RS1905

500kbps RS-485 Transceivers with ±20kV IEC ESDProtection
FEATURES•••••••••••••High-Performance and Compliant with RS-485
TIA/EIA-485 Standard
3.0V to 5.5V Supply Voltage
Bus I/O Protection- ±20kV HBM ESD- ±6kV IEC 6100-4-2 Contact Discharge-7V to +12V Common-Mode Input Voltage
Up to 256 Nodes on the Same Bus (1/8 unitload)
Low Stand-By Current: <5μA
Full Fail-safe Guarantees Known Receiver
Output State
Glitch-Free during Power on/Power off
Short-Circuit Protection
Over Temperature Protection|VOD| >2.1V @ 5V Supply Voltage
Operating Temperature Range: -40°C to +125°C
Packages: SOIC-8

DESCRIPTION

The RS1905 is a robust half-duplex RS-485 transceiver forindustrial applications. The bus pins are immune to high levelsof IEC Contact Discharge ESD events eliminating need ofadditional system level protection components.
The device operates from a single 3.3V to 5.0V supply.
The RS1905 device can transmit and receive at data rate up to500kbps. The wide common-mode voltage range and low input
leakage on bus pins make RS1905 suitable for multi-point
applications over long cable runs.
The RS1905 is available in industry standard 8-pin SOIC,package for drop-in compatibility. It operates over an ambient
temperature range of -40°C to +125°C.

Device Information (1)PART NUMBER

PACKAGEBODY SIZE(NOM)

RS1905

SOIC-8(SOP8)

4.90mm x 3.90mm(1)

APPLICATIONS
••
•
•
•

For all available packages, see the orderable addendum at theend of the data sheet.

Electricity Meters (E-Meters)
Inverters
HVAC Systems
Video Surveillance Systems
Industrial Automation & Control

TYPICAL APPLICATIONREV A.1

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RS1905
Revision History

Note: Page numbers for previous revisions may different from page numbers in the current version.
VERSION

Change Date

Change Item

A.0

2022/11/11

A.1

2023/06/25

A.2

2023/09/21

Preliminary version completed.
1、 Update Features description on Page1
2、 Change Parameter description on Page8
1、 Update ESD Rating---Air Gap Contact on Page5.

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RS1905
Pin configuration and Functions (Top View)
TOP VIEW

SOIC-8

Pin Description
NAME

PIN
SOIC-8I/O

DESCRIPTION

R1O

Receiver Data Output/RE2I

Receiver Enable, Active low (with internal pull-up)

DE

3I

Driver Enable, Active high (with internal pull-down)

D

4I

Driver Data Input (with internal pull-up)

GND

5GroundA

6I/O

Bus I/O port, AB

7I/O

Bus I/O port, B

VCC

8PowerPower supply

Ground3 / 17

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RS1905
PACKAGE/ORDERING INFORMATIONPRODUCT

ORDERING
NUMBERTEMPERATURE
RANGE

PACKAGELEAD

PACKAGEMARKING (1/2)

PACKAGE OPTION

RS1905

RS1905XK-40°C ~+125°C

SOIC-8RS1905

Tape and Reel,4000

NOTE:(1) There may be additional marking, which relates to the lot trace code information(data code and vendor code)，the logo or theenvironmental category on the device.

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RS1905
SPECIFICATIONS

Absolute Maximum Ratings

over operating free-air temperature range (unless otherwise noted) (1)(2)
SYMBOL
VCC
VIO

MIN

MAX

Supply voltage

-0.5

7

V

Bus A&B voltage

-8

13

V

Logic input pin (/RE, DE, D )-0.3

Vcc+0.3

VV

Logic output pin (R )-0.3

Vcc+0.3

TA

Operating temperature-40+125

TJ

Junction temperatureTstg
(1)

(2)

UNIT°C150

Storage temperature-65

150

Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, and functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating
Conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
All voltages are with respect to the GND pin.

ESD Ratings

V(ESD)

Electrostatic
discharge

Human-body model (HBM), per
ANSI/ESDA/JEDEC JS-001
Charge device model (CDM), per JESD22C101
Contact Discharge, per IEC 61000-4-2

VALUEUNIT

Bus A &B

±20kV

Other pins

±8kVAll pins

±2kV

Bus A &B

±6kV

Air Gap Discharge, per IEC 61000-4-2
Bus A &B
±6Notes:
1. Per JEDEC document JEP155, 500V HBM allows safe manufacturing of standard ESD control process.
2. Per JEDEC document JEP157, 250V CDM allows safe manufacturing of standard ESD control process.

kV

Recommended Operating Conditions

over operating free-air temperature range (unless otherwise noted)
SYMBOLPARAMETERMINMAX

UNIT

VCC

Supply voltage

3.05.5VVIN

Bus input voltage-7.012V

VIH

Input high voltage

2.0VCCVVIL

Input low voltage

00.8

V

1/tUI

Data rate

0.5Mbps

RL

Differential Load54

TA

Operating ambient temperature-405 / 17

Ω125°C

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RS1905

Thermal Information
RS1905
THERMAL METRIC

SOIC-8UNIT

8 PINS
RθJA

Junction-to-ambient thermal resistance

124.7°C/W

RθJC (top)Junction-to-case (top) thermal resistance

66.9°C/W

RθJB

Junction-to-board thermal resistance

67.9°C/W

ψJT

Junction-to-top characterization parameter

19.2°C/WψJB

Junction-to-board characterization parameter

67.2°C/W

RθJC (bot)Junction-to-case (bottom) thermal resistance

N/A°C/W

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RS1905
ELECTRICAL CHARACTERISTICS
at TA = 25°C, and VCC = 5 V (unless otherwise noted)
PARAMETER

Driver differential output
voltage magnitude|VOD|

TEST CONDITIONS

MIN

TYP

RL = 60 Ω, -7 V ≤ Vtest ≤ 12

1.5

3.6

RL = 60 Ω, -7 V ≤ Vtest ≤ 12, 4.5V ≤VCC ≤ 5.5V

2.1

3.6

RL = 100 Ω, CL = 50pF

2.04.2

RL = 54 Ω, CL = 50pF

1.53.6MAXUNITV

Change in differential outputvoltage∆|VOD|RL = 54 Ω or 100 Ω, CL = 50pF-50

Common-mode output voltage

VOC

RL = 54 Ω or 100 Ω, CL = 50pF

1∆VOC(SS)RL = 54 Ω or 100 Ω, CL = 50pF

-50

∆VOC(PP)RL = 54 Ω or 100 Ω, CL = 50pF

450IOS

DE = VCC, -7 V ≤ VO ≤ 12 V

100150mA

DE=0,VCC=0V or 5.5V, VI=12V

75

125μA

Steady-state commonmode
output voltage
Peak-to-peak commonmode
output voltage
Short-circuit output current
Bus input current
Bus input impedance

RI

DE=0,VCC=0V or 5.5V, VI=-7V-100

VA=-7V, VB= 12V or
VA=12V, VB=-7V

96

Positive-going input threshold
VTH+voltage
Negative-going input threshold
VTHvoltage

-200

VHYS

Output high voltage

VOH

IOH = -4mA

Output low voltage

VOL

IOL = 4mA

VCC-0.5

VO=0V or VCC, /RE =VCC

Output short-circuit current

IOSR/RE=0, DE=0

Input current (D, DE, RE)

IIN

ICC

V

50mVmVμA-50mV-140mV30mV

VCC0.3V
0.4V+1μA

95mA+5μA

0.95

1.5mA

0.55

1.0mA

0.50.9mA

5.0μA-1-5

Driver and receiver enabled/RE=0V, DE=VCC, no load
Driver enabled, receiver disabled/RE=VCC, DE=VCC, no load
Driver disabled, receiver enabled/RE=0V, DE=0V, no load
Driver and receiver disabled/RE=VCC, DE=0V, no load

3.3kΩ

0.2

Output high-impedance current IOZ

mV-40

-110

Input hysteresis

Supply current (quiescent)

VCC/2

50

Note:
1. Under any condition, ensure that VTH+is at least VHYShigher than VTH–.

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RS1905
SWITCHING CHARACTERISTICS
Over recommended operating conditions
PARAMETERTEST CONDITIONS

MIN

TYP

MAX

UNIT

DriverDifferential output rise/fall time tr, tf

RL = 54 Ω, CL = 50pF

150500ns

Propagation delaytPHL, tPLH

RL = 54 Ω , CL = 50pF

100250ns

Pulse skew,|tPHL - tPLH|tsk(P)RL = 54 Ω , CL = 50pF

10ns

Disable time

tPHZ, tPLZ

1030

ns

tPZH, tPZL/RE = 0V

300

800

nstPZH, tPZL/RE = VCC

612μs

Differential output rise/fall time tr, tf

CL = 15pF

1020ns

Propagation delaytPHL, tPLH

CL = 15pF

50100ns

Pulse skew,|tPHL - tPLH|tsk(P)CL = 15pF

7ns

Disable time

tPHZ, tPLZ

3060

ns

Enable time

tPZH, tPZL

50100

ns

612μs

Enable time
ReceiverDE = VCC

Output high voltage
tPZH, tPZL
DE = 0Note:
1. CL includes external circuit (fixture and instrumentation etc.) capacitance.

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RS1905
TYPICAL CHARACTERISTICS

At TA = 25°C, VIN= 5V power supply, Min/Max specs are over recommended operating conditions unless otherwise specified

Figure 1. Differential Output Voltage vs. Temperature(RL=54Ω)Figure 2. Differential Output Voltage vs. Temperature(RL=100Ω)Figure 3. Differential Output Voltage vs Supply Voltage

Figure 5. Common Output Voltage vs. Supply voltage

Figure 4. Common-mode Output Voltage vs.
Temperature

Figure 6. Bus Input Current vs. Temperature

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RS1905
TYPICAL CHARACTERISTICS

At TA = 25°C, VIN= 5V power supply, Min/Max specs are over recommended operating conditions unless otherwise specified.

Figure 7. Bus Input Current vs. Supply Voltage,
Vi=12V

Figure 8. Bus Input Current vs. Temperature,
Vi=-7V

Figure 9. Bus Input Current vs. Supply Voltage,
Vi=-7V

Figure 10. Receiver Output Low vs. Temperature

Figure 11. Driver Propagation Delay vs. Temperature

Figure 12. Receiver Propagation Delay vs.
Temperature

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RS1905
TYPICAL CHARACTERISTICS

At TA = 25°C, VIN= 5V power supply, Min/Max specs are over recommended operating conditions unless otherwise specified.

Figure 13. Driver Output Short Current vs.
Temperature

Figure 14. Propagation Delay of Receiver

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RS1905
Parameter Measurement Information

Figure 15 Measurement of Driver Differential Output Voltage With Common-Mode Load

Figure 16 Measurement of Driver Differential and Common-Mode Output With RS-485 Load

Figure 17 Measurement of Driver Differential Output Rise and Fall Times and Propagation Delays

Figure 18 Measurement of Driver Enable and Disable Times With Active High Output and Pull
Down Load

Figure 19 Measurement of Driver Enable and Disable Times With Active Low Output and Pull- UpLoad

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RS1905
Detailed Description
Overview

The RS1905 s a low-power, half-duplex RS-485 transceiver suitable for data transmission up to 500 kbps..

Functional Block Diagram

Feature Description

Internal ESD protection circuits protect the transceiver against Electrostatic Discharges (ESD) according to IEC
61000-4-2 of up to ±6 kV (Contact Discharge), ±20 kV (Human-body model). The RS1905 provides internalbiasing of the receiver input thresholds in combination with large input threshold hysteresis. With a positive input
threshold of VIT+ = –50 mV and an input hysteresis of VHYS = 50 mV, the receiver output remains logic highunder a bus-idle or bus-short conditions without the need for external failsafe biasing resistors. Device operationis specified over a wide temperature range from –40°C to 125°C.

Device Functional Modes

When the driver enable pin, DE, is logic high, the differential outputs A and B follow the logic states at data input
D. A logic high at D causes A to turn high and B to turn low. In this case, the differential output voltage definedas VOD = VA – VB is positive. When D is low, the output states reverse, B turns high, A becomes low, and VOD
is negative. When DE is low, both outputs turn high-impedance. In this condition the logic state at D is irrelevant.
The DE pin has an internal pull-down resistor to ground, thus when left open the driver is disabled (highimpedance) by default. The D pin has an internal pull-up resistor to VCC, thus, when left open while the driveris enabled, output A turns high and B turns low.

Table 1. Driver Function TableInput Enable Output
DDEA BHHH LLHL HXLZ ZXOPEN Z ZOPENHH L

Note:
X means don’t care,
Z means high resistance

Function
Actively drive bus highActively drive bus low
Driver disabled
Driver disabled by default
Actively drive bus high by default

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RS1905
When the receiver enable pin, /RE, is logic low, the receiver is enabled. When the differential input voltage
defined as VID = VA – VB is positive and higher than the positive input threshold, VIT+, the receiver output, R,turns high. When VID is negative and lower than the negative input threshold, VIT-, the receiver output, R, turns
low. If VID is between VIT+ and VIT- the output is indeterminate. When RE is logic high or left open, the receiver
output is high-impedance and the magnitude and polarity of VID are irrelevant. Internal biasing of the receiver
inputs causes the output to go failsafe-high when the transceiver is disconnected from the bus (open-circuit),
the bus lines are shorted (short-circuit), or the bus is not actively driven (idle bus).

Table 2. Receiver Function Table
Differential Input Enable
OutputFunction
VID = VA-VB/RER
VIT+ < VID
L
H
Receive valid bus high
VIT- < VID < VIT+L
Indeterminate
Indeterminate bus state
VID < VITL
L
Receive valid bus lowX
H
Z
Receiver disabled
X
OPEN
Z
Receiver disabled by default
Open-circuit bus
L
H
Fail-safe high output
Short-circuit bus
L
H
Fail-safe high output
Idle(terminated) bus
L
H
Fail-safe high output
Note:
X means don’t care
Z means high resistance

Application Information

The RS1905 is a half-duplex RS-485/RS-422 transceiver commonly used for asynchronous data transmissions.
The driver and receiver enable pins allow for the configuration of different operating modes.

Typical Application

An RS-485 bus consists of multiple transceivers connecting in parallel to a bus cable. To eliminate linereflections, each cable end is terminated with a termination resistor, RT, whose value matches thecharacteristic impedance, Z0 , of the cable. This method, known as parallel termination, allows for higher data
rates over longer cable length.

Figure 20. Typical RS-485 Network With Half-Duplex Transceivers
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RS1905
Supply Voltage Design Requirements

In order to ensure the reliability of data transmission and power supply, it is recommended to place decoupling
capacitors from 100nF to 220nF as close as possible to the VCC pin of each transceiver.

LayoutLayout Guidelines

Robust and reliable bus node design often requires the use of external transient protection devices inorder to protect against surge transients that may occur in industrial environments. Since thesetransients have a wide frequency bandwidth (from approximately 3 MHz to 300 MHz), high-frequency
layout techniques should be applied during PCB design.
1. Place the protection circuitry close to the bus connector to prevent noise transients frompropagating across the board.
2. Use VCC and ground planes to provide low inductance. Note that high-frequency currents tend tofollow the path of least impedance and not the path of least resistance.
3. Design the protection components into the direction of the signal path. Do not force the transientcurrents to divert from the signal path to reach the protection device.
4. Apply 100-nF to 220-nF bypass capacitors as close as possible to the VCC pins of transceiver,
UART and/or controller ICs on the board.
5. Use at least two vias for VCC and ground connections of bypass capacitors and protection devices
to minimize effective via inductance.
6. Use 1-kΩ to 10-kΩ pullup and pulldown resistors for enable lines to limit noise currents in theses
lines during transient events.
7. Insert pulse-proof resistors into the A and B bus lines if the TVS clamping voltage is higher than thespecified maximum voltage of the transceiver bus pins. These resistors limit the residual clamping
current into the transceiver and prevent it from latching up.
8. While pure TVS protection is sufficient for surge transients up to 1 kV, higher transients require
metal-oxide varistors (MOVs) which reduce the transients to a few hundred volts of clamping voltage,
and transient blocking units (TBUs) that limit transient current to less than 1 mA.

Layout Example

Figure 21. Layout Example

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RS1905
PACKAGE OUTLINE DIMENSIONSSOIC-8be

5.2
EE1

2.2

D

1.27

0.6

RECOMMENDED LAND PATTERN (Unit: mm)

A2cA

A1LSymbol

Dimensions In MillimetersθDimensions In Inches

MinMaxMinMax

A

1.350

1.750

0.053

0.069

A1

0.100

0.250

0.004

0.010

A2

1.350

1.550

0.053

0.061

b0.330

0.510

0.013

0.020

c

0.170

0.250

0.007

0.010

D

4.800

5.000

0.189

0.197

e

1.270 (BSC)

0.050 (BSC)

E

5.800

6.200

0.228

0.244

E1

3.800

4.000

0.150

0.157

L

0.400

1.270

0.016

0.050

θ

0°

8°

0°

8°

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RS1905
TAPE AND REEL INFORMATIONREEL DIMENSIONSTAPE DIMENSION

Reel
DiameterReel Width(W1)

DIRECTION OF FEEDNOTE: The picture is only for reference. Please make the object as the standard.

KEY PARAMETER LIST OF TAPE AND REEL
Package Type

Reel
Diameter

SOIC-813’’

Reel
Width(mm)12.4

A0(mm)

B0(mm)

K0(mm)

P0(mm)

P1(mm)

P2(mm)

W(mm)Pin1
Quadrant

6.40

5.40

2.10

4.0

8.0

2.0

12.0

Q117 / 17

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