Convertors keep it quiet for Bluetooth

A new range of synchronous-rectification-type step-down DC/DC convertors features ultralow ripple, making them an ideal choice for noise-sensitive RF applications such as Bluetooth.

The ultralow ripple performance of Torex Semiconductor's new XC9215/16/17 series of synchronous-rectification-type step-down DC/DC convertors in chip scale USB-6B (2.0 x 1.8 x 0.88mm) packages, makes them an ideal choice for noise sensitive RF applications such as Bluetooth and next-generation mobile phones.

With a built-in 0.5ohm P-channel driver transistor and 0.6ohm N-channel switching transistor, these highly integrated DC/DC convertors require only the external connection of a chip inductor and two small ceramic capacitors to realise a stable power supply with an output current of 400mA.

Achieving efficiencies of up to 94%, the XC9215/16/17 series employs the very latest current/voltage multiple feedback technique to achieve low output ripple of less than 10mV (peak to peak).

Three different types of switching control are available.

The XC9215 provides synchronous-rectified PWM switching control, the XC9216 automatically switches between PWM/PFM depending on output load, and the switching operation of the XC9217 can be manually controlled between PWM and PFM/PWM using the device's CE/mode pin.

This mode pin function gives the designer ultimate control over the switching mode of the IC, which is a big advantage in RF applications.

However, regardless of which version is selected, the IC provides fast response, low ripple output and high efficiency over a broad range of output loads.

Input voltage range is 2.0 to 6.0V.

Output voltage is internally programmable between 0.9 and 4.0V in increments of 0.1V.

The switching frequency is 600kHz or 1.2MHz, the higher frequency allowing the designer to use small chip-style inductors.

A "soft-start" circuit provides the devices with protection against inrush currents when power is switched on and voltage overshoot.

In standby all circuits are shutdown to reduce current consumption to less than 0.5uA.

The new XC9215/16/17 can be supplied in either small SOT-23-5 or ultracompact USP-6B (2.0 x 1.8 x 0.8mm) packages.

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