Acrobat Distiller, Job 20
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1. AN1900 Ay APPLICATION NOTE HARDWARE IMPLEMENTATION FOR ST7DALI EVAL INTRODUCTION This application note describes how to implement a DALI Digital Addressable Lighting Inter face in an existing high frequency dimmable tube lamp ballast application Figure 1 Hardware overview with MCU handling only DALI communication ANALOG ANALOG H Di H B Controller Lres I Feedback Feedback If necessary please refer to Application Note AN1756 Choosing a DALI implementation Strategy with ST7DALI for further background This application note is issued with the ST7DALI evaluation board which can be purchased with the sales type ST7DALI EVAL Figure 2 ST7DALI EVAL principle _N SN 1 Ballast Ballast DALI Slave Software DALI 1 10 V 1 10 V IN Master DALI DALI Slave Slave Board Board Up to 64 slaves DALI Evaluation Kit Please refer to the ST 7DALI EVAL Evaluation Kit user manual Rev 1 0 AN1900 0504 1 9 HARDWARE IMPLEMENTATION FOR ST7DALI EVAL 1 HARDWARE 1 1 ST7DALI FEATURES Table 1 List of Requirements for the Microcontroller Minimum Requirements ST7DALI Features 26 bytes of EEPROM to save non vola 256 bytes data internal EEPROM tile parameters 3 Kbytes program memory 8 Kbytes Flash program memory A timer with Input Capture Output Com pare capabilities to receive and transmit DALI communication module DCM DALI signals Low consumption mode to save energy Halt2. I OVO d adran obs DO OSU SHI A be PN NT LS a Avid aS Hed Pe Wind eS Hod Ovid iS Heed AL ares Hi d al JSH d er z980 1g HATALI SO Aog BLO dugg SATS E BLO BRAT BRAT oo cd fd bY ADG r 4400 z 1 qA aaag Addns amod 400 sro gE IAL 2 Ply eld 2 z AOE Get As f 4nzz LAL IPONA eae In g0 Dd 1 sro up MEH age oly OGOH 4S Z OGLGH4S a r ER 410 r om k ALL TESE H LH z HH F BH 90 Fi Wi oa OO H n g4 SZAN JHS IN l g ITA z E F JOST Ir apwann MIQ0SrI086ZUT1 w an i ods JOAZ 7 9 D HARDWARE IMPLEMENTATION FOR ST7DALI EVAL 2 2 PCB The PCB has been designed to look like the add on to an existing ballast design see Figure 8 Gerber files are delivered with the ST7DALI EVAL kit Figure 8 EVAL6574 and ST7DALI EVAL demoboards together 2 3 BILL OF MATERIAL Please refer to the ST7DALI EVAL User Manual 31 8 9 HARDWARE IMPLEMENTATION FOR ST7DALI EVAL THE PRESENT NOTE WHICH IS FOR GUIDANCE ONLY AIMS AT PROVIDING CUSTOMERS WITH INFORMATION REGARDING THEIR PRODUCTS IN ORDER FOR THEM TO SAVE TIME AS A RESULT STMICROELECTRONICS SHALL NOT BE HELD LIABLE FOR ANY DIRECT INDIRECT OR CONSEQUENTIAL DAMAGES WITH RESPECT TO ANY CLAIMS ARISING FROM THE CONTENT OF SUCH A NOTE AND OR THE USE MADE BY CUSTOMERS OF THE INFORMATION CONTAINED HEREIN IN CONNECTION WITH THEIR PRODUCTS Information furnished is believed to be accurate and reliable However STMic
3. U4 and one for the reception U5 For cost reasons the transmission opto coupler cannot sustain the 250mA required to pull the DALI bus down it is high in steady state so a power stage has to be implemented via Q1 For the bus to be kept down during transmission capacitor C7 is used since a voltage must remain on the base of Q1 To avoid a discharge of this capacitor via the optocoupler U5 the diode D6 is required Finally the zener diode D5 is used to ensure that the wide voltage specifications of the DALI bus High level 9 5 to 22 5 V Typical 16 V Low level 6 5 to 6 5 V Typical 0 V can be ful filled The ST7 In Circuit Communication ICC allows In Circuit Programming ICP and In Applica tion Programming IAP Please refer to the FLASH PROGRAM MEMORY section of the ST7DALI datasheet A standard dimmable ballast can be easily driven through the evaluation board with the 1 10V Interface A PWM with programmable duty cycle is generated by the ST7DALI filtered to a DC value proportional to the duty cycle and amplified from 0 5V to 1 10V through to the opera tional amplifier U2A Regardless of whether a ballast is available or not the LED LD3 gives an overview of the light level q 6 9 HARDWARE IMPLEMENTATION FOR ST7DALI EVAL Figure 7 ST7DALI EVAL DALI Slave Schematic aBa WOLTS Sle PTO UOWESIUNLWILWOT 1In241 ui Bl AOL old aIeLAu AOL BL zd Mts OI ALS LIT TZ Ad Gad ON NIT Wa MOT
4. ballast controller Based on this topology a DALI demonstration board based on the ST72F334J4 has been built For this purpose a dedicated ST7DALI has been developed and its associated evalua tion board can be seen in Figure 3 q 2 9 HARDWARE IMPLEMENTATION FOR ST7DALI EVAL Figure 3 ST7DALI EVAL DALI Slave demo board 1 3 HANDLING DALI RECEPTION AND TRANSMISSION WITH DCM PERIPHERAL The major embedded feature of the ST7DALI microcontroller is the DALI Communication Module DCM It allows decoding of the DALI forward frame and sending of the backward frame without any CPU overhead or need for a timer with Input Capture or Output Compare capabilities It simplifies the software saves processing time and eases interrupt manage ment The DCM drivers can be found in the ST7 Software Library or in the AN1601 Software Implementation for ST7DALI_EVAL 1 4 POWER CONSUMPTION CONSIDERATIONS One of the biggest issues when designing a DALI ballast is the power supply of the microcon troller when the lamp is off When the lamp is on supplying all devices can be quite easily done via a charge pump taken from the middle point of the half bridge But in stand by the mi crocontroller should always be powered on and ready to receive a DALI command This en ergy can only come from the mains The current taken should then be as low as possible to avoid constant dissipation ST7DALI has a power saving mode called halt using the smalle
5. od trade off please refer to the I O ports section of the ST7DALI data sheet Here is a summary depending on the frequency chosen Table 2 Power Consumption Overview Halt Mode Run Mode Finally the accuracy of the ST7DALI ADC is directly proportional to the Vpp regulation accu racy If the microcontroller supply is regulated with a standard zener diode for example the ADC precision would be around 10 If precise measurements have to be performed then a voltage regulator with low quiescent current and high precision is needed typically from the LD2980 series Ky 5 9 HARDWARE IMPLEMENTATION FOR ST7DALI EVAL 2 SCHEMATICS AND PCB 2 1 SCHEMATICS Aside from the ST7DALI microcontroller itself the ST7DALI EVAL DALI Slave board has four main sections Power Supply DALI Bus ST7DALI Interface In Circuit Communication 1 10V Interface see Figure 7 The power supply section is very simple A LD2980 provides an accurate 5V output while jumper 4 allows you to easily measure the current used by the power supply the microcon troller and the interface with the DALI Bus The bridge diode protects the DALI Bus ST7DALI interface against wrong polarity wiring how ever it is not protected from over voltage from accidental mains connection between the con trol wires For such protection a high voltage switch is needed Since the DALI Protocol specifies that isolation is required two optocouplers are needed one for transmission
6. power saving mode between commands Up to 15 multi functional I Os one 12 bit Auto reload Timer with 4 PWM outputs input capture and output compare func tions In addition to DALI protocol handling but without fully controlling the ballast the microcon troller can also monitor or customize some ballast parameters e g for easy calibration of var ious power levels in the factory and or act as a supervisor of the complete ballast parameters I Os and PWM outputs to perform the in terface with the ballast controller 1 2 INTERFACE BETWEEN MICROCONTROLLER AND ANALOG HALF BRIDGE CONTROLLER A potential hardware problem is the interface between the microcontroller and the analog half bridge controller One possibility is to use PWM outputs and to filter them to create analog set points for the half bridge controller The 4 PWM outputs of the Autoreload timer enable ST7DALI to act on up to 4 different external parameter pins of the half bridge controller for example L6574 without computation load Please refer to AN993 L6574 amp Microcontroller in ballast applications The designer is then in total control of the lamp Another easier solution is to keep the 1 10V input widely used for dimming level control and use the microcontroller as a gateway or interface between the DALI bus and the analog input of a conventional analog dimmable ballast The microcontroller is then no longer in direct con nection with the analog
7. riod of 256 clock cycles At 8MHz this means around 32us Since the DCM starts sampling 125us worst case after the falling edge the microcontroller frequency can be reduced to 4 9 ky HARDWARE IMPLEMENTATION FOR ST7DALI EVAL 4MHz i e 64us to wake up from halt Although the software can work at 1MHz and still comply fully with DALI it is then not possible to use Halt mode for additional power saving at this frequency because the wake up is not fast enough to catch the beginning of the incoming frame When the lamp is off the microcontroller is not the only source of power dissipation The hard ware interface between the DALI bus and the microcontroller also takes quite some current as shown in Figure 6 Figure 6 DALI Bus ST7DALI interface MISO AIN2Z PB2 MOSI AIN3 PB3 CLKIN AIN4 PB4 PB5 Wake up from Halt DALI IN En q ST7FDALIF2M6 DALI Bus s A SFH6156 2 When the bus is high steady state 500A is always flowing through the resistor Because the microcontroller should always know if the bus is constantly low bus failure an alternative and more power saving topology is not possible On the one hand current in the resistor should be as low as possible but on the other hand it should not be so low that any noise fools the microcontroller When the transistor turns off the current should be high enough to evac uate the carriers within the right time frame 10KOhms is a go
8. roelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use No license is granted by implication or otherwise under any patent or patent rights of STMicroelectronics Specifications mentioned in this publication are subject to change without notice This publication supersedes and replaces all information previously supplied STMicroelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics The ST logo is a registered trademark of STMicroelectronics All other names are the property of their respective owners 2004 STMicroelectronics All rights reserved STMicroelectronics GROUP OF COMPANIES Australia Belgium Brazil Canada China Czech Republic Finland France Germany Hong Kong India Israel Italy Japan Malaysia Malta Morocco Singapore Spain Sweden Switzerland United Kingdom United States www st com 9 9 31
9. st power consumption since everything inside the MCU core peripherals and clock source is frozen After entering this mode only a reset or an external interrupt can wake up the microcontroller The interrupt can be triggered by the first falling edge of the DALI frame When this happens Run mode is not immediately operational mainly because of the stabili zation time of the clock source This time has to be short enough to be able to detect the second rising edge of a DALI frame The first falling edge is not significant but helps to wake up from Halt mode Figure 4 shows on channel 1 the DALI frame on the DALI IN pin of the microcontroller a pulse on channel 3 shows the beginning of the run mode and a high STA 3 9 HARDWARE IMPLEMENTATION FOR ST7DALI EVAL level on channel 4 shows that a proper DALI frame has been received and that the data is ready to be handled by the software Figure 4 Overview of a forward frame reception DALI forward frame 2 ms 2 00 V Wake up from Halt mode interrupt routine H ve m ala end of frame Interrupt 2 ms HALT Mode RUN Mode To better understand how the ST7DALI can wake up fast enough a zoom on the first edge is needed as shown in Figure 5 Figure 5 Zoom on the first edges When the first falling edge is detected the microcontroller leaves Halt mode for a transition pe
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