Diodes has added to its Zetex range of continuous-mode inductive step-down LED drivers, acquired when it bought UK-based Zetex earlier this year.

"The three miniature drivers offer improved accuracy and thermal performance," said Diodes. "Provided in TSOT23-5 and thermally enhanced DFN6, the ZXLD1352, 1356 and 1366 deliver adjustable output currents of 350mA, 550mA and 1A respectively."

Similar to the firm's 1360, the '56 and '66 have an improved output current accuracy - 2.5% worst case and typically better than 1%.

"For one lamp, the eye will not be able to distinguish 50% change in current. However the eye is sensitive to differential brightness changes of less than 5%," said Diodes spokesman Ronnie Doctor. "The real issue is brightness matching and the build-up of tolerances in multiple strings of LEDs were the matching requirement is better than 4% per string. As the sense resistor to set the current is usually 1%, you need a better than 3% to avoid tolerance build up."

Both work from up to 60V, differing only in their internal power switches and delivering 30 and 48W respectively.

Whereas the '60 comes only in a 2.8x2.9mm 82 deg C/W TSOT23-5, the '66 is also available in a larger (3x3mm) 44 deg C/W DFN3030-6.

"These TSOT23-5 and DFN6 packaged drivers will support up to 15 LEDs," said Doctor.
Operating from a 7V to 30V, the TSOT23-5 1352 is an upgrade of the earlier 1350: moving from a 100:1 dimming range at 500Hz, said Doctor, to 1,000:1.

It provides up to 8W to chains of up to 10 LEDs.

In all the chips, nominal output current is set by a resistor and brightness is adjusted by varying the duty cycle or DC voltage on a pin.

A low level control signal turns the output off and puts the driver into standby. Three discrete external components are required.

See http://www.diodes.com or http://www.zetex.com