WIDE INPUT 3A STEP-DOWN CONVERTER
FSP3128
FEATURES
3A Output Current
Up to 95% Efficiency
4.5V to 30V Input Range
6µA Shutdown Supply Current
400kHz Switching Frequency
Adjustable Output Voltage
Cycle-by-Cycle Current Limit Protection
Thermal Shutdown Protection
Internal Soft-Start Function
Frequency Fold Back at Short Circuit
Stability with Wide Range of Capacitors,
Including Low ESR Ceramic Capacitors
SOP8L/EP(Exposed Pad) Package
GENERAL DESCRIPTION
The FSP3128 is a current-mode step-down DC/DC
converter that generates up to 3A output current at
400kHz switching frequency. The device can
operate with input voltage up to 30V.
Consuming only 6µA in shutdown mode, the
FSP3128 is highly efficient with peak efficiency at
95% when in operation. Protection features include
cycle-by-cycle current limit, thermal shutdown, and
frequency fold back at short circuit. The device also
includes an internal soft start function to prevent
overshoot.
The FSP3128 is available in SOP8L/EP package and
requires very few external devices for operation.
TYPICAL APPLICATION
TFT
LCD Monitors or Televisions and HDTV
Portable DVD Players
Car-Powered or Battery-Powered Equipment
Set-Top Boxes
Telecom Power Supplies
DSL and Cable Modems and Routers
PIN ASSIGNMENT
(Top View)
BS 1
IN
2
8
7
6
EP
5
N/C
EN
COMP
FB
SW 3
G
4
PIN DESCRIPTION
Pin Number Pin Name
1
2
3
4
5
6
7
8
EP
BS
IN
SW
G
FB
COMP
EN
N/C
EP
Pin Description
Bootstrap. This pin acts as the positive rail for the high-side switch’s gate driver.
Connect a 10nF between this pin and SW.
Input Supply. Bypass this pin to G with a low ESR capacitor. See Input Capacitor in
Application Information section.
Switch Output. Connect this pin to the switching end of the inductor.
Ground.
Feedback Input. The voltage at this pin is regulated to 1.222V. Connect to the resistor
divider between the output and ground to set output voltage.
Compensation Pin. See Compensation Technique in Application information section.
Enable Input. When higher than 1.3V, this pin turns the IC on. When lower than 0.7V,
this pin turns the IC off. Output Voltage is discharged when the IC is off. This pin has a
small internal pull up current to a high level voltage when pin is not connected.
Not Connected.
Exposed Pad shown as dashed box. The exposed thermal pad should be connected to
board ground plane and pin 4. The ground plane should include a large exposed copper
pad under the package for thermal dissipation. The leads and exposed pad should be
flush with the board, without offset from the board surface.
2007-1-4
1/10
FOSLINK [ FOSLINK SEMICONDUCTOR CO.,LTD ]
