Page 28

EETE JAN 2014

ANALOG & MIXED SIGNAL DESIGN Latching digital Hall-effect sensor IC has built-in pull-up resistors Honeywell Sensing and Control’s latest latching Hall-effect sensor ICs, the SS360PT and SS460P feature built-in pull-up resistors and provide reliable switching points with a high magnetic sensitivity of 30 Gauss typical, at 25°C, and 55 Gauss maximum over the full -40 to 125°C temperature range. This allows the use of smaller magnets or a wider air gap. These sensor ICs do not use chopper stabilization on the Hall element, providing a cleaner output signal and a faster latch response time when compared to competing chopper-stabilized, high sensitivity Hall-effect bipolar latching sensor ICs. Latching magnetics make these sensors well-suited for accurate speed sensing and RPM (revolutions per minute) measurement. The sub-miniature, SOT-23 surface mount package (SS360PT) allows for compact design with automated component placement. The small, leaded, flat TO-92- style package (SS460P) allows for a compact PC board layout design. The devices operate from 3 Vdc to 24 Vdc, with built-in reverse voltage capability to further protect the sensor and the circuits. Honeywell www.honeywell.com Backlight panel LED driver ICs include voltage step-up controller Ams has posted detail of a series of high precision LED controllers with PWM input for driving external bipolar transistors in LED backlight panels, also optimised for 2D and 3D operation in TV applications. AS3834/3834B are 4 channel devices with integrated step-up controller to provide the necessary output voltage for the LED string supply. The SMPS feedback control optimises the power efficiency by adjusting the LED string supply voltage. Output current is up to 270mA per channel and built-in safety features include under-voltage and thermal shutdown as well as open and short LED detection. The AS3833 is a 6 channel LED controller with a similar specification, delivering output current up to 250mA per channel. Ams www.ams.com LDO adds features for monitoring, protection & cable drop compensation Linear Technology’s LT3086 is an addition to the LDO+ family, with features previously unavailable in linear regulators. The 40V, 2.1A low dropout linear regulator (LDO) includes current monitoring with externally settable current limit and temperature monitoring with external control of thermal limit temperature. The device includes a programmable power good status flag, cable drop compensation and easy paralleling. The current reference in the LT308x LDO family provides regulation, independent of output voltage. The LT3086 features a 1.4V to 40V input voltage range. A single resistor programs output voltage from 0.4V to 32V and dropout voltage is 330 mV at 2.1A. Line and load regulation is to 0.1%, independent of output voltage. The trimmed, precision 50 μA current reference is ±1% accurate, providing ±2% output voltage tolerance over line, load and temperature. Output voltage regulation, bandwidth, transient response and noise (40 μVRMS) remain independent of output voltage due to the device’s unity-gain voltage follower architecture. Internal circuitry allows paralleling of multiple LT3086s for higher load current and heat spreading without needing external ballast resistors. Programmable cable drop compensation cancels regulation errors caused by line drops to the load. Output current and temperature monitoring, in addition to a power-good flag with programmable threshold, provide system monitoring and diagnostic/debug capability. Internal fault circuitry includes thermal shutdown and current limit with foldback. Thermal limit and current limit are externally programmable. The device’s reverse battery and reverse current protection add robustness to the end design. The LT3086 is offered in a variety of thermally enhanced surface mount packages, including a low profile (0.75 mm) 16-lead 4x5mm DFN, a 16-lead thermally enhanced TSSOP and a 7-lead DD-Pak; all dissipate 2W in surface mount applications with no heat sink. The LT3086 is also available in a 7-lead TO-220 power package for vertical mounting. Linear Technology www.linear.com/product/LT3086 LED driver is optimized for dimmable off-line LED bulb/tube applications Supertex has introduced a constant frequency (67kHz), constant duty cycle LED driver optimized for dimmable offline LED bulb/tube applications, providing high power factor correction (PFC). The PS30 is intended to drive a single switch, single inductor power converter (flyback for isolated version and buck-boost for non-isolated version) directly from AC line, 110 V or 220 V, for power levels up to 20 W. PS30DB1 demo board provides a 6.3 W design solution, achieving 93% PFC and greater than 81% efficiency with ±4% current accuracy. The device can be modified for other power levels up to 20 W. PS30 offers smooth dimming to extinction for a wide variety of dimmer types such as leading edge dimmers, trailing edge dimmers, and dimmers with microprocessor controls. The device implements a PFC LED driver solution, operating from a 10V shunt regulator derived from the power supply snubber, and provides for a simple design by eliminating feedback components and the optocoupler typical in isolated solutions. The device minimizes line induced brightness variation, and protects against open circuit failure with over voltage protection. Two novel features, covered by filed patents, enhance the performance and value of PS30. The device is designed to implement a simpler, lower cost open loop solution. The potential limitation of open loop design is that the output choke tolerance normally results in variation in output current amplitude across product builds in production. PS30 includes proprietary control techniques that largely mitigate this output current variation. Supertex www.supertex.com 28 Electronic Engineering Times Europe January 2014 www.electronics-eetimes.com


EETE JAN 2014
To see the actual publication please follow the link above