Document Number: MC34844 Freescale Semiconductor Rev. 10.0, 8/2014 Technical Data 10 Channel LED Backlight Driver 34844 with Integrated Power Supply 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. LED DRIVER Current in the 10 strings is matched to within 2%, and can be programmed via 2 the I C/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 2 the I C/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 2 600 kHz, but may be programmed via I C to 150/300/600/1200 kHz. The PWM EP SUFFIX (PB-FREE) frequency can be set from 100 Hz to 25 kHz, or can be synchronized to an 98ASA10800D 32-PIN QFN-EP 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. Applications The 34844 has a default boost frequency of 320 kHz, but may be 2 programmed via I C to 160/320/650/1300 kHz. The PWM frequency can be set Monitors and HDTV - up to 42 inch from 110 Hz to 27 kHz, or can be synchronized to an external input. If not Personal Computer Notebooks synchronized to another source, the internal PWM rate outputs on the CK pin. GPS Screens This enables multiple devices to be synchronized together. Small screen Televisions 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) 2 I C/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 Freescale Semiconductor, Inc., 2009-2014. All rights reserved.34844 7.0 to 28 V VIN SWA VDC1 SWB VDC2 VOUT VDC3 PGNDA COMP VCC PGNDB SLOPE FAIL SCK ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ Control Unit SDA VDC1 I0 PWM I1 A0/SEN I2 CK VDC1 I3 I4 M/~S I5 EN I6 ISET I7 VDC1 PIN I8 NIN I9 GND Figure 1. MC34844 Simplified Application Diagram (SM Bus Mode) 34844 VIN 7.0 to 28V SWA VDC1 SWB VDC2 VOUT VOUT VDC3 PWM PGNDA COMP VCC PGNDB SLOPE FAIL SCK ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ SDA PWM I0 PWM Control Unit VOUT I1 A0/SEN I2 CK I3 VDC1 M/~S I4 EN I5 I6 ISET I7 VDC1 PIN I8 NIN I9 GND Figure 2. MC34844 Simplified Application Diagram (Manual Mode) 34844 Analog Integrated Circuit Device Data 2 Freescale Semiconductor