ON Semiconductor's 4A Single-Chip Driver for Supercapacitor-Based LED Camera Flash Applications

The CAT3224 offers an easy-to-use solution with three fully independent operational modes (charging, flash and torch) activated via a simple parallel logic interface and the operating current of each mode easily programmed by three external resistors. Additional higher power supercapacitor-based LED flash drives will be released later this quarter.

High megapixel camera phones and standalone cameras require a very high-intensity flash to produce good quality photos, particularly in low or medium light conditions. New LEDs on the market are designed to address this need, however the camera battery alone cannot deliver a high enough peak current pulse to drive the LED flash to the brightness levels required for high-resolution pictures. The power issues are further exacerbated by the additional system functions that require high-peak current, such as zoom, auto-focus, image capture, Class D audio and RF amplification.

The new ON Semiconductor LED driver works in combination with the latest generation of supercapacitors to help designers effectively eliminate these power management issues. The supercapacitor discharges its power for peak-load functions and recharges continuously, even during the flash peaks. The CAT3224 LED driver controls the supercapacitor charge to create additional energy for the other high-peak current circuits. This supercapacitor LED driver design approach enables true, high-intensity flash and more system functionality, while significantly extending battery life.

The high peak current benefits of supercapacitor technology, combined with the simple parallel logic interface of the CAT3224 also make the device a good choice for industrial applications where LEDs are being used to replace xenon-based lighting.

“The CAT3224 supercapacitor LED driver provides an integrated, easy-to-use, cost-effective solution for high-intensity LED flash capability,” said Scott Brown, vice president of marketing for the Catalyst Group of ON Semiconductor. “We believe this device, along with significant improvements in supercapacitor technology from companies such as CAP-XX Limited and the ever-increasing performance of white LEDs, will combine to make true high brightness LED flash viable for the first time in next-generation, high-megapixel camera phones and standalone cameras.”

The CAT3224 supercapacitor LED driver supports three key functions: precise supercapacitor charging control, management of the current discharge into the LED flash, and constant current for LED torch mode. The CAT3224 sources up to 4 amp LED flash pulses and up to 400 mA torch-mode current, with simple programming via external resistors on the analog control inputs. The device incorporates a dual-mode 1x/2x charge pump, which charges the stacked supercapacitor to a nominal voltage of 5.4 V, while an active balance control circuit ensures that both capacitor cell voltages are matched during the charging cycle. In addition the CAT3224 provides the user with a dedicated logic output to flag the completion of the supercapacitor charging sequence.

Packaged in a space-saving, 16-lead TQFN 3 mm x 3 mm x 0.8 mm package, the CAT3224 features thermal shutdown, overvoltage protection (OVP) and protection against external resistor programming faults. The device also supports reverse output voltage for all conditions.

The CAT3224 is a key addition to the portfolio of ON Semiconductor products targeted at the four primary subsystems typically found in portable applications. This device specifically addresses the challenging requirements within the Display and Lighting subsystem. ON Semiconductor also offers solutions for the Interconnect, the Power Management and the Audio/Video subsystems for handheld portable devices.