7.1 Overview

The LMZ21700 SIMPLE SWITCHER® Nano Module is an easy-to-use step-down DC-DC solution capable of driving up to 650 mA load in space-constrained applications. Only an input capacitor, an output capacitor, a softstart capacitor, and two resistors are required for basic operation. The Nano Module comes in 8-pin DFN footprint package with an integrated inductor. The LMZ21700 architecture is based on DCS-Control™ (Direct Control with Seamless Transition into Power Save Mode). This architecture combines the fast transient response and stability of hysteretic type converters along with the accurate DC output regulation of voltage mode and current mode regulators.

The LMZ21700 architecture uses Pulse Width Modulation (PWM) mode for medium and heavy load requirements and Power Save Mode (PSM) at light loads for high efficiency. In PWM mode the switching frequency is controlled over the input voltage range. The value depends on the output voltage setting and is typically reduced at low output voltages to achieve higher efficiency. In PSM the switching frequency decreases linearly with the load current. Since the architecture of the device supports both operation modes (PWM and PSM) in a single circuit building block, the transition between the modes of operation is seamless with minimal effect on the output voltage.