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LM2748MTC View Datasheet(PDF) - National ->Texas Instruments

Part NameLM2748MTC National-Semiconductor
National ->Texas Instruments National-Semiconductor
DescriptionSynchronous Buck Controller with Pre-bias Startup, and Optional Clock Synchronization
LM2748MTC Datasheet PDF : 23 Pages
1 2 3 4 5 6 7 8 9 10 Next Last
Electrical Characteristics (Continued)
VCC = 3.3V unless otherwise indicated. Typicals and limits appearing in plain type apply for TA= TJ= 25˚C. Limits appearing in
boldface type apply over full Operating Temperature Range. Datasheet min/max specification limits are guaranteed by design,
test, or statistical analysis.
Symbol
Parameter
Conditions
Min
Typ
Max Units
GATE DRIVE
IQ-BOOT
RHG_UP
BOOT Pin Quiescent Current
High-Side MOSFET Driver
Pull-Up ON resistance
VBOOT = 12V, VSD = 0
VBOOT = 5V @ 350 mA Sourcing
18
90
µA
2.7
RHG_DN
High-Side MOSFET Driver
Pull-Down ON resistance
350 mA Sinking
0.8
RLG_UP
Low-Side MOSFET Driver Pull-Up
ON resistance
VBOOT = 5V @ 350 mA Sourcing
2.7
RLG_DN
Low-Side MOSFET Driver
Pull-Down ON resistance
350 mA Sinking
0.8
OSCILLATOR
RFADJ = 750 k
PWM Frequency
fSW
RFADJ = 100 k
RFADJ = 42.2 k
RFADJ = 18.7 k
LM2745 External Synchronizing
Signal Frequency
Voltage Swing = 0V to VCC
50
300
475
600
725
kHz
1000
250
1000
SYNCL
LM2745 Synchronization Signal
Low Threshold
fSW = 250 kHz to 1 MHz
1
V
LM2745 Synchronization Signal
SYNCH
High Threshold
fSW = 250 kHz to 1 MHz
2
V
DMAX
Max High-Side Duty Cycle
LOGIC INPUTS AND OUTPUTS
fSW = 300 kHz
fSW = 600 kHz
fSW = 1 MHz
86
78
%
67
VSTBY-IH
Standby High Trip Point
VSTBY-IL
Standby Low Trip Point
VSD-IH
VSD-IL
VPWGD-TH-LO
VPWGD-TH-HI
VPWGD-HYS
SD Pin Logic High Trip Point
SD Pin Logic Low Trip Point
PWGD Pin Trip Points
PWGD Pin Trip Points
PWGD Hysteresis
VFB = 0.575V, VBOOT = 3.3V
VSD Rising
VFB = 0.575V, VBOOT = 3.3V
VSD Falling
VSD Rising
VSD Falling
VFB Falling
VFB Rising
VFB Falling
VFB Rising
1.1
V
0.232
V
1.3
V
0.8
V
0.408 0.434 0.457
V
0.677 0.710 0.742
V
60
mV
90
Note 1: Absolute maximum ratings indicate limits beyond which damage to the device may occur. Operating ratings indicate conditions for which the device
operates correctly. Operating Ratings do not imply guaranteed performance limits.
Note 2: The power MOSFETs can run on a separate 1V to 14V rail (Input voltage, VIN). Practical lower limit of VIN depends on selection of the external MOSFET.
See the MOSFET GATE DRIVERS section under Application Information for further details.
Note 3: ESD using the human body model which is a 100pF capacitor discharged through a 1.5 kresistor into each pin.
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DESCRIPTION
The LM2745/8 are high-speed synchronous buck regulator controllers with an accurate feedback voltage accuracy of ±1.5%. It can provide simple down conversion to output voltages as low as 0.6V. Though the control sections of the IC are rated for 3 to 6V, the driver sections are 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 MOSFETs 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 LM2745/8 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 LM2745 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 between component size, cost and efficiency.

FEATURES
• Switching Frequency from 50 kHz to 1 MHz
• Switching Frequency Synchronize Range 250 kHz to 1 MHz (LM2745 Only)
• Startup with a Pre-biased Output Load
• Power Stage Input Voltage from 1V to 14V
• Control Stage Input Voltage from 3V to 6V
• Output Voltage Adjustable Down to 0.6V
• Power Good Flag and Shutdown
• Output Overvoltage and Undervoltage Detection
• ±1.5% Feedback Voltage Accuracy Over Temperature
• Low-side Adjustable Current Sensing
• Adjustable Soft-start
• Tracking and Sequencing with Shutdown and Soft Start Pins
• TSSOP-14 Package

APPLICATIONS
• Down Conversion from 3.3V
• Cable Modem, DSL and ADSL
• Laser Jet and Ink Jet Printers
• Low Voltage Power Modules
• DSP, ASIC, Core and I/O

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