Maxim’s White-LED Charge Pumps Integrate Camera Support
Maxim Integrated Products introduced the MAX8645X/MAX8645Y, which it claims are the smallest white-LED (WLED) drivers with two built-in LDOs for camera supply. These charge pumps are said to reduce total required area by 40% by integrating white-LED (backlight) drivers, camera-flash drivers, and camera power supplies into a single IC. These devices are suitable for flip, folder, and slide-style cell phones and smartphones in which the liquid-crystal display (LCD) and camera module are located in the upper half of the phone, and space is at a premium.
The MAX8645X/MAX8645Y integrate two programmable 200mA LDOs for powering the camera module. These LDOs feature low-noise (40µVrms, typ) performance to ensure a clean, stable power source during image acquisition. This is particularly important for minimizing picture noise with the high-resolution cameras typically used in current and next-generation cell phones. Two control pins allow for the selection of nine different output-voltage combinations, which simplifies ordering and stocking requirements.
The use of a charge-pump regulator enables the thinnest of designs, as no inductor is required. Additionally, use of a proprietary adaptive 1x/1.5x/2x charge pump and very-low-dropout current regulators enable exceptional 85% efficiency (PLED/PBATT over Li+ battery life). The MAX8645X/MAX8645Y provide 1MHz fixed-frequency switching, which allows for tiny external components and further reduces total solution size. These devices drive six WLEDs at up to 30mA/LED with 5-bit dimming resolution and 0.2% (typ) current matching; they also drive two flash LEDs at up to 200mA/LED with 5-bit resolution. Dimming control can be accomplished using either a simple 2-bit logic interface, or, for finer resolution, the logic pins can be connected together and used as a serial-pulse interface. Other features include soft-start to reduce in-rush current and a proprietary thermal-derating function, which protects the LEDs by scaling back the drive current at high operating temperatures.
The MAX8645X/MAX8645Y are available in tiny, 4mm x 4mm x 0.8mm TDFN packages, and they are fully specified over the extended temperature range (-40 to +85°C). Prices start at $2.81 (1000-up, FOB USA). An evaluation kit is available to speed designs.
