EETimes India - September 16-30, 2008 - (Page 14) In Focus | Green Tech Use non-maskable interrupt to manage dynamic power in MCUs continued from page 12 Events ISA Solar PV Conclave 200 Sept. 29, 2008 New Delhi RESET function as the primary pin configuration (Figure 3). An RC circuit with optimal RC time constant is placed across the RST/NMI pin of MCU to ensure that power is not drained from the coin cell in the absence of a main power supply. The presence of the RC circuit makes the RESET pin sense logic low after 2.3RC seconds, and hence the software present on the MCU must configure RST to NMI pin functionality before this time constant. dramatically increase the life span of non-rechargeable coin cells. RTC value * Time taken to update RTC value)) / (Timer resolution) = ((Ilow * T1) + (Ihigh * T2)) / T = ((Ilow * (T – T2)) + (Ihigh * T2)) /T = (0.8 * (1,000 – 10) + (1,000 * 10))/ (1,000) = 10.792μA Design benefits Consider that the MCU is running from a coin cell (non-rechargeable) of 20mAh capacity. The typical power consumption of an MCU (MSP430) in its normal (running) power state is 3mA; by comparison, it consumes less than 1μA of current in its lowpower state. The lifetime of the coin cell is calculated using the following equation: Coin cell life time (in hr) = Battery capacity (mAh) / MCU current consumption (mA). If the MCU is allowed to run in its normal state at all times, then the coin cell will last for less than 7hrs in the absence of other sources; but if the MCU is intelligently switched to its lower-power state most of the time, the battery can last as long as 20,000hrs (i.e. more than 2 years). Thus, implementing the power management scheme can Scheme limitations Consider the timer module of an MCU used for RTC in its normal state with millisecond resolution—i.e. the timer interrupt occurs every 1ms to update the RTC value. When the MCU switches to its low-power state, all its peripherals are turned off except for the timer required to keep the RTC value updated. T1 is the amount of time MCU is present in low-power state; T2 is the time taken to update the RTC value; T = Timer resolution/Time interval between two successive timer interrupts; Ilow = MCU low-power state current consumption = 0.8μA; and Ihigh = Current consumption by MCU to update RTC value =1mA. Lowpower current consumption by the MCU (MSP430) is 0.8μA, but every time an RTC value update is performed, current consumption goes up to 1mA. Assume that the MCU program takes a minimum of 10μs to update the RTC value. If the timer is allowed to run at millisecond resolution when the MCU switches to low-power state, then the average current consumption by MCU is given as follows: Average current consumption by MCU = ((MCU low power state current consumption * Amount of time the MCU is present in its low power state) + (Current consumption by the MCU to update the The annual conference addresses the needs of the evolving PV sector in India. View more. Cleantech Oct. 7-9, 2008 Mumbai If the timer is allowed to run at a second resolution (i.e. a resolution of one second) when the MCU switches to its low-power state, then the average current consumption by MCU is as follows: = ((Ilow * (T – T2)) + (Ihigh * T2)) /T = (0.8 * (1,000,000 – 10) + (1,000 * 10)) / (1,000,000) = 0.809992μA The forum connects Indian investors, technology innovators, policymakers and clean technology influencers with their counterparts from Asia, Europe, North America, the Middle East and elsewhere. View more. Embedded Systems Conference India Sept. 25 to 26, 2008 Hyderabad Sept. 29 to 30, 2008 Pune Oct. 7 to 8, 2008 Noida Oct. 14 to 17, 2008 Bangalore Thus, the current consumption by the MCU in its low-power state with the timer configured to run at a second resolution is over 10 times lower than when the timer is configured to run at a millisecond resolution. This current consumption value is almost equal to the low-power current consumption of the MCU with all its peripherals turned off including the timer module. Read the full article to learn more about MCU interrupts in embedded systems. | ESC India 2008 offers a combination of informative, technological presentations and an exhibition of embedded products from the world’s leading companies operating in the embedded space. View more. More events Online Imp rove immuni t y o f M CU - b as e d embedded design Integrate SMPS control in LED applications Expert creates large-area solar cell using nanotech shobhan says, “Solar panels are being used by Indian Railways to power interlocking arrangements and signalling systems The experience has been encouraging as dependence on the local grid has been reduced… White LED flash drivers brighten DSCs continued from page 10 example is 33 per cent more efficient at producing light than the LED in the first one. Converter efficiency, while important when flash LED drivers are running in a continuous movie/torch mode due to potentially long on-times, is not as important in the traditional sense during a flash condition due to the short duration. What is important is that higher efficiencies allow a higher amount of output power to be delivered to the flash LED for a given input power, allowing for a brighter flash. Picking a flash LED with high luminous efficacy in conjunction with an efficient flash LED driver can help minimise the current drawn off of the battery during a flash event, allowing the handset designer more flexibility in the power management scheme for the rest of the system. Read the full article to learn more about optimising light output, increasing the drive current and much more. Online | More online Introduction to low-power As power starts to replace performance as the key competitive aspect of SoC design, new methodologies are emerging based on the CPF standard. Read this first chapter of Cadence Design Systems’ e-book on low-power design. How to implement small LCD backlighting-LED driver considerations How to design a microcontroller-based three-channel LED driver 14 EE Times-India | September 16-30, 2008 | www.eetindia.com http://www.eetindia.co.in/STATIC/REDIRECT/Newsletter_080916_ISA.htm http://www.eetindia.co.in/STATIC/REDIRECT/Newsletter_080916_cleantech.htm http://www.eetindia.co.in/STATIC/REDIRECT/Newsletter_080916_esci.htm http://www.eetindia.co.in/EVENT_DISPLAY_EE.HTM?ClickFromNewsletter_080916 http://forum.eetindia.co.in/FORUM_POST_1000039165_1200084439_0.HTM?ClickFromNewsletter_080916 http://www.embeddeddesignindia.co.in/ART_8800543556_2800001_TA_b3d74d00.HTM?ClickFromNewsletter_080916 http://www.embeddeddesignindia.co.in/article/emailToFriend.do?articleId=8800543556&catId=2800001 http://www.embeddeddesignindia.co.in/article/sendInquiry.do?articleId=8800543556&catId=2800001 http://www.eetindia.co.in/ART_8800525398_1800002_TA_abed098c.HTM?ClickFromNewsletter_080916 http://www.eetindia.co.in/ART_8800534593_1800010_TA_d8fa9703.HTM?ClickFromNewsletter_080916 http://forum.eetindia.co.in/?ClickFromNewsletter_080916 http://www.eetindia.co.in/ART_8800543557_1800010_TA_4a4352a5.HTM?ClickFromNewsletter_080916 http://www.eetindia.co.in/ART_8800543338_1800000_TA_a787f238.HTM?ClickFromNewsletter_080916 http://www.eetindia.co.in/article/email_friend.php3?article_id=8800515679&type=TA&cat_id=1800000&back_url=%2Farticle%2Farticle_content.php3%3Fin_param%3D8800515679_1800000_TA_427b9233%26 http://www.eetindia.co.in/article/emailToFriend.do?articleId=8800543557&catId=1800010 http://www.eetindia.co.in/article/sendInquiry.do?articleId=8800543557&catId=1800010 http://www.eetindia.co.in/ART_8800512630_1800010_TA_634e642b.HTM?ClickFromNewsletter_080916 http://www.eetindia.co.in/ART_8800511465_1800000_TA_023cd5b0.HTM?ClickFromNewsletter_080916 http://www.eetindia.com/STATIC/REDIRECT/Newsletter_080901_EETI02.htm?ClickFromNewsletter_080916
For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.