The new LED driver family is perfect for applications like smart phones, portable multimedia devices, personal navigation systems and digital photo frames where battery life, display size, resolution and brightness are critical.
Each device in the new LED driver family features a patent-pending, integrated synchronous rectifier which abolishes the external Schottky diode and the requirement for complicated and costly isolation FETs. This decreases the bill of material and footprint of the display sub-system, and simplifies the design-in process and time to market of the end product.
The new LED driver drives up to 10 LEDs with factory-preset maximum LED current values of 20, 25 or 30mA with 1% accuracy. This removes the requirement for an external sense resistor and further simplifies the system. Since the new LED driver family operates at a fixed switching frequency, small low profile passive components (10 – 22 mH inductors and 0.1 mF high voltage ceramic capacitors) can be utilized, which further decreases the system’s bill of material and enables for a thin backlight unit profile. Moreover, the use of the 40V rated integrated synchronous rectifier makes the efficiency dependent upon only one external component parameter: the inductor DCR. This further simplifies the system design, while simultaneously achieving greater than 83% efficiency.
We are pleased to bring to the market the first LED Driver family featuring our patent-pending integrated synchronous rectifier. This novel architecture has been thought out with one main goal in mind: simplify our customers’ design experience and accelerate their time-to-market, stated Donato Montanari, vice president at Leadis. By reducing the number of external components, allowing customers to pre-select maximum current ratings, implementing robust protection (over voltage, under voltage, over temperature and over current) and offering wide PWM dimming frequencies (100Hz to 10K Hz), every feature of the LDS8710 family is meant to improve our customer’s time-to-market and reduce their bill of material.
About the LDS8710, LDS8716 and LDS8714:
The new LED driver is a fixed 0.7MHz frequency, current mode, boost converter with internal 40V rated synchronous rectifier and cycle-by-cycle switch current-limit. The device operates down to 2.5V to accommodate new chemistry Li-ion single-cell batteries or two-cell alkaline batteries. Under-voltage protection disables the part at a threshold of 2.1V. Thermal shut-down is set at 150 degrees C, above which the boost converter stops switching. Normal operation is resumed when the temperature drops below 130 degrees C. Output over-voltage protection prevents system damage if one LED is accidentally disconnected. The EN/PWM pin functions both as logic chip-enable pin with low shut down current (< 1uA) and as LED-current PWM control pin. The LDS8710, LDS8716 and LDS8714 are available in a tiny 2 x 3 x 0.8 mm 8-pin TDFN package. Samples of the LDS8710 are available now. Samples of the LDS8716 and LDS8714 are scheduled for availability in June 2009.
