DC2063A - Demo Manual

DEMO MANUAL DC2063A
LTC2875
±60V Fault Protected 3.3V or 5V
High Speed CAN Transceiver
Description
Demonstration circuit 2063A is a robust high speed, low
power, ISO 11898-2 compliant CAN transceiver featuring
the LTC®2875. The demo circuit operates on 3.3V or 5V
supplies and features ±60V overvoltage fault protection on
the data transmission lines during all modes of operation.
The demo circuit contains all the components necessary
to demonstrate the features of the LTC2875 in a CAN
network, including a terminated SMB jack for TXD data
input, jumper selectable CAN bus termination (supporting
either single or split termination configurations), and a
jumper selectable variable slew rate control.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2063A
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
Performance Summary
Specifications are at TA = 25°C
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
VCC
Input Supply Range
3.3V VCC Range
3.0
3.3
3.6
5V VCC Range
4.5
5.0
5.5
fMAX
Maximum Data Rate
JP3 in ‘MAX’ position
Interface I/O: CANH, CANL
Bus Differential Voltage (CANH-CANL)
4
–60
JP2 in ‘SINGLE’ or ‘SPLIT’ position
UNITS
V
V
Mbps
60
V
10
V
operating principles
The LTC2875 is enabled by pulling the RS pin low. The
slew rate of the transmitter can be controlled by pulling RS
low with a resistor ≤ 200kΩ, with the slew rate decreasing
with increasing resistor value. The DC2063A provides two
jumper positions to enable the LTC2875. With a jumper
in the JP3:MAX position, the RS pin is grounded and the
LTC2875 operates at its maximum slew rate. With a jumper
in the JP3:ADJ position, the transmitter slew rate can be
varied from its minimum to maximum using 200kΩ variable resistor RV1. When no jumper is placed on JP3, the
RS pin in the LTC2875 is pulled up by an internal 250kΩ
resistor, putting the chip in the shut-down state.
The data input signal can be applied to the LTC2875 TXD pin
through either the TXD turret or the SMB jack J1. To apply
the TXD signal through the SMB jack J1, place a jumper
on the JP1:SMB position. The SMB input is terminated to
GND by a 50Ω resistor. To apply the TXD signal through the
TXD turret, place a jumper on the JP1:TURRET position.
The TXD turret input contains a 100Ω series resistor but is
not terminated. Jumpers may be applied to both JP1:SMB
and JP1:TURRET to enable applying a signal from a pulse
generator through the SMB jack J1 and monitoring the
signal with a scope probe on the TXD turret.
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DEMO MANUAL DC2063A
operating principles
When TXD is low, the LTC2875 drives the dominant state
onto the CANH and CANL bus lines, with CANH pulled high
and CANL pulled low. When TXD is high, the LTC2875 is
in the recessive state, with both CANH and CANL drivers
in the high impedance state, and the differential voltage on
the CAN bus lines is returned to near zero by the termination resistors. The TXD pin is pulled high by an internal
500kΩ resistor when it is left floating.
The CAN bus must be terminated at both ends by resistors matched to the impedance of the bus cable, typically
120Ω, while all other nodes on the CAN bus must be
unterminated. The DC2063A provides three jumper selectable termination configurations: split termination, single
termination, and no termination. The split termination
is selected by placing two jumpers on JP2 in the SPLIT
(vertical) configuration. This provides 120Ω termination
consisting of two series 60Ω resistors with the LTC2875
SPLIT pin and a 4.7nF decoupling capacitor biasing the
termination center point. This configuration lowers the
EME of the transmitted signal by reducing common mode
voltage fluctuations. The single termination is selected by
placing two jumpers on JP2 in the SINGLE (horizontal)
configuration. This provides 120Ω termination consisting
of two series 60Ω resistors with no biasing of the center
point. No termination may be selected by removing both
jumpers from JP2.
The LTC2875 receiver senses the differential voltage on
the CAN bus lines and produces a digital output on the
RXD pin. When a dominant state is sensed on the bus
lines, the RXD output will pull low. When a recessive state
is sensed on the bus lines, the RXD output will pull high.
When the LTC2875 is in the shutdown state, the RXD pin
is pulled high by an internal 500kΩ resistor. The LTC2875
RXD pin is connected directly to the DC2063A RXD turret.
Quick Start Procedure
Demonstration circuit 2063A is easy to set up and evaluate
the performance of the LTC2875.
1.Verify the jumpers are in the following default positions:
JP1:SMB ON; JP1:TURRET OFF
JP2: SPLIT
JP3:MAX ON; JP3:ADJ OFF
2.With power off, connect the input power supply to VCC
and GND turrets.
NOTE: Make sure the input voltage does not exceed 6V.
4.Connect a function generator to SMB jack J1 and set
to square wave with a low of 0V, high = VCC. Set frequency to 100kHz (200kbps). Enable output of function
generator.
5.Connect oscilloscope to pin RXD and observe 100kHz
waveform. This demonstration shows that data applied
to TXD is transmitted to the CAN bus, looped back
through the receiver, and outputted on RXD.
3.Turn on the power at the input.
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DEMO MANUAL DC2063A
Parts List
ITEM
QTY
REFERENCE
PART DESCRIPTION
MANUFACTURER/PART NUMBER
IC, CAN Transceiver
LINEAR LTC2875IDD
Required Circuit Components
1
1
U1
Hardware/Components (For Demo Board Only)
2
1
C1
Capacitor, 2.2µF, 10%, 0603, 10V, X7R
Murata/GRM188R71A225KE15D
3
1
C2
Capacitor, 4700pF 20% 0603, 100V, X7R
AVX/06031C472MAT2A
4
1
C3
Capacitor, Tantalum, 6.8µF, 10%, 3216, 16V
AVX/TAJA685K016RNJ
5
2
E1, E2
Turret
Mill Max/2308-2-00-80-00-00-07-0
6
2
E3, E4
Turret
Mill Max/2501-2-00-80-00-00-07-0
7
1
J1
Connector, SMB Male Jack, Straight, 50Ω
Amphenol/142138
8
1
J2
Terminal Block, 3 Position, Side Entry 3.5mm
TE Connectivity/284391-3
9
3
JP1-3
Header, 2 x 2 0.1"
Samtec/TSW-102-07-G-D
10
1
R1
Resistor, 49.9Ω, 1%, 1210
Panasonic/ERJ-14NF49R9U
11
1
R2
Resistor, 100Ω, 5%, 1206
AAC/CR10-101JM
12
2
R3, R4
Resistor 60.4Ω, 1%, 1210
Vishay/CRCW121060R4FKEA
13
1
RV1
Trimmer, 200kΩ, 1-Turn
Panasonic/EVM-3VSX50B25
14
4
Standoff, Snap-on
Keystone/8833
Schematic Diagram
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Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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DEMO MANUAL DC2063A
DEMONSTRATION BOARD IMPORTANT NOTICE
Linear Technology Corporation (LTC) provides the enclosed product(s) under the following AS IS conditions:
This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT
OR EVALUATION PURPOSES ONLY and is not provided by LTC for commercial use. As such, the DEMO BOARD herein may not be complete
in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety
measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union
directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations.
If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date
of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU
OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS
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ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES.
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arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all
appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or
agency certified (FCC, UL, CE, etc.).
No License is granted under any patent right or other intellectual property whatsoever. LTC assumes no liability for applications assistance,
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Please read the DEMO BOARD manual prior to handling the product. Persons handling this product must have electronics training and
observe good laboratory practice standards. Common sense is encouraged.
This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a LTC application engineer.
Mailing Address:
Linear Technology
1630 McCarthy Blvd.
Milpitas, CA 95035
Copyright © 2004, Linear Technology Corporation
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Linear Technology Corporation
LT 1014 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
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●
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