LM2833ZMYEVAL National Semiconductor, LM2833ZMYEVAL Datasheet

LM2833ZMYEVAL

Manufacturer Part Number

LM2833ZMYEVAL

Description

BOARD EVAL LM2833 3MHZ 10MSOP

Manufacturer

National Semiconductor

Datasheets

1.LM2833XSDNOPB.pdf (22 pages)

2.LM2833ZMYEVAL.pdf (6 pages)

Specifications of LM2833ZMYEVAL

Main Purpose

DC/DC, Step Down

Outputs And Type

1, Non-Isolated

Voltage - Output

1.2V

Current - Output

Voltage - Input

3 ~ 5.5V

Regulator Topology

Buck

Frequency - Switching

3MHz

Board Type

Fully Populated

Utilized Ic / Part

LM2833

Silicon Manufacturer

National

Silicon Core Number

LM2833

Kit Application Type

Power Management - Voltage Regulator

Application Sub Type

Step Down Switching Regulator

Kit Contents

Board, Doc

Lead Free Status / RoHS Status

Lead free / RoHS Compliant

Power - Output

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LM2833Z LLP Demo Board

Introduction

The LM2833Z LLP Demo Board is designed to demonstrate

the capabilities of the LM2833Z 3MHz switching regulator in

an LLP-10 package.

The demo board is configured to provide an output of 1.2V at

up to 3A from an input voltage range of 3V to 5.5V. The board

is thermally optimized with the small solution size of 1.2" X

1.1", shown in the demo board schematic in Figure 1. The

output voltage can be configured to a different value by

changing the ratio between R1 and R2 according to the fol-

lowing equation:

The feedback voltage VFB is regulated at 0.60V typically.

The board has C5 reserved for two purposes given different

application scenarios. First, at high VOUT applications, the

control loop bandwidth is not as large as at low VOUT. Adding

C5 at high VOUT can significantly improve the load step re-

sponse by boosting the loop bandwidth without significantly

compromising phase margin. Secondly, it also helps to mini-

mize output voltage overshoot during sluggish startup, short

circuit release, and recovery from thermal shutdown, since it

creats a feed-forward path between VOUT and VFB, thus

speeding up Gm-amplifier recovery. In practice, for a few

kΩ of voltage divider bottom resistor R2, a 47nF ceramic ca-

pacitor is usually a good choice for C5. Note for applications

where VOUT is close to VFB, since R1 is small, the effective-

ness of adding C5 becomes decreasingly appreciable. There-

R1 = R2 x (VOUT / VFB - 1)

FIGURE 1. LM2833Z LLP Demo Board Schematic

300623

National Semiconductor

Application Note 1845

Alex Gao

February 27, 2009

fore, other measures need to be taken to achieve the desired

performance. For example, to minimize output overshoot dur-

ing slow startup at high VOUT, an alternative approach is to

apply a separate signal at the EN terminal after VIN is fully

established.

Another component which is not populated on the board is

C4, which is reserved for applications where a large output

capacitor is desired.

Table 1 lists the bill of materials of this demo board. The mea-

sured performance characteristics and layout of this board

are also included below.

Powering up the Board

Powering up the LM2833Z LLP demo board is a single-step

procedure, simply by applying a DC voltage of 3V to 5.5V to

VIN and GND terminals. By default, VINC is connected to VIN

through a low pass filter to remove any high frequency noise

present at the input. EN is connected to VINC through a

100kΩ resistor. A separate logic signal at the EN terminal can

be used, if startup and shutdown need to be controlled. A load

can be connected between VOUT and GND terminals before

or after the board is powered up. At VOUT of 1.2V, the internal

soft-start circuit can bring up VOUT smoothly regardless of

load or input voltage.

The LM2833Z is designed to skip some pulses at very light

loads to maintain output voltage regulation. Depending on

load levels, the circuit may operate in either discontinuous or

continuous conduction mode.

30062301

www.national.com

Related parts for LM2833ZMYEVAL

LM2833ZMYEVAL Summary of contents

Page 1

... R2, a 47nF ceramic ca- pacitor is usually a good choice for C5. Note for applications where VOUT is close to VFB, since R1 is small, the effective- ness of adding C5 becomes decreasingly appreciable. There- © 2009 National Semiconductor Corporation National Semiconductor Application Note 1845 Alex Gao ...

Page 2

Typical Performance Characteristics Efficiency vs Load Current Load Regulation Startup (V Slew Rate = 1V/ www.national.com Efficiency vs Load Current 30062302 Startup (V 30062304 Steady-state (CCM Mode) 30062306 2 30062303 Slew Rate = 0.2V/µ 30062305 30062307 ...

Page 3

Steady-state (DCM Mode) 30062308 Load Transient (Slew Rate = 0.1A/µs) (C5 not installed) 30062314 Line Transient 30062316 Steady-state (Pulse Skipping) Load Transient (Slew Rate = 0.1A/µs) (C5 = 47nF) Loop Gain 3 30062309 30062315 30062317 www.national.com ...

Page 4

... TABLE 1. Bill of Materials Part Value 3 C3216X5R0J226MT GRM216R71A224KC01D JMK316BJ476ML-T Open Open CRCW08052K00FKEA CRCW08052K00FKEA CRCW080510R0FKEA CRCW0805100KFKEA 4 Bottom Layer Internal Plane 2 (VIN) Part Number Manufacturer LM2833ZSD National Semiconductor NP04SZB1R0N Taiyo Yuden TDK Murata Taiyo Yuden CMS01 Toshiba Vishay Vishay Vishay Vishay 30062311 30062313 ...

Page 5

Notes 5 www.national.com ...

Page 6

... For more National Semiconductor product information and proven design tools, visit the following Web sites at: Products Amplifiers www.national.com/amplifiers Audio www.national.com/audio Clock and Timing www.national.com/timing Data Converters www.national.com/adc Interface www.national.com/interface LVDS www.national.com/lvds Power Management www.national.com/power Switching Regulators www.national.com/switchers LDOs www.national.com/ldo LED Lighting www ...

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