Datasheet > LM34919B_1

LM34919B_1

更新时间： 2024-09-17 11:34:59

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美国国家半导体 - NSC		/
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12页	641K
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Evaluation Board provides the design engineer with a fully functional

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LM34919B_1 数据手册

National Semiconductor

Application Note 2016

Dennis Morgan

LM34919B Evaluation Board

May 27, 2010

The board’s specification are:

Introduction

•

Input Voltage: 6V to 24V

Output Voltage: 3.3V

The LM34919BEVAL evaluation board provides the design

engineer with a fully functional buck regulator, employing the

constant on-time (COT) operating principle. This evaluation

board provides a 3.3V output over an input range of 6V to 24V.

The circuit delivers load currents to 600 mA, with current limit

set at a nominal 800 mA. The board is populated with all

components except R5, C9 and C10. These components pro-

vide options for managing the output ripple as described later

in this document.

Maximum load current: 600 mA

Minimum load current: 0A

Current Limit: 780 mA to 815 mA

Measured Efficiency: 88.7% (V_IN= 6V, I_OUT= 300 mA)

Nominal Switching Frequency: 1.5 MHz

Size: 2.6 in. x 1.6 in. x 0.5 in

30110020

FIGURE 1. Evaluation Board - Top Side

versely with VIN to maintain a nearly constant switching fre-

Theory of Operation

quency. At the end of each on-time the Minimum Off-Timer

ensures the buck switch is off for at least 88 ns. In normal

operation, the off-time is much longer. During the off-time, the

load current is supplied by the output capacitor (C7, C8).

When the output voltage falls sufficiently that the voltage at

FB is below 2.5V, the regulation comparator initiates a new

on-time period. For stable, fixed frequency operation, a min-

imum of 25 mV of ripple is required at FB to switch the

regulation comparator. The current limit threshold is ≊780 mA

at Vin = 6V, and ≊812 mA at Vin = 24V. The variation is due

to the change in ripple current amplitude as Vin varies. Refer

to the LM34919B data sheet for a more detailed block dia-

Refer to the evaluation board schematic in Figure 1, which

contains a simplified block diagram of the LM34919B. When

the circuit is in regulation, the buck switch is on each cycle for

a time determined by R1 and VIN according to the equation:

The on-time of this evaluation board ranges from ≊424 ns at

VIN =6V, to ≊129 ns at VIN = 24V. The on-time varies in-

301100

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与LM34919B_1相关器件

型号	品牌	获取价格	描述	数据表
LM34919B_15	TI	获取价格	Ultra-Small 40-V 600-mA Constant On-Time Buck Switching Regulator
LM34919B-Q1	TI	获取价格	Ultra-Small 40-V 600-mA Constant On-Time Buck Switching Regulator
LM34919BQTL	NSC	获取价格	Ultra Small 40V, 600 mA Constant On-Time Buck Switching Regulator
LM34919BQTL/NOPB	TI	获取价格	Ultra-Small 40-V 600-mA Constant On-Time Buck Switching Regulator
LM34919BQTLX	NSC	获取价格	Ultra Small 40V, 600 mA Constant On-Time Buck Switching Regulator
LM34919BQTLX/NOPB	TI	获取价格	Ultra-Small 40-V 600-mA Constant On-Time Buck Switching Regulator
LM34919BTL	NSC	获取价格	Ultra Small 40V, 600 mA Constant On-Time Buck Switching Regulator
LM34919BTL/NOPB	TI	获取价格	Ultra-Small 40-V 600-mA Constant On-Time Buck Switching Regulator
LM34919BTLX	NSC	获取价格	Ultra Small 40V, 600 mA Constant On-Time Buck Switching Regulator
LM34919BTLX/NOPB	TI	获取价格	Ultra-Small 40-V 600-mA Constant On-Time Buck Switching Regulator

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