24V Internal Switch, 100% Duty Cycle, Step-Down Converters

The MAX1836/MAX1837 high-efficiency step-down converters provide a preset 3.3V or 5V output voltage from supply voltages as high as 24V. Using external feedback resistors, the output voltage can be adjusted from 1.25V to VIN. An internal current-limited switching MOSFET delivers load currents up to 125mA (MAX1836) or 250mA (MAX1837).

The unique current-limited control scheme, operating with duty cycles up to 100%, minimizes the dropout voltage (120mV at 100mA). Additionally, this control scheme reduces supply current under light loads to 12µA. High switching frequencies allow the use of tiny surface-mount inductors and output capacitors.

The MAX1836/MAX1837 step-down converters with internal switching MOSFETs are available in 6-pin SOT23 and 3mm x 3mm TDFN packages, making them ideal for low-cost, low-power, space-sensitive applications. For increased output drive capability, use the MAX1776 step-down converter that uses an internal 24V switch to deliver up to 500mA. For even higher currents, use the MAX1626/MAX1627 step-down controllers that drive an external P-channel MOSFET to deliver up to 20W.

Applications

* 4mA to 20mA Loop Power Supplies * 9V Battery Systems * Backup Supplies * Distributed Power Systems * Handheld Devices * Industrial Control Supplies * Notebook Computers

* 4.5V to 24V Input Voltage Range

* Preset 3.3V or 5V Output

* Adjustable Output from 1.25V to VIN

* Output Currents Up to 125mA (MAX1836) or 250mA (MAX1837)

* Efficiency Over 90%

* 12µA Quiescent Current

* 3µA Shutdown Current

* 100% Maximum Duty Cycle for Low Dropout

* Small 6-Pin SOT23 and TDFN Packages