LM2747 Datasheet PDF - National Semiconductor
| Part Number | LM2747 | |
| Description | Synchronous Buck Controller | |
| Manufacturers | National Semiconductor | |
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March 2006
LM2747
Synchronous Buck Controller with Pre-bias Startup, and
Optional Clock Synchronization
General Description
The LM2747 is a high-speed synchronous buck regulator
controller with a feedback voltage accuracy of ±1%. It can
provide simple down conversion to output voltages as low as
0.6V. Though the control section of the IC is rated for 3 to 6V,
the driver section is designed to accept input supply rails as
high as 14V. The use of adaptive non-overlapping MOSFET
gate drivers helps avoid potential shoot-through problems
while maintaining high efficiency. The IC is designed for the
more cost-effective option of driving only N-channel MOS-
FETs in both the high-side and low-side positions. It senses
the low-side switch voltage drop for providing a simple,
adjustable current limit.
The LM2747 features a fixed-frequency voltage-mode PWM
control architecture which is adjustable from 50 kHz to 1
MHz with one external resistor. In addition, the LM2747 also
allows the switching frequency to be synchronized to an
external clock signal over the range of 250 kHz to 1 MHz.
This wide range of switching frequency gives the power
supply designer the flexibility to make better tradeoffs be-
tween component size, cost and efficiency.
Features include the ability to startup with a pre-biased load
on the output, soft-start, input undervoltage lockout (UVLO)
and Power Good (based on both undervoltage and overvolt-
age detection). In addition, the shutdown pin of the IC can be
used for providing startup delay, and the soft-start pin can be
used for implementing precise tracking, for the purpose of
sequencing with respect to an external rail.
Features
n ±1% feedback voltage accuracy over temperature
n Switching frequency from 50 kHz to 1 MHz
n Switching frequency synchronize range 250 kHz to 1
MHz
n Startup with a pre-biased output load
n Power stage input voltage from 1V to 14V
n Control stage input voltage from 3V to 6V
n Output voltage adjustable down to 0.6V
n Power Good flag and shutdown
n Output overvoltage and undervoltage detection
n Low-side adjustable current sensing
n Adjustable soft-start
n Tracking and sequencing with shutdown and soft start
pins
n TSSOP-14 package
Applications
n Down Conversion from 3.3V
n Cable Modem, DSL and ADSL
n Laser Jet and Ink Jet Printers
n Low Voltage Power Modules
n DSP, ASIC, Core and I/O
Typical Application
© 2006 National Semiconductor Corporation DS201509
20150901
www.national.com
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Typical Performance Characteristics
Efficiency (VOUT = 1.2V)
VCC = 3.3V, fSW = 1 MHz
Internal Reference Voltage vs Temperature
20150940
Frequency vs Temperature
20150958
Output Voltage vs Output Current
20150960
Switch Waveforms
VCC = 3.3V, VIN = 5V, VOUT = 1.2V
IOUT = 3A, CSS = 12 nF, fSW = 1 MHz
20150956
Start-Up (Full-Load)
VCC = 3.3V, VIN = 5V, VOUT = 1.2V
IOUT = 3A, CSS = 12 nF, fSW = 1 MHz
20150946
5
20150948
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Part DetailsOn this page, you can learn information such as the schematic, equivalent, pinout, replacement, circuit, and manual for LM2747 electronic component. |
| Information | Total 23 Pages | |
| Link URL | [ Copy URL to Clipboard ] | |
| Download | [ LM2747.PDF Datasheet ] | |
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