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Ultra-small charge pumps target cell phones

Camarillo, Calif. — Semtech Corp. has released its SC62X family of ultra-small (3.0 x 3.0 x 0.6 mm) and highly programmable charge pumps for providing power to LCD backlights, LED flash and camera modules in mobile phones.

The SC62X platform family includes a high-power charge pump based on Semtech's mAhXLife high-efficiency power conversion technology along with five programmable current sinks for powering four 25 mA 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 400 mA or 700 mA, with a 250 mA 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 devices 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 specifically designed for “slider” style phones.

The SC62X devices support 1x, 1.5x and 2x charge pump modes and adaptively change between these modes depending on 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 32-step programmability range from a minimum of 0.5 mA to a maximum of 25 mA. The flash current sink is programmable in 50 mA increments up to either 400 mA or 700 mA. The two LDOs are independently programmable in 100-mV steps.

Key features include a one second safety timer that can automatically turn off the flash in the event that the processor does not, and a programmable backlight auto-ramping mode that provides a display fade-in and fade-out effect when the brightness is changed.

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

Pricing: In quantities of 1,000, the SC621 is priced at $2.34, SC622 at $1.44, SC623 at $1.80, SC624 at $1.44 and the SC627 at $2.70.
Availability: All SC62X products are available immediately in production quantities.
Product information: SC62X family

Semtech Corp. 1-805-498-2111, www.semtech.com

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