General Description

The MIC2172 and MIC3172 are complete 100kHz SMPS current-mode controllers with internal 65V 1.25A power switches. The MIC2172 features external frequency synchronization or frequency adjustment, while the MIC3172 features an enable/shutdown control input.

Although primarily intended for voltage step-up applications, the floating switch architecture of the MIC2172/3172 makes it practical for step-down, inverting, and Cuk configurations as well as isolated topologies.

Features

• 1.25A, 65V internal switch rating

• 3V to 40V input voltage range

• Current-mode operation

• Internal cycle-by-cycle current limit

• Thermal shutdown

• Low external parts count

• Operates in most switching topologies

• 7mA quiescent current (operating)

• <1µA quiescent current, shutdown mode (MIC3172)

• TTL shutdown compatibility (MIC3172)

• External frequency synchronization (MIC2172)

• External frequency trim (MIC2172)

• Fits most LT1172 sockets (see applications info)

Applications

• Laptop/palmtop computers

• Toys

• Hand-held instruments

• Off-line converter up to 50W (requires external power switch)

• Predriver for higher power capability

• Master/slave configurations (MIC2172)