150KHZ 500MA STEP DOWN VOLTAGE REGULATOR
FSP3127
FEATURES
3.3V, 5V, 12V, and adjustable output versions
Adjustable version output voltage range, 1.2V to
37V ±4% max over line and load conditions
Available in 8-pin surface mount and DIP-8
package
Guaranteed 0.5A output current
Input voltage range up to 40V
Requires only 4 external components
150 kHz fixed frequency internal oscillator
TTL Shutdown capability
Low power standby mode, I
Q
typically 85 µA
High Efficiency
Uses readily available standard inductors
Thermal shutdown and current limit protection
GENERAL DESCRIPTION
The FSP3127 series of regulators are monolithic
integrated circuits that provide all the active functions
for a step-down (buck) switching regulator, capable
of driving a 0.5A load with excellent line and load
regulation. These devices are available in fixed
output voltages of 3.3V, 5V, 12V, and an adjustable
output version, and are packaged in a 8-lead DIP and
a 8-lead surface mount package.
Requiring a minimum number of external
components, these regulators are simple to use and
feature internal frequency compensation, a
fixed-frequency oscillator, and improved line and
load regulation specifications.
The FSP3127 series operates at a switching
frequency of 150 kHz thus allowing smaller sized
filter components than what would be needed with
lower frequency switching regulators. Because of its
high efficiency, the copper traces on the printed
circuit board are normally the only heat sinking
needed.
A standard series of inductors (both through hole and
surface mount types) are available from several
different manufacturers optimized for use with the
FSP3127 series. This feature greatly simplifies the
design of switch-mode power supplies.
Other features include a guaranteed ±4% tolerance
on output voltage under all conditions of input
voltage and output load conditions, and ±15% on the
oscillator frequency. External shutdown is included,
featuring typically 85 µA stand-by current. Self
protection features include a two stage frequency
reducing current limit for the output switch and an
over temperature shutdown for complete protection
under fault conditions.
Typical Application
Simple
high-efficiency
step-down
(buck)
regulator
Efficient pre-regulator for linear regulators
On-card switching regulators
Positive to Negative convertor
PIN ASSIGNMENT
(Top View)
*
*
*
1
2
3
8 OUTPUT
7 VIN
6
GND
FB 4
5 ON/OFF
*: Pin 1,2,3 No internal connection, but should be soldered to PC board for best heat transit
ABSOLUTE MAXIMUM RATINGS(NOTE1)
Parameter
Value
Unit
Maximum Supply Voltage
45
V
ON/OFF Pin Input Voltage
-0.3 to 25
V
Feedback Pin Voltage
– 0.3 to 25
V
Output Voltage to Ground(Steady State)
-1
V
Power Dissipation
Internally limited
Maximum Junction Temperature
+150
°C
ESD Susceptibility(Note 2)
2000
V
Storage Temperature
-65 to 150
°C
Vapor Phase (60 sec.)
215
Lead Temperature (SOP8L)
°C
Infrared (15 sec.)
220
Lead Temperature (PDIP8L) (Soldering, 10 sec)
260
°C
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating
Ratings indicate conditions for which the device is intended to be functional, but do not guarantee specific
performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics.
Note 2: The human body model is a 100 pF capacitor discharged through a 1.5k resistor into each pin.
2007-4-9
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150KHZ 500MA STEP DOWN VOLTAGE REGULATOR
FSP3127
FUNCTIONAL BLOCK DIAGRAM
FUNCTIONAL DESCROPTION
Pin Functions
V
IN
This is the positive input supply for the IC switching regulator. A suitable input bypass capacitor must be present at
this pin to minimize voltage transients and to supply the switching currents needed by the regulator.
Ground
Circuit ground.
Output
Internal switch. The voltage at this pin switches between (V
IN
- V
SAT
) and approximately +0.5V, with a duty cycle of
V
OUT
/V
IN
. To minimize coupling to sensitive circuitry, the PC board copper area connected to this pin should be kept to
a minimum.
Feedback
Senses the regulated output voltage to complete the feedback loop.
ON/OFF
Allows the switching regulator circuit to be shut down using logic level signals thus dropping the total input supply
current to approximately 80 mA. Pulling this pin below a threshold voltage of approximately 1.3V turns the regulator
on, and pulling this pin above 1.3V (up to a maximum of 25V) shuts the regulator down. If this shutdown feature is not
needed, the ON/OFF pin can be wired to the ground pin or it can be left open, in either case the regulator will be in the
ON condition.
TYPICAL APPLICATION CIRCUIT
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2007-4-9
Industrial Control Electronics
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EEWORLD
