XR3070-78X
LOW POWER 18V TOLERANT RS-485/RS-422 +3.3V TRANSCEIVERS
REV. 1.0.0
GENERAL DESCRIPTION
FEATURES
The XR3070-78X family of high performance RS-485/
422 devices are designed for improved performance in
noisy industrial environments and increased tolerance
to system faults.
10% Higher SNR (Signal-to-Noise Ratio)
The analog bus pins can withstand direct shorts up to
±18V, and are protected against ESD events up to
±15kV. The differential high output driver delivers 10%
higher SNR than standard RS-485/422 devices, affording additional noise margin or extended cable lengths.
The receivers include full fail-safe circuitry, guaranteeing a logic-high receiver output when the receiver
inputs are open, shorted, or undriven. The receiver
input impedance is at minimum 96k (1/8 unit load),
allowing up to 256 devices on the bus while preserving
the full signal margin.
The drivers are protected by short circuit detection as
well as thermal shutdown, and maintain high impedance in shutdown or when powered off. The XR307075X drivers are slew limited for reduced EMI and errorfree communication over long or unterminated data
cables.
compared to other RS-485 devices (1.65V vs. 1.5V)
±18V Fault Tolerance on Analog Bus pins
Robust ESD (ElectroStatic Discharge) Protection:
■
±15kV IEC 61000-4-2 Air Gap Discharge
■
± 8kV IEC 61000-4-2 Contact Discharge
■
±15kV Human Body Model
■
± 4kV Human Body Model on non-bus pins
+3.0V to +3.6V Operation (3.3V ± 10%)
300μA Idle Current, 1nA Shutdown Current
Enhanced Receiver Fail-Safe Protection for Open,
Shorted, or Terminated but Idle Data Lines
Hot-Swap Glitch Protection on DE and RE Pins
Driver Short Circuit Current Limit and Thermal
Shutdown for Overload Protection
1/8th Unit Load Allows up to 256 Devices on Bus
Industry Standard 8 and 14 NSOIC Packages
The devices with DE and RE pins include hot swap circuitry to prevent false transitions on the bus during
powerup or live insertion, and can enter a 1nA low current shutdown mode for extreme power savings.
The transceivers draw less than 600μA from a +3.3V
supply, and typically only 300μA when idling with the
receivers active.
:
E X C E L L E N C E
&
R E L I A B I L I T Y
SEPT 2013
RO
1
RE
R
8
VCC
2
7
B
DE
3
6
A
DI
4
5
GND
D
Motor Control
Security Systems
Building and Process Automation
Remote Utility Meter Reading
Energy Monitoring and Control
Long or Unterminated Transmission Lines
X
S E R I E S
TYPICAL APPLICATIONS
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • (510) 668-7000 • FAX (510) 668-7017 • www.exar.com
XR3070-78X
LOW POWER 18V TOLERANT RS-485/RS-422 +3.3V TRANSCEIVERS
REV. 1.0.0
ABSOLUTE MAXIMUM RATINGS
These are stress ratings only and functional operation of the device at these ratings or any other above those
indicated in the operation sections to the specifications below is not implied. Exposure to absolute maximum
rating conditions for extended periods of time may affect reliability and cause permanent damage to the device.
VCC
-0.3V to +7.0V
Input Voltage at Control and Driver Input (RE, DE, and DI)
-0.3V to +7.0V
-0.3V to (VCC + 0.3V)
Receiver Output Voltage (RO)
Driver Output Voltage (A, B, Y and Z)
±18V
Receiver Input Voltage (A and B, half or full duplex)
±18V
Transient Voltage Pulse, through 100
±70V
Driver Output Current
±250mA
Storage Temperature Range
-65°C to +150°C
Lead Temperature (soldering, 10s)
+300°C
Package Power Dissipation
8-Pin SO
JA = 128.4°C/W
Maximum Junction Temperature = +150°C
14-Pin SO JA = 86°C/W
CAUTION:
ESD (Electrostatic Discharge) sensitive device. Permanent damage may occur on unconnected devices
subject to high energy electrostatic fields. Unused devices must be stored in conductive foam or shunts.
Personnel should be properly grounded prior to handling this device. The protective foam should be
discharged to the destination socket before devices are removed.
ORDERING INFORMATION
PART NUMBER
DUPLEX
DATA RATE
PACKAGE
TEMPERATURE RANGE
XR3070XID-F
Full
250kbps
14-pin Narrow SOIC
-40°C to +85°C
XR3071XID-F
Full
250kbps
8-pin Narrow SOIC
-40°C to +85°C
XR3072XID-F
Half
250kbps
8-pin Narrow SOIC
-40°C to +85°C
XR3073XID-F
Full
1Mbps
14-pin Narrow SOIC
-40°C to +85°C
XR3074XID-F
Full
1Mbps
8-pin Narrow SOIC
-40°C to +85°C
XR3075XID-F
Half
1Mbps
8-pin Narrow SOIC
-40°C to +85°C
XR3076XID-F
Full
20Mbps
14-pin Narrow SOIC
-40°C to +85°C
XR3077XID-F
Full
20Mbps
8-pin Narrow SOIC
-40°C to +85°C
XR3078XID-F
Half
20Mbps
8-pin Narrow SOIC
-40°C to +85°C
NOTE: Tape and Reel part numbers are XR30xxXIDTR-F, -F = Green / RoHS Compliant
2
XR3070-78X
LOW POWER 18V TOLERANT RS-485/RS-422 +3.3V TRANSCEIVERS
REV. 1.0.0
ELECTRICAL CHARACTERISTICS
Unless otherwise noted: VCC = +3.3V ±10%, TA = TMIN to TMAX. Typical values are at VCC = 3.3V, TA = +25°C.
SYMBOL
PARAMETERS
MIN.
TYP.
MAX.
UNITS
CONDITIONS
3.0
3.6
V
3
VCC
V
No Load
2
VCC
V
RL = 100 (RS-422), Figure 3
1.65
VCC
V
RL = 54 (RS-485), Figure 3
1.5
VCC
V
-7V VCM +12V, Figure 4
±0.2
V
3
V
±0.2
V
DRIVER DC CHARACTERISTICS
VCC
VOD
Supply Voltage Range
Differential Driver Output
VOD
Change in Magnitude of
Differential Output Voltage
VCM
Driver Common-Mode Output
Voltage (steady state)
VCM
VIH
VIL
VHYS
IIN
VCC / 2
Change in Magnitude of
Common-Mode Output Voltage
2.0
0.8
Input Hysteresis (DI, DE, RE)
100
Logic Input Current (DI, DE, RE)
V
Logic Input Low
100
±1
μA
±200
μA
125
μA
Input Current (A and B)
μA
125
μA
Output Leakage (Y and Z)
Full Duplex (Note 2)
-100
IOSD
Logic Input High
mV
-100
IOL
V
Logic Input Thresholds (DI, DE, RE)
Logic Input Current (DE and RE)
IA, B
RL = 100 (RS-422), or
RL = 54 (RS-485),
Figure 3, Note 1
±250
Driver Short-Circuit Output Current
0V VIN VCC,
After first transition, Note 2
Until first transition, Note 2
VOUT = +12V, DE = 0V,
VCC = 0V or 5.5V
VOUT = -7V, DE = 0V,
VCC = 0V or 5.5V
VOUT = +12V, DE = 0V,
VCC = 0V or 5.5V
μA
VOUT = -7V, DE = 0V,
VCC = 0V or 5.5V
mA
-7V VOUT +12V, Figure 5
DRIVER THERMAL CHARACTERISTICS
TTS
Thermal Shutdown Temperature
175
°C
Junction temperature, Note 4
TTSH
Thermal Shutdown Hysteresis
15
°C
Note 4
3
XR3070-78X
LOW POWER 18V TOLERANT RS-485/RS-422 +3.3V TRANSCEIVERS
REV. 1.0.0
Unless otherwise noted: VCC = +3.3V ±10%, TA = TMIN to TMAX. Typical values are at VCC = 3.3V, TA = +25°C.
SYMBOL
PARAMETERS
MIN.
TYP.
MAX.
UNITS
CONDITIONS
-200
-125
-50
mV
-7V VCM +12V
mV
VCM = 0V
RECEIVER DC CHARACTERISTICS
VTH
VOH
Receiver Differential Threshold
Voltage (VA - VB)
Receiver Input Hysteresis
VOH
Receiver Output High Voltage (RO)
VOL
Receiver Output Low Voltage (RO)
IOZR
High-Z Receiver Output Current
RIN
Receiver Input Resistance
IOSC
Receiver Output Short-Circuit
Current
25
V
IOUT = -1mA
0.4
V
IOUT = 1mA
±1
μA
0V VOUT VCC
k
-7V VCM +12V
±80
mA
0V VRO VCC
425
600
μA
330
600
μA
300
500
μA
No Load, RE = 0V, DE = 0V
Receiver A and B inputs open
0.001
1
μA
RE = VCC, DE = 0V
±15
kV
Human Body Model
±15
kV
IEC 61000-4-2 Airgap
±8
kV
IEC 61000-4-2 Contact
±4
kV
Human Body Model
VCC-0.6
96
SUPPLY CURRENT
ICC
ISHDN
Supply Current
Supply Current in Shutdown Mode
No Load, RE = 0V, DE = VCC
DI = 0V
No Load, RE = VCC, DE = VCC
DI = 0V
ESD PROTECTION
ESD Protection for A, B, Y, and Z
ESD Protection for all other pins
4
XR3070-78X
LOW POWER 18V TOLERANT RS-485/RS-422 +3.3V TRANSCEIVERS
REV. 1.0.0
Unless otherwise noted: VCC = +3.3V ±10%, TA = TMIN to TMAX. Typical values are at VCC = 3.3V, TA = +25°C.
SYMBOL
PARAMETERS
MIN.
TYP.
DRIVER AC CHARACTERISTICS
MAX.
UNITS
XR3070X, XR3071X and XR3072X (250kbps)
tDPLH
Driver Prop. Delay (Low to High)
250
1500
ns
tDPHL
Driver Prop. Delay (High to Low)
250
1500
ns
200
ns
1600
ns
|tDPLH-tDPHL|
tDR, tDF
CONDITIONS
Differential Driver Output Skew
20
Driver Differential Output
Rise or Fall Time
350
Maximum Data Rate
250
kbps
CL = 50pF, RL = 54,
Figure 6
1/tUI, Duty Cycle 40 to 60%
tDZH
Driver Enable to Output High
200
2500
ns
tDZL
Driver Enable to Output Low
200
2500
ns
CL = 50pF, RL = 500,
tDHZ
Driver Disable from Output High
6
100
ns
Figure 7
tDLZ
Driver Disable from Output Low
6
100
ns
tDZH(SHDN)
Driver Enable from Shutdown to
Output High
5500
ns
tDZL(SHDN)
Driver Enable from Shutdown to
Output Low
5500
ns
600
ns
tSHDN
Time to Shutdown
50
200
RECEIVER AC CHARACTERISTICS
Figure 7
Notes 3 and 4
XR3070X, XR3071X and XR3072X (250kbps)
tRPLH
Receiver Prop. Delay (Low to High)
200
ns
tRPHL
Receiver Prop. Delay (High to Low)
200
ns
|tRPLH-tRPHL|
Receiver Propagation Delay Skew
30
ns
Maximum Data Rate
CL = 50pF, RL = 500,
250
kbps
CL = 15pF, VID = ±2V,
VID Rise and Fall times < 15ns
Figure 8
1/tUI, Duty Cycle 40 to 60%
tRZH
Receiver Enable to Output High
50
ns
tRZL
Receiver Enable to Output Low
50
ns
CL = 15pF, RL = 1k,
tRHZ
Receiver Disable from Output High
50
ns
Figure 9
tRLZ
Receiver Disable from Output Low
50
ns
tRZH(SHDN)
Receiver Enable from Shutdown
to Output High
3500
ns
tRZL(SHDN)
Receiver Enable from Shutdown
to Output Low
3500
ns
600
ns
tSHDN
Time to Shutdown
50
200
5
CL = 15pF, RL = 1k,
Figure 9
Notes 3 and 4
XR3070-78X
LOW POWER 18V TOLERANT RS-485/RS-422 +3.3V TRANSCEIVERS
REV. 1.0.0
Unless otherwise noted: VCC = +3.3V ±10%, TA = TMIN to TMAX. Typical values are at VCC = 3.3V, TA = +25°C.
SYMBOL
PARAMETERS
MIN.
TYP.
DRIVER AC CHARACTERISTICS
MAX.
UNITS
XR3073X, XR3074X and XR3075X (1Mbps)
tDPLH
Driver Prop. Delay (Low to High)
150
300
ns
tDPHL
Driver Prop. Delay (High to Low)
150
300
ns
5
50
ns
200
300
ns
|tDPLH-tDPHL|
tDR, tDF
Differential Driver Output Skew
Driver Differential Output
Rise or Fall Time
Maximum Data Rate
CONDITIONS
100
CL = 50pF, RL = 54,
Figure 6
Mbps 1/tUI, Duty Cycle 40 to 60%
1
tDZH
Driver Enable to Output High
1000
2500
ns
tDZL
Driver Enable to Output Low
1000
2500
ns
CL = 50pF, RL = 500,
tDHZ
Driver Disable from Output High
60
100
ns
Figure 7
tDLZ
Driver Disable from Output Low
60
100
ns
tDZH(SHDN)
Driver Enable from Shutdown to
Output High
3500
ns
tDZL(SHDN)
Driver Enable from Shutdown to
Output Low
3500
ns
600
ns
tSHDN
Time to Shutdown
50
200
RECEIVER AC CHARACTERISTICS
Figure 7
Notes 3 and 4
XR3073X, XR3074X and XR3075X (1Mbps)
tRPLH
Receiver Prop. Delay (Low to High)
200
ns
tRPHL
Receiver Prop. Delay (High to Low)
200
ns
|tRPLH-tRPHL|
Receiver Propagation Delay Skew
30
ns
Maximum Data Rate
CL = 50pF, RL = 500,
CL = 15pF, VID = ±2V,
VID Rise and Fall times < 15ns
Figure 8
Mbps 1/tUI, Duty Cycle 40 to 60%
1
tRZH
Receiver Enable to Output High
50
ns
tRZL
Receiver Enable to Output Low
50
ns
CL = 15pF, RL = 1k,
tRHZ
Receiver Disable from Output High
50
ns
Figure 9
tRLZ
Receiver Disable from Output Low
50
ns
tRZH(SHDN)
Receiver Enable from Shutdown
to Output High
3500
ns
tRZL(SHDN)
Receiver Enable from Shutdown
to Output Low
3500
ns
600
ns
tSHDN
Time to Shutdown
50
200
6
CL = 15pF, RL = 1k,
Figure 9
Notes 3 and 4
XR3070-78X
LOW POWER 18V TOLERANT RS-485/RS-422 +3.3V TRANSCEIVERS
REV. 1.0.0
Unless otherwise noted: VCC = +3.3V ±10%, TA = TMIN to TMAX. Typical values are at VCC = 3.3V, TA = +25°C.
SYMBOL
PARAMETERS
MIN.
TYP.
DRIVER AC CHARACTERISTICS
MAX.
UNITS
XR3076X, XR3077X and XR3078X (20Mbps)
tDPLH
Driver Prop. Delay (Low to High)
25
ns
tDPHL
Driver Prop. Delay (High to Low)
25
ns
Differential Driver Output Skew
5
ns
|tDPLH-tDPHL|
tDR, tDF
Driver Differential Output
Rise or Fall Time
Maximum Data Rate
CONDITIONS
15
CL = 50pF, RL = 54,
Figure 6
ns
Mbps 1/tUI, Duty Cycle 40 to 60%
20
tDZH
Driver Enable to Output High
45
ns
tDZL
Driver Enable to Output Low
45
ns
CL = 50pF, RL = 500,
tDHZ
Driver Disable from Output High
40
ns
Figure 7
tDLZ
Driver Disable from Output Low
40
ns
tDZH(SHDN)
Driver Enable from Shutdown to
Output High
250
ns
tDZL(SHDN)
Driver Enable from Shutdown to
Output Low
250
ns
600
ns
tSHDN
Time to Shutdown
50
200
RECEIVER AC CHARACTERISTICS
Figure 7
Notes 3 and 4
XR3076X, XR3077X and XR3078X (20Mbps)
tRPLH
Receiver Prop. Delay (Low to High)
50
ns
tRPHL
Receiver Prop. Delay (High to Low)
50
ns
|tRPLH-tRPHL|
Receiver Propagation Delay Skew
5
ns
Maximum Data Rate
CL = 50pF, RL = 500,
CL = 15pF, VID = ±2V,
VID Rise and Fall times < 15ns
Figure 8
Mbps 1/tUI, Duty Cycle 40 to 60%
20
tRZH
Receiver Enable to Output High
30
ns
tRZL
Receiver Enable to Output Low
30
ns
CL = 15pF, RL = 1k,
tRHZ
Receiver Disable from Output High
30
ns
Figure 9
tRLZ
Receiver Disable from Output Low
30
ns
tRZH(SHDN)
Receiver Enable from Shutdown
to Output High
1800
ns
tRZL(SHDN)
Receiver Enable from Shutdown
to Output Low
1800
ns
600
ns
tSHDN
Time to Shutdown
50
200
7
CL = 15pF, RL = 1k,
Figure 9
Notes 3 and 4
XR3070-78X
LOW POWER 18V TOLERANT RS-485/RS-422 +3.3V TRANSCEIVERS
REV. 1.0.0
NOTE:
1.
Change in Magnitude of Differential Output Voltage and Change in Magnitude of Common Mode Output Voltage
are the changes in output voltage when DI input changes state.
2.
The hot swap feature disables the DE and RE inputs for the first 10μs after power is applied. Following this time
period these inputs are weakly pulled to their disabled state (low for DE, high for RE) until the first transition, after
which they become high impedance inputs.
3.
The transceivers are put into shutdown by bringing RE High and DE Low simultaneously for at least 600ns. If the
control inputs are in this state for less than 50ns, the device is guaranteed to not enter shutdown. If the enable
inputs are held in this state for at least 600ns the device is assured to be in shutdown. Note that the receiver and
driver enable times increase significantly when coming out of shutdown.
4.
This spec is guaranteed by design and bench characterization.
8
XR3070-78X
LOW POWER 18V TOLERANT RS-485/RS-422 +3.3V TRANSCEIVERS
REV. 1.0.0
BLOCK DIAGRAMS
FIGURE 1. HALF DUPLEX (XR3072X, XR3075X, XR3078X)
RO
1
RE
R
8
VCC
2
7
B
DE
3
6
A
DI
4
5
GND
D
FIGURE 2. FULL DUPLEX (XR3070X, XR3071X, XR3073X, XR3074X, XR3076X, XR3077X)
VCC
1
RO
2
DI
3
GND
4
R
D
N/C
1
R
14
VCC
13
N/C
8
A
RO
2
7
B
RE
3
12
A
6
Z
DE
4
11
B
5
Y
DI
5
10
Z
GND
6
9
Y
GND
7
8
N/C
9
D
XR3070-78X
LOW POWER 18V TOLERANT RS-485/RS-422 +3.3V TRANSCEIVERS
REV. 1.0.0
TEST FIGURES
FIGURE 3. DIFFERENTIAL DRIVER OUTPUT VOLTAGE
Z
DI = 0V or VCC
D
RL
2
VOD
VCM
RL
2
Y
DE = VCC
FIGURE 4. DIFFERENTIAL DRIVER OUTPUT VOLTAGE OVER COMMON MODE
Z
375æ
DI = 0V or VCC
D
VOD
VCM
60æ
375æ
Y
DE = VCC
FIGURE 5. DRIVER OUTPUT SHORT CIRCUIT CURRENT
Z
DI = 0V or VCC
IOSD
D
-7V to +12V
Y
DE = 0V or VCC
10
V
XR3070-78X
LOW POWER 18V TOLERANT RS-485/RS-422 +3.3V TRANSCEIVERS
REV. 1.0.0
FIGURE 6. DRIVER PROPAGATION DELAY TEST CIRCUIT & TIMING DIAGRAM
Z
DI
VOD
D
RL
Y
DE = VCC
DI
3V
1.5V
0V
Z
CL
1.5V
tDPLH
tSKEW = |tDPHL è tDPLH|
tDPHL
VOD
VOD
(VY - VZ)
Y
VOD+
0V
VOD-
90%
90%
10%
10%
tDR
11
tDF
XR3070-78X
LOW POWER 18V TOLERANT RS-485/RS-422 +3.3V TRANSCEIVERS
REV. 1.0.0
FIGURE 7. DRIVER ENABLE AND DISABLE TIMING TEST CIRCUITS & TIMING DIAGRAMS
Z
Testing Z: DI = 0V
VOUT
D
Testing Y: DI = VCC
DE
DE
RL
Y
CL
3V
1.5V
1.5V
0V
tDZH
VOH
VOUT
tDHZ
VOH + VOL
2
VOL
VOH - 0.25V
VCC
Z
RL
Testing Z: DI = VCC
VOUT
D
Testing Y: DI = 0V
DE
DE
CL
Y
3V
1.5V
1.5V
0V
tDZL
VOH
VOUT
VOL
tDLZ
VOH + VOL
2
VOL + 0.25V
12
XR3070-78X
LOW POWER 18V TOLERANT RS-485/RS-422 +3.3V TRANSCEIVERS
REV. 1.0.0
FIGURE 8. RECEIVER PROPAGATION DELAY TEST CIRCUIT & TIMING DIAGRAM
B
RO
R
CL
A
RE = 0V
B
+1V
0V
-1V
A
tRPLH
tRPHL
VOH
RO
1.5V
13
1.5V
VOL
XR3070-78X
LOW POWER 18V TOLERANT RS-485/RS-422 +3.3V TRANSCEIVERS
REV. 1.0.0
FIGURE 9. RECEIVER ENABLE AND DISABLE TEST CIRCUITS & TIMING DIAGRAMS
B
RO
R
RE
A
RE
RL
CL
3V
1.5V
1.5V
0V
VA = VCC
VB = 0V
tRZH
VOH
tRHZ
VOH
2
RO
0V
VOH - 0.25V
VCC
B
RL
RO
R
RE
CL
RE
A
3V
1.5V
1.5V
0V
VA = 0V
VB = VCC
tRZL
VCC
RO
VOL
tRLZ
VCC + VOL
2
VOL + 0.25V
14
XR3070-78X
LOW POWER 18V TOLERANT RS-485/RS-422 +3.3V TRANSCEIVERS
REV. 1.0.0
PIN DESCRIPTIONS
PIN NUMBER
HALF DUPLEX
FULL DUPLEX
XR3072X
XR3075X
XR3078X
XR3071X
XR3074X
XR3077X
XR3070X
XR3073X
XR3076X
1
2
2
2
3
-
-
3
4
PIN NAME
TYPE
RO
Out
RE
DE
DESCRIPTION
Receiver Output. When RE is low and
if (A-B) -50mV, RO is high.
If (A-B) -200mV, RO is Low.
In
Receiver Output Enable (Hot Swap).
When RE is low, RO is enabled. When RE is High,
RO is high impedance. RE should be high and DE
should be low to enter shutdown mode.
In
Driver Output Enable (Hot Swap).
When DE is high, outputs are enabled. When DE is
low, outputs are high impedance. DE should be low
and RE should be high to enter shutdown mode.
Driver Input.
With DE high, a low level on DI forces non-Inverting
output low and inverting output high. Similarly, a
high level on DI forces non-Inverting output high
and inverting output low.
4
3
5
DI
In
5
4
6, 7
GND
Pwr
Ground.
6
-
-
A
I/O
Non-Inverting Receiver Input and
Non-Inverting Driver Output.
7
-
-
B
I/O
Inverting Receiver Input and
Inverting Driver Output.
8
1
14
VCC
Pwr
+3.3V Power Supply Input.
Bypass to ground with 0.1 μF capacitor.
-
8
12
A
In
Non-Inverting Receiver Input.
-
7
11
B
In
Inverting Reciever Input.
-
5
9
Y
Out
Non-Inverting Driver Output.
-
6
10
Z
Out
Inverting Driver Output.
-
-
1, 8, 13
N/C
-
15
No Connect, not internally connected.
XR3070-78X
LOW POWER 18V TOLERANT RS-485/RS-422 +3.3V TRANSCEIVERS
REV. 1.0.0
PRODUCT DESCRIPTION
The XR3070-78X RS-485/422 devices are part of Exar’s X Series high performance serial interface product
line. The analog bus pins can survive direct shorts up to ±18V, and are protected against ESD events up to
±15kV. The high output differential driver delivers 10% higher SNR than other RS-485/422 devices, affording
additional noise margin or extended cable lengths.
ENHANCED FAILSAFE
Ordinary RS-485 differential receivers will be in an indeterminate state whenever the data bus is not being
actively driven. The enhanced failsafe feature of the XR3070-78X family guarantees a logic-high receiver
output when the receiver inputs are open, shorted, or when they are connected to a terminated transmission
line with all drivers disabled. In a terminated bus with all transmitters disabled, the receivers’ differential input
voltage is pulled to 0V by the termination. The XR3070-78X family interprets 0V differential as a logic high with
a minimum 50mV noise margin while maintaining compliance with the EIA/TIA-485 standard of ±200mV.
Although the XR3070-78X family does not need failsafe biasing resistors, it can operate without issue if biasing
is used.
RECEIVER INPUT FILTERING
XR3070-75X receivers incorporate internal filtering in addition to input hysteresis. This filtering enhances noise
immunity by ignoring signals that do not meet a minimum pulse width of 30ns. Receiver propagation delay
increases slightly due to this filtering. The high speed XR3076X, XR3077X and XR3078X devices do not have
this input filtering.
HOT-SWAP CAPABILITY
When VCC is first applied the XR3070-78X devices with DE and RE pins (70, 72, 73, 75, 76, & 78) hold the
driver enable and receiver enable inactive for approximately 10 microseconds. During power ramp-up other
system ICs may drive unpredictable values, or tristated lines may be influenced by stray capacitance. The hotswap feature prevents these devices from driving any output signal until power has stabilized. After the initial
10μs, the driver and receiver enable pins are weakly pulled to their disabled states (low for DE, high for RE)
until the first transition. After the first transition, the DE and RE pins operate as high impedance inputs.
If circuit boards are inserted into an energized backplane (commonly called "live insertion" or "hot-swap")
power may suddenly be applied to all circuits. Without the hot-swap capability, this situation could improperly
enable the transceiver’s driver or receiver, driving invalid data onto shared busses and possibly causing driver
contention or device damage.
DRIVER OUTPUT PROTECTION
Two mechanisms prevent excessive output current and power dissipation caused by faults or by bus
contention. First, a driver current limit on the output stage provides immediate protection against short circuits
over the whole common-mode voltage range. Second, a thermal-shutdown circuit forces the driver outputs into
a high-impedance state if junction temperature becomes excessive.
LINE LENGTH
The RS-485/RS-422 standard covers line lengths up to 4000ft. Maximum achievable line length is a function of
signal attenuation and noise. Termination prevents signal reflections by eliminating the impedance mismatches
on a transmission line. Line termination is generaly used if rise and fall times are shorter than the round-trip
signal propagation time. Higher output drivers may allow longer cables to be used.
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XR3070-78X
REV. 1.0.0
LOW POWER 18V TOLERANT RS-485/RS-422 +3.3V TRANSCEIVERS
±15kV ESD PROTECTION
ESD protection structures are incorporated on all pins to protect against electrostatic discharges encountered
during handling and assembly. The driver outputs and receiver inputs of the XR3070-78X family have extra
protection against static electricity. Exar uses state of the art structures to protect these pins against ESD of
±15kV without damage. The ESD structures withstand high ESD in all states: normal operation, shutdown and
powered down. After an ESD event, the XR3070-78X keep operating without latch-up or damage.
ESD protection can be tested in various ways. The transmitter outputs and receiver inputs of the XR3070-78X
are characterized for protection to the following limits:
■
±15kV using the Human Body Model
■
± 8kV Contact Discharge Model
■
±15kV Air-gap Discharge Model
ESD TEST CONDITIONS
ESD performance depends on a variety of conditions. Contact Exar for a reliability report that documents test
setup, methodology and results.
IEC 61000-4-2
The IEC 61000-4-2 standard covers ESD testing and performance of finished equipment. However, it does not
specifically refer to integrated circuits. The XR3070-78X family helps you design equipment to meet
IEC 61000-4-2, without sacrificing board-space and cost for external ESD-protection components.
The major differences between tests done using the Human body model and IEC 61000-4-2 is a higher peak
current in IEC 61000-4-2. Series resistance is lower in the IEC 61000-4-2 model. Hence, the ESD withstand
voltage measured to IEC 61000-4-2 is generally lower than that of human body model.
The air-gap test involves approaching the device with a charged probe. The contact discharge method
connects the probe to the device before the probe is energized.
256 TRANSCEIVERS ON THE BUS
The standard RS-485 receiver input impedance is 12k Ohms (1 unit load). A standard driver can drive up to 32
unit loads. The XR3070-78X family of transceivers have a 1/8th unit load receiver input impedance of 96k,
allowing up to 256 transceivers to be connected in parallel on a communication line. Any combination of these
devices and other RS-485 transceivers up to a total of 32 unit loads may be connected to the line.
LOW POWER SHUTDOWN MODE
Low-power shutdown mode is initiated by bringing both RE high and DE low simultaneously. While in shutdown
devices draw less than 1μA of supply current. DE and RE may be tied together and driven by a single control
signal. Devices are guaranteed not to enter shutdown if RE is high and DE is low for less than 50ns. If the
inputs are in this state for at least 600ns, the parts will enter shutdown.
Enable times tZH and tZL apply when the part is not in low-power shutdown state. Enable times tZH(SHDN) and
tZL(SHDN) apply when the parts are shutdown. The drivers and receivers take longer to become enabled from
low-power shutdown tZH(SHDN) and tZL(SHDN) than from driver / receiver disable mode (tZH and tZL).
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XR3070-78X
LOW POWER 18V TOLERANT RS-485/RS-422 +3.3V TRANSCEIVERS
REV. 1.0.0
FUNCTION TABLES
TABLE 1: FULL DUPLEX 14 PIN - XR3070X, XR3073X AND XR3076X
TRANSMITTING
Inputs
Outputs
RE
DE
DI
Y
Z
X
1
1
1
0
X
1
0
0
1
0
0
X
High-Z
1
0
X
Shutdown
TABLE 2: FULL DUPLEX 8 PIN - XR3071X, XR3074X AND XR3077X
TRANSMITTING
Input
Outputs
DI
Y
Z
1
1
0
0
0
1
TABLE 3: HALF DUPLEX 8 PIN - XR3072X, XR3075X AND XR3078X
TRANSMITTING
Inputs
Outputs
RE
DE
DI
A
B
X
1
1
1
0
X
1
0
0
1
0
0
X
High-Z
1
0
X
Shutdown
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XR3070-78X
LOW POWER 18V TOLERANT RS-485/RS-422 +3.3V TRANSCEIVERS
REV. 1.0.0
TABLE 4: FULL DUPLEX 14 PIN - XR3070X, XR3073X AND XR3076X
RECEIVING
Inputs
Ouptut
RE
DE
VA - VB
RO
0
X
-50mV
1
0
X
-200mV
0
0
X
Open/Shorted
1
1
1
X
High-Z
1
0
X
Shutdown
TABLE 5: FULL DUPLEX 8 PIN - XR3071X, XR3074X AND XR3077X
RECEIVING
Inputs
Output
VA - VB
RO
-50mV
1
-200mV
0
Open/Shorted
1
TABLE 6: HALF DUPLEX 8 PIN - XR3072X, XR3075X AND XR3078X
RECEIVING
Inputs
Output
RE
DE
VA - VB
RO
0
X
-50mV
1
0
X
-200mV
0
0
X
Open/Shorted
1
1
1
X
High-Z
1
0
X
Shutdown
Note: Receiver inputs -200mV VA - VB -50mV are considered indeterminate.
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XR3070-78X
LOW POWER 18V TOLERANT RS-485/RS-422 +3.3V TRANSCEIVERS
REV. 1.0.0
PRODUCT SELECTOR GUIDE
TABLE 7: SELECTION GUIDE
SHUTDOWN
RECEIVER
AND DRIVER
ENABLE
TRANS ON
BUS
FOOTPRINT
Yes
Yes
256
SN75180
No
No
256
SN75179
Half
Yes
Yes
256
SN75176
XR3073XID-F
Full
Yes
Yes
256
SN75180
XR3074XID-F
Full
No
No
256
SN75179
XR3075XID-F
Half
Yes
Yes
256
SN75176
XR3076XID-F
Full
Yes
Yes
256
SN75180
XR3077XID-F
Full
No
No
256
SN75179
XR3078XID-F
Half
Yes
Yes
256
SN75176
PART
NUMBER
DUPLEX
XR3070XID-F
Full
XR3071XID-F
Full
XR3072XID-F
DATA RATE
250kbps
1Mbps
20Mbps
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XR3070-78X
REV. 1.0.0
LOW POWER 18V TOLERANT RS-485/RS-422 +3.3V TRANSCEIVERS
PACKAGE DRAWINGS
FIGURE 10. 8 NSOIC
21
XR3070-78X
LOW POWER 18V TOLERANT RS-485/RS-422 +3.3V TRANSCEIVERS
FIGURE 11. 14 NSOIC
22
REV. 1.0.0
XR3070-78X
LOW POWER 18V TOLERANT RS-485/RS-422 +3.3V TRANSCEIVERS
REV. 1.0.0
REVISION HISTORY
DATE
REVISION
Sept 2013
1.0.0
DESCRIPTION
Production Release
NOTICE
EXAR Corporation reserves the right to make changes to the products contained in this publication in order to
improve design, performance or reliability. EXAR Corporation assumes no responsibility for the use of any
circuits described herein, conveys no license under any patent or other right, and makes no representation that
the circuits are free of patent infringement. Charts and schedules contained here in are only for illustration
purposes and may vary depending upon a user’s specific application. While the information in this publication
has been carefully checked; no responsibility, however, is assumed for inaccuracies.
EXAR Corporation does not recommend the use of any of its products in life support applications where the
failure or malfunction of the product can reasonably be expected to cause failure of the life support system or to
significantly affect its safety or effectiveness. Products are not authorized for use in such applications unless
EXAR Corporation receives, in writing, assurances to its satisfaction that: (a) the risk of injury or damage has
been minimized; (b) the user assumes all such risks; (c) potential liability of EXAR Corporation is adequately
protected under the circumstances.
Copyright 2013 EXAR Corporation
Datasheet Sept 2013.
For technical support please email Exar’s Serial Technical Support group at: serialtechsupport@exar.com.
Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited.
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