PFM Step-Up DC/DC Regulators
• Assured Start-up at 0.9V
• PFM (100kHz Max Operating Frequency)
• 40µA Maximum Supply Current
(VOUT = 3V @ 30mA)
• 0.5µA Shutdown Mode (TC125)
• Voltage Sense Input (TC126)
• Requires Only Three External Components
• 80mA Maximum Output Current
• Small Package: 5-Pin SOT-23A
• Battery-Operated Systems
• Portable Communicators
Device Selection Table
TC125501ECT 5.0 5-Pin SOT-23A -40°C to +85°C
TC125331ECT 3.3 5-Pin SOT-23A -40°C to +85°C
TC125301ECT 3.0 5-Pin SOT-23A -40°C to +85°C
TC126503ECT 5.0 5-Pin SOT-23A -40°C to +85°C
TC126333ECT 3.3 5-Pin SOT-23A -40°C to +85°C
TC126303ECT 3.0 5-Pin SOT-23A -40°C to +85°C
*Other output voltages are available. Please contact
Microchip Technology Inc. for details.
5 45 4
NOTE: 5-Pin SOT-23A is equivalent to the EIAJ SC-74A
The TC125/126 step-up (Boost) switching regulators
furnish output currents to a maximum of 80mA
(VIN = 2V, VOUT = 3V) with typical efficiencies above
80%. These devices employ pulse frequency modula-
tion (PFM) for minimum supply current at low loads.
They are ideal for battery-operated applications
powered from one or more cells. Maximum supply
current is less than 70µA at full output load, and less
than 5µA in standby (VOUT = 3V). Both devices require
only an external inductor, diode, and capacitor to
implement a complete DC/DC regulator.
The TC126 has separate output voltage sensing and
chip power inputs for greater application flexibility. The
TC125 combines the output voltage sensing and chip
power inputs onto a single package pin, but adds a
power-saving shutdown mode that suspends regulator
operation and reduces supply current to less than
0.5µA when the shutdown control input (SHDN) is low.
The TC125/TC126 are available in a small 5-Pin
SOT-23A package, occupy minimum board space and
use small external components. The TC125 accepts
input voltages from 2V to 10V. The TC126 accepts
input voltages from 2.2V to 10V. Both the TC125 and
TC126 have a start-up voltage of 0.9V at light load.
2 x "AA"
Two Cell to 5V Boost Regulator
© 2002 Microchip Technology Inc.