200mA boost converter for single-cell Li-ion-powered designs

October 15, 2015 // By Graham Prophet
From ams, the AS1383’s 3.5 MHz fixed-frequency switching enables use of small external components, suiting it for use in space-constrained products such as wristbands

Mixed-signal IC and sensor maker ams (Unterpremstaetten, Austria) has introduced the AS1383, an ultra-compact switching boost converter which offers high efficiency and helps extend run-time in applications powered by a single-cell lithium-ion battery.

The converter provides outputs of between 2.7V and 5.0V from a 2.7V-5.5V input voltage range. It is available with an adjustable output voltage, or a factory-programmed fixed output voltage. Depending on the input voltage, it can provide a maximum output current of up to 200 mA.

The AS1383, which implements peak current-mode PWM control for accurate line and load regulation, features internal NMOS and PMOS power switches with very low on-resistance and gate charge. This helps the converter to achieve high efficiency, peaking at 92%, across the range from moderate to full loads.

In addition, it offers a ‘Powersave’ mode in which all circuitry except that required to monitor the output voltage is turned off when the output current falls below the point at which the energy supplied in the switch's minimum on-time is greater than the energy consumed by the load. This Powersave mode keeps power consumption down to a typical 25 µA when supplying light loads.

Operating at a fixed switching frequency of 3.5 MHz, the AS1383 requires only a small input and output capacitor and an inductor rated at 1µH. Two additional components, external resistors for setting the output voltage, are required only in the adjustable-output version of the device.

The converter itself is a six-pin wafer-level chip-scale package, with a footprint of 1.2 x 0.8 mm and a pitch of 0.4 mm, to fit in the latest sleek designs for consumer products such as wristbands, media players, digital cameras and mobile phones.

The fixed switching frequency used by the AS1383, and integrated anti-ringing control implemented in the device, help system designers to realise low-noise end product designs. At 20 mV peak-to-peak for a 150 mA load, output voltage ripple is also low enough