Semtech Releases Charge Pump Platform For LCD Backlight, LED Flash and Camera Module Power In Cellular Phones

Semtech Corp. announced the SC62X family of ultra-small (3.0 x 3.0 x 0.6 mm) and highly programmable charge pumps for providing backlight, flash and camera module power in mobile phones.

The SC62X platform family includes a high power charge pump based upon Semtech’s mAhXLife™ high-efficiency power conversion technology along with five programmable current sinks for powering four 25mA white LED backlights plus a high current LED for a camera flash. Depending on the model, the maximum output of the camera flash current sink is either 400mA or 700mA, with 250mA continuous spotlight capability.

Most variants of the SC62X devices also provide two low-dropout (LDO), low-noise linear regulators for powering a CMOS camera module or other peripheral circuits. The fully featured SC627 is aimed at high-end phones, the SC621, SC622 and SC623 target mid-range handsets, and the SC624 is aimed at lower-end camera-phones without an LED flash. All of these devices target "folding" and "candy bar" style phones, while the SC622 is especially designed for "slider" style phones.

The SC62X devices support 1x, 1.5x and 2x charge pump modes and adaptively change between these modes depending upon battery and load conditions. This capability gives the devices the same high efficiency as an inductor-based solution, with an 83% average efficiency over the lithium ion battery life and 94% peak efficiency. The backlight current sinks feature a very wide 32-step programmability range, from a minimum of 0.5mA to a maximum of 25mA. The flash current sink is programmable in 50mA increments up to either 400mA or 700mA. The two LDOs are independently programmable in 100mV steps.

Among the unique features of these devices is a one second safety timer that can automatically turn off the flash in the event that the processor does not, thereby alleviating battery drain, potential damage to the flash LED and the possibility of finger burn for users who touch the flash. Also, the SC62X devices support a programmable backlight autoramping mode that provides an elegant display fade-in and fade-out effect when the brightness is changed, without the need to program this capability into the baseband processor.

The devices can be programmed using either an I2C bus or Semtech’s own SemWire™ single-wire interface, which minimizes microcontroller and interface pin counts. These programming interfaces control all functions of the device, including backlight and flash currents as well as the two LDO voltage outputs.

All SC62X products are available immediately in production quantities. Pricing for the devices, in 1,000-pc lots, is as follows: the SC621 is $2.34, the SC622 is $1.44, the SC623 is $1.80, the SC624 is $1.44 and the SC627 is $2.70.