TC120

TC120 PWM/PFM Step-Down Combination Regulator/Controller Features Internal Switching Transistor Supports 600mA Output Current External Switching Transistor Control for Output Currents of 2A+ 300kHz Oscillator Frequency Supports Small Inductor Size Short Circuit Protection Built-In Undervoltage Lockout 95% Typical Efficiency Automatic Switchover to Current-Saving PFM Mode at Low Output Loads Automatic Output Capacitor Discharge While in Shutdown Programmable Soft-Start Power-Saving Shutdown Mode Small 8-Pin SOP Package Package Type 8-Pin SOP VIN 1 EXTW 2 CPC 3 SHDN/SS 4 8 LX EXT GND SENSE TC120 7 6 5 General Description TC120 is a 300kHz PFM/PWM step-down (Buck) DC/ DC regulator/controller combination for use in systems operating from two or more cells, or in line-powered applications. It uses PWM as the primary modulation scheme, but automatically converts to PFM at low output loads for greater efficiency. It requires only an external inductor, Schottky diode, and two capacitors to implement a step-down converter having a maximum output current of 600mA (VIN = 5V, VOUT = 3.3V). An external switching transistor (P-channel MOSFET) can be added to increase output current capability to support output loads of 2A or more. The TC120 consumes only 55µA (max) of supply current (VOUT = 3.3V) and can be placed in shutdown mode by bringing the shutdown input (SHDN) low. During shutdown, the regulator is disabled, supply current is reduced to 2.5µA (max), and V...