TC120_13 Datasheet, PDF (1/16 Pages) Microchip Technology – PWM/PFM Step-Down Combination Regulator/Controller

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
Applications
• Portable Test Equipment
• Local Logic Supplies
• Portable Audio Systems
• Portable Scanners
• Palmtops
• Electronic Organizers
Device Selection Table
Part
Number
Output
Voltage Package
(V)
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
Package Type
8-Pin SOP
V_IN 1
EXTW 2
CPC 3
SHDN/SS 4
TC120
8 ^LX
7 EXT
6 GND
5 SENSE
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 (V_IN = 5V, V_OUT = 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 55A (max) of supply
current (V_OUT = 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 2.5A (max), and V_OUT is
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
V_IN
C_IN
V_IN
L_X
EXTW
EXT
TC120XX03
CPC
GND
L1
D1
V_OUT
C_OUT
SHDN/SS
C_SS
4.7nF
SENSE
 2001-2012 Microchip Technology Inc.
DS21365C-page 1