MIC2172/3172
100 kHz, 1.25A Switching Regulators
Features
General Description
• 1.25A, 65V Internal Switch Rating
• 3V to 40V Input Voltage Range
• Current Mode Operation
The MIC2172 and MIC3172 are complete 100 kHz
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.
• Internal Cycle-by-Cycle Current Limit
• Low External Parts Count
• Operates in Most Switching Topologies
• 7 mA Quiescent Current (Operating)
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.
• <1 μA Quiescent Current, Shutdown Mode
(MIC3172)
• TTL Shutdown Compatibility (MIC3172)
• External Frequency Synchronization (MIC2172)
• External Frequency Trim (MIC2172)
Operating from 3V to 40V, the MIC2172/3172 draws
only 7 mA of quiescent current, making it attractive for
battery-operated supplies.
• Fits Most LT1172 Sockets (see Section 5.0,
Applications Information)
The MIC3172 is for applications that require on/off
control of the regulator. The MIC3172 is externally shut
down by applying a TTL-low signal to EN (enable).
When disabled, the MIC3172 draws only leakage
current (typically less than 1 μA). EN must be high for
normal operation. For applications not requiring
control, EN must be tied to VIN or TTL high.
Applications
• Laptop/Palmtop Computers
• Toys
• Handheld Instruments
• Off-Line Converter up to 50W (Requires External
Power Switch)
The MIC2172 is for applications that require two or
more SMPS regulators that operate from the same
input supply. The MIC2172 features a SYNC input that
allows locking of its internal oscillator to an external
reference. This makes it possible to avoid the audible
beat frequencies that result from the unequal oscillator
frequencies of independent SMPS regulators.
• Predriver for Higher Power Capability
• Master/Slave Configurations (MIC2172)
A reference signal can be supplied by one MIC2172
designated as a master. To ensure locking of the
slave’s oscillators, the reference oscillator frequency
must be higher than the slave. The master MIC2172’s
oscillator frequency is increased up to 135 kHz by
connecting a resistor from SYNC to ground (see
Section 5.0, Applications Information).
The MIC2172/3172 is available in an 8-pin plastic DIP
or SOIC for –40°C to +85°C ambient temperature
operation.
2019 Microchip Technology Inc.
DS20006208A-page 1