LX1681_05 Datasheet, PDF (1/9 Pages) Microsemi Corporation – Voltage-Mode PWM Controllers

LX1681/1682
TM
®
Voltage-Mode PWM Controllers
PRODUCTION DATA SHEET
DESCRIPTION
The LX1681/1682 are monolithic, Hiccup-mode fault protection reduces
pulse-width modulator controller ICs. average power to the power elements
They are designed to implement a during short-circuit conditions.
flexible, low cost buck (step-down) Switching frequency is fixed at
regulator supply with minimal external 200kHz for optimal cost and space.
components.
Under-voltage lockout and soft-start
The LX1681 is a non-synchronous for optimal start-up performance. Pulling
controller; the LX1682 has a the soft-start pin to ground can disable
synchronous driver for higher efficiency. the LX1681/82.
The output voltage is adjustable by Small 8-pin SOIC packaging reduces
means of a resistor divider to set the board space. Optimized for 5V-to-3.3V
voltage between 1.25V and 4.5V.
or 5V-to-2.5V conversion, the
Short-circuit current limiting can be LX1681/82 can also be used for
implemented without expensive current converting 12V to 5V, 3.3V or other
sense resistors. Current is sensed using voltages with high efficiency,
the voltage drop across the R_DS(ON) of the eliminating the need for bulky heat sinks.
MOSFET — sensing is delayed for 1µs
to eliminate MOSFET ringing errors.
IMPORTANT: For the most current data, consult MICROSEMI’s website: http://www.microsemi.com
KEY FEATURES
ƒ Fixed 200kHz Switching Frequency
ƒ Constant Frequency Voltage-Mode
Control Requires NO External
Compensation
ƒ Hiccup-Mode Over-Current
Protection
ƒ High Efficiency
ƒ Output Voltage Set By Resistor
Divider
ƒ Under-Voltage Lockout
ƒ Soft-Start And Enable
ƒ Synchronous Rectification
(LX1682)
ƒ Non-Synchronous Rectification
(LX1681)
ƒ Small, 8-pin Surface Mount
Package
APPLICATIONS
ƒ 5V to 3.3V Or Less Buck
Regulators
ƒ FPGA Supplies
ƒ Microprocessor Chipset Supplies
(e.g. Camino, Whitney, etc.)
ƒ Rambus^© RIMM™ Supplies
ƒ Hard Disk Drives
ƒ Computer Add-on Cards
PRODUCT HIGHLIGHT
V_BOOST
V _IN
12V
5V
C₃
1µF
C_SS
0.1µF
V_FB
V_C2
SS
CS
LX1681
N.C.
V_C1
GND
TDRV
C₁
1500µF
x3
Q₁
IRL3103S
L₁
5µH
C₂
1500µF
x3
V_OUT
R₁
C₃
1µF
C_SS
0.1µF
V_FB
V_C2
SS
CS
LX1682
GND
V_C1
BDRV
TDRV
R_SET
D_{2 MBR2545}
R₂
V_BOOST
V_IN
12V
5V
C₁
1500µF
x3
Q₁
IRL3103S
L₁
5µH
V_OUT
C₂
R₁
1500µF
x3
R_SET
R₂
Q₂
IRL3103S
LX1681 Non-Synchronous Controller
LX1682 Synchronous Controller
Copyright © 2000
Rev. 1.1b,2005-03-09
PACKAGE ORDER INFO
T_A (°C)
0 to 70
OUTPUT
Non-Synchronous
Synchronous
Plastic SOIC
DM _8-PIN
RoHS Compliant / Pb-free
Transition D/C: 0440
LX1681CDM
LX1682CDM
Note: Available in Tape & Reel. Append the letters “TR” to the part number. (i.e. LX1681CDM-TR)
Microsemi
Linfinity Microelectronics Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: [phone]
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