the most popular.
They allow high data rates and excellent signal quality.
Occasionally in noisy environments, fast pulses or noise appearing on the bus lines cause errors. One way of alleviating such errors
without adding circuit delays is to place a series resistor in the bus line. Depending on the power supply, the resistor should be
between 300 Ω (3 V supply) and 500 Ω (5 V supply).
1000
100
40
4000
100 1K 10K 100K
1M 10M
Data Rate (bps)
Cable Length (feet)
IL3185/IL3122
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Typical Coil Connections
R
RE
A
B
V
DD2
V
COIL2
V
COIL1
V
DD1
DE
D
R1
16pF ±50%
16pF ±50%
16pF ±50%
R2
R3
A
B
Z
R
RE
Y
V
COIL2
V
DD2
V
COIL1
V
DD1
DE
D
R1
R2
R3
16pF ±50%
16pF ±50%
16pF ±50%
VDD1 = VDD2 = 5 V R1, R2, R3 = 820 Ω
VDD1 = 3.3 V R1, R2 = 510 Ω; R3 = 820 Ω
VDD1 = VDD2 = 5 V R1, R2, R3 = 820 Ω
VDD1 = 3.3 V R1, R2 = 510 Ω; R3 = 820 Ω
Fail-Safe Operation
“Fail-safe operation” is defined here as the forcing of a logic high state on the “R” output in response to an open-circuit condition
between the “A” and “B” lines of the bus, or when no drivers are active on the bus.
Proper biasing can ensure fail-safe operation, that is a known state when there are no active drivers on the bus. IL3185 and IL3122
Isolated Transceivers include internal pull-up and pull-down resistors of approximately 30 kΩ in the receiver section (RFS-INT; see
figure on following page). These internal resistors are designed to ensure failsafe operation but only if there are no termination
resistors. The entire VDD will appear between inputs “A” and “B” if there is no loading and no termination resistors, and there will
be more than the required 200 mV with up to four RS-485/RS-422 worst-case Unit Loads of 12 kΩ. Many designs operating below
1 Mbps or less than 1,000 feet are unterminated. Termination resistors may not be necessary for very low data rates and very short
cable runs because reflections have time to settle before data sampling, which occurs at the middle of the bit interval.
In busses with low-impedance termination resistors, however, the differential voltage across the conductor pair will be close to
zero with no active drivers. In this case the state of the bus is indeterminate, and the idle bus will be susceptible to noise. For
example, with 120 Ω termination resistors (RT) on each end of the cable, and four Unit Loads (12 kΩ each), without external fail-
safe biasing resistors the internal pull-up and pull-down resistors will produce a voltage between inputs “A” and “B” of only about
5 mV. This is not nearly enough to ensure a known state. External fail-safe biasing resistors (RFS-EXT) at one end of the bus can
ensure fail-safe operation with a terminated bus. Resistors should be selected so that under worst-case power supply and resistor
tolerances there is at least 200 mV across the conductor pair with no active drivers to meet the input sensitivity specification of the
RS-422 and RS-485 standards.
Using the same value for pull-up and pull-down biasing resistors maintains balance for positive- and negative going transitions.
Lower-value resistors increase inactive noise immunity at the expense of quiescent power consumption. Note that each Unit Load
on the bus adds a worst-case loading of 12 kΩ across the conductor pair, and 32 Unit Loads add 375 Ω worst-case loading. The
more loads on the bus, the lower the required values of the biasing resistors.
In the example with two 120 Ω termination resistors and four Unit Loads, 560 Ω external biasing resistors provide more than
200 mV between “A” and “B” with adequate margin for power supply variations and resistor tolerances. This ensures a known
state when there are no active drivers. Other illustrative examples are shown in the following table:
IL3185/IL3122
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NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344-3617 Phone: (952) 829-9217 Fax: (952) 829-9189 www.IsoLoop.com ©NVE Corporation
Fail-Safe Biasing
Fail-Safe
RTLoadin
g
O
p
eration?
None Four unit loads (12 kΩ ea.) 238 mV Yes
120 ΩFour unit loads (12 kΩ ea.) 5 mV No
560 Ω120 ΩFour unit loads (12 kΩ ea.) 254 mV Yes
510 Ω120 Ω32 unit loads (12 kΩ ea.) 247 mV Yes
Nominal VA-B
(inactive)
RFS -EXT
Internal Only
Internal Only
Power Supply Decoupling
Both VDD1 and VDD2 should be bypassed with 47 nF low-ESR ceramic capacitors. These should be placed as close as possible to
VDD pins. VDD2 should also be bypassed with a 10 µF tantalum capacitor.
Maintaining Creepage
Creepage distances are often critical in isolated circuits. In addition to meeting JEDEC standards, NVE isolator packages have
unique creepage specifications. Standard pad libraries often extend under the package, compromising creepage and clearance.
Similarly, ground planes, if used, should be spaced to avoid compromising clearance. Package drawings and recommended pad
layouts are included in this datasheet.
Magnetic Field Immunity
IsoLoop Isolators operate by imposing a magnetic field on a GMR sensor, which translates the change in field into a change in
logic state. A magnetic shield and a Wheatstone Bridge configuration provide good immunity to external magnetic fields.
Immunity to external magnetic fields can be enhanced by proper orientation of the device with respect to the field direction and
larger boost capacitors.
An applied field in the “H1” direction is the worst case for magnetic immunity. In this case the external field is in the same
direction as the applied internal field. In one direction it will tend to
help switching; in the other it will hinder switching. This can cause
unpredictable operation.
An applied field in the direction of “H2” has considerably less effect on
the sensor and will result in significantly higher immunity levels as
shown in Table 1.
The greatest magnetic immunity is achieved by adding a larger boost
capacitor across the input resistor. Very high immunity can be achieved
with this method.
Figure 3. Orientation of External Magnetic Field
V
DD1
V
COIL2
GND
1
V
COIL1
GND
2
RNC
RE B
DE A
D
V
DD2
NC
GND
1
GND
2
H1
H2
RB
V
DD
30K 30K
GND
A
5 V
RFS-EXT
RT
RT
RFS-EXT
RFS-INT RFS-INT
IL3185/IL3122
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Method Approximate Immunity Immunity Description
Field applied in direction H1 ±20 Gauss A DC current of 16 A flowing in a conductor
1 cm from the device could cause disturbance
Field applied in direction H2 ±70 Gauss A DC current of 56 A flowing in a conductor
1 cm from the device could cause disturbance
Field applied in any direction but with boost
capacitor (470 pF) in circuit ±250 Gauss A DC current of 200 A flowing in a conductor
1 cm from the device could cause disturbance
Table 1. Magnetic Immunity
Data Rate and Magnetic Field Immunity
It is easier to disrupt an isolated DC signal with an external magnetic field than it is to disrupt an isolated AC signal. Similarly, a
DC magnetic field will have a greater effect on the device than an AC magnetic field of the same effective magnitude. For
example, signals with pulses longer than 100 μs are more susceptible to magnetic fields than shorter pulse widths. For input signals
faster than 1 MHz, rising in less than 3 ns, a 470 pF field-boost capacitor provides as much as 400 Gauss immunity, while the
same input capacitor might provide just 70 Gauss immunity at 50 kHz.
IL3185/IL3122
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NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344-3617 Phone: (952) 829-9217 Fax: (952) 829-9189 www.IsoLoop.com ©NVE Corporation
Package Drawings
0.15" 16-pin SOIC Package (-3 suffix)
0.386 (9.8)
0.394 (10.0)
0.049 (1.24)
0.051 (1.30)
0.007 (0.2)
0.013 (0.3)
Pin 1 identified
by either an
indent or a
marked dot
0.004 (0.1)
0.012 (0.3)
0.016 (0.4)
0.050 (1.3)
NOTE: Pin spacing is a BASIC
dimension; tolerances
do not accumulate
0.054 (1.4)
0.072 (1.8)
0.228 (5.8)
0.244 (6.2)
0.150 (3.81)
0.157 (3.99)
0.055 (1.40)
0.062 (1.58)
0.013 (0.3)
0.020 (0.5)
NOM
Dimensions in inches (mm); scale = approx. 5X
0.3" 16-pin SOIC Package (no suffix)
0.049 (1.24)
0.051 (1.30)
0.017 (0.43)*
0.022 (0.56)
0.292 (7.42)*
0.299 (7.59)
0.007 (0.18)*
0.010 (0.25)
0.260 (6.60)*
0.280 (7.11)
0.033 (0.85)*
0.043 (1.10)
0.007 (0.2)
0.013 (0.3)
Pin 1 identified by
either an indent
or a marked dot 0.08 (2.0)
0.10 (2.5)
0.397 (10.08)
0.413 (10.49)
0.394 (10.00)
0.419 (10.64)
0.092 (2.34)
0.105 (2.67)
0.004 (0.1)
0.012 (0.3)
0.016 (0.4)
0.050 (1.3)
NOTE: Pin spacing is a BASIC
dimension; tolerances
do not accumulate
0.013 (0.3)
0.020 (0.5)
Dimensions in inches (mm); scale = approx. 5X
*Specified for True 8™ package to guarantee 8 mm creepage per IEC 60601.
IL3185/IL3122
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NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344-3617 Phone: (952) 829-9217 Fax: (952) 829-9189 www.IsoLoop.com ©NVE Corporation
Recommended Pad Layouts
0.15" 16-pin SOIC Pad Layout
0.050 (1.27)
0.275 (6.99)
0.020 (0.51)
16 PLCS
0.160 (4.06)
Dimensions in inches (mm); scale = approx. 5X
0.3" 16-pin SOIC Pad Layout
0.050 (1.27)
0.449 (11.40)
0.020 (0.51)
16 PLCS
0.317 (8.05)
Dimensions in inches (mm); scale = approx. 5X
IL3185/IL3122
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NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344-3617 Phone: (952) 829-9217 Fax: (952) 829-9189 www.IsoLoop.com ©NVE Corporation
Ordering Information and Valid Part Numbers
IL 31 85 -3 E TR13
Bulk Packaging
Blank = Tube
TR13 = 13'' Tape and Reel
Package
E = RoHS Compliant
Package Type
Blank = 0.3'' SOIC
-3 = 0.15'' SOIC
Channel Configuration
22 = RS-422
85 = RS-485
Base Part Number
31 = Passive-In, 5 Mbps Transceiver
Product Family
IL = Isolators
Valid Part Numbers
IL3185E
IL3185E TR13
IL3185-3E
IL3185-3E TR13
IL3122E
IL3122E TR13
IL3122-3E
IL3122-3E TR13
RoHS
COMPLIANT
IL3185/IL3122
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NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344-3617 Phone: (952) 829-9217 Fax: (952) 829-9189 www.IsoLoop.com ©NVE Corporation
Revision History
ISB-DS-001 IL3185/22-P
November 2013
Changes
• IEC 60747-5-5 (VDE 0884) certification.
• Upgraded from MSL 2 to MSL 1.
• Rearranged low level input current specification so maximum is more than minimum.
ISB-DS-001 IL3185/22-O
Changes
• Added VDE 0884 pending.
• Clarified switching specifications.
• Updated package drawings.
• Added recommended solder pad layouts.
ISB-DS-001 IL3185/22-N
Changes
• Detailed isolation and barrier specifications.
• Cosmetic changes.
ISB-DS-001-IL3185/22-M Changes
• Added minimum/maximum coil resistance specifications.
• Misc. cosmetic changes.
ISB-DS-001-IL3185/22-L
Changes
• Update terms and conditions.
ISB-DS-001-IL3185/22-K
Changes
• Clarified ground pin connections (pp. 3-4).
ISB-DS-001-IL3185/22-J
Changes
• Changes to current-limiting resistor values (pp. 7 and 10).
• Details for boost capacitor selection (p. 7).
ISB-DS-001-IL3185/22-I
Changes
• Noted UL1577 approval.
ISB-DS-001-IL3185/22-H Changes
• Added bus-protection ESD specification (15 kV).
ISB-DS-001-IL3185/22-G
Changes
• Added typical coil resistance and temperature coefficient specifications.
• Added note on package drawings that pin-spacing tolerances are non-accumulating.
ISB-DS-001-IL3185/22-F
Changes
• Changed ordering information to reflect that devices are now fully RoHS compliant with
no exemptions.
ISB-DS-001-IL3185/22-E
Changes
• Eliminated soldering profile chart
IL3185/IL3122
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NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344-3617 Phone: (952) 829-9217 Fax: (952) 829-9189 www.IsoLoop.com ©NVE Corporation
Datasheet Limitations
The information and data provided in datasheets shall define the specification of the product as agreed between NVE and its customer, unless NVE and
customer have explicitly agreed otherwise in writing. All specifications are based on NVE test protocols. In no event however, shall an agreement be
valid in which the NVE product is deemed to offer functions and qualities beyond those described in the datasheet.
Limited Warranty and Liability
Information in this document is believed to be accurate and reliable. However, NVE does not give any representations or warranties, expressed or
implied, as to the accuracy or completeness of such information and shall have no liability for the consequences of use of such information.
In no event shall NVE be liable for any indirect, incidental, punitive, special or consequential damages (including, without limitation, lost profits, lost
savings, business interruption, costs related to the removal or replacement of any products or rework charges) whether or not such damages are based on
tort (including negligence), warranty, breach of contract or any other legal theory.
Right to Make Changes
NVE reserves the right to make changes to information published in this document including, without limitation, specifications and product descriptions
at any time and without notice. This document supersedes and replaces all information supplied prior to its publication.
Use in Life-Critical or Safety-Critical Applications
Unless NVE and a customer explicitly agree otherwise in writing, NVE products are not designed, authorized or warranted to be suitable for use in life
support, life-critical or safety-critical devices or equipment. NVE accepts no liability for inclusion or use of NVE products in such applications and such
inclusion or use is at the customer’s own risk. Should the customer use NVE products for such application whether authorized by NVE or not, the
customer shall indemnify and hold NVE harmless against all claims and damages.
Applications
Applications described in this datasheet are illustrative only. NVE makes no representation or warranty that such applications will be suitable for the
specified use without further testing or modification.
Customers are responsible for the design and operation of their applications and products using NVE products, and NVE accepts no liability for any
assistance with applications or customer product design. It is customer’s sole responsibility to determine whether the NVE product is suitable and fit for
the customer’s applications and products planned, as well as for the planned application and use of customer’s third party customers. Customers should
provide appropriate design and operating safeguards to minimize the risks associated with their applications and products.
NVE does not accept any liability related to any default, damage, costs or problem which is based on any weakness or default in the customer’s
applications or products, or the application or use by customer’s third party customers. The customer is responsible for all necessary testing for the
customer’s applications and products using NVE products in order to avoid a default of the applications and the products or of the application or use by
customer’s third party customers. NVE accepts no liability in this respect.
Limiting Values
Stress above one or more limiting values (as defined in the Absolute Maximum Ratings System of IEC 60134) will cause permanent damage to the
device. Limiting values are stress ratings only and operation of the device at these or any other conditions above those given in the recommended
operating conditions of the datasheet is not warranted. Constant or repeated exposure to limiting values will permanently and irreversibly affect the
quality and reliability of the device.
Terms and Conditions of Sale
In case an individual agreement is concluded only the terms and conditions of the respective agreement shall apply. NVE hereby expressly objects to
applying the customer’s general terms and conditions with regard to the purchase of NVE products by customer.
No Offer to Sell or License
Nothing in this document may be interpreted or construed as an offer to sell products that is open for acceptance or the grant, conveyance or implication
of any license under any copyrights, patents or other industrial or intellectual property rights.
Export Control
This document as well as the items described herein may be subject to export control regulations. Export might require a prior authorization from national
authorities.
Automotive Qualified Products
Unless the datasheet expressly states that a specific NVE product is automotive qualified, the product is not suitable for automotive use. It is neither
qualified nor tested in accordance with automotive testing or application requirements. NVE accepts no liability for inclusion or use of non-automotive
qualified products in automotive equipment or applications.
In the event that customer uses the product for design-in and use in automotive applications to automotive specifications and standards, customer (a) shall
use the product without NVE’s warranty of the product for such automotive applications, use and specifications, and (b) whenever customer uses the
product for automotive applications beyond NVE’s specifications such use shall be solely at customer’s own risk, and (c) customer fully indemnifies
NVE for any liability, damages or failed product claims resulting from customer design and use of the product for automotive applications beyond NVE’s
standard warranty and NVE’s product specifications.
IL3185/IL3122
18
NVE Corporation 11409 Valley View Road, Eden Prairie, MN 55344-3617 Phone: (952) 829-9217 Fax: (952) 829-9189 www.IsoLoop.com ©NVE Corporation
An ISO 9001 Certified Company
NVE Corporation
11409 Valley View Road
Eden Prairie, MN 55344-3617 USA
Telephone: (952) 829-9217
Fax: (952) 829-9189
www.nve.com
e-mail: iso-info@nve.com
©NVE Corporation
All rights are reserved. Reproduction in whole or in part is prohibited without the prior written consent of the copyright owner.
ISB-DS-001-IL3185/22-P
November 2013