STEVAL-ILL002V2

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 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) 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 Please Read Carefully: Information in this document is provided solely in connection with ST products. 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