I expect there will be lots of Smartphone designers who will welcome the arrival of Intersil’s ISL98611 power management IC which integrates the display power and backlight LED driver functions in a single chip. The ISL98611 also has a so-called hybrid dimming feature which Intersil says will improve display brightness uniformity and color consistency.
The highly integrated ISL98611 has a boost regulator, LDO and inverting charge pump for generating two output rails at +5V and -5V in a single device. It also includes a boost regulator with 3-channel current sinks for the LED backlight driver.
Their single-chip solution offers designers four key benefits. They’ve done such a good job of describing them that I’ll simply post them verbatum:
• Extended battery life: When used for web browsing and emails, a smartphone’s backlight LEDs and display power consume the majority of its battery power. The ISL98611 backlight LED driver delivers seven percent higher efficiency (up to 93 percent) than competitive multi-chip solutions and generates +/-5V display power supplies with greater than 88 percent efficiency at 15mA load using a 2.5x2mm2 size inductor, compared to 85 percent efficiency of the nearest competitor.
• Improved display uniformity: The ISL98611 provides excellent LED current matching at very low LED current: it achieves +/- 2.2 percent matching down to 1mA and +/- 2.8 percent at 50μA.
• Improved display color consistency: The ISL98611 includes hybrid dimming to eliminate white LED color shift issues at low LED current, which occur with DC dimming.
• Smallest footprint: The ISL98611’s total display power plus backlight solution uses 24 percent less PCB area compared to the competition, while requiring only eight external components. This provides additional space to house the phone’s battery.
Lee’s Take: Bravo Intersil! If the ISL98611 performs as-promised, you’ve got a winner on your hands. What designer could say no to a device which saves them precious board space while adding much-needed slack to their power budget? And the hybrid dimming capability is icing on the cake. I’m not an expert on displays but I’ve written enough about the challenges involved with maintaining consistent white values across a wide dimming range and think Intersil’s approach may be an excellent solution. I’d have to see some test results before I was entirely confident but if it works as claimed I suspect that Smartphones will be only the first of several high-volume products where it will be warmly welcomed. I’d also like to take some small exception to Intersil’s claims that the ISL98611’s improved efficiency can increase smartphone battery life by an hour or more. Given the company’s excellent track record in power and analog devices, I’m confident it delivers excellent efficiency but the power draw and battery capacity of these devices varies significantly between models and I’d expect the added run time made possible by the ISL98611 to do the same.
ISL98611 features and specs:
• Powers two or three strings of backlight LEDs with up to 93 percent efficiency
• Generates +/-5V display power supplies with 88 percent efficiency at 15mA load using a 2.5x2mm2 size inductor
• Analog, PWM and hybrid dimming
• +/-2.2 percent current matching down to 1mA and +/-2.8 percent at 50μA
• 2.5V to 5V input voltage range
• VP and VN output adjustable from +/4.5V up to +/-6V with 50mV steps
• I2C, adjustable output voltage settings
• 1uA shutdown supply current
Source: http://www.edn.com/electronics-products/electronic-product-reviews/other/4433623/Integrated-display-power-and-LED-driver-IC-improves-Smartphones–battery-life—display-quality
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