Controlled brightness

Vishay Intertechnology

has released two new white LED drivers that are said to deliver high efficiency up to 80% during operation in compact handheld and battery-operated electronics.

The new SiP12401 boost controller and SiP12501 boost converter are optimised to provide controlled brightness in applications including white LED backlighting for LCD displays in portable electronics such as cell phones and digital cameras.

The SiP12401 boost controller IC uses double-cell NiMH or Alkaline and Li-ion batteries to drive white LEDs connected in series for uniformly bright backlighting without the need for ballast resistors. It supports an input voltage range of 1.8 V to 5.0 V.

Designed to drive white LEDs connected in parallel, the SiP12501 is a boost converter IC for single or double-cell NiMH or Alkaline battery packs. An internal low-threshold power MOSFET allows the device to start up with a low battery voltage of 0.65 V.

The SiP12501 accepts input voltages from 0.65 V to 3.3 V and regulates an output current up to 60 mA from a 0.9-V input. The performance of the converter is enhanced through thermal shutdown protection and anti-ringing control that minimises EMI.

Both devices are said to feature a voltage-mode PWM design with internal frequency compensation to help reduce overall component count and enable design of smaller, lighter end products.

For prolonged battery life, operation in PWM mode with 600-kHz switching yields high typical efficiency of 80% and 75%, respectively, for the SiP12401 and SiP12501. The LED current may be adjusted externally for analogue control over intensity. Logic-controlled shutdown is provided with one microamp of standby current.

Samples and production quantities of the new SiP12401 and SiP12501 are available now, with lead times of six to eight weeks for larger orders.