Texas Instruments has introduced a 6MHz step-down converter chip, claimed to be "industry’s thinnest 500mA power converter solution", said TI. "It achieves a 13mm sq. solution size with a 0.6mm total height."

The 0.9x1.3mm chip scale device, dubbed TPS62601, delivers up to 89% efficiency with typically 30[micro]A quiescent current.

In the chip is a frequency locked ring oscillating modulator that the firm claims achieves best-in-class load and line response. Both switching and synchronous rectifier mosfets are integrated.

At the beginning of each switching cycle, the p-channel mosfet is turned on and the inductor current ramps up rising the output voltage until the main comparator trips, then the control logic turns off the switch. "There is no traditional feed-back loop," said TI. "The loop response to change in V(out) is essentially instantaneous, which explains the transient response."

There are two current limits, one each for the p and n-mosfets. "When the current in the p-channel mosfet reaches its current limit, it is turned off and the n-channel mosfet is turned on," said TI. "When the current in the n-channel mosfet is above its current limit, it remains on until the current drops below its current limit."

The current limit in the n-channel mosfet is important for small duty-cycle operation when the current in the inductor does not decrease because of the p-channel mosfet current limit delay, said the firm, or because of start-up conditions where the output voltage is low.

The converter is normally pulse-width modulated, but automatically enters a power saving pulse frequency modulation mode at light load currents.

This can be defeated using the ‘mode’ pin which retains fixed frequency PWM operation at light loads to ease EMI filtering.

Output is 1.8V +/-1.5% from 2.3 to 5.5V. Current is under 1µA in shutdown.

Applications including support for memory, GPS , Bluetooth and Wi-Fi modules are foreseen in smart phones, digital still cameras, portable disk drives and media players.