16-channel LED backlight driver enhances TV picture quality with advanced dimming capability
The iW7025 was developed by Dialog’s Power Conversion Business Group (formerly iWatt Inc.) and extends Dialog’s addressable market into the LCD TV backlighting power management space.
Dialog’s patented AnyMode dimming claims to give TV OEMs the industry’s most comprehensive dimming options to improve picture quality and the most extensive set of short protection features to prevent circuit failures and safety issues.
A key challenge for LED TV designers is how to easily reduce motion blur and deliver a high contrast ratio. With conventional LED drivers this requires complex calculations and algorithms to configure the LED current phases to optimally synchronize the LCD panel backlight to the video frame refresh rate. The iW7025’s AnyMode dimming solves this issue by providing comprehensive, simple and flexible dimming options that improve LED TV picture quality and reduce design complexity. These dimming modes include high frequency pulse width modulation (PWM) up to 4 kHz, scanning-mode PWM, configurable phase-shift, 8-bit analog, 13-bit local and hybrid dimming.
AnyMode dimming enables continuous PWM signals or burst PWM signals that are fully synchronized to the video frame at the same or higher frequency. The PWM duty cycle can be updated in each video frame and with user-configurable tail or head delays. This gives designers more options to reduce motion blur and improve the contrast ratio. A built-in phase-locked loop (PLL) further ensures jitter-free operation even with a noisy VSYNC signal.
The iW7025 also helps TV OEMs address safety and reliability issues by incorporating the most robust short detection and protection features. These include individual LED short, channel-to-channel short, current sink MOSFET drain-to-source short, bipolar junction transistor (BJT) collector-to-emitter short, current sense resistor short, and chip-to-chip string short protection across multiple LED drivers. LED open-fault detection and over-temperature protection are also included.
The rich features of the iW7025 make it an ideal choice for edge-lit and direct-lit LED LCD TV designs. The iW7025 uses external LED current sinks and up to two external DC converters (boost, buck, LLC, etc.) for the LED driver to enable easy current and voltage scaling (600 mA or more per channel and Vout to 85 V maximum). This allows designers to source one part type to meet requirements spanning medium- to large-size LCD TVs and monitors.
The iW7025 reduces the bill of materials (BOM) cost in a number of ways. The digital control engine generates the PWM wave form and manages all fault conditions, eliminating the need for expensive microcontrollers. In addition to external MOSFETs, the iW7025 supports lower cost BJTs for further BOM cost savings. The 85V drain sensing capability removes the need for external diodes usually required for LED short-circuit fault management, as well as cascodes or zener clamps typically required for protection. A wide, 10V to 28V input supply voltage range makes the iW7025 compatible with existing TV power systems, eliminating the need for a separate voltage rail.
The PWM dimming range of the iW7025 is 0% to 100%, with 13-bit resolution. Precise control of the PWM output position and the PWM duty cycle offer the flexibility to support both patterned retarder (PR) and shutter glass (SG) 3D technologies, while hybrid dimming lets users mix PWM and analog dimming modes to maximize system efficiency. Phase-shift dimming allows the use of smaller output capacitors, eliminating audible noise, improving electromagnetic interference (EMI), and lowering cost.
The iW7025 provides high, ±2% channel-to-channel matching accuracy and ±0.5% absolute current accuracy to deliver uniform brightness across the entire display. The device comes in two package options: a 64-pin, 10 mm x 10 mm, thin QFP with 0.5 mm pitch and a 64-pin, 14 mm x 14 mm, thin QFP with 0.8 mm pitch, both with pin-outs optimized for single-layer PCB layout.
iW7025’s SPI daisy-chain interface simplifies design when supporting more than 16 LED strings.
Availability and Pricing
The iW7025 is available now in production quantities and is priced at $1.54 each in 1000-piece quantities, for either the 64-pin 10 mm x 10 mm TQFP or 64-pin 14 mm x 14 mm TQFP package.
More information about the iW7025 16-channel LED backlight driver at
https://iwatt.com/files/iw7025-product-brief/
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