Convertors boast precise linear output

The XC9228/29 series are synchronous-rectification type step-down DC/DC convertors that allow the output voltage to be adjusted via an external voltage reference input.

The XC9228/29 series are synchronous-rectification type step-down DC/DC convertors that allow the output voltage to be adjusted via an external voltage reference input.

The convertors feature a comparator that gives a precise linear output selectable from 1.2 or 2.4 times the reference voltage.

This dynamic output can be used, for example, with a 3G/UMTS radio where the power needed for the TX/RX depends on the distance from the handset to the basestation: the nearer the basestation, the less power needed.

One way to regulate this TX/RX power is to dynamically control the voltage of the RF chipset.

The XC9228/29 has a built in 0.6ohm P-channel driver transistor and 0.7ohm N-channel switching transistor and can provide high efficiencies (92%), a stable power supply and output currents of 500mA using only a coil and two ceramic capacitors connected externally.

Quiescent current is only 18mA and during standby, all circuits are shutdown to reduce current consumption to 1.0uA or less.

Minimum operating voltage of the series is 2.0V.

With a built-in oscillator, the IC's switching frequency is selectable from 600kHz and 1.2MHz to make available the frequency best suited to a particular application.

As for operation mode, the XC9228 series is a PWM control type, whereas the XC9229 series has automatic PWM/PFM switching control, allowing fast response, low ripple and high efficiency over the full range of current load.

False pulse output caused by unstable operation is prevented by the built-in undervoltage lockout (UVLO) function, whereby the internal P-channel driver transistor is forced off when the input voltage drops below 1.4V.

The series is available in either SOT-25 or USP-6B packages.

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