Texas Instruments LM21305 Evaluation Board LM21305EVM/NOPB LM21305EVM/NOPB Scheda Tecnica
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LM21305EVM/NOPB
User's Guide
SNVA432C – March 2010 – Revised May 2013
AN-2042 LM21305 Evaluation Board
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LM21305 Overview
The LM21305 is a full-featured adjustable frequency synchronous buck point-of-load regulator capable of
delivering up to 5A of continuous output current. The device is optimized to work over an input voltage
range of 3V to 18V and an output voltage range of 0.598V to 5V, making it suitable for wide variety of
applications. The LM21305 provides excellent output voltage accuracy and superior line and load transient
response for digital loads. The device offers flexible system configuration via programmable switching
frequency through an external resistor with ability to synchronize the switching frequency to an external
clock. The frequency can be set from 300 kHz to 1.5 MHz. The device also provides internal soft-start to
limit in-rush current, pre-biased and monotonic startup capability, cycle-by-cycle current limiting, and
thermal shutdown.
delivering up to 5A of continuous output current. The device is optimized to work over an input voltage
range of 3V to 18V and an output voltage range of 0.598V to 5V, making it suitable for wide variety of
applications. The LM21305 provides excellent output voltage accuracy and superior line and load transient
response for digital loads. The device offers flexible system configuration via programmable switching
frequency through an external resistor with ability to synchronize the switching frequency to an external
clock. The frequency can be set from 300 kHz to 1.5 MHz. The device also provides internal soft-start to
limit in-rush current, pre-biased and monotonic startup capability, cycle-by-cycle current limiting, and
thermal shutdown.
The device features internal over-voltage protection (OVP) and over-current protection (OCP) circuits for
increased system reliability. A precision enable pin and integrated under-voltage lock-out (UVLO) allows
the turn-on of the device to be tightly controlled and sequenced. Fault detection and supply sequencing
are possible with the integrated power good circuit.
increased system reliability. A precision enable pin and integrated under-voltage lock-out (UVLO) allows
the turn-on of the device to be tightly controlled and sequenced. Fault detection and supply sequencing
are possible with the integrated power good circuit.
The LM21305 is offered in a WQFN-28 package with an exposed pad for enhanced thermal performance.
The LM21305 evaluation board comes ready to operate at the following conditions:
The LM21305 evaluation board comes ready to operate at the following conditions:
Parameter
Default
Range and Options
PVIN
12V
External supply 5V to 18V
AVIN
=PVIN
Connect to PVIN or to a separate supply (3V to 18V) selected by JP1
VOUT
3.3V
0.598V to 5V by changing R5 and/or R6
Switching Frequency
500 kHz
300 kHz to 1.5 MHz by changing R4
I
OUT
0A to 5A
Size
2 inches x 1.5 inches
No. of PCB Layers
4
WEBENCH is a registered trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
All other trademarks are the property of their respective owners.
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SNVA432C – March 2010 – Revised May 2013
AN-2042 LM21305 Evaluation Board
Copyright © 2010–2013, Texas Instruments Incorporated