The DCS-Control topology supports power save mode operation. At light loads, the device operates in PFM (pulse frequency modulation) mode that generates a single switching pulse to ramp up the inductor current and recharge the output capacitor, followed by a sleep period where most of the internal circuits are shut down to achieve lowest operating quiescent current. During this time, the load current is supported by the output capacitor. The duration of the sleep period depends on the load current and the inductor peak current. During the sleep periods, the current consumption is reduced to typically 2.3 µA. This low quiescent current consumption is achieved by an ultra-low power voltage reference, an integrated high impedance feedback divider network, and an optimized power save mode operation.
In PFM mode, the switching frequency varies linearly with the load current. At medium and high load conditions, the device automatically enters PWM (pulse width modulation) mode and operates in continuous conduction mode with a nominal switch frequency, fsw, of typically 4 MHz or 1.5 MHz. The switching frequency in PWM mode is controlled and depends on VIN and VOUT. The boundary between PWM and PFM mode is when the inductor current becomes discontinuous.
If the load current decreases, the converter seamlessly enters PFM mode to maintain high efficiency down to very light loads. Since DCS-Control supports both operation modes within one single building block, the transition from PWM to PFM ,mode is seamless with minimum output voltage ripple.