The MAXM38643 is an ultra-low-IQ (330nA) buck module that steps down input voltages in the range of 1.8V to 5.5V to a wide range of output voltages between 0.7V to 3.3V (using a single resistor at the RSELpin). The output voltage is programmable upon startup using a single external resistor from the RSELpin to GND. Factory-preprogrammed fixed output voltage versions from 0.5V to 5V are also available that do not use the RSELpin to set the output voltage. In this case, the RSELpin in the module is left floating.The module offers robust performance features. To optimize efficiency and transient response across the load operation range, the module automatically switches between ultra-low-power mode (ULPM), low-power mode (LPM), and highpower mode (HPM) to better service the load, depending on the load current. The device overregulates in ULPM to improve efficiency and allow the output capacitor to handle the transient load currents. The device has 90% duty cycle limitation. An active discharge resistor pulls OUT to ground when the part is in shutdown.ApplicationsBluetooth®LE DevicesHearablesPortable Space-Constrained ProductsSingle Li+ and Coin Cell Battery ProductsUltra-Low-Power IoT, NB IoTWearablesWired, Wireless Products