SN65HVD21A Extended Common-Mode RS-485 Transceiver |


Extended Common-Mode RS-485 Transceiver

Extended Common-Mode RS-485 Transceiver - SN65HVD21A


The SN65HVD21A offers performance far exceeding typical RS−485 devices. In addition to meeting all requirements of the TIA/EIA−485−A standard, the device operates over an extended range of common-mode voltage, and has features such as high ESD protection, wide receiver hysteresis, and failsafe operation. This device is ideally suited for long-cable networks, and other applications where the environment is too harsh for ordinary transceivers.

The device is designed for bidirectional data transmission on multipoint twisted-pair cables. Example applications are digital motor controllers, remote sensors and terminals, industrial process control, security stations, and environmental control systems.

The device combines a 3-state differential driver and a differential receiver, which operate from a single 5-V power supply. The driver differential outputs and the receiver differential inputs are connected internally to form a differential bus port that offers minimum loading to the bus. This port features an extended common-mode voltage range making the device suitable for multipoint applications over long cable runs.

The SN65HVD21A allows up to 256 connected nodes at moderate data rates (up to 6 Mbps). The driver output slew rate is controlled to provide reliable switching with shaped transitions which reduce high-frequency noise emissions.

The receivers also include a failsafe circuit that provides a high-level output within 250 microseconds after loss of the input signal. The most common causes of signal loss are disconnected cables, shorted lines, or the absence of any active transmitters on the bus. This feature prevents noise from being received as valid data under these fault conditions. This feature may also be used for Wired-Or bus signaling.

The SN65HVD21A is characterized for operation over the temperature range of –40°C to 85°C.


  • Common-Mode Voltage Range (–20 V to 25 V)
    More Than Doubles TIA/EIA-485 Requirement
  • Reduced Unit-Load for up to 256 Nodes
  • Bus I/O Protection to Over 16-kV HBM
  • Failsafe Receiver for Open-Circuit, Short-Circuit
    and Idle-Bus Conditions
  • Low Standby Supply Current 1-µA Max
  • More Than 100 mV Receiver Hysteresis
    • Long Cable Solutions
      • Factory Automation
      • Security Networks
      • Building HVAC
    • Severe Electrical Environments
      • Electrical Power Inverters
      • Industrial Drives
      • Avionics

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Parametrics Compare all products in RS-485/RS-422

Supply Voltage(s) (Nom) (V)
No. of TX
No. of RX
Signaling Rate (Max) (Mbps)
IEC 61000-4-2 Contact (+/- kV)
Fault Protection (V)
Number of Nodes
Common Mode Range
ICC (Max) (mA)
Operating Temperature Range (C)
Package Group
Approx. Price (US$)
5     5     5     5     5     5    
1     1     1     1     1     1    
1     1     1     1     1     1    
Half     Half     Half     Half     Half     Half    
6     25     5     0.5     25     3    
N/A     N/A     N/A     N/A     N/A     N/A    
16     16     16     16     16     16    
-27 to 27     -27 to 27     -27 to 27     -27 to 27     -27 to 27     -27 to 27    
256     64     256     256     64     256    
-20 to 25     -20 to 25     -20 to 25     -20 to 25     -20 to 25     -20 to 25    
12     9     12     9     11     14    
No     No     No     No     No     No    
Catalog     Catalog     Catalog     Catalog     Catalog     Catalog    
-40 to 85     -40 to 85     -40 to 85     -40 to 85     -40 to 85     -40 to 85    
1.50 | 1ku     1.40 | 1ku     1.50 | 1ku     1.40 | 1ku     1.80 | 1ku     1.80 | 1ku