© 2002 Microchip Technology Inc.

DS21365B-page 1

TC120

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

Applications

• Portable Test Equipment

• Local Logic Supplies

• Portable Audio Systems

• Portable Scanners

•Palmtops

• Electronic Organizers

Device Selection Table

Package Type

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

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 55

µA (max) of supply

mode by bringing the shutdown input (SHDN)low.

During shutdown, the regulator is disabled, supply

current is reduced to 2.5

internally pulled to ground, discharging the output

capacitor. Normal operation resumes when SHDN is

brought high. Other features include a built-in under-

voltage lockout (UVLO), an externally programmable

soft start time, and output short circuit protection. The

TC120 operates from a maximum input voltage of 10V

and is available in a low-profile 8-Pin SOP package.

Functional Block Diagram

Part

Number

Output

Voltage

(V)

Package

Operating

Temp.

Range

TC120503EHA

5.0

8-Pin SOP -40°C to +85°C

TC120333EHA

3.3

8-Pin SOP -40°C to +85°C

TC120303EHA

3.0

8-Pin SOP -40°C to +85°C

1

2

3

4

8

7

6

5

TC120

8-Pin SOP

EXTW

CPC

SHDN/SS

GND

EXT

SENSE

TC120XX03

EXTW

CPC

SHDN/SS

EXT

GND

SENSE

D1

L1

4.7nF

PWM/PFM Step-Down Combination Regulator/Controller