UM0425 User manual
STLED316S Front panel LED controller/driver evaluation board
Introduction
LED displays are widely used on consumer electronics and household appliances. Both push button keys and LED displays form the front panel of these products. Figure 1. Typical front panel application
In conventional systems, a sub MCU (Microcontroller) is used to control the front panel functions. Depending on the number of LED digit/segment and push button keys, an MCU with a high pin count might be required. Other disadvantages of an MCU solution:
External discrete current driver Current limiting resistors Additional cost of crystal for MCU clock
The STLED316S is a complete front panel LED controller/driver that is able to solve these disadvantages. A common anode LED driver can drive 40 mA of current on each segment output. No current limiting resistor is required as the current is set by a single RSET resistor. It has the additional advantage of brightness control up to 8 increments. Display brightness can be adjusted by modifying the brightness register value. It also has the capability of controlling each 7-segment LED digit and discrete LED brightness individually. The device can handle a maximum of 16 front panel keys. If any front panel key event is detected, IRQ out is asserted. IRQ is released once the key data is read. Current matching on each segment is guaranteed to be within 3%. When no digit and segment are ON, STLED consumes much less current of around 200 A which is achieved by turning OFF internal current mirror circuitry.
June 2007
Rev 1
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Contents
UM0425
Contents
1 2 3 4 5 6 Evaluation board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 General User Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Front panel keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 7-Segment display and discrete LED . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
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Evaluation board
1
Evaluation board
The demo board is integrated with six 7-segment LED digits, eight discrete LEDs, 16 push button keys, and other components for interfacing to a PC parallel port and power supply. One LED indicates the status of IRQ output. If IRQ is asserted, the LED is turned ON. Figure 2. STLED316S Evaluation board
The board can be powered from a DC power supply or center positive AC to DC adaptor. If it is to be powered from a DC power supply, the power pad labeled VCC 5 V should be connected to 5 V and the power pad labeled GND should be connected to power supply ground. A center positive AC to DC adaptor with output voltage between 6 V to 15 V can also be used to power the board. The adaptor should be plugged to the DC connector labeled CON2. CON1 provides the connection to the PC parallel port. General User Interface (GUI) communicates with the board through this parallel port. The parallel port address should be set to 0378h. The STLED316S_GUI.exe and io.dll files are contained in a zip file. Before operating the GUI, both files should be extracted to the same folder.
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R3
2.2K 2.2K 2.2K 2.2K 2.2K 2.2K 2.2K 10K
1
1A V C C 3Y 1Y 2A 3A G N D 2Y
1A V C C 3Y 1Y 2A 3A G N D 2Y
VIN VOUT
74V2G07
74V2G07
GND
C H 16
R11
220
CH8
D IG 1 SEG 2/KS2
DIG1
C H 15
IRQ
CH7
SEG 1/KS1 1 SEG 6/KS6 2 D IG 1 3 4 5 6 SEG 5/KS5 7
a com f b com N C NC g NC c NC Dp e d
14 13 12 11 10 9 8
SEG 7/KS7 SEG 3/KS3 SEG 8/KS8 SEG 4/KS4
VCC5V
VCC5V
C H 14
D IG 2 SEG 2/KS2
CH6
IRQ*
DIG4 DIG5 DIG6
DIG2
DOUT CLK STB IRQ* LED DIG1 DIG2 DIG3
C H 13 CH5 C H 12 CH4
SEG 1/KS1 1 SEG 6/KS6 2 3 D IG 2 4 5 6 SEG 5/KS5 7
a com f b com N C NC g NC c NC Dp e d
14 13 12 11 10 9 8
SEG 7/KS7 SEG 3/KS3 SEG 8/KS8 SEG 4/KS4
D IG 3 SEG 2/KS2
Size Number
Title
STLED316
Evaluation board
Figure 3.
Evaluation board schematic
UM0425
Date: Fil 5/23/2007 C \D t d S tti Sheet of \ \STLED316 S DD h B
DIG3
C H 11 CH3 C H 10 CH2 CH9 CH1
SEG 1/KS1 1 SEG 6/KS6 2 D IG 3 3 4 5 6 SEG 5/KS5 7
a com f b com N C NC g NC c NC Dp e d
14 13 12 11 10 9 8
SEG 7/KS7 SEG 3/KS3 SEG 8/KS8 SEG 4/KS4
D IG 4 SEG 2/KS2
SEG 1/KS1 1 SEG 6/KS6 2 D IG 4 3 4 5 6 SEG 5/KS5 7
a com f b com N C NC g NC c NC Dp e d
14 13 12 11 10 9 8
SEG 7/KS7 SEG 3/KS3 SEG 8/KS8 SEG 4/KS4
SEG1/KS1_D SEG2/KS2_D SEG3/KS3_D SEG4/KS4_D SEG5/KS5_D SEG6/KS6_D SEG7/KS7_D SEG8/KS8_D
D IG 5 SEG 2/KS2
SEG 1/KS1 D1 SEG 2/KS2 D2 SEG 3/KS3 D3 SEG 4/KS4 D4 SEG 5/KS5 D5 SEG 6/KS6 D6 SEG 7/KS7 D7 SEG 8/KS8 D8
SEG 1/KS1 SEG 2/KS2 SEG 3/KS3 SEG 4/KS4 SEG 5/KS5 SEG 6/KS6 SEG 7/KS7 SEG 8/KS8
LED1 LED2 LED3 LED4 LED5 LED6 LED7
SEG 1/KS1 1 SEG 6/KS6 2 D IG 5 3 4 5 6 SEG 5/KS5 7
a com f b com N C NC g NC c NC Dp e d
14 13 12 11 10 9 8
SEG 7/KS7 SEG 3/KS3 SEG 8/KS8 SEG 4/KS4
D IG 6 SEG 2/KS2
SEG 1/KS1 1 SEG 6/KS6 2 3 D IG 6 4 5 6 SEG 5/KS5 7
a com f b com N C NC g NC c NC Dp e d
14 13 12 11 10 9 8
SEG 7/KS7 SEG 3/KS3 SEG 8/KS8 SEG 4/KS4
LED
LED8
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CON1 DB25-M HDR5 HDR1 13 25 12 24 11 23 10 22 9 21 8 20 7 19 6 18 5 17 4 16 3 15 2 14 1 VCC5V 1 2 STB 3 1 2 STB_P 3 GND VCC5V VCC GND GND C1 10uF 1 2 3 C4 10uF 3 C5 100nF LD1117V50 A Revision U4 VCC5V 2 C2 C3 100nF 100nF CON2 DIN_P STB_P DOUT_P HDR6 HDR2 IRQ_P CLK_P DOUT_P DIN_P CLK_P STB_P DOUT CLK STB IRQ_P VCC5V 1 2 CLK 3 1 2 DOUT 3 KEY2 KEY1 VCC5V 1 2 CLK_P 3 1 DOUT_P 2 DIN_P 3 4 HDR7 R1 R2 10K 10K HDR3 HDR4 R12 10K CLK_P 1 IRQ_P 2 STB_P 3 4 1 2 DIN_P 3 1 2 DOUT_P 3 1 2 3 4 5 6 7 8 9 10 11 12 U1 360 R13 DAT CLK STB *IRQ LED DIG1 DIG2 DIG3 VCC DIG4 DIG5 DIG6 ISET KEY1 KEY2 SEG1/KS1 SEG2/KS2 SEG3/KS3 SEG4/KS4 GND SEG5/KS5 SEG6/KS6 SEG7/KS7 SEG8/KS8 24 23 22 21 20 19 18 17 16 15 14 13 SEG5/KS5 SEG6/KS6 SEG7/KS7 SEG8/KS8 KEY1 KEY2 SEG1/KS1 SEG2/KS2 SEG3/KS3 SEG4/KS4 U3 U2 R4 R5 R6 R7 R8 R9 R10 8 7 6 5 VCC5V CLK IRQ* STB 8 7 6 5 VCC5V VCC5V DIG4 DIG5 DIG6 DOUT
UM0425
General User Interface
2
General User Interface
Connect the evaluation board to the computer by a parallel port cable. Run STLED316S_GUI.exe and then power up the demo board. Figure 4. Default GUI setting
The setting of GUI when it is first run is the default setting of STLED316S upon power-up. The number of 7-segment LED on evaluation board is six. The DISPLAY MODE (red circle in Figure 4 ) should be modified from the default value of 4-digit, 8-segment to 6-digit, 8segment. By default also, DISPLAY is OFF. Modify DISPLAY ON/OFF (red circle in Figure 4) setting to ON.
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Front panel keys
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3
Front panel keys
There are 16 front panel keys on the board. If any key press is detected, STLED316S asserts interrupt. For this evaluation board, the interrupt is sent to GUI. Once the GUI detects an interrupt, it reads front panel key data on the STLED316S key register. Having decoded the data, GUI then writes to the 7-segment display the key that has been pressed. For example if the push button labeled CH6 is pressed, CH.06 will be displayed on 7segment display as shown below: Figure 5. CH.06 corresponding to CH6 push button press
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UM0425
7-Segment display and discrete LED
4
7-Segment display and discrete LED
The STLED316S is able to drive up to 56 LED segments (48 segments for 7-segment display and 8 segments for discrete LED). Figure 6. Discrete LED control
On the top right of the GUI (red circle in Figure 6) is the control for turning ON and OFF each individual discrete LED on the board. Click on the LED to be turned ON and press the send button. The corresponding LED on board turns ON. Figure 7. Discrete LED ON
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7-Segment display and discrete LED
UM0425
To observe the effect of brightness variation, it is better to turn ON all discrete LED and 7segment displays. Click both ALL LED ON and ALL DISPLAY ON (red circle in Figure 8). All segments are then turned ON. Figure 8. Turning ON all segments
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UM0425 Figure 9. All segments ON
7-Segment display and discrete LED
By default the brightness mode is constant. Default constant brightness LEVEL is 14/16. Constant brightness mode means that the brightness level applies uniformly for all the 56 segments (7-segment and discrete LED). Figure 10. Brightness mode and level
Modify constant brightness level (red circle in Figure 10) to another setting all the 56 segments change brightness accordingly.
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Summary
UM0425 The brightness mode setting (red circle in Figure 10) can be changed to variable. Variable brightness mode means that each 7-segment digit and discrete LED brightness can be controlled individually and independently of each other. The default variable brightness level for all the digit and discrete LEDs is 1/16. Modify the variable brightness level (red circle in Figure 10) for each individual 7-segment digit and discrete LED, and the 7-segment display and discrete LED brightness change accordingly. Segments for 7-segment display can also be used for discrete LED and vice versa. Segments for 7-segment display and discrete LED operate in the same way. The only difference is that in variable brightness mode, the brightness of segments for 7-segment displays are controlled in groups of eight, which is per digit, whereas discrete LED segment brightness is controlled individually.
5
Summary
The STLED316S is the right solution for front panel LED controller/drivers. With its adjustable brightness level, 3% current matching, integrated front panel key detection, and low stand-by current, it enhances performance and at the same time simplifies front panel design.
6
Revision history
Table 1.
Date 05-Jun-2007
Revision history
Revision 1 First issue Changes
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UM0425
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