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

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

Microsemi Proprietary and Confidential. User Guide Revision 1.0

LX7186A 1.4 MHz 1A Synchronous Buck Converter Evaluation Board

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.

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LX7186A 1.4 MHz 1A Synchronous Buck Converter Evaluation Board

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 on­resistance. 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

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LX7186A 1.4 MHz 1A Synchronous Buck Converter Evaluation Board

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

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LX7186A 1.4 MHz 1A Synchronous Buck Converter Evaluation Board

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

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LX7186A 1.4 MHz 1A Synchronous Buck Converter Evaluation Board

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

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LX7186A 1.4 MHz 1A Synchronous Buck Converter Evaluation Board

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

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LX7186A 1.4 MHz 1A Synchronous Buck Converter Evaluation Board

Figure 6 • LX7186A Bottom Layer

Figure 7 • LX7186A-UDFN Top Silkscreen

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LX7186A 1.4 MHz 1A Synchronous Buck Converter Evaluation Board

Figure 8 • LX7186A-UDFN Top Layer

Figure 9 • LX7186A-UDFN Bottom Layer

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LX7186A 1.4 MHz 1A Synchronous Buck Converter Evaluation Board

7 Bill of Materials

The following table lists the bill of materials for the LX7186A evaluation board.

Table 2 • Bill of Materials

Item Part Type Part Description Reference Qty

1 Miscellaneous Components Microsemi IC—LX7186A U1 1

2 Miscellaneous Components Test Point SW, VIN, VOUT, GND, GND 5

3 Miscellaneous Components Terminal VIN, VOUT, GND, GND 4

4 Miscellaneous Components Jumper/3-pin J1 1

5 Miscellaneous Components Scope Test Point JVOUT 1

6 Capacitors 4.7 µF/10 V/X5R C5 1

7 Capacitors 0.1 µF/6.3 V/X5R C7 1

8 Capacitors 22 µF/6.3 V/X5R C9 1

9 Resistors 75 kΩ R3 1

10 Resistors 24 kΩ R4 1

11 Inductor 2.2 µH/DO1813H-222 ML L2 1

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LX7186A 1.4 MHz 1A Synchronous Buck Converter Evaluation Board

8 Efficiency Plot

The following graph shows LX7186A efficiency at a voltage output of 2.5 V.

Figure 10 • LX7186A Efficiency with 2.5 V VOUT

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LX7186A 1.4 MHz 1A Synchronous Buck Converter Evaluation Board

9 Dynamic Load Response

The following graphs show the dynamic load response of the LX7186A device.

Figure 11 • Dynamic Load Response with IOUT = 35 mA↔600 mA

VIN = 5 V, VOUT = 3.3 V, Load 35 mA↔0.6 A.

Figure 12 • Dynamic Load Response 0.6 A↔1 A

VIN = 5 V, VOUT = 3.3 V, Load 0.6 A↔1 A.

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LX7186A 1.4 MHz 1A Synchronous Buck Converter Evaluation Board

10 Soft Start

The following graphs show the soft start for the LX7186A device.

Figure 13 • Startup with No Load

VIN= 5 V, VOUT= 3.3 V, no load.

Figure 14 • Startup with No Load

VIN= 5 V, VOUT= 3.3 V, no load.

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LX7186A 1.4 MHz 1A Synchronous Buck Converter Evaluation Board

Figure 15 • Startup with 1 A Resistive Load

VIN = 5 V, VOUT = 3.3 V, 1 A load.

Figure 16 • Start up with 1 A Resistive Load

VIN = 5 V, VOUT = 3.3 V, 1 A load .

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LX7186A 1.4 MHz 1A Synchronous Buck Converter Evaluation Board

Figure 17 • Start up with Fast VIN Rise and 10 mA Resistive Load

VIN = 5 V, VOUT = 3.3 V, 10 mA load.

Figure 18 • Start up with Fast VIN Rise and 800 mA Resistive Load

VIN = 5 V, VOUT = 3.3 V, 800 mA load.

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LX7186A 1.4 MHz 1A Synchronous Buck Converter Evaluation Board

11 Ordering Information

The following table lists the ordering information for the LX7186A evaluation board.

Table 3 • Ordering Information

Part Order Number Description

LX7186AISE SOT23-5L

LX7186AILD UDFN 2x2 6L

LX7186A EVALUATION BOARD Evaluation PCB for LX7186AISE

LX7186A-UDFN EVALUATION BOARD Evaluation PCB for LX7186AILD

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LX7186A 1.4 MHz 1A Synchronous Buck Converter Evaluation Board

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