Southchip has released the SC3606 chip, designed to control piezoelectric fans. This type of active cooling is considered by the company to be ideal for thin gadgets such as smartphones. Currently, Southchip has not disclosed information about specific devices that will use this chip.
A piezoelectric fan is characterized by the absence of a motor, bearings, shaft, or mechanical friction. It consists of a thin membrane that vibrates at ultrasonic frequencies. Southchip claims that such fans can have a thickness of less than 1 mm, operate at a noise level of about 30 dB, consume hundreds of milliwatts of energy, and react in less than a millisecond.
The main challenge is that the piezoactuator cannot independently find its resonant point or regulate its own power consumption; it requires a driver capable of outputting high voltage, precisely locking onto resonance, and maintaining high efficiency.
Technical specifications and capabilities of the chip
The SC3606 comes in an FCQFN package measuring 2.3 mm by 2.75 mm and 0.5 mm thick, featuring 22 pins. It accepts an input voltage ranging from 2.1 V to 5.5 V, allowing it to be installed directly on the battery bus without needing an additional LDO or DC-DC converter at the front end. This range is also compatible with lower voltages of silicon-anode batteries.
The integrated bidirectional buck-boost circuit increases the output signal amplitude up to 46 Vpp, or plus-minus 23 V, within a frequency range of 2 kHz to 40 kHz.
A key feature is resonance tracking. Since the resonant point of the piezo fan changes due to individual device variations, mounting voltage, temperature, and aging, the chip combines full-range scanning and segmented approximate scanning with real-time frequency tracking. This allows it to autonomously find the optimal operating point within 15 kHz and 40 kHz. As a result, device manufacturers do not need to calibrate every batch of fans on the production line or implement temperature compensation.
The chip supports both sinusoidal and square wave control. Sinusoidal control, which has low harmonic content, ensures that the actuator vibrates only in the target mode, avoiding audible high-frequency whistling that harmonics might excite. Since the piezoelectric element functions like a large capacitor that charges and discharges with each cycle, the energy recovery architecture returns stored energy back to the power bus, thereby reducing the overall system power consumption.
The 1.2 V I2C interface allows the chip to connect directly to flagship SoCs and PMICs, enabling thermal management software to quickly activate and run the fan. Protection features include overvoltage protection, overheat protection, low voltage lockout, and short-circuit protection.
In conjunction with the previously released SC3601 driver for liquid cooling using a piezo micropump, the SC3606 offers device developers the choice among piezo-oriented cooling drivers from a single supplier.
