LMH2180SDEVAL National Semiconductor, LMH2180SDEVAL Datasheet

LMH2180SDEVAL

Manufacturer Part Number

LMH2180SDEVAL

Description

BOARD EVALUATION FOR LMH2180

Manufacturer

National Semiconductor

Datasheets

1.LMH2180SDENOPB.pdf (16 pages)

2.LMH2180SDEVAL.pdf (4 pages)

Specifications of LMH2180SDEVAL

Main Purpose

Timing, Clock Buffer / Driver / Receiver / Translator

Utilized Ic / Part

LMH2180

Lead Free Status / RoHS Status

Contains lead / RoHS non-compliant

Secondary Attributes

Embedded

Primary Attributes

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LMH2180 Evaluation Board

in LLP

General Description

This evaluation board is designed to aid in the characteriza-

tion of National Semiconductors LMH2180 75 MHz Dual

Clock Buffer. This board simplifies the connection and ease

of use of any oscillating input device. Use this evaluation

board as a guide for high frequency layout and as a tool to aid

in device testing and characterization.

Basic Operation

The LMH2180 is a device that contains two 75 MHz Clock

Buffer amplifiers. These amplifiers are specially designed to

minimize the effects of spurious signals from the digital chip

to other analog or mixed–signal chip. The LMH2180 also min-

imizes the influence of varying load resistance and capaci-

tance to the oscillator and increases the drive capability. The

buffers have a 106 V/µs internal slew rate at a supply current

of only 1.3 mA for one channel enabled and 2.3 mA for two

enabled channels. Each amplifier in the LMH2180 is capable

of driving loads up to 20 pF. The input of each buffer is inter-

nally biased at 1V. This allows AC coupling on the input. Each

buffer offers an enable pin that can be used to disable the

corresponding channel and to optimize consumption.

Channel Activation

Either channel can be independently enabled or shut down.

The enable logic can be provided to the evaluation board by

shunting a jumper on JR1 and JR2. Refer to States of

LMH2180 for the required control logic.

States of LMH2180

Layout Considerations

Careful consideration for circuitry design and PCB layout will

eliminate problems and will optimize the performance of the

LMH2180. It is best to have the same ground plane on the

PCB for all decoupling and other ground connections.

To ensure a clean supply voltage it is best to place decoupling

capacitors close to the LMH2180, between V

the Evaluation Board this capacitor C1 is placed on the bottom

side.

Another important issue is the value of the components, which

also determines the sensitivity to disturbances. Resistor val-

Channel On

IN1 to OUT1

IN2 to OUT2

Enable1

High

Don't Care

300492

Enable2

Don't Care

High

and V

. On

National Semiconductor

Application Note 1776

Gerrit de Wagt

August 21, 2008

ues have to be low enough to prevent noise coupling and

large enough to avoid a significant increase in power con-

sumption while loading inputs or outputs to heavily.

FIGURE 1. Schematic of the Evaluation Board

FIGURE 2. Layout of the Evaluation Board

www.national.com

30049201

30049204

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LMH2180SDEVAL Summary of contents

Page 1

... LLP General Description This evaluation board is designed to aid in the characteriza- tion of National Semiconductors LMH2180 75 MHz Dual Clock Buffer. This board simplifies the connection and ease of use of any oscillating input device. Use this evaluation board as a guide for high frequency layout and as a tool to aid in device testing and characterization ...

Page 2

The Bill of Material (BOM) of the evaluation board is given in the table below. Designator Description R1, R5 0603 Resistor R2, R7 0603 Resistor R3, R6 0603 Resistor R4, R8 0603 Resistor C1 Case B, Tantalum Capacitor C2, C5, ...

Page 3

Notes 3 www.national.com ...

Page 4

... 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 Conditioners www.national.com/timing Data Converters www.national.com/adc Displays www.national.com/displays Ethernet www.national.com/ethernet Interface www.national.com/interface LVDS www.national.com/lvds Power Management www.national.com/power Switching Regulators www.national.com/switchers LDOs www ...

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