Texas Instruments TLC5924EVM User manual

1 Introduction
User's GuideSLVU187A – September 2006 – Revised June 2007
TLC5924EVM
This user’s guide describes the characteristics, operation, and use of the TLC5924EVM-186 evaluationmodule (EVM). This EVM is designed to help the user evaluate and test the various operating modes ofthe TLC5923 and TLC5924 LED drivers. This user’s guide includes setup instructions for the hardwareand software, a schematic diagram, a bill of materials (BOM), and PCB layout drawings for the evaluationmodule.
Contents1 Introduction ................................................................................................................... 12 Board Layout ................................................................................................................. 63 Schematic and Bill of Materials ............................................................................................ 9
List of Figures
1 Hardware Setup .............................................................................................................. 32 Assembly Layer .............................................................................................................. 63 Top Layer Routing ........................................................................................................... 74 Layer 2 Routing .............................................................................................................. 75 Layer 3 Routing .............................................................................................................. 86 Bottom Layer Routing ....................................................................................................... 87 TLC5924EVM-186 Schematic (a) ......................................................................................... 98 TLC5924EVM-186 Schematic (b) ........................................................................................ 10
List of Tables
1 J1 – Interface Connector .................................................................................................... 42 J2, J3, J4, J5 – Power Connectors ........................................................................................ 43 EVM Power Requirements ................................................................................................. 44 TLC5924EVM-186 Bill of Materials ...................................................................................... 11
The Texas Instruments TLC5923 is a 16-channel, constant-current LED driver that is capable of driving upto 80 mA per channel. The integrated circuit (IC) contains integrated DOT correction circuitry that adjuststhe DC current for each output channel to compensate for brightness difference among LEDs. DOTcorrection information can be written into internal registers. The TLC5924 is a device nearly identical tothe TLC5923, with the exception of an added precharge FET. The precharge FET eliminates the ghosting,or spike current effect, that is associated with driving time-multiplexed strings of LEDs from a single IC.
This EVM contains a TLC5923 IC connected in parallel with a TLC5924 IC. The two ICs drive 16 red and16 green light-emitting diodes (LED). The LEDs are separated into two banks, so that all red LEDs resideon bank A, while all green LEDs reside on bank B. Both the TLC5923 and TLC5924 contain 16 outputseach and every output is connected to a different pair of red and green LEDs. A switch on the EVM (S1)selects which IC to activate, so that only one IC is on during normal operation. Using the suppliedsoftware, the user individually controls the DOT correction and on/off values for each LED. Two modes ofoperation are present in the software: Single-Bank Mode and Multiplex Mode. In Single-Bank Mode, theuser selects which bank of LEDs to activate, so that only the red or green LEDs are programmable. InMultiplex Mode, both rows of LEDs are programmed sequentially at a high rate, giving the appearance
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1.1 Requirements
1.1.1 Software
1.1.2 Host Computer Requirements
1.1.3 Power Supply Requirements
1.1.4 Printed-Circuit Board Assembly
1.1.5 USB Interface Adapter
1.2 Setup
1.2.1 Software Installation
Introduction
that both rows of LEDs are on at the same time. In reality, two FETs continuously switch the two banks ofLEDs in and out of the circuit. Therefore, only the red or green LEDs are connected to the IC at any giventime. Because this switching occurs hundreds of times per second, both rows of LEDs appear to bealways on. To accomplish multiplexing, the selected LED driver has to be reprogrammed every cycle sothat different patterns can be displayed on the two LED banks.
In both modes of operation, the software allows the user to enter the LED DOT correction and enableinformation for every LED. The software then communicates with the TLC5924EVM via an USB InterfaceAdapter. This interface board generates the individual data signals necessary to program theTLC5924EVM so that it properly drives the LEDs.
In order to operate this EVM, the following components must be connected and properly configured. Allcomponents, software, and connectors are supplied in the EVM except for the host computer and the twoDC power supplies.
Texas Instruments has provided the software necessary to evaluate this EVM. Check the TLC5924product folder on the TI Web site for the latest revision of the software.
•The host computer, or personal computer (PC), operating system must have either the Windows™ XPor Windows™ 2000 operating system installed.•Must have a USB port•Must have a minimum of 100 MB of free hard disk space for the EVM software installation•Must have a minimum of 256 MB of RAM to run the LED Frame Designer program
•DC power source capable of supplying a minimum of 5.5 V at 2 A•DC power source capable of supplying 3.3 V at 500 mA
The TLC5924EVM-186 PCB contains a TLC5923 IC configured in parallel with a TLC5924 IC.
The USB Interface Adapter
(1)
is the communications link between the PC and the EVM. One end of theinterface board connects to the PC with the supplied USB cable and the other end of the interface boardconnects to the EVM with the supplied SCSI-1 cable. When the user programs the LEDs to turn on or off,the PC sends the proper commands to the USB Interface Adapter. The USB Interface Adapter receivesthese USB commands, and its firmware converts the commands into the proper bit stream necessary tocontrol the LEDs on the EVM.(1)
"USBINTERFACEADAPTEREVM" is the orderable part number for the USB Interface Adapter.
The following discussion describe how to set up the EVM software and hardware.
To install the software, insert the enclosed CD into the CD-ROM drive of your computer. Browse thecontents of the CD for the Setup.exe file. Run this file to start the software installation process.
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1.2.2 Hardware Setup
1.3 Input/Output Connector Descriptions
1.3.1 J1 – Interface Connector
Introduction
See Figure 1 when setting up the TLC5924EVM hardware.
Attach the 10-pin ribbon cable between the USB Interface Adapter and the TLC5924EVM board (theconnectors on the boards and the ribbon cable are keyed to only allow connection with the properorientation)
Attach the 5.5-V (2-A) power supply to the LED board between J4 (VLED) and J5 (GND).
Attach the 3.3-V (500-mA) power supply to the LED board between J4 (VIN) and J7 (GND).
Connect the host computer to the USB Interface Adapter using the provided USB cable. If the computer isrunning, you may see a message about installing new hardware. Follow the on-screen instructions andallow Windows™ to install the default drivers for this device. Note that the USB board appears to Windowsas a generic Human Interface Device (like a keypad or a mouse), so there is no custom driver to install.
Figure 1. Hardware Setup
This connector is used to connect TLC5924EVM to the USB Interface Adapter. The connectorspecifications are shown in Table 1 . For a more detailed description of each signal, see the TLC5923 datasheet (SLVS550 ) and the TLC5924 data sheet (SLVS626 ).
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1.3.2 J2, J3, J4, J5 – Power Connectors
1.4 Jumper/Switch/Test Point Descriptions
1.4.1 S1 – IC Select
Introduction
Table 1. J1 – Interface Connector
Pin Number Pin Symbol Signal Description Function
1 SIN_IN Serial data input Used to input data into the TLC5923 and TLC5924 ICs2 ENA_IN Enable A Controls bank A LEDs. When ENA_IN is high, the anodes of all bank ALEDs (red) are connected to VLED via Q1. When ENA_IN is low, theanodes of all bank A LEDs are disconnected from VLED.3 ENB_IN Enable B Controls bank B LEDs. When ENB_IN is high, the anodes of all bank BLEDs (green) are connected to VLED via Q2. When ENB_IN is low, theanodes of all bank B LEDs are disconnected from VLED.4 SCLK_IN Serial data input Shifts SIN data into internal registers of TLC5923 and TLC5924clock5 3.3V 3.3V This pin is the 3.3V bus from the interface board. It is not connected tothe VIN pins on the PWB.6 GND Ground Signal ground7 BLNK_IN Blank input Activates/Deactivates all OUTx signals.8 MODE_IN Mode select Controls whether SIN programs ON/OFF control logic or dot-correctionlogic.9 XLAT_IN Data latch Rising edge latches data from shift registers into ON/OFF registers ordot-correction registers.10 N/A N/A This pin is floating and is not connected to any signals on the board.
Note: The extension _IN is simply used to refer to the signals that arrive at the EVM viaconnector J1. Each signal on Table 1 is accessible through its corresponding test point.For example, attaching a voltage probe to TP4 would allow the user to observe the signalSCLK_IN. The test points and their corresponding signals are clearly labeled on theschematic and PCB.
These connectors provide power to the ICs and LEDs on the EVM.
Table 2 shows pin assignment and Table 3 shows the power requirements of the EVM. Ensure that thepower supplies connected to VIN and VLED have the required current capability.
Table 2. J2, J3, J4, J5 – Power Connectors
Connector Symbol Function
J2 VIN Supplies bias power for the ICs on the EVM board.J3, J5 GND GroundJ4 VLED Supplies power to drive the LEDs. VLED is connected to the anodes of all LEDs via Q1 and Q2.
Table 3. EVM Power Requirements
Connector Symbol Voltage Range Max. Current
J2 VIN 3.3V ±0.1V > 500mAJ4 VLED 4.0V – 17V > 2000mA
S1 is a 3-pin switch that allows the user to activate either the TLC5923 or TLC5924. Moving the switch tothe right applies power to the TLC5923 and deactivates the TLC5924. Moving the switch to the left appliespower the TLC5924 and deactivates the TLC5923.
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1.4.2 JP2, JP3 – LED Current Measurement
1.4.3 TP1 to TP11 – Voltage Test Points
1.5 EVM Operation
1.5.1 Turning on the EVM
1.5.2 Software Operation
Introduction
These jumpers provide an easy place to measure the current flowing through D15A (JP2) and D15B(JP3). To measure the current through an LED, remove the corresponding shunt and connect a currentmeter across the jumper pins. Note that no current can flow through the LEDs if the shunts are removedand a current meter is not installed. Therefore, a shunt should be placed on JP2 and JP3 when they arenot being used to measure current, or the IC may activate the error LED because it would be detecting anopen circuit on its OUT15 pin. The IC considers this event an LOD fault (LED open detect).
The EVM contains 11 test points labeled from TP1 to TP11. These connections are used as convenientlocations to attach oscilloscope probes or voltmeter leads when performing measurements. Each testpoint is connected to its corresponding signal. For a detailed description of each signal, see Table 1 or theTLC5924 data sheet.
After the software is installed and the hardware is connected as described earlier in this document, theEVM is ready for use. The start-up procedure for the EVM is as follows:1. Connect all hardware.2. Turn on the 3.3-V and 5.5-V power supplies3. If not yet running, run the TLC5924EVM software program on the PC. To do this, click on the Startmenu, then under Programs, navigate to Texas Instruments Incorporated. Click on the TLC5924EVMSoftware to run the program. A message appears that states Verifying Applications Requirements. Thismay take a few moments. At this point, the software may load an update message. If it does, click‘Install’ and wait for the program to update and then load. The program may also ask you to update thefirmware. If it does, click OK and then Yes. After it updates the firmware, follow the instructions tounplug the USB adapter and plug it back in. Then click OK.
If the USB cable is removed and reinserted while the software is running, or if power is removed fromVCC, the DOT correction data may become corrupted. To correct this problem, click on the triangularPLAY button in the software.
The default state at start-up is to program the LED drivers to 100% DOT correction and all LEDs enabled.The Help section of the software details the operation of the program.
The TLC5924EVM software allows the user to control the operation of the evaluation module. The userinterface displays the current values of DOT correction and enable for each LED. A tab allows the user toselect between Single-Bank Mode and Multiplex Mode.
In Single-Bank Mode, only one bank of LEDs can be controlled at a time. The user can choose whichbank to activate and can adjust DOT correction values for each LED on the chosen bank. Using the switchS1 to change the activated IC is not recommended in Single-Bank Mode, because the software updatesthe data only when a change is made in the user interface; so, switching ICs causes the newly activatedIC to turn on a random number of LEDs. This can be easily corrected, however, by changing any value(DOT correction or on/off) in the program so that the software updates the data. Also, both the TLC5924and TLC5923 operate identically in Single-Bank Mode, so using the switch to change ICs results in nodiscernible difference in operation.
In Multiplex Mode, both banks of LEDs are driven using time-multiplexing. Two FETs continuously switchthe two banks of LEDs in and out of the circuit. Therefore, only the red or green LEDs are connected tothe IC at any given time. Because this switching occurs hundreds of times per second, both rows of LEDsappear to be always on. Using switch S1 to change the activated IC allows the user to better observe theadvantage of the precharge FET on the TLC5924.
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1.5.3 Signal-Conditioning Buffer
2 Board Layout
2.1 Layout
Board Layout
Both modes of operation also allow the user to create and play multiple frames. A frame is a particularconfiguration of DOT correction data and on/off values for all LEDs. Creating and configuring multipleframes allows the user to select which frames to activate or play the frames sequentially.
For a more detailed description of software operation, see the Help section of the software.
Note: When the EVM is in operation, the LEDs may flash briefly. This is normal and is causedby an interrupt on the USB connection; it is not a malfunction of the EVM or LED drivers.
The TLC5924EVM PWB contains a buffer to condition the input signals to the EVM. This buffer,SN74AVC16244, eliminates any noise on the input signals, generates fast, clean rise and fall times, andimproves the drive capability of the signals. Due to a weak pullup capability on the USB Interface Adapter,all input signals on J1 are connected to 3.3V via 10-k Ωpullup resistors to improve signal integrity. Thebuffer also controls which IC receives the input signals, so that only the selected IC receives the signalinputs, while the deactivated IC’s inputs are floating. For these reasons, SCLK24 and SCLK23 are cleanversions of the SCLK_IN signal.
This section provides the TLC5924EVM-186 board layout and illustrations.
Figure 2. Assembly Layer
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Board Layout
Figure 3. Top Layer Routing
Figure 4. Layer 2 Routing
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Board Layout
Figure 5. Layer 3 Routing
Figure 6. Bottom Layer Routing
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3 Schematic and Bill of Materials
3.1 Schematics
Schematic and Bill of Materials
This section provides the TLC5924EVM-186 schematic and bill of materials.
Figure 7. TLC5924EVM-186 Schematic (a)
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Schematic and Bill of Materials
Figure 8. TLC5924EVM-186 Schematic (b)
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