MAX38647B

The MAX38647B is an ultra-low I_Q (440nA) buck converter that steps-down an input voltage range of 1.8V to 5.5V to a wide range of output voltages from 0.5V to 1.8V. Through a single external resistor (R_SEL) on the RSEL pin, it is possible to program four different output voltages as given in Table 1 in the data sheet. The output voltage can be changed dynamically between the selected four output voltages using two voltage select pins VSEL1 and VSEL2 by pulling them high or low. The four output voltages are determined during start-up. The output voltage transition from low voltage to high voltage is open-loop current-limit controlled. The voltage transition from high voltage to low voltage is purely dependent on the load.

The buck converter automatically switches between ultra-low-power mode (ULPM), low-power mode (LPM) and high-power mode (HPM) to service the load at the highest possible efficiency depending on the load current. The buck converter overregulates in ULPM to allow the output capacitor to prevent output undershoot during load transients. See Figure 1 in the data sheet for the MAX38647B mode transitions. The device supports 100% duty-cycle operation.

The active discharge resistor pulls OUT to ground when the part is in shutdown. In applications where the ambient temperature is more than +85°C, a load current of >10μA may be required to prevent the output from soaring due to power FET leakage.

APPLICATIONS

• Portable Space-Constrained Consumer Products
• Wearable Devices Ultra-Low-Power IoT, NB IoT, and Bluetooth^® LE
• Single Li-ion and Coin-Cell Battery Products
• Wired, Wireless Industrial Products