Exar Corporation 48720 Kato Road, Fre mont CA, 94538 • (510) 668 -7000 • FAX (510) 668-7017 • www.exar.com
XR3170E-3178E
3.3V HIGH SPEED RS-485/RS-422 TRANSCEIVERS WITH 1/8th UNIT LOAD
DECEMBER 2009 REV. 1.0.0
GENERAL DESCRIPTION
The XR3170E - XR3178E family of RS-485 devices
are designed for reliab le, bi directio na l communicatio n
on multipoint bus transmission lines. Each device
contains one differential driver and one differential
receiver. XR3172E, XR3175E and XR3178E are half-
duplex devices; other part numbers are full-duplex.
All devices comply with TIA/EIA-485 and TIA/EIA-422
standards. Lead free and RoHS compliant packages
are available for all models.
These devices are ruggedized for use in harsh
operating conditions over the entire common-mode
voltage range from -7V to +12V. Receivers are
specially designed to fail-safe to a logic high output
state if the inputs are left un-driven or shorted. All RS-
485 bus pins are protected against severe ESD
events up to +/-15kV (Air-Gap and Human Body
Model) and up to +/-8kV Contact Discharge (IEC
61000-4-2). Drivers are protected from excess
current flow caused by bus contention or output
short-circuits by both an internal current limit and a
thermal-overload shutdown. Devices are rated for
Industrial (-40 to +85°C) operating temperatures.
Receivers have exceptionally high input impedance,
which places only 1/8th the standard load on a shared
bus. Up to 256 transceivers may coexist while
preserving full signal margin.
All devices operate from a single 3.3V power supply
and draw negligible quiescent power. All versions
except the XR3171E, XR3174E and XR3177E may
independently enable and disable their driver and
receiver and enter a low power shutdown mode if
both driver and receiver are disabled. All outputs
maintain high impedance in shutdown or when
powered off.
FEATURES
•3.3V Single Supply Operation
•High Speed 20Mbps Data Rate
•Slew Rate Limited - 250kbps And 500kbps Data
Rate
•1/8th Unit Load, 256 Transceivers On Bus
•Enhanced Failsafe For Receiver - Open, Short Or
Terminated Lines
•Robust ESD Protection For RS-485 Pins
■+/-15kV Air-Gap Discharge
■+/-15kV Human Body Model
■+/-8kV Contact Discharge
•Hot Swap Glitch Protection
•Driver Short Circuit Current Limit And Thermal
Shutdown For Overload Protection
•Ultra-Low 650uA Quiescent Current
•1µA Shutdown Mode
•Industry Standard Package Footprints
TYPICAL APPLICATIONS
•Motor Control
•Building Automation
•Security Systems
•Remote Utility Meter Reading
•Long Or Un-Ter m ina te d Transmission Lines
FIGURE 1. TYPICAL APPLICATION CIRCUIT
RTRT
STUB
XR3178E XR3178E
XR3178E
XR3178E
A
AA
A
B
BB
B
DI
RO
RE
DE DE
DE DE
RE
RE
DI DI
DI
RO RO
RO
RE
FIGURE 2. PIN OUT ASSIGNMENT
NC
NC
VCC
2
1
3
4
5
6
78
9
10
11
12
13
14
DI
NC
RO
RE
DE
GND
GND
Y
Z
B
A
2
1
3
45
6
7
8
VCC
RO
DI
GND
A
B
Z
Y
2
1
3
45
6
7
8
8-Pin N S OIC
Half Duplex
XR3172E
XR3175E
XR3178E
RO
RE
DE
DI GND
A
B
VCC
8-Pin N S OIC
F u ll Du p le x
XR3171E
XR3174E
XR3177E
14-Pin N SO IC
F u ll Du p le x
XR3170E
XR3173E
XR3176E
ORDERING INFORMATION
PART NUMBER PACKAGE OPERATING TEMPERATURE
RANGE DEVICE STATUS
XR3170EID 14-pin Narrow SOIC -40°C to +85°C Active
XR3171EID 8-pin Narrow SOIC -40°C to +85°C Active
XR3172EID 8-pin Narrow SOIC -40°C to +85°C Active
XR3173EID 14-pin Narrow SOIC -40°C to +85°C Active
XR3174EID 8-pin Narrow SOIC -40°C to +85°C Active
XR3175EID 8-pin Narrow SOIC -40°C to +85°C Active
XR3176EID 14-pin Narrow SOIC -40°C to +85°C Active
XR3177EID 8-pin Narrow SOIC -40°C to +85°C Active
XR3178EID 8-pin Narrow SOIC -40°C to +85°C Active
XR3170E-3178E
2
3.3V HIGH SPEED RS-485/RS-422 TRANSCEIVERS WITH 1/8th UNIT LOAD REV. 1.0.0
Note: Please visit www.exar.com for tape and reel option part numbers.
XR3170E-3178E
3
REV. 1.0.0 3.3V HIGH SPEED RS-485/RS-422 TRANSCEIVERS WITH 1/8th UNIT LOAD
PIN DESCRIPTIONS
Pin Assignments
PIN NUMBER
PIN NAME TYPE DESCRIPTION
HALF DUPLEX FULL DUPLEX
122 RO OReceiver Output. When RE is low and if (A-
B) ≥ -50mV, RO is High. If (A-B) ≤ -200mV,
RO is Low.
2 - 3 RE I
Receiver Output Enable. 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.
RE is a hot-swap input.
3 - 4 DE I
Driver Output Enable. When DE is High,
outputs are enabled. When DE is low, out-
puts are high impedance. DE should be low
and RE should be High to ente r shutdown
mode. DE is a hot-swap input.
435 DI I
Driver Input. With DE high, a low level on DI
forces Non-Inverting output low and invert-
ing output high. Similarly, a high level on DI
forces Non-Inverting output High and Invert-
ing output Low .
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 with
0.1uF capacitor.
- 8 12 A I Non-Inverting Receiver Input.
- 7 11 B I Inverting Reciever Input.
- 5 9 Y O Non-Inverting Driver Output.
- 6 10 Z O Inverting Driver Output.
- - 1, 8, 13 NC -No Connect, not internally connected.
Pin type: I=Input, O=Output.
XR3172E
XR3175E
XR3178E
XR3171E
XR3174E
XR3177E
XR3170E
XR3173E
XR3176E
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 +6.0V
Input Voltage at control pins (RE, DE and DI) -0.3V to (VCC + 0.3V)
Driver Output Voltage (A, B, Y and Z) -8V to +13V
Receiver Output Voltage (RO) -0.3V to (VCC + 0.3V)
Receiver Input Voltage (A and B) -8V to +13V
Storage Temperature Range -65°C to + 150°C
Lead Temperature (soldering, 10s) +300°C
Package Power Dissipation
Maximum Junction Temperature 150°C
8-Pin SO θJA = 128.4°C /W
14-Pin SO θJA = 86°C/W
XR3170E-3178E
4
3.3V HIGH SPEED RS-485/RS-422 TRANSCEIVERS WITH 1/8th UNIT LOAD REV. 1.0.0
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.
ELECTRICAL CHARACTERISTICS
UNLESS OTHERWISE NOTED: VCC = +3.0V TO +3.6V WITH TA FROM -40OC TO +85OC. TYPICAL VALUES ARE AT
VCC = +3.3V AND 25OC.
SYMBOL PARAMETERS MIN.TYP. MAX. UNITS CONDITIONS
DRIVER DC CHARACTERISTICS
VOD Differential Driver Output Vcc VNo Load
2.0 2.65 RL = 100Ω (RS-422), Figure 3
1.7 2.35 RL = 54Ω (RS-485), Figure 3
1.7 2.35 VCM = -7V, Figure 4
1.7 2.35 VCM = +12V, Figure 4
∆VOD Change in Magnitude of Differential
Output -0.20 0.20 V RL = 100Ω (RS-422), Figure 3,
See Note 1
-0.20 0.20 RL = 54Ω (RS-485), Figure 3,
See Note 1
-0.20 0.20 VCM = -7V, Figure 4, See
Note 1
-0.20 0.20 VCM = +12V, Figure 4, See Note
1
VOC Driver Common Mode Output
Voltage steady state 3.0 VFigure 3
XR3170E-3178E
5
REV. 1.0.0 3.3V HIGH SPEED RS-485/RS-422 TRANSCEIVERS WITH 1/8th UNIT LOAD
∆VOC Change in Magnitude of Common
Mode Output Voltage -0.2 0.2 VFigure 3, See No te 1
IOSD Driver Short Circuit Current Limit -250 250 mA -7V ≤ VOUT ≤ 12V, Figure 5
VIH Logic Input Thresholds (DI, DE, RE)2.0 VLogic Input High
VIL 0.8 VLogic Input Low
VHYS Driver Input Hysteresis 100 mV TA = 25°C
IIN Logic Input Current (DI, DE and RE)-1 1µA0V ≤ IN ≤ +Vcc, after first tran-
sition, Note 2
IOL Output Leakage Current (Full-Duplex
versions, Y and Z pins) Note 2 125 µAVout = 12V, DE = 0V, RE = 0V,
Vcc = 0V or 3.3V.
-100 µAVout = -7V, DE = 0V, RE = 0V,
Vcc = 0V or 3.3V.
RECEIVER DC CHARACTERISTICS
RIN Receiver Input Resistance 96 160 KΩ-7V ≤ VCM ≤ 12V
IIN Input Current (A, B pins) 70 125 µADE = 0V, Vcc = 0V or 3.3V, VIN
= 12V
-100 -55 µADE = 0V, Vcc = 0V or 3.3V, VIN
= -7V
VIH,VIL Receiver Differential Thresholds
(VA - VB)-200 -120 -50 mV -7V ≤ VCM ≤ 12V
Receiver Input Hysteresis 25 mV VCM = 0V
VOH Receiver Output Voltage High Vcc -
0.6 V IOUT = -8mA, VID = -50mV
VOL Receiver Output Voltage Low 0.4 V IOUT = 8mA, VID = -200mV
IOZ High-Z Receiver Output Current +/-
0.03 +/-1.0 µAVcc = 3.3V,
0.40V ≤ Vout ≤ 2.4V
IOSC Receiver Output Short Circuit Cur-
rent +/-95 mA 0V ≤ VRO ≤ Vcc
SUPPLY AND PROTECTION
ICC1 Supply Current - Driver Enabled 650 950 µANo Load, DE = Vcc, DI = 0V or
Vcc
ICC2 Supply Current - Shutdown Mode 1µADE = 0V, RE = Vcc, DI = 0V or
Vcc
TSD Thermal Shutdown Temperature 165 °C Junction temperature, Note 4
Thermal Shutdown Hysteresis 15 °C Note 4
XR3170E, XR3171E, XR3172E
DRIVER AC CHARACTERISTICS
freq Max. Data Signaling Rate 250 kbps 1/tUI, Duty Cycle 40 to 60%
UNLESS OTHERWISE NOTED: VCC = +3.0V TO +3.6V WITH TA FROM -40OC TO +85OC. TYPICAL VALUES ARE AT
VCC = +3.3V AND 25OC.
SYMBOL PARAMETERS MIN.TYP.MAX.UNITS CONDITIONS
XR3170E-3178E
6
3.3V HIGH SPEED RS-485/RS-422 TRANSCEIVERS WITH 1/8th UNIT LOAD REV. 1.0.0
tPLH Driver Propagation Delay (Low to
High) 250 1500 ns CL = 50pF, RL = 54Ω, Figures 6
and 7
tPHL Driver Propagation Delay (High to
Low) 250 1500 ns CL = 50pF, RL = 54Ω, Figures 6
and 7
tRDriver Rise Time 350 1600 ns CL = 50pF, RL = 54Ω, Figures 6
and 7
tFDriver Fall Time 350 1600 ns CL = 50pF, RL = 54Ω, Figures 6
and 7
|tPLH-tPHL|Differential Pulse Skew 200 ns Figures 6 and 7
tZH Driver Enable to Output High 2500 ns CL = 50pF, RL = 500Ω, Figures
8 and 9
tZL Driver Enable to Output Low 2500 ns CL = 50pF, RL = 500Ω, Figures
10 and 11
tHZ Driver Disable from Output High 150 ns CL = 50pF, RL = 500Ω, Figures
8 and 9
tLZ Driver Disable from Output Low 150 ns CL = 50pF, RL = 500Ω, Figures
10 and 11
tOZV Shutdown to Driver Output Valid 3500 ns CL = 50pF, RL = 500Ω
tSHDN Time to Shutdown 50 200 600 ns Notes 3 and 4
RECEIVER AC CHARACTERISTICS
freq Data Signaling Rate 250 kbps 1/tUI, Duty Cycle 40 to 60%
tPLH Receiver Propagation Delay (Low to
High) 200 ns VID = +/-2V, CL = 15pF, Figures
12 and 13
tPHL Receiver Propagation Delay (High to
Low) 200 ns VID = +/-2V, CL = 15pF, Figures
12 and 13
skew Receiver Propagation Delay Skew 30 ns VID = +/-2V, C L = 15pF, Figures
12 and 13
skew = |tPLH-tPHL|
tRReceiver Output Rise Time 3 6 ns CL = 15pF, Figure 12
tFReceiver Output Fall Time 3 6 ns CL = 15pF, Figure 12
tZH Receiver Enable to Output High 50 ns CL = 15pF, Figure 14
tZL Receiver Enable to Output Low 50 ns CL = 15pF, Figure 14
tHZ Receiver Disable from Output High 50 ns CL = 15pF, Figure 14
tLZ Receiver Disable from Output Low 50 ns CL = 15pF, Figure 14
tZH(SHDN) Shutdown to Receiver Output Valid
High 3500 ns CL = 15pF, Figure 14
tZL(SHDN) Shutdown to Receiver Output Valid
Low 3500 ns CL = 15pF, Figure 14
UNLESS OTHERWISE NOTED: VCC = +3.0V TO +3.6V WITH TA FROM -40OC TO +85OC. TYPICAL VALUES ARE AT
VCC = +3.3V AND 25OC.
SYMBOL PARAMETERS MIN.TYP.MAX.UNITS CONDITIONS
XR3170E-3178E
7
REV. 1.0.0 3.3V HIGH SPEED RS-485/RS-422 TRANSCEIVERS WITH 1/8th UNIT LOAD
tSHDN Time to Shutdown 50 200 600 ns Notes 3 and 4
XR3173E, XR3174E and XR3175E
DRIVER AC CHARACTERISTICS
freq Max. Data Signaling Rate 500 kbps 1/tUI, Duty Cycle 40 to 60%
tPLH Driver Propagation Delay (Low to
High) 180 800 ns CL = 50pF, RL = 54Ω, Figures 6
and 7
tPHL Driver Propagation Delay (High to
Low) 180 800 ns CL = 50pF, RL = 54Ω, Figures 6
and 7
tRDriver Rise Time 200 800 ns CL = 50pF, RL = 54Ω, Figures 6
and 7
tFDriver Fall Time 200 800 ns CL = 50pF, RL = 54Ω, Figures 6
and 7
|tPLH-tPHL|Differential Pulse Skew 100 ns Figures 6 and 7
tZH Driver Enable to Output High 2500 ns CL = 50pF, RL = 500Ω, Figures
8 and 9
tZL Driver Enable to Output Low 2500 ns CL = 50pF, RL = 500Ω, Figures
10 and 11
tHZ Driver Disable from Output High 150 ns CL = 50pF, RL = 500Ω, Figures
8 and 9
tLZ Driver Disable from Output Low 150 ns CL = 50pF, RL = 500Ω, Figures
10 and 11
tOZV Shutdown to Driver Output Valid 3500 ns CL = 50pF, RL = 500Ω
tSHDN Time to Shutdown 50 200 600 ns Notes 3 and 4
RECEIVER AC CHARACTERISTICS
freq Data Signaling Rate 500 kbps 1/tUI, Duty Cycle 40 to 60%
tPLH Receiver Propagation Delay (Low to
High) 200 ns VID = +/-2V, CL = 15pF, Figures
12 and 13
tPHL Receiver Propagation Delay (High to
Low) 200 ns VID = +/-2V, CL = 15pF, Figures
12 and 13
skew Receiver Propagation Delay Skew 30 ns VID = +/-2V, C L = 15pF, Figures
12 and 13
skew = |tPLH-tPHL|
tRReceiver Output Rise Time 3 6 ns CL = 15pF
tFReceiver Output Fall Time 3 6 ns CL = 15pF
tZH Receiver Enable to Output High 50 ns CL = 15pF, Figure 14
tZL Receiver Enable to Output Low 50 ns CL = 15pF, Figure 14
tHZ Receiver Disable from Output High 50 ns CL = 15pF, Figure 14
UNLESS OTHERWISE NOTED: VCC = +3.0V TO +3.6V WITH TA FROM -40OC TO +85OC. TYPICAL VALUES ARE AT
VCC = +3.3V AND 25OC.
SYMBOL PARAMETERS MIN.TYP.MAX.UNITS CONDITIONS
XR3170E-3178E
8
3.3V HIGH SPEED RS-485/RS-422 TRANSCEIVERS WITH 1/8th UNIT LOAD REV. 1.0.0
tLZ Receiver Disable from Output Low 50 ns CL = 15pF, Figure 14
tZH(SHDN) Shutdown to Receiver Output Valid
High 3500 ns CL = 15pF, Figure 14
tZL(SHDN) Shutdown to Receiver Output Valid
Low 3500 ns CL = 15pF, Figure 14
tSHDN Time to Shutdown 50 200 600 ns Notes 3 and 4
XR3176E, XR3177E and XR3178E
DRIVER AC CHARACTERISTICS
freq Max. Data Signaling Rate 20 Mbps 1/tUI, Duty Cycle 40 to 60%
tPLH Driver Propagation Delay (Low to
High) 412 40 ns CL = 50pF, RL = 54Ω, Figures 6
and 7
tPHL Driver Propagation Delay (High to
Low) 412 40 ns CL = 50pF, RL = 54Ω, Figures 6
and 7
tRDriver Rise Time 2 3 10 ns CL = 50pF, RL = 54Ω, Figures 6
and 7
tFDriver Fall Time 2 3 10 ns CL = 50pF, RL = 54Ω, Figures 6
and 7
|tPLH-tPHL|Differential Pulse Skew 5ns Figures 6 and 7
tZH Driver Enable to Output High 150 ns CL = 50pF, RL = 500Ω, Figures
8 and 9
tZL Driver Enable to Output Low 150 ns CL = 50pF, RL = 500Ω, Figures
10 and 11
tHZ Driver Disable from Output High 150 ns CL = 50pF, RL = 500Ω, Figures
8 and 9
tLZ Driver Disable from Output Low 150 ns CL = 50pF, RL = 500Ω, Figures
10 and 11
tOZV Shutdown to Driver Output Valid 3500 ns CL = 50pF, RL = 500Ω
tSHDN Time to Shutdown 50 200 600 ns Notes 3 and 4
RECEIVER AC CHARACTERISTICS
freq Data Signaling Rate 20 Mbps 1/tUI, Duty Cycle 40 to 60%
tPLH Receiver Propagation Delay (Low to
High) 422 40 ns VID = +/-2V, C L = 15pF, Figures
12 and 13
tPHL Receiver Propagation Delay (High to
Low) 422 40 ns VID = +/-2V, C L = 15pF, Figures
12 and 13
skew Receiver Propagation Delay Skew 5ns VID = +/-2V, C L = 15pF, Figures
12 and 13
skew = |tPLH-tPHL|
tRReceiver Output Rise Time 3 6 ns CL = 15pF
UNLESS OTHERWISE NOTED: VCC = +3.0V TO +3.6V WITH TA FROM -40OC TO +85OC. TYPICAL VALUES ARE AT
VCC = +3.3V AND 25OC.
SYMBOL PARAMETERS MIN.TYP.MAX.UNITS CONDITIONS
XR3170E-3178E
9
REV. 1.0.0 3.3V HIGH SPEED RS-485/RS-422 TRANSCEIVERS WITH 1/8th UNIT LOAD
NOTE:
1. Change in Magnitude of Dif ferential Output Voltage and Cha nge in Magnitude of Common Mode Output Voltage
are the changes in output voltage when DI input changes state.
2. Except devices which do not have DE or RE inputs.
3. The transceivers are put into sh utdown 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 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 during shutdown.
4. Guaranteed by design and bench characterization.
tFReceiver Output Fall Time 3 6 ns CL = 15pF
tZH Receiver Enable to Output High 50 ns CL = 15pF, Figure 14
tZL Receiver Enable to Output Low 50 ns CL = 15pF, Figure 14
tHZ Receiver Disable from Output High 50 ns CL = 15pF, Figure 14
tLZ Receiver Disable from Output Low 50 ns CL = 15pF, Figure 14
tZH(SHDN) Shutdown to Receiver Output Valid
High 3500 ns CL = 15pF, Figure 14
tZL(SHDN) Shutdown to Receiver Output Valid
Low 3500 ns CL = 15pF, Figure 14
tSHDN Time to Shutdown 50 200 600 ns Notes 3 and 4
UNLESS OTHERWISE NOTED: VCC = +3.0V TO +3.6V WITH TA FROM -40OC TO +85OC. TYPICAL VALUES ARE AT
VCC = +3.3V AND 25OC.
SYMBOL PARAMETERS MIN.TYP.MAX.UNITS CONDITIONS
FIGURE 3. DRIVER DC TEST CIRCUIT
R
L
/2
R
L
/2 V
OC
D
V
CC
V
OD
DI
FIGURE 4. DRIVER COMMON MODE LOAD TEST
A/Y
B/Z
D
DI = 0 or Vcc 60Ω
DE = 3.3V
VOD
375Ω
375Ω VCM
FIGURE 5. DRIVER SHORT CIRCUIT CURRENT LIMIT TEST
A/Y
D
DI = 0 or Vcc
B/Z
DE = 0 or Vcc
I
OS D
-7V to +12V V
XR3170E-3178E
10
3.3V HIGH SPEED RS-485/RS-422 TRANSCEIVERS WITH 1/8th UNIT LOAD REV. 1.0.0
FIGURE 6. DRIVER PROPAGATION DELAY TEST CIRCUIT
Y
Z
D
DI
RL
54Ω
CL
50pF
3.3V
VOD
FIGURE 7. DRIVER PROPAGATION DELAY TIMING DIAGRAM
Vcc
0V
DI
Y
Z
VO+
VDIFF
VY – VZ
0V
VO–
Vcc/2 Vcc/2
tPLH
tF
tR
VO1/2V
O1/2V
O
tPHL
tSKEW
= |tDPLH
- tDPHL|
tDPLH tDPHL
10%
90%
10%
90%
FIGURE 8. DRIVER ENABLE AND DISABLE TIME TEST CIRCUIT 1
GENERATOR 50Ω
S1
R
L
= 500Ω
OUT
C
L
= 50pF
D
0 or Vcc
Z
Y
DI
XR3170E-3178E
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REV. 1.0.0 3.3V HIGH SPEED RS-485/RS-422 TRANSCEIVERS WITH 1/8th UNIT LOAD
FIGURE 9. DRIVER ENABLE DISABLE TIMING DIAGRAM 1
DE
OUT
Vcc/2
tZH, tZH(SHDN)
VOM = (VOL + Vcc)/2
tHZ
0.25V
Vcc
0
0
FIGURE 10. DRIVER ENABLE AND DISABLE TIME TEST CIRCUIT 2
GENERATOR 50Ω
S1
R
L
= 500Ω
OUT
C
L
= 50pF
D
0 or Vcc
Z
Y
DI
Vcc
XR3170E-3178E
12
3.3V HIGH SPEED RS-485/RS-422 TRANSCEIVERS WITH 1/8th UNIT LOAD REV. 1.0.0
FIGURE 11. DRIVER ENABLE AND DISABLE TIMING DIAGRAM 2
DE
OUT
Vcc/2
t
ZL
, t
ZL(SHDN)
V
OM
= (V
OL
+ Vcc)/2
tLZ
0.25V
Vcc
0
V
OL
FIGURE 12. RECEIVER PROPAGATION DELAY TEST CIRCUIT
OUT
R
A
B
VID
RE
CL
15pF
FIGURE 13. RECEIVER PROPAGATION DELAY TIMING DIAGRAM
B
A
OUT
t
PHL
t
PLH
+1V
-1V
VOH
VOL
1.5V
XR3170E-3178E
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REV. 1.0.0 3.3V HIGH SPEED RS-485/RS-422 TRANSCEIVERS WITH 1/8th UNIT LOAD
FIGURE 14. RECEIVER ENABLE AND DISABLE TIMES TEST CIRCUIT
1.5V
-1.5V
S3
A
GENERATOR
50Ω
CL= 15pF
R
1kΩ
S1
S2
Vcc
B
RE
FIGURE 15. RECEIVER ENABLE AND DISABLE TIMING DIAGRAM 1
3V
1.5V
0V
RE
OUT
S1 is open, S2 is closed, S3 = 1.5V
VOH
tZH, tZH(SHDN)
VOH /2
FIGURE 16. RECEIVER ENABLE AND DISABLE TIMING DIAGRAM 2
3V
0V
1.5V
VCC
RE
OUT
S1 is closed, S2 is open, S3 = -1.5V
tZL, tZL(SHDN)
VO L = VCC /2
VOL
XR3170E-3178E
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3.3V HIGH SPEED RS-485/RS-422 TRANSCEIVERS WITH 1/8th UNIT LOAD REV. 1.0.0
FIGURE 17. RECEIVER ENABLE AND DISABLE TIMING DIAGRAM 3
3V
1.5V
0V
RE
OUT
S1 is open, S2 is closed, S3 = 1.5V
VOH
t
HZ
0.25V
FIGURE 18. RECEIVER ENABLE AND DISABLE TIMING DIAGRAM 4
3V
0V
1.5V
V
CC
RE
OUT
S1 is closed, S2 is open, S3 = -1.5V
t
LZ
V
OL
0.25V
XR3170E-3178E
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REV. 1.0.0 3.3V HIGH SPEED RS-485/RS-422 TRANSCEIVERS WITH 1/8th UNIT LOAD
XR3170E-3178E
16
3.3V HIGH SPEED RS-485/RS-422 TRANSCEIVERS WITH 1/8th UNIT LOAD REV. 1.0.0
1.0 PRODUC T DESCR IPTION
XR3170E-XR3178E is a family of advanced RS-485/RS-422 transceivers. Each contains one driver and one
receiver. All devices operate from a single +3.3V supply. The XR3172E, XR3175E and XR3178E are a half-
duplex design while the other dev ices are full-duple x designs. The co ntrol pins RE and DE feature a hotswap
capability allowing live insertion without spurious data transfer. Drivers are output short-circuit current limited.
Thermal-shutdown circuitry protects drivers against excessive power dissipation. When activited, the thermal-
shutdown circuitry forces the driver outptus into a high-impedance state.
ADVANCED FAILSAFE
Ordinary RS-485 differential receivers will be in an indeterminate state whenever the data bus is not being
actively driven. The Advanced Failsafe feature of the XR3170E family guarantees a logic-high receiver output
when the receiver inputs are open or 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 XR3170E family interprets 0V differential as a logic high with a
minimum 50mV noise margin while maintaining compliance with the EIA/TIA-485 standard of +/-200 mV.
RECEIVER INPUT FILTERING
XR3170E-XR3175E r eceivers incor popra te in put filter ing in addition to input hysteresis. This filtering enhances
noise immunity with differential signals that have very slow rise and fall times. Receiver propagation delay
increases slightly due to this filtering. XR3176E, XR3177E abd XR3178E high speed devices do not ha ve this
input filtering.
HOT-SWAP CAPABILITY
When Vcc is first applied the XR3170E family holds the driver enable and receiver enable inactive for
approximately 10 microseconds. During power ramp-up other system IC’s may drive unpredictable values.
Hot-swap capability prevents the XR3170E family from driving any output signal until power has stabilized.
After the initial power-up sequence, the hot-swap circuit becomes transparent and driver enable and receiver
enable resume their normal functions and timings.
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 inva lid da ta onto shar ed b usse s and poss ibly cau sing drive r
contention or device damage.
+/-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 XR3170E 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 XR3170E-XR3 178E keep operating without latch-up or damage.
ESD protection can be tested in various ways. The transmitter outputs and receiver inputs of the XR3170E-
XR3178E are characterized for protection to the following limits:
■+/-15kV using the Human Body Model
■+/-8kV using the 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.
XR3170E-3178E
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REV. 1.0.0 3.3V HIGH SPEED RS-485/RS-422 TRANSCEIVERS WITH 1/8th UNIT LOAD
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 XR3170E family helps you design equipment to meet
IEC 61000-4-2, without sacrificing board-space and cost for external ESD-protection components.
The major difference s between tests done usin g 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.
MACHINE MODEL
The machine model for ESD tests all pins using a 200pF storage ca p a cito r an d zero d ischa rg e resistance. The
objective is to emulate the stress caused when I/O pins are contacted by handling equipment during test and
assembly.
256 TRANSCEIVERS ON THE BUS
The stan dard RS-4 85 recei ver inp ut impeda nce is 12 k Ohms (1 un it lo ad) . A standard driver can drive up to 3 2
unit loads. The XR3170E family of transceivers have only a 1/8th unit load receiver input impedance of 96k
Ohms, thereby allowing eight times as many, 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 shut down mode is initiate d by bringing both RE high and DE low simult aneously. 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).
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 th e driver outpu t s into
a high-impedance state if junction temperature becomes excessive.
LINE LENGTH
The RS-485/RS-422 st andar d covers line lengths up to 4000ft. Maximum achievable line length is a function of
signal attenuation and noise. Termination prevent s signal reflections by elim inating 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
XR3170E-3178E
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3.3V HIGH SPEED RS-485/RS-422 TRANSCEIVERS WITH 1/8th UNIT LOAD REV. 1.0.0
2.0 FUNCTION TABLES
TABLE 1: FULL DUPLEX 14 PIN - XR3170E, XR3173E AND XR3176E
Inputs Outputs
RE DE DI Y Z
X1110
X1001
0 0 X High-Z
1 0 X Shutdown
TABLE 2: FULL DUPLEX 8 PIN - XR3171E, XR3174E AND XR3177E
Input Outputs
DI Y Z
110
001
TABLE 3: HALF DUPLEX 8 PIN - XR3172E, XR2175E AND XR3178E
Inputs Outputs
RE DE DI A B
X1110
X1001
0 0 X High-Z
1 0 X Shutdown
TRANSMITTING
TRANSMITTING
TRANSMITTING
TABLE 4: FULL DUPLEX 14 PIN - XR3170E, XR3173E AND XR3176E
Inputs Ouptut
RE DE V - V 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 - XR3171E, XR3174E AND XR3177E
Inputs Output
V - V RO
≥ -50mV1
≤ -200mV 0
Open/Shorted 1
TABLE 6: HALF DUPLEX 8 PIN - XR3172E, XR2175E AND XR3178E
Inputs Output
RE DE V - V RO
0 X ≥ -50mV 1
0 X ≤ -200mV 0
0 X Open/Shorted 1
1 1 X High-Z
1 0 X Shutdown
XR3170E-3178E
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REV. 1.0.0 3.3V HIGH SPEED RS-485/RS-422 TRANSCEIVERS WITH 1/8th UNIT LOAD
Note: Receiver inputs -200mV < VA - VB < -50mV should be considered indeterminate.
RECEIVING
A B
RECEIVING
A B
RECEIVING
A B
XR3170E-3178E
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3.3V HIGH SPEED RS-485/RS-422 TRANSCEIVERS WITH 1/8th UNIT LOAD REV. 1.0.0
3.0 PRODUC T SELECTOR GUIDE
TABLE 7: SELECTION GUIDE
BPS
XR3170E Full 250k Yes Yes 256 SN75180
XR3171E Full 250k No No 256 SN75179
XR3172E Half 250k Yes Yes 256 SN75176
XR3173E Full 500k Yes Yes 256 SN75180
XR3174E Full 500k No No 256 SN75179
XR3175E Half 500k Yes Yes 256 SN75176
XR3176E Full 20M Yes Yes 256 SN75180
XR3177E Full 20M No No 256 SN75179
XR3178E Half 20M Yes Yes 256 SN75176
PART
NUMBER DUPLEX DATA RATE SHUTDOWN RECEIVER
AND DRIVER
ENABLE
TRANS ON
BUS FOOT-PRINT
XR3170E-3178E
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REV. 1.0.0 3.3V HIGH SPEED RS-485/RS-422 TRANSCEIVERS WITH 1/8th UNIT LOAD
4.0 TYPICAL APPLICATIONS:
RTRT
STUB
Half-Duplex Network
Bi-D irecti onal Full-D u p le x N etwork
Repeater
(optional)
Repeater
(optional)
Po int to M ulti -point with Repeater
PACKAGE DIMENSIONS (14 PIN NSOIC)
XR3170E-3178E
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3.3V HIGH SPEED RS-485/RS-422 TRANSCEIVERS WITH 1/8th UNIT LOAD REV. 1.0.0
PACKAGE DIMENSIONS (8 PIN NSOIC)
XR3170E-3178E
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REV. 1.0.0 3.3V HIGH SPEED RS-485/RS-422 TRANSCEIVERS WITH 1/8th UNIT LOAD
REVISION HISTORY
DATE REVISION DESCRIPTION
12/03/09 1.0.0 Production Release .
24
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 descr ibed herein , conveys no license unde r any p atent or other r ight, and makes no rep resent ation 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 it s safety or effectiveness. Products ar e 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 un de r the circumstances.
Copyright 2009 EXAR Corporation
Datasheet December 2009.
Send your UART technical inquiry with technical details to hotline: uarttechsupport@exar.com.
Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited.
XR3170E-3178E
3.3V HIGH SPEED RS-485/RS-422 TRANSCEIVERS WITH 1/8th UNIT LOAD REV. 1.0.0
