Texas Instruments RS485HFDPLXDRCEVM User manual

User’s Guide
RS485HFDPLXDRCEVM User Guide
ABSTRACT
This document is the EVM User’s guide for the RS485HFDPLXDRCEVM which provides a quick way to evaluate
TI’s Half Duplex RS-485 Transceivers in 10-Pin VSON (DRC) Packages such as the THVD2450DRC
!
Caution Read the user's guide before use
The information in the warning statement is provided for personal protection and the information in the caution
statement is provided to protect the equipment from damage. Read each caution and warning statement
carefully.
This EVM contains components that can potentially be damaged by electrostatic discharge. Always transport
and store the EVM in its supplied ESD bag when not in use. Handle using an antistatic wristband. Operate on an
antistatic work surface. For more information on proper handling, see Electrostatic Discharge (ESD).
Table of Contents
1 Board Description...................................................................................................................................................................3
1.1 Features............................................................................................................................................................................. 3
1.2 Applications........................................................................................................................................................................3
1.3 Board Description...............................................................................................................................................................3
2 Powering the EVM...................................................................................................................................................................7
2.1 Dual Supply Operation (Separate Digital Logic and Driver Supplies)................................................................................ 7
3 Operating The EVM.................................................................................................................................................................8
3.1 Default Operation............................................................................................................................................................... 8
3.2 Potential Modifications for Single Ended Pins....................................................................................................................9
3.3 Potential Modifications for Differntial Pins........................................................................................................................10
4 Schematic.............................................................................................................................................................................. 11
5 Layout.................................................................................................................................................................................... 13
6 Bill of Materials..................................................................................................................................................................... 17
List of Figures
Figure 3-1. Jumper, Header Configuration Map.......................................................................................................................... 8
Figure 4-1. Schematic - DNI Components Shown..................................................................................................................... 11
Figure 4-2. Schematic with DNI Components Marked...............................................................................................................12
Figure 5-1. 3D View - Top.......................................................................................................................................................... 13
Figure 5-2. 3D View - Bottom.....................................................................................................................................................14
Figure 5-3. PCB Top Layer........................................................................................................................................................ 15
Figure 5-4. PCB Bottom Layer...................................................................................................................................................16
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List of Tables
Table 1-1. Jumpers, Headers, Terminals Descriptions................................................................................................................ 3
Table 1-2. Resistor Pad Descriptions...........................................................................................................................................4
Table 1-3. Capacitor Pad Descriptions........................................................................................................................................ 5
Table 1-4. LED Pad Descriptions.................................................................................................................................................6
Table 1-5. IC Pad Descriptions.................................................................................................................................................... 6
Table 2-1. Single Supply Operation Configuration.......................................................................................................................7
Table 2-2. Dual Supply Operation Configuration......................................................................................................................... 7
Table 3-1. Jumper Configuration for Default Operation............................................................................................................... 9
Table 3-2. Modifications For Single Ended Pins.......................................................................................................................... 9
Table 3-3. Modifications for Differential Pins..............................................................................................................................10
Table 6-1. Bill of Materials..........................................................................................................................................................17
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1 Board Description
1.1 Features
• Footprints for Both 10-Pin VSON (DRC) and 8-Pin SOIC (D) Half Duplex RS-485 Transceivers Indicated as
U1 and U2 Respectively.
• THVD2450VDRC Installed as U1 by Default
• 2 Power Supply Terminals (J5 and J6) to Supply a Power Signal to VL (DRC packages only) and VCC
Respectively.
• Can Short Power Supplies Together Via J15 if Single Supply for Logic and Device Are Wanted
• Power Supply Terminals allow for Power, Board-Ground, and Earth Connections.
• Power Supply Capacitors (2, 47 µF and 2, 10 µF – 1 of each Between Power and Board Ground and the
Other Between Board-Ground and Earth) Installed by J6 and Pads Available for J5.
• Ground Current Limiting Resistor Pads (R14 and R15) Available Between Board Ground and Earth on Both
J5 and J6
• Common Mode Voltage Connections (J12, J13, and J14) Available to Add a Common Mode Voltage to the
RS-485 Differential Bus (Pins A and B); Check Specific IC Datasheet for Details on Common Mode Ranges
• 120 Ω Termination Resistor (R17) Installed by Default on Board
• Capacitor Pad Between A and B Pins (C12) Available to Test Termination Capacitance Effects.
• Single Ended Inputs DE, /RE, and D All Have Pads to Support Pull-Up or Pull-Down Resistors.
• Single Ended Output R has Pads for a Pull-Up Resistor and a Capacitive Load
• Devices with SLR Pins Can be Controlled Via the J11 Jumper
• LED’s on R, D, and VCC Indicate Whether the Device is Receiving Data, Transmitting Data, and/or if the
Device has an Active Supply.
• Test Points on A and B Lines Near Termination Resistor.
1.2 Applications
• Motor drives
• Factory automation and control
• HVAC systems
• Building automation
• Grid infrastructureElectricity meters
• Process analytics
• Video surveillance
1.3 Board Description
The RS485HFDPLXDRCEVM is ready to operate directly out of box with a THVD2450DRC installed at U1. All
the signal and power jumpers/Inputs (J1 – J15) come pre-installed on board. Please see Table 1-1 through Table
1-5 for description for pads on the board, and to determine if it is pre-installed by default.
Table 1-1. Jumpers, Headers, Terminals Descriptions
Jumper ID Function Package Comment Installed?
J1 R Pin Output 8 Pin Header N/A Yes
J2 Enable 1 Input 8 Pin Header DE on DRC Packages Yes
J3 Enable 2 Input 8 Pin Header /RE on DRC Packages Yes
J4 D Pin Output 8 Pin Header N/A Yes
J5 VL Power Input 3 Pin Terminal Block N/A Yes
J6 VCC Power Input 3 Pin Terminal Block N/A Yes
J7 Termination Resistor
Connect
2 Pin Header Shunt J7 to Terminate A/B
with 120 Ωs
Yes
J8 Differential Bus Jumper 4 Pin Header N/A Yes
J9 Differential Bus Jumper 4 Pin Header N/A Yes
J10 RS-485 Bus Output 3 Pin Terminal Block N/A Yes
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Table 1-1. Jumpers, Headers, Terminals Descriptions (continued)
Jumper ID Function Package Comment Installed?
J11 SLR (Selectable Data
Rate) Pin Control
8 Pin Header SLR Pin not On Every IC
That is Approved for this
Board.
Yes
J12 Common Mode
Connection
4 Pin Header N/A Yes
J13 Common Mode A Input 4 Pin Header N/A Yes
J14 Common Mode B Input 4 Pin Header N/A Yes
J15 VL to VCC Shunt 2 Pin Header Shunt VCC to VL for
Single Supply Use Cases
Yes
Table 1-2. Resistor Pad Descriptions
Resistor ID Function Package Comment Installed?
R1 0 Ω Connection Series
Resistor
0603 For R Pin Yes
R2 Pull Up Resistor 0603 For R Pin No
R3 Current Limiting Resistor
for Diode
0603 For R LED D1 (R pin) Yes
R4 0 Ω Connection Series
Resistor
0603 For Enable 1 (DE on DRC
Pkg and /RE on D Pkg)
Yes
R5 Pull Up Resistor 0603 For Enable 1 (DE on DRC
Pkg and /RE on D Pkg)
No
R6 Pull Down Resistor 0603 For Enable 1
(DE on DRC Pkg and /RE
on D Pkg)
No
R7 0 Ω Connection Series
Resistor
0603 For Enable 2 (/RE on DRC
Pkg and DE on D Pkg)
Yes
R8 Pull Up Resistor 0603 For Enable 2 (/RE on DRC
Pkg and DE on D Pkg)
No
R9 Pull Down Resistor 0603 For Enable 2 (/RE on DRC
Pkg and DE on D Pkg)
No
R10 0 Ω Connection Series
Resistor
0603 For D Pin Yes
R11 Pull Up Resistor 0603 For D Pin No
R12 Pull Down Resistor 0603 For D Pin No
R13 Current Limiting Resistor
for Diode
0603 For D LED D2 (D Pin) Yes
R14 GND to EARTH Pull Down
for VL supply
0603 N/A No
R15 GND to EARTH Pull Down
For VCC Supply
0603 N/A No
R16 Current Limiting Resistor
for Diode
0603 for VCC LED (D3) Yes
R17 120ΩTermination Resistor 0805 Needed for RS-485
applications
Yes
R18 0 Ω Series connection
Resistor “B” Line
0603 N/A Yes
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Table 1-2. Resistor Pad Descriptions (continued)
Resistor ID Function Package Comment Installed?
R19 0 Ω Series connection
Resistor “A” Line
0603 N/A Yes
R20 Common Mode Voltage to
Bus Resistor for “B” Line
0603 Common Mode Test
Resistor = 375Ω; Found
on Backside of Board
No
R21 Common Mode Voltage to
Bus Resistor for “A” Line
0603 Common Mode Test
Resistor = 375Ω; Found
on Backside of Board
No
Table 1-3. Capacitor Pad Descriptions
Capacitor ID Function Package Comment Installed?
C1 Load Capacitance for “R” 0603 N/A No
C2 47 uF | 10 V Decoupling
Capacitor
0805 From GND to EARTH on
VL Supply
No
C3 47 uF | 10 V Decoupling
Capacitor
0805 From VL to GND on VL
supply
No
C4 10uF | 6.3V Decoupling
Capacitor
0805 From GND to EARTH on
VL Supply
No
C5 10uF | 6.3V Decoupling
Capacitor
0805 FROM VL to GND on VL
Supply
No
C6 47 uF | 10 V Decoupling
Capacitor
0805 From GND to EARTH on
VCC Supply
Yes
C7 47 uF | 10 V Decoupling
Capacitor
0805 From VCC to GND on
VCC Supply
Yes
C8 10 uF | 6.3 V Decoupling
Capacitor
0805 From GND to EARTH on
VCC Supply
Yes
C9 10uF | 6.3V Decoupling
Capacitor
0805 From VCC to GND on
VCC Supply
Yes
C10 100 nF | 6.3 V Decoupling
Capacitor
0603 From VL pin on U1 to
GND
Yes
C11 100 nF | 6.3 V Decoupling
Capacitor
0603 From VCC pin on U1 and
U2 to GND
Yes
C12 Termination Capacitance
Pad
0805 A to B Capacitor pad
to test different capacitive
loading conditions
No
C13 100 nF | 25 V Decoupling
Capacitor
0603 “A” Line Common Mode
Decoupling Capacitor
Yes
C14 100 nF | 25 V Decoupling
Capacitor
0603 “B” Line Common Mode
Decoupling Capacitor
Yes
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Table 1-4. LED Pad Descriptions
LED ID Function Package Comment Installed?
D1 “R” Line LED – Red Non-Standard N/A Yes
D2 “D” Line LED – Green Non-Standard N/A Yes
D3 “VCC” LED – Blue Non-Standard N/A Yes
Table 1-5. IC Pad Descriptions
IC ID Function Package Comment Installed?
U1 Half Duplex RS-485 IC
in DRC (10 Pin VSSON)
Package
DRC Comes Pre-installed with
THVD2450VDRC
Yes
U2 Half Duplex RS-485 IC in
D (8 Pin SOIC) Package
D N/A No
The default setup is optimized to work with the THVD2450VDRC operating in a single supply mode without a
common mode voltage. By shorting headers J7 (device termination) and J15 (VL = VCC) the board is ready
to operate in the default state. Please see section "Powering The EVM" for information on power supplies and
operational modes of the board respectively.
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2 Powering the EVM
Single Supply Operation (Logic Supply Equals Voltage Supply or DUT does not have VL pin)
Half Duplex RS-485 Transceivers in the DRC (VSSON) package from TI can have an additional logic supply pin,
VL. This is used to power the internal digital logic circuits inside of the device. In single supply operation mode
for devices, such as the THVD2450VDRC, the VL pin should be shorted to VCC by shorting J15 header pins,
so that the digital circuits are properly powered. If using an 8-pin D (SOIC) device in place of the DRC package,
there is only one supply pin and J15 can be left open. Please see Table 2-1 for single supply configuration based
on package.
Table 2-1. Single Supply Operation Configuration
Component ID IC Package Comment
J15 VSSON Shorted For Single Supply Operation
J15 SOIC Can be Left Open or Shorted – no VL pin to connect to.
J5 Either VL Supply – Leave Open
J6 Either VCC Power Terminal
C2 Either Leave DNI for Single Supply
C3 Either Leave DNI for Single Supply
C4 Either Leave DNI for Single Supply
C5 Either Leave DNI for Single Supply
R14 Either Leave DNI for Single Supply
To apply power onto the board, VCC is applied through the J6 terminal. With the board oriented with J6 on the
top left, as shown in Figure 3-1, the signals are, from right to left, EARTH, GND, and VCC. The EARTH and
GND distinction are used to help the end user determine operational qualities w.r.t. ground potential differences.
If testing methods on reducing ground loop current, install a resistor on pad R15. Check the datasheet for proper
powering considerations as this either recommend 3.3 V, 5 V or 3.3 V to 5 V.
2.1 Dual Supply Operation (Separate Digital Logic and Driver Supplies)
Half Duplex RS-485 Transceivers in the DRC (VSSON) package from TI can have an additional logic supply pin,
VL. In Dual Supply operation the digital circuit supply, the supply which supplies the R, D, RE, and DE pins, can
be held at a low level – typically from 1.65 V to 5 V to be able to interface a RS-485 transceiver to digital systems
using 1.8V logic. J15 should be left open. This option is only available for DRC (VSSON) packages. Please see
Table 2-2 for information on power supply components.
Table 2-2. Dual Supply Operation Configuration
Component ID IC Package Comment
J15 VSSON Left Open for Dual Supply Operation
J15 SOIC Dual Supply Not an Supported for SOIC
J5 VSSON VL Power Input
J6 VSSON VCC Power Input
C2 VSSON 47uF | 10V Decoupling Capacitor
C3 VSSON 47uF | 10V Decoupling Capacitor
C4 VSSON 10 uF | 6.3 V Decoupling Capacitor
C5 VSSON 10 uF | 6.3 V Decoupling Capacitor
R14 VSSON Can be added – however will be in parallel with R15 so make any
resistance calculations based on what’s on R15 and R14
Powering the board is like single supply option. J5 and J6 have the same pin orientation – from left to right it is
the EARTH pin, GND pin, and voltage supply pin. Attach VL power source to J5 and VCC power source to J6.
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3 Operating The EVM
3.1 Default Operation
With an understanding of how the board is setup and how to power the board for both supply situations the
next topic is how to operate the board. Out of the box the board, when powered, can operate the THVD2450V
as a half duplex RS-485 transceiver. The devices pins can be broken down into 4 distinct groups: single ended
communication pins, differential communication pins, power pins, and control pins. Power pins are discussed
in Powering the EVM and Dual Supply Operation (Separate Digital Logic and Driver Supplies). The following
details are for the other 3 categories.
The single ended communication pins are to be connected directly, through their respective jumpers, to a single
ended bus – these pins are the “R” and “D” pins and represent RX and TX single ended data respectively. For
both package types R is referenced to J1 and D is reference to J4 – these are the signal connection points for
the EVM.
Control signals can vary between devices. A a minimum this board supports an Active High Driver Enable (DE)
and an Active Low Receiver Enable (RE) these are accessed through Jumpers J2 and J3; however, the order
of these pins is dependent on package. Devices such as the THVD2450VDRC also contains a slew rate limiting
pin which turns on / off slew rate limiting for the device. In DRC packages without this feature, this pin should be
grounded. This pin is accessed through jumper J11.
Also, the last group of signals are the differential bus pins A and B. This connects to the differential bus through
terminal block J10. All differential data should be output/input through J10 to model the bus performance for a
specific application. For terminated bus operation J7 should be shunted.
A jumper configuration map is shown in Figure 3-1, where pin 1 is the top left corner of the shown jumpers with
every subsequent pin increasing by one in a clockwise direction. A summary table of component configuration in
Table 3-1 is shown below Figure 3-1.
Figure 3-1. Jumper, Header Configuration Map
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Table 3-1. Jumper Configuration for Default Operation
Jumper ID Signal – Jumper Pin Comment
J1 RX –Pin 4 or 7 Receive Data – to keep always high or low
shunt J1 I/O pins to VCC or GND.
J2 Enable – Pin 4 or 7 DE for VSSON and /RE for SOIC – shunt J2
I/O pins to VCC or GND if only 1 mode is to
be used.
J3 Enable – Pin 3 or 8 /RE for VSSON and DE for SOIC – shunt J3
I/O pins to VCC or GND if only 1 is to be
used
J4 TX – Pin 3 or 8 Transmit Data – to keep always high or low
shunt J4 I/O pins to VCC or GND
J11 SLR – Pin 2 and 7 Shunt I/O pin on J11 to either High or Low on
VSSON packages with SLR – if not included
Ground This Pin.
J7 N/A Shunt for Terminated Bus
Open for Unterminated Bus
J10 N/A Differential Bus Output Terminal.
J5 N/A Leave Floating for single supply applications,
attach digital supply if dual operation is used.
J6 N/A Attach VCC to J6
J15 N/A Shunt for Single Supply
Open for Dual Supply
3.2 Potential Modifications for Single Ended Pins
There are a few options with respect to the single ended data and control signals for modification on this EVM.
Jumpers J1 through J4 all contain pads that are blank by default. For D, DE, and RE signals there are 0603
sized pads for either pull-up or pull-down resistors to have a default logic on these pins with the added benefit of
still being able to external signals to this pin. The R pin also contains a pull-up resistor 0603 sized, as is common
in UART based applications, as well as a 0603 sized pad to ground for a capacitive load if testing requires
capacitive loading on the R pin. A summary of possible single ended signal pathway modifications on the EVM
are in Table 3-2.
Table 3-2. Modifications For Single Ended Pins
Associated Jumper / Signal `Pad ID Comment
J1 / R R2 Pull Up Resistor Pad
J1 / R C1 Capacitive Load Pad
J2 / EN1 R5 Pull Up Resistor Pad
J2 / EN1 R6 Pull Down Resistor Pad
J3 / EN2 R8 Pull Up Resistor Pad
J3 / EN2 R9 Pull Down Resistor Pad
J4 / D R11 Pull Up Resistor Pad
J4 / D R12 Pull Down Resistor Pad
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3.3 Potential Modifications for Differntial Pins
The Differential side of the RS-485 transceiver also has a few minor modifications that can be made. There is
the option for a termination capacitor, C12, along with the termination resistor. This capacitor can be used to help
estimate effects of capacitive cabling on the signal pathway. The other modification is by applying a common
mode voltage through the common mode jumpers J12 – J14 that is routed to the A and B lines through common
mode resistors, R20 and R21, which by default are not installed. For full common mode testing R20 and R21
should be selected to be 375 Ω as this is the standard for RS-485 devices. A summary of modifications can be
shown in Table 3-3.
Table 3-3. Modifications for Differential Pins
Associated Jumper / Signal Pad ID Comment
J12 and J13 / Common Mode on “A” R21 Common Mode Resistor to “A”
J12 and J14 / Common Mode on “B” R20 Common Mode Resistor to “B”
N/A / A and B C12 Termination Capacitor Pad
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