IXYS intros demo boards for new LED driver family

MILPITAS, USA & BIEL, SWITZERLAND: IXYS Corp. has released demo boards for the LDS8710/11, LDS8720/24/26, an innovative inductor-based, high efficiency family of LED drivers that eliminates the external Schottky diode normally used in the rectification loop.

The LDS8711 uses a patent pending SmartOne Wire Interface to set maximum LED current in the range from 0.5 to 32 mA in 0.25 mA steps and PWM dimming control and it is able to drive a string of 10 WLEDs.

The LDS8710 drives a string of 10 LEDs with factory-preset maximum LED current values of 20, 25 and 30 mA with 1 percent accuracy and it uses PWM dimming to adjust LED brightness. LDS8720/24 and LDS8726 use PWM dimming to adjust the LED brightness and are able to drive up to 40 LEDs and 42 WLEDs, respectively, at 30 mA current each. The LED drivers provide full output power from a single-cell Lithium-Ion battery or supply voltage in the range from 2.7 to 5.5 V.

LDS8710/11/20/24/26 family demo boards
Demo boards are a two-layer fully assembled and tested surface mount boards, which provide easy probe access points to all LED Driver’s inputs and outputs allowing the user to quickly connect and measure electrical characteristics and waveforms. Demo boards contain one driver with LED matrix corresponding to the maximum number of LEDs that may be driven by a particular driver.

The LED matrix common wire has a 1-ohm 1 percent resistor in series that allows easy current measurement without circuit interruption. Every 1 mV of voltage drop across this resistor is equal to a 1mA LED current. The test points allow direct current measurement of the drivers. To measure the current across the LED, a current meter should be connected instead of a 1-ohm resistor.

The demo boards allow both internal and external LED brightness control. Jumper is used for selection between an internal PWM generator and an external signal source. The external PWM input is TTL compatible. The Demo boards can be powered either from three AAA alkaline batteries inserted in the battery holder, or from an external voltage source connected between the GND and Vin pin.

The LDS8710/11 are ideal for (up to 7”) LCD display backlight applications such as smart phones, portable multimedia devices, E-books, personal navigation systems, personal medical displays and digital photo frames where battery life, display size, resolution and brightness are critical.

The LDS8720/24/26 are ideal for (up to 15”) LCD display backlight applications such as automotive displays, GPS, NetBooks, laptop PCs, tablet computers and industrial and medical displays. Both device families are suitable to drive high brightness LEDs for lighting applications, such as battery powered high intensity flash lights, security lights, automotive lights and street lights.

Coupled with the Zilog micro-controllers (MCUs), and the Zilog motion sensing technology, with these drivers, IXYS provides the whole system solution for automated high efficiency lighting control based on occupancy and as needed.

Each device in the family is a fixed frequency current-mode boost converter with a cycle-by-cycle current limit and features a patent pending, integrated synchronous rectifier, which eliminates the external Schottky diode and the need for complicated and costly isolation FETs. This reduces the bill of material and footprint of the display subsystem and also simplifies the design-in process and time to market of the end product.

The LDS8710/11/20 drivers are fixed 0.7MHz frequency drivers, while the LDS8724/26 drivers operate at 1 MHz. The devices offer a wide PWM dimming frequency range (100Hz to 10 KHz) and a robust protection system (over-voltage, over-temperature, under-voltage and over-current), while the shut down current is below 1 microamp.

The LDS8710/11 drivers do not need an external current-sense resistor and this further simplifies the system; the LDS8720/24/26 drivers require an external current-sense resistor to set LED current.

Since this family of LED drivers operates at a high switching frequency, small low profile passive components (10-33 microhenry inductors and 1 microfarad 50V ceramic capacitor) can be used, which further reduces the system’s bill of material cost and allows a thin profile of the backlight unit. The system achieves higher than 86 percent efficiency.

All devices are available in a tiny 2x3x0.8 mm 8-pin TDFN package.