Microsemi LX7186A User manual

User Guide

LX7186A 1.4 MHz 1A Synchronous Buck Converter

Evaluation Board

LX7186A 1.4 MHz 1A Synchronous Buck Converter Evaluation Board

Microsemi Proprietary and Confidential. User Guide Revision 1.0

Contents

1 Revision History ............................................................................................................................. 1

1.1 Revision 1.0 ........................................................................................................................................ 1

2 Product Description ....................................................................................................................... 2

2.1 Applications ........................................................................................................................................ 2

2.2 Key Features ....................................................................................................................................... 2

3 Evaluation Board Schematic .......................................................................................................... 3

4 Basic Connection Instructions ........................................................................................................ 4

5 Recommended Operating Conditions ............................................................................................ 5

5.1 Setting the Output Voltage ................................................................................................................. 5

6 PCB Layout of Evaluation Board ..................................................................................................... 6

7 Bill of Materials .............................................................................................................................. 9

8 Efficiency Plot ............................................................................................................................... 10

9 Dynamic Load Response .............................................................................................................. 11

10 Soft Start ..................................................................................................................................... 12

11 Ordering Information .................................................................................................................. 15

LX7186A 1.4 MHz 1A Synchronous Buck Converter Evaluation Board

Microsemi Proprietary and Confidential. User Guide Revision 1.0 1

1 Revision History

The revision history describes the changes that were implemented in the document. The changes are

listed by revision, starting with the most current publication.

1.1 Revision 1.0

Revision 1.0 was published in August 2017. It was the first publication of this document.

LX7186A 1.4 MHz 1A Synchronous Buck Converter Evaluation Board

Microsemi Proprietary and Confidential. User Guide Revision 1.0 2

2 Product Description

The LX7186A is 1.4 MHz fixed frequency, current-mode, synchronous PWM buck (step-down) DC-to-DC

converter, capable of driving a 1 A load with high efficiency, and excellent line and load regulation. The

devices integrate synchronous P-channel and N-channel power MOSFET switches with low on-

resistance. They accept an input voltage range from 2.5 V to 5.5 V and will enter 100% duty cycle at

dropout making them ideal for powering portable equipment that runs from a single Li-ion battery.

A standard series of inductors (available from several different manufacturers) is optimized for use with

the LX7186A. This feature greatly simplifies the design of switch-mode power supplies.

The converter includes standard safety features, such as over-current, short-circuit, and thermal

shutdown protection. This device is available in SOT23-5L and UDFN 2x2 6L packages.

2.1 Applications

Datacom

Portable devices

Smart phone

2.2 Key Features

Input supply range: 2.5 V–5.5 V

Output adjustable from 0.6 V–~VIN

100% duty cycle in dropout

Integrated NMOS and PMOS switches

Current mode control

1 A maximum output current

Fixed 1.4 MHz frequency

High efficiency: up to 98%

Built-in soft-start

Built-in OV, UV, and OT protection

Built-in short circuit protection

RoHS-compliant and Halogen-free

SOT23-5L or UDFN 2x2 6L packages

LX7186A 1.4 MHz 1A Synchronous Buck Converter Evaluation Board

Microsemi Proprietary and Confidential. User Guide Revision 1.0 3

3 Evaluation Board Schematic

The following illustrations show the evaluation board schematic for the LX7186A and LX7186A-UDFN

device.

Figure 1 • LX7186A Evaluation Board Schematic

Figure 2 • LX7186A-UDFN Evaluation Board Schematic

LX7186A 1.4 MHz 1A Synchronous Buck Converter Evaluation Board

Microsemi Proprietary and Confidential. User Guide Revision 1.0 4

4 Basic Connection Instructions

The following illustration shows how to connect the evaluation board to the power supply.

Figure 3 • Power Supply and Load Connection

LX7186A 1.4 MHz 1A Synchronous Buck Converter Evaluation Board

Microsemi Proprietary and Confidential. User Guide Revision 1.0 5

5 Recommended Operating Conditions

The following table lists the recommended operating conditions for the LX7186A evaluation board.

Table 1 • Recommended Operating Conditions

Description Symbol Min Max Unit

Input voltage VIN 2.5 5.5 V

Output current IOUT 0 1 A

Operating ambient temperature TA–40 85 °C

Enable chip EN 1.5 V

Shut down chip EN 0.4 V

5.1 Setting the Output Voltage

The following equation defines the value of V , where V = 0.6 V and R = 24 kΩ.OUT REF 4

LX7186A 1.4 MHz 1A Synchronous Buck Converter Evaluation Board

Microsemi Proprietary and Confidential. User Guide Revision 1.0 6

6 PCB Layout of Evaluation Board

The LX7186A evaluation board is four layers. The following illustrations depict each of the board's four

layers.

Figure 4 • LX7186A Top Silkscreen

Figure 5 • LX7186A Top Layer

LX7186A 1.4 MHz 1A Synchronous Buck Converter Evaluation Board

Microsemi Proprietary and Confidential. User Guide Revision 1.0 7

Figure 6 • LX7186A Bottom Layer

Figure 7 • LX7186A-UDFN Top Silkscreen

LX7186A 1.4 MHz 1A Synchronous Buck Converter Evaluation Board

Microsemi Proprietary and Confidential. User Guide Revision 1.0 8

Figure 8 • LX7186A-UDFN Top Layer

Figure 9 • LX7186A-UDFN Bottom Layer

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