COM20020I3V-HT SMSC, COM20020I3V-HT Datasheet - Page 21

• Manufacturer Part Number: COM20020I3V-HT
• Description: Network Controller & Processor ICs ARCNET Contrllr
• Manufacturer: SMSC

Specifications of COM20020I3V-HT

• Product: Controller Area Network (CAN)
• Number Of Transceivers: 1
• Data Rate: 5 Mbps
• Supply Voltage (max): 3.465 V
• Supply Voltage (min): 3.135 V
• Supply Current (max): 35 mA
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Package / Case: TQFP-48
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

5Mbps ARCNET (ANSI 878.1) Controller with 2K x 8 On-Chip RAM
In typical applications, the serial backplane is terminated at both ends and a bias is provided by the external pull-up
resistor.
The RXIN signal is directly connected to the cable via an internal Schmitt trigger. A negative pulse on this input indicates
a logic "1". Lack of pulse indicates a logic "0". For typical single-ended backplane applications, RXIN is connected to
nPULSE1 to make the serial backplane data line. A ground line (from the coax or twisted pair) should run in parallel with
the signal. For applications requiring different treatment of the receive signal (like filtering or squelching), nPULSE1 and
RXIN remain as independent pins. External differential drivers/receivers for increased range and common mode noise
rejection, for example, would require the signals to be independent of one another.
When the device is in Backplane Mode, the clock provided by the nPULSE2 signal may be used for encoding the data
into a different encoding scheme or other synchronous operations needed on the serial data stream.
Differential Driver Configuration
The Differential Driver Configuration is a special case of the Backplane Mode.
It is a dc coupled configuration
recommended for applications like car-area networks or other cost-sensitive applications which do not require direct
compatibility with existing ARCNET nodes and do not require isolation.
The Differential Driver Configuration cannot communicate directly with nodes utilizing the Traditional Hybrid Configuration.
Like the Backplane Configuration, the Differential Driver Configuration does not isolate the node from the media.
The Differential Driver interface includes a RS485 Driver/Receiver to transfer the data between the cable and the
COM20020I 3V. The nPULSE1 signal transmits the data, provided the Transmit Enable signal is active. The nPULSE1
signal issues a 200nS (at 2.5Mbps) negative pulse to transmit a logic "1". Lack of pulse indicates a logic "0". The RXIN
signal receives the data, the transmitter portion of the COM20020I 3V is disabled during reset and the nPULSE1,
nPULSE2 and nTXEN pins are inactive.
Programmable TXEN Polarity
To accommodate transceivers with active high ENABLE pins, the COM20020I 3V contains a programmable TXEN output.
To program the TXEN pin for an active high pulse, the nPULSE2 pin should be connected to ground. To retain the normal
active low polarity, nPULSE2 should be left open. The polarity determination is made at power on reset and is valid only
for Backplane Mode operation. The nPULSE2 pin should remain grounded at all times if an active high polarity is
desired.
SMSC COM20020I 3.3V Rev.E
Page 21
Revision 09-11-06
DATASHEET