cd00129340

AN2415
Application note
Using the output detection feature of the high-brightness
LED driver STP08CDC596 evaluation board
Introduction
This document describes how to implement a complete solution for driving a high-brightness
LED array. Based on STP08CDC596 drivers and controlled by an ST7FLITE3x
microcontroller, there are two versions of the evaluation board:
Note:
■
STEVAL-ILL002V1 using OSRAM LEDs
■
STEVAL-ILL002V2 using Toshiba LEDs
The STP08CDC596 LED driver is replaced by the new, higher performing STP08DP05 LED
driver. The two available versions of the evaluation board with the STP08DP05 replace the
STEVAL-ILL002V1 and the STEVAL-ILL002V2, and are described in application note
AN2478.
The new boards available are:
■
STEVAL-ILL002V3 using OSRAM LEDs
■
STEVAL-ILL002V4 using VISHAY LEDs
Forty high-brightness LEDs are arranged on the board in a 5x8 matrix. The matrix is driven
by five 8-channel STP08CDC596 drivers.
The main features of the evaluation board are:
■
Brightness and blinking regulation
■
Animated text
■
Error detection on output
■
GUI (graphic user interface)
■
DC-DC converter
The innovative feature of the STP08CDC596 is the full output error detection function which
enables output status checking without invasive testing (via software only).
Figure 1.
STEVAL-ILL002Vx evaluation board
For more information about other boards based on the STPxxC/L596 driver family, refer to
application note AN2141 which provides details concerning the basic features of the driver
family, the microcontroller interface and chip power dissipation. Refer to user manual
UM0181 for information about how to get started using the evaluation boards.
August 2007
Rev 4
1/11
www.st.com
Contents
AN2415
Contents
1
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2
Operation mode switching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3
4
2/11
2.1
Normal mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2
Error detection mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Firmware implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1
Timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2
Option byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.3
GUI features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
AN2415
List of figures
List of figures
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
STEVAL-ILL002Vx evaluation board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
STEVAL-ILL002Vx evaluation board block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Error Detection mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Normal mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
MCU option bytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
LED matrix board application diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3/11
Overview
1
AN2415
Overview
The STEVAL-ILL002Vx evaluation board can be powered with voltages from 7 V up to 32 V.
The SMPS DC-DC converter block is based on the L5970D step-down switching regulator
and the DC-DC block is based on the LE50ABD voltage regulator. The power topology
makes it possible to power the board using a laptop power supply.
Figure 2 shows the block diagram of the evaluation board.
Figure 2.
STEVAL-ILL002Vx evaluation board block diagram
SMPS
DC/DC
Power Supply
LED Matrix
DC/DC
……
Control Panel
LED Driver
8-bit µC
SPI
SPI
…….
RS232 Driver
The brain of the board is the 8-bit ST7FLITE39 microcontroller. It receives inputs from the
control panel, sends and receives data from the LED drivers through the serial peripheral
interface (SPI) and enables PC communication through the serial communications interface
(SCI). The control panel consists of switches, potentiometers and jumpers. Switches are
used to reset the microcontroller and to enter Detection mode. Potentiometers change the
brightness and text speed. Jumpers are used to simulate errors (open and short circuit) on
the LED matrix.
A LED matrix consists of 40 LEDs arranged in a 5x8 matrix. A dedicated PC GUI displays
the status of the LEDS.
4/11
AN2415
2
Operation mode switching
Operation mode switching
To enter Error Detection or Normal mode, the drivers must receive a particular sequence on
the OE and LE pins.
When a one-clock-wide short pulse “101” is sent on the OE pin, the drivers enter the
switching phase. If the LE pin is sampled as high voltage at the 4th rising edge of CLK, the
drivers switch to Error Detection mode (Figure 3). Otherwise, they switch to Normal mode
(Figure 4).
Note:
2.1
In the firmware, with SW2 pressure only the drivers enter Error Detection mode, and after an
error detection check, they re-enter Normal mode.
Figure 3.
Error Detection mode
Figure 4.
Normal mode
Normal mode
In Normal mode, the serial data is transferred from the microcontroller to the drivers via the
SPI. The serial data from microcontroller is sent to the drivers via the SDI pin, undergoes a
shift in the Shift Register, and exits via the SDO pin. The LE pin can latch the serial data in
the Shift Register to the output latch. The OE pin enables the output driver sink current.
Current is modulated by the potentiometer, which changes the PWM duty cycle on the OE
pin (PWM frequency is set at 244 Hz).
5/11
Firmware implementation
Note:
At start-up, the evaluation board works in Normal mode.
2.2
Error detection mode
AN2415
After entering Error Detection mode as shown in Figure 3, it is recommended to send all
data to the drivers as “1”.
As long as the OE pin is high, the serial data can still be shifted to the Shift Register via the
SDI pin, and out via the SDO pin. The LE pin can also send the data in the Shift Register to
the output latch.
When the state of the OE pin is pulled down to low voltage for at least 2 µs, the drivers
execute the error detection function and load the error status into the Shift Register. The
error status codes saved in the Shift Register can then be shifted out via the SDO pin bit-bybit along with the clock. The SDO pin of the last driver of the chain is connected to the MISO
pin of the microcontroller. Incoming data can be sent to the PC through the SCI and
displayed on the GUI. For more information, refer to the timing diagram shown in Figure 5.
3
Firmware implementation
The purpose of this application note is to explain how to manage the error detection features
of the drivers. Refer to AN2141 for an explanation of the basic driver features.
3.1
Timing diagram
At power-up, the microcontroller sends data to the drivers’ Shift Register via the SPI
configured at 250 kHz. The maximum communication frequency for this driver is 25 MHz to
satisfy high volume data transmissions. (Please refer to the device datasheet for more
details). The two potentiometers are connected to ADC inputs. The analog voltage inputs
are converted to a digital value. According to this digital value, it will change the PWM
duty-cycle signal for brightness and data time delay for text speed. By default, the
microcontroller works in Normal mode and only enters Error Detection mode when an
external interrupt pin connected to SW2 is triggered. The related ISR disables the SPI I/O
function and sends a specific sequence to the driver via the CLK, OE, and LE pins as shown
in Figure 5.
After the driver has received the specific sequence, the microcontroller enables the SPI and
sends 0xFF data for each driver. The drivers have already entered Error Detection mode
and the microcontroller maintains pin OE low for detecting the error status. Drivers send
back the LED status to the microcontroller via the MISO pin (connected to the SDO pin).
Then, the microcontroller resumes Normal mode operation, sending the specific sequence
to the drivers. Figure 5 shows each phase, switching from Error Detection to Normal modes.
6/11
AN2415
Firmware implementation
Figure 5.
Timing diagram
Note:
TA must be at least 2 µs to detect the error status.
Note:
The SDO of the E driver is connected to the MISO pin of the MCU.
3.2
Option byte
Figure 6 shows the option byte settings.
Figure 6.
3.3
MCU option bytes
GUI features
A dedicated graphical user interface (GUI) displays the LEDs, status on the PC. The serial
parameters are: 4800, 8, N, 1 (baud rate, 8 bit, parity none, 1 bit stop). The microcontroller,
7/11
VCC
VCC
RES
SD0
SW1
ICP
RDI
ST7lite3
U8
TDO
20
19
18
17
16
15
14
13
12
11
VCC
VCC
10nF
C16
R9
10k
10nF
C14
J1
INPUT VOLTAGE
FROM 7V UP TO 32V
10k
2
R1
10k
2
R2
C2 C13
+
10nF
10uF
1
3
1
3
1
2
3
4
5
6
7
8
9
10
1
2
3
J5 CON3
RES
SW2
10k
R8
SMAJ33A-TR
D44
VCC
16
15
14
13
12
11
10
9
10uF/35V
C19
1k3
R3
220pF
C20
4k7
R10
22nF
C18
6
8
2
4
1
2
3
4
5
6
7
8
8
VIN
U7
5
1
16
15
14
13
12
11
10
9
1
LE50/SO
VOUT
2
1
C15
2K2
R12
6k8
VCC
R4
1K3
360
R13
100nF
R11
33uH
STPS340U
D41
L1
VCC
D13 D14 D15 D16
STP08CDC596/B
GND
Vdd
SDI R-EXT
CLK SDO
/LE
/OE
5
12
6
11
7
10
8
9
U2
D9 D10 D11 D12
IO5 L5970D
100nF
C17
D5 D6 D7 D8
STP08CDC596/A
GND
Vdd
SDI R-EXT
CLK SDO
/LE
/OE
5
12
6
11
7
10
8
9
U1
D1 D2 D3 D4
1
2
3
4
5
6
7
8
GND
2
1 2
3 4
5 6
7 8
9 10
C4
GND
3
VCC
3
7
100nF
GND
6
VCC
GND
7
100nF
INHIB
5
8/11
JP2
U3
D42
560
R14
100nF
C5
16
15
14
13
12
11
10
9
100uF/16V
C22
+
C8
470nF
220uF/25V
C21
C9
470nF
C10 470nF
1k3
R5
VCC
D21 D22 D23 D24
STP08CDC596/C
GND
Vdd
SDI R-EXT
CLK SDO
/LE
/OE
5
12
6
11
7
10
8
9
D17 D18 D19 D20
1
2
3
4
5
6
7
8
GREEN LED
C1
2.2uF
JUMPER
2
1
1
2
3
4
5
6
7
8
C11 470nF
1k3
R6
VCC
Size
B
Title
16
15
14
13
12
11
10
9
VCC
RxD
TDO
RDI
2.2uF
C12
P1
CONNECTOR DB9
5
9
4
8
3
7
2
6
1
16
15
14
13
12
11
10
9
R7
VCC
SD0
1k3
Rev
<RevCode>
JP1
JUMPER
D37 D38 D39 D40
STP08CDC596/E
GND
Vdd
SDI R-EXT
CLK SDO
/LE
/OE
5
12
6
11
7
10
8
9
U5
D33 D34 D35 D36
1
2
3
4
5
6
7
8
100nF
C7
Document Number STEVAL-ILL002V1 (OSRAM LEDs)
<Doc>
STEVAL-ILL002V2 (TOSHIBA LEDs)
Diagnostic LED Driver
TxD
D29 D30 D31 D32
ST232ABN
C1+
Vdd
V+
GND
C1T1OUT
C2+
R1IN
C2R1OUT
VT1IN
T2OUT T2IN
R2IN R2OUT
U6
16
15
14
13
12
11
10
9
STP08CDC596/D
GND
Vdd
SDI R-EXT
CLK SDO
/LE
/OE
5
12
6
11
7
10
8
9
U4
D25 D26 D27 D28
1
2
3
4
5
6
7
8
100nF
C6
Figure 7.
2
Appendix A
1
C3
Application diagram
AN2415
after resuming Normal mode, manages the SCI peripheral and sends data to the PC using
the ST232ABN driver interface.
Application diagram
LED matrix board application diagram
AN2415
Bill of materials
Appendix B
Table 1.
Bill of materials
Bill of materials
Item Qty
Reference
Part
Description
1
2
C1 and C12
2.2 µF/50 V
Electrolytic capacitor
2
1
C2
10 µF/35 V
Electrolytic capacitor
3
7
C3, C4, C5, C6,
C7, C15 and
100 nF/50 V
C17
Ceramic capacitor
SMD 0805
4
4
C8, C9, C10
and C11
470 nF/16 V
Ceramic capacitor
SMD 0805
5a
2
C14 and C16
10 nF/50 V
Ceramic capacitor
SMD 0805
5b
1
C13
10 nF/50 V
Ceramic capacitor
SMD 1206
6
1
C18
22 nF/50 V
Ceramic capacitor
SMD 0805
7
1
C19
10 µF/35 V
Tantal capacitor
8
1
C20
220 pF/50 V
Ceramic capacitor
SMD 0805
9
1
C21
220 µF/25 V
Electrolytic capacitor
10
1
C22
100 µF/16 V
Tantal capacitor
11
40
D1, D2, D3, D4,
D5, D6, D7, D8,
D9, D10, D11,
D12, D13, D14,
D15, D16, D17,
D18, D19, D20,
D21, D22, D23, LED
D24, D25, D26,
D27, D28, D29,
D30, D31, D32,
D33, D34, D35,
D36, D37, D38,
D39 and D40
OSRAM SMD BLUE
LED LB T68C-P2S1-35
or TOSHIBA
LED - TLGE1100
12
1
D41
STPS340U
Diode
13
1
D42
GREEN LED
SMD LED 1206
14
1
D44
SMAJ33A-TR
15
1
IO5
16
2
17
18
Order code
Supplier
OSRAM or
TOSHIBA
STPS340U
STMicroelectronics
Transil
SMAJ33A-TR
STMicroelectronics
L5970D
DC-DC converter
L5970D
STMicroelectronics
JP1 and JP2
JUMPER
Jumpers + switches
1
J1
ICP
Programming connector
1
J5
CON3
Input connector
9/11
Revision history
Table 1.
AN2415
Bill of materials (continued)
Item Qty
Reference
Part
Description
Order code
19
1
L1
33 µH
Inductor
20
1
P1
CONNECTOR
DB9
CAN connector - 9 pin
21a
2
R1 and R2
10 k
Potentiometers with
axis
21b
2
R8 and R9
10 k
SMD resistors 0805
22
5
R3, R4, R5, R6
and R7
1k3
SMD resistors 1206
23
1
R10
4k7
SMD resistors 0805
24
1
R11
6k8
SMD resistors 1206
25
1
R12
2K2
SMD resistors 1206
26
1
R13
360
SMD resistors 1206
27
1
R14
560
SMD resistors 1206
28
2
SW1 and SW2
Push-button
switch
Switch
29
5
U1, U2, U3, U4
and U5
STP08CDC596 LED drivers
STP08CDC596TTR STMicroelectronics
30
1
U6
ST232ABD
RS232 driver
ST232ABD
31
1
U7
LE50/SO
Linear voltage regulator LE50ABD
STMicroelectronics
32
1
U8
ST7lite3
Microcontroller
STMicroelectronics
4
ST7FLITE39F2M6
Coilcraft
STMicroelectronics
Revision history
Table 2.
10/11
DO3316P-333ML
Supplier
Revision history
Date
Revision
Changes
7-Sept-2006
1
Initial release.
31-Jan-2007
2
Bill of materials table and LED matrix board application diagram
modified.
08-Feb-2007
3
Bill of materials table modified.
30-Aug-2007
4
Minor text changes
AN2415
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