NXP MC34844

Description

The 34844 is a SMARTMOS high efficiency, LED driver for use in backlighting LCD displays from 10" to 20"+. Operating from supplies of 7.0 to 28 V, the MC34844 is capable of driving up to 160 LEDs in 10 parallel strings. Current in the 10 strings is matched to within 2%, and can be programmed via the I2C/SM Bus interface.The 34844 also includes a Pulse Width Monitor (PWM) generator for LED dimming. The LEDs can be dimmed to one of 256 levels, programmed through the I2C/SM Bus interface. Up to 65,000:1 (256:1 PWM, 256:1 Current DAC) dimming ratio.The integrated boost converter generates the minimum output voltage required to keep all LEDs illuminated with the selected current, providing the highest efficiency possible.The 34844 has an integrated boost self-clock at a default frequency of 600 kHz, but may be programmed via I2C to 150/300/600/1200 kHz. The PWM frequency can be set from 100 Hz to 25 kHz, or can be synchronized to an external input. If not synchronized to another source, the internal PWM rate outputs on the CK pin. This enables multiple devices to be synchronized together.The 34844 has a default boost frequency of 320 kHz, but may be programmed via I2C to 160/320/650/1300 kHz. The PWM frequency can be set from 110 Hz to 27 kHz, or can be synchronized to an external input. If not synchronized to another source, the internal PWM rate outputs on the CK pin. This enables multiple devices to be synchronized together.The 34844 also supports optical/temperature closed loop operation and features LED overtemperature protection, LED short protection, and LED open circuit protection. The IC includes overvoltage protection, overcurrent protection, and undervoltage lockout.

Features

• Input voltage of 7.0 to 28 V
• 2.5 A integrated boost FET
• Up to 80 mA on the 34844 LED current per channel
• 90% efficiency (DC:DC)
• I2C/SM Bus interface
• 10 channel current mirror with ±2.0% current matching
• Boost output voltage up to 60V, with Dynamic Headroom Control (DHC)
• PWM frequency programmable or synchronizable from 110 to 27,000 Hz
• 32-Ld 5x5x1.0 mm TQFN Package

Typical applications

• Small screen Televisions
• Personal Computer Notebooks

More information

• Datasheet
• IC product information