LM34914_14 datasheet(7/21 Pages) TI1

部件名	LM34914

功能描述	Ultra Small 1.25A Step-Down Switching Regulator with Intelligent Current Limit

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制造商	TI1 [Texas Instruments]

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UVLO

VIN

VCC

SW Pin

Inductor

Current

SS Pin

t2

VOUT

7.0V

2.5V

t1

LM34914

www.ti.com

SNVS453A – MAY 2007 – REVISED DECEMBER 2007

Figure 2. Startup Sequence

Functional Description

The LM34914 Step Down Switching Regulator features all the functions needed to implement a low cost, efficient

buck bias power converter capable of supplying at least 1.25A to the load. This high voltage regulator contains

an N-Channel buck switch, is easy to implement, and is available in the thermally enhanced 3mm x 3mm LLP-10

package. The regulator’s operation is based on a constant on-time control scheme where the on-time is

determined by VIN. This feature results in the operating frequency remaining relatively constant with load and

input voltage variations. The feedback control scheme requires no loop compensation resulting in very fast load

transient response. The valley current limit scheme protects against excessively high currents if the output is

short circuited when VIN is high. To aid in controlling excessive switch current due to a possible saturating

inductor the valley current limit threshold changes with input and output voltages, and the on-time is reduced by

approximately 50% when current limit is detected.The LM34914 can be applied in numerous applications to

efficiently regulate down higher voltages. Additional features include: Thermal shutdown, VCC under-voltage lock-

out, gate drive under-voltage lock-out, and maximum duty cycle limit.

Control Circuit Overview

The LM34914 buck DC-DC regulator employs a control scheme based on a comparator and a one-shot on-timer,

with the output voltage feedback (FB) compared to an internal reference (2.5V). If the FB voltage is below the

reference the buck switch is switched on for a time period determined by the input voltage and a programming

resistor (RON). Following the on-time the switch remains off until the FB voltage falls below the reference, but not

less than the minimum off-time forced by the LM34914. The buck switch is then turned on for another on-time

period.

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类似零件编号 - LM34914_14

制造商	部件名	数据表	功能描述
Texas Instruments	LM34914	1Mb / 24P	[Old version datasheet] Ultra Small 1.25A Step-Down Switching Regulator with Intelligent Current Limit

制造商	部件名	数据表	功能描述
Texas Instruments	LM34914	1Mb / 24P	[Old version datasheet] Ultra Small 1.25A Step-Down Switching Regulator with Intelligent Current Limit
National Semiconductor ...	LM34914	328Kb / 14P	Ultra Small 1.25A Step-Down Switching Regulator with Intelligent Current Limit
National Semiconductor ...	LM34917A	554Kb / 16P	Ultra Small 33V, 1.25A Constant On-Time Buck Switching Regulator with Intelligent Current Limit
Texas Instruments	LM34917A	967Kb / 22P	[Old version datasheet] Ultra Small 33V, 1.25A Constant On-Time Buck Switching Regulator with Intelligent Current Limit
Texas Instruments	LM34917A	919Kb / 21P	[Old version datasheet] Ultra Small 33V, 1.25A Constant On-Time Buck Switching Regulator with Intelligent Current Limit
Linear Technology	LT3663	352Kb / 16P	1.2A Step-Down Switching Regulator with Output Current Limit
National Semiconductor ...	LM34930	371Kb / 18P	Ultra Small 33V, 1A Constant On-Time Buck Switching Regulator with Intelligent Current Limit
Monolithic Power System...	MP28127	420Kb / 9P	1.25A, 5.5V Synchronous Step-Down Switching Regulator
Texas Instruments	LM34910C	848Kb / 19P	[Old version datasheet] High Voltage (50V, 1.25A) Step Down Switching Regulator
National Semiconductor ...	LM34910C	270Kb / 12P	High Voltage (50V, 1.25A) Step Down Switching Regulator