LM21305
www.ti.com
SNVS639F –DECEMBER 2009–REVISED MARCH 2013
5A Adjustable Frequency Synchronous Buck Regulator
Check for Samples: LM21305
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FEATURES
APPLICATIONS
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High Efficiency Switcher Core With Integrated
Low RDSon Power MOSFETs
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POL Regulation From 3.3V, 5V, and 12V
Supply Rails
Resistor Programmable Switching Frequency
With Frequency Synchronization
High Efficiency Supply for DSPs, FPGAs,
ASICs and Processors
Internal Soft-Start With Monotonic and Pre-
Biased Startup
Broadband, Networking and Optical
Communications Infrastructure
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Low Shutdown Quiescent Current
Precision Enable With Hysteresis
PGOOD Indicator Function
DESCRIPTION
The LM21305 is a full-featured 5A synchronous buck
POL regulator optimized for solution size, flexibilty,
and high conversion efficiency. High power density
LM21305 designs are achieved via monolithic
integration of the high-side and low-side power
MOSFETs, high switching frequency, current-mode
control, and optimized thermal design. The efficiency
of the LM21305 is elevated at light loads with diode
emulation mode operation and at heavy loads by
optimal design of the MOSFET gate drivers to
minimize switch dead-times and body-diode
conduction losses.
Input Under-Voltage Lock-Out (UVLO)
Output Over-Voltage Protection (OVP)
High-Bandwidth Load Transient Response
With Peak Current-Mode Control
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Cycle-by-Cycle Current Limiting
Thermal Shutdown
KEY SPECIFICATIONS
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3V to 18V Single-Rail Input Voltage
0.598V Feedback Voltage Reference
300 kHz to 1.5 MHz Switching Frequency
The LM21305 accepts a wide input voltage range of
3V to 18V, facilitating interface to all intermediate bus
voltages, including 3.3V, 5V and 12V rails. An output
voltage as low as 0.598V is supported with excellent
setpoint accuracy and low ripple and RMS noise.
WQFN-28 Package (5 x 5 x 0.8 mm, 0.5 mm
Pitch)
Typical Application Circuit
VIN
PVIN
CBOOT
CIN
RF
CF
CBOOT
VOUT
0.6V - 5V
L
SW
FB
AVIN
EN
RFB1
REN1
COUT
RFB2
LM21305
REN2
Cc1
Rc
2V5
5V0
C2V5
COMP
FREQ
C5V0
RPG
CFRQ
SYNC
PGOOD
AGND PGND
RFRQ
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2
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
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