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