LM2745MTCX Datasheet, PDF (1/37 Pages) Texas Instruments – LM2745 / LM2748 Synchronous Buck Controller with Pre-Bias Startup, and Optional Clock

LM2745, LM2748
www.ti.com
SNOSAL2E – APRIL 2005 – REVISED APRIL 2013
LM2745 / LM2748 Synchronous Buck Controller with Pre-Bias Startup, and Optional Clock
Synchronization
Check for Samples: LM2745, LM2748
FEATURES
1
•2 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
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 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 overvoltage
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.
Typical Application
VCC = 3.3V
D1
CBOOT
RCC
RPULL-UP
CCC
Clk
CClk
RFADJ
CSS
VCC
HG
LM2745
SD
BOOT
PWGD
ISEN
FREQ/SYNC
LG
SS/TRACK
PGND
SGND
PGND
EAO
FB
CC1
CC2
RC1
Q1
RCS
L1
Q2
RC2
CC3
VIN = 3.3V
+ _CIN1,2
VOUT = 1.2V@16A
RFB2
+
CO1,2
RFB1
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
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.
Copyright © 2005–2013, Texas Instruments Incorporated