Applications Information

Applications Information Output-Capacitor Selection and Regulator Stability

For stable operation over the full temperature range, with fixed 3.3V and 5.0V output voltages, use a low-ESR 2.2µF capacitor. For resistor-programmed output voltages, a 10µF low-ESR ceramic capacitor is recommended for stable operation. Use larger output-capacitor values (such as 22µF) to reduce noise while improving load-transient response and power-supply rejection. Some ceramic dielectrics exhibit large capacitance and ESR variations with temperature. To improve power-supply rejection and transient response, use a capacitor larger than the minimum 1µF capacitor between IN and GND.

Exposed Pad

The MAX25210 features an exposed thermal pad on its underside that should be used as a heatsink. This pad lowers the package’s thermal resistance by providing a direct heat-conduction path from the die to the PCB. Connect the exposed pad and GND to the system ground using a large pad or ground plane, or multiple vias to the ground plane layer.

Selecting Timeout Capacitor

The reset timeout period is adjustable to accommodate a variety of microprocessor applications. Adjust the reset timeout period by connecting a capacitor between TIMEOUT and GND.

t_RP = (1.25× C_TIMEOUT)/I_TO

where tRP is in ms and CTIMEOUT is in nF. Leave TIMEOUT unconnected to select the internally fixed timeout period. C_TIMEOUT must be a low-leakage (< 10nA) type capacitor. Ceramic capacitors are recommended. To avoid the influence of parasitic capacitances, do not use capacitor values lower than 100pF.