Ultra high-precision resistors target portable LED lighting applications

Vishay Precision Group's (VPG) two new ultra high-precision resistors are now available from Farnell elemnt14. The Bulk Metal Z-Foil current sensing resistors are designed to improve LED brightness and efficiency in portable battery-powered applications. Screen brightness is a very important function In portable devices’ LED-backlit LCD displays and it is controlled via an LED panel mounted on the rear of the LCD, which boosts the input voltage connected to the panel. These devices need stable and precise current resistors with low thermal EMF and low absolute TCR to avoid brightness flickering and to control the stability of the LED output voltage. The LED1625 and LED221 provide low TCR of 0.05 ppm/C nominal (0C to +60C) and 0.2 ppm/C nominal (–55C to +125C,+25C ref.), load-life stability of ±0.005%, and tight tolerances to ±0.01%. The LED1625 also offers a 1W power rating and a resistance range from 0.3ohm to 10ohm, while the LED221 features power ratings to 8 W and a resistance range from 0.5ohm to 500ohm. Any conceivable value within the devices' resistance ranges, to six digits, is available with no additional cost or lead-time effect, says the company.