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pulse Linear’s approach is to use a small transformer per cell with the IC acting as a fault-protected controller IC for transformerbased bidirectional active balancing. The part uses a nonisolated bidirectional synchronous flyback topology to balance up to six series-connected cells. Charge can be transferred to or from a selected cell and 12 or more adjacent cells. All balancers can operate independently and simultaneously with charge/discharge currents up to 10A. Bidirectional operation and simultaneous balancing minimises the time required to equalise the stae-of-charge in the stack, and the parts’ high transfer efficiency (up to 92%) enables high current balancing with minimal power dissipation. You control each individual balancer via a level-shifting SPIcompatible serial interface which enables multiple LTC3300-1 devices to be connected in series, without optocouplers or isolators – this is an approach Linear has developed with previous cell-balancing ICs. Linear has, previously, introduced precision monitor ICs such as the LTC6803-1, that have the dynamic range to accurately measure the small increments that represent state-of-charge differences. The part’s stackable architecture together with interleaved transformer connections enable efficient balancing of every cell in an arbitrarily long string of series-connected batteries, even at the level of packs with a voltage of over 1000V. The chip integrates all associated gate drive circuitry, precision current sensing, fault protection circuitry and serial data interface, together with watchdog timer and cyclic redundancy check (CRC) data error checking are integrated. It comes in thermally-enhanced surface-mount compatible packages: a low profile (0.75mm) 48-lead 7 x 7mm QFN and a 48-pin 7 x 7mm LQFP package. Operating junction temperature range is -40°C to +125°C and the part costs $5.95 (1000). www.linear.com/product/LT C3300-1 Smallest ARM-based MCU, claims Freescale Kinetis KL02, packaged in an outline of 1.9 x 2.0 mm lays claim to being the smallest-available microcontroller with an ARM core: Freescale intends that you use it in small, connected devices or the “Internet of Things” - or any space- and powerconstrained application. The chip hosts an ARM Cortex-M0+ processor, configured with analogue and communication peripherals. Small physical size is enabled by use of waferlevel chip-scale packaging (CSP) that connects the die directly to the solder ball interconnects and, in turn, to the PCB. This, Freescale observes, removes the need for bond wires or interposer connections, reducing die-to-PCB inductance and improves thermal conduction and package durability for physically harsh environments. The KL02 device is the third CSP MCU in the Kinetis portfolio, joining the larger 120/143- pin Kinetis K series K60/K61 variants. The KL02 sets a new minimum power level for the Kinetis family at 15.9 CM/mA; that is, the benchmark “CoreMark 1.0” rating – the conditions under which this was measured are profiled in the note below. Rated otherwise, Freescale puts the performance at 50 μA/MHz with a 4-μsec wake-up time. Kinetis KL02 has sufficient processing power for complex algorithms, commuications stacks and human-interfaces, Freescale asserts: the chip also includes autonomous, poweraware peripherals (in this case, an ADC, UART and timer), 10 flexible power modes and extensive clock and power gating to minimise power loss. A low-power boot mode reduces power spikes during the boot sequence or deep sleep wake-up. This is useful, Freescale says, for systems in which battery chemistry limits the allowable peak current, such as those employing lithium-ion batteries frequently used in portable devices. Onchip is a 48-MHz ARM Cortex-M0+ core, operating over 1.71 to 3.6V; a bit manipulation engine for faster, more code-efficient bit-oriented mathematics; 32 KB of flash memory and 4 KB of RAM; a fast 12-bit ADC and a fast analogue comparator; and a range of low-power serial interfaces. There are also timers for applications including motor control. You can develop systems on the “stackable” Freedom/Tower platform, with access to all of the usual sources of ARM code development tools. There is a software generation tool for creating device drivers and writing start-up code (Processor Expert/Solutions Advisor) and you can use Freescale’s MQX real-time operating system. Rated for operation over -40 to +85C, the chip begins sampling now and will be in production in July 2013: volume (100k) pricing is $0.75.- by Graham Prophet CoreMark 1.0 configuration: 108.69/IAR for ARM V6.50 --debug --endian=little --cpu=Cortex-M0 -e --fpu=None -Ohs --use_ c++_inline/Code in internal FLASH, Data in internal RAM, Stack/ Processor operating frequency = 48MHz, operating voltage 3.0V Freescale, www.freescale.com/Kinetis/KL02CSP 12 EDN Europe | MARCH 2013 www.edn-europe.com


EDNE MARCH 2013
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