Microsemi LX7180A User Manual

LX7180A

User Guide

LX7180A 4 Amp Step-Down Converter Evaluation Board

LX7180A 4 Amp Step-Down 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 Enabling Regulator from I²C Bus ......................................................................................................... 5

5.2 Setting the Output Voltage ................................................................................................................. 5

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

7 Bill of Materials ............................................................................................................................ 10

8 Efficiency Plot ............................................................................................................................... 11

9 Dynamic Load Response Scope Shots .......................................................................................... 12

10 Start-up and Short Condition Scope Shots ................................................................................. 15

11 Ordering Information .................................................................................................................. 17

Microsemi Proprietary and Confidential. LX7180A User Guide Revision 1.0

LX7180A 4 Amp Step-Down 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

This document was published in November 2017. It was the first publication of this document.

Microsemi Proprietary and Confidential. LX7180A User Guide Revision 1.0 1

LX7180A 4 Amp Step-Down Converter Evaluation Board

2 Product Description

The LX7180A is a 4 A step-down regulator with integrated MOSFETs packaged in a space-saving QFN12
2 mm × 2 mm for today’s mobile devices. It uses an ultra-fast, constant frequency hysteretic control
method to minimize external filter components while maintaining excellent regulation. The LX7180A
reference voltage is programmable from 0.6 V to 1.195 V through a high speed (up to 3.4 MHz), bi­directional I C bus.

2

The LX7180A operates from 3 V to 5.5 V rails and outputs 0.6 V to 100% of the input voltage.

Cycle-by-cycle current limiting protects against over-current conditions. Hiccup mode provides
protection for heavy over-load or short-circuit faults. Thermal protection shuts down the regulator
under over-temperature conditions. Over voltage conditions will immediately shut off the output to
protect against permanent damage. The LX7180A automatically restarts when all fault conditions are
cleared.

2.1 Applications

High-performance HDDs
LCD TVs
Notebooks/netbooks
Servers and workstations
Video cards
PoE-powered devices
Smartphones

2.2 Key Features

0 A–4 A step-down regulator
Operational input supply voltage range: 3.0 V–5.5 V (short durations to 6.5 V)
Hysteretic control offers best transient response
PWM switching at a constant 1.65 MHz
Power save mode (PSM) can be selected to improve light load efficiency
100% duty ratio operation
Input under-voltage and over-voltage protection
Enable and Power Good function
I C serial interface at 3.4 Mbps

2

Internal soft-start
Cycle-by-cycle over current protection
Hiccup mode protects against short circuit faults
Seven-bit adjustable reference voltage through I C bus

2

RoHS-compliant

Microsemi Proprietary and Confidential. LX7180A User Guide Revision 1.0 2

LX7180A 4 Amp Step-Down Converter Evaluation Board

3 Evaluation Board Schematic

The following illustration shows the evaluation board schematic.

Figure 1 • Evaluation Board Schematic

Microsemi Proprietary and Confidential. LX7180A User Guide Revision 1.0 3

LX7180A 4 Amp Step-Down Converter Evaluation Board

4 Basic Connection Instructions

The following illustration shows how to connect the evaluation board to the power supply while I C is

2

implemented.

Figure 2 • Power Supply and Load Connection with I²C Implemented

The following illustration shows how to connect the board to the power supply without I C.

2

Figure 3 • Power Supply and Load Connection Without I²C Implemented

Microsemi Proprietary and Confidential. LX7180A User Guide Revision 1.0 4

LX7180A 4 Amp Step-Down Converter Evaluation Board

5 Recommended Operating Conditions

The following table lists the recommended operating characteristics for the LX7180A evaluation board.

Table 1 • Operating Conditions

Description Symbol Minimum Maximum Unit

Input voltage VIN 3.0 5.5 V

Output voltage VOUT 0.6 5.5 V

Output current (V = 3 V to 5 V)IN IOUT 0 4 A

Operating ambient temperature TA 0 85 °C

Enable chip EN VIN

Shut down chip EN Pull to GND

5.1 Enabling Regulator from I²C Bus

In addition to the EN pin, the regulator can be enabled and disabled through the I C bus by

2

programming the control register. During disable, the regulator and most of the support circuitry is
turned off. However, the I C bus circuitry is still active and may be programmed.

2

5.2 Setting the Output Voltage

Using the I C interface, you can adjust V from 0.6 V to 1.2 V. When the I C interface is implemented,

2

OUT

2

the reference voltage is programmed with the I C bus VSEL register value.

2

Where V is the decimal value of the 7 VSEL bits.SEL

In case a higher output voltage is needed, it must be programmed through an external resistor divider
connected from software to V then to GND.OUT

The following formula calculates the value of V based on the resistor divider R1 and R2.OUT

V is determined by the chip. For example, to set the LX7180A to a VOUT= 1.8 V, given V = 0.6 V, first REF REF
pick the lower resistor R2= 120K, calculate the upper resistor R1= 240K.

Microsemi Proprietary and Confidential. LX7180A User Guide Revision 1.0 5

LX7180A 4 Amp Step-Down Converter Evaluation Board

6 PCB Layout of Evaluation Board

The LX7180A evaluation board is a four-layer board. The recommended distance between ground layer
and the top layer is 6 mil. The following illustrations depict each of the board's four layers.

Figure 4 • Layer 1: Top

Microsemi Proprietary and Confidential. LX7180A User Guide Revision 1.0 6

LX7180A 4 Amp Step-Down Converter Evaluation Board

Figure 5 • Layer 2: Ground

Microsemi Proprietary and Confidential. LX7180A User Guide Revision 1.0 7

LX7180A 4 Amp Step-Down Converter Evaluation Board

Figure 6 • Layer 3: Sense

Microsemi Proprietary and Confidential. LX7180A User Guide Revision 1.0 8

LX7180A 4 Amp Step-Down Converter Evaluation Board

Figure 7 • Layer 4: Bottom

Microsemi Proprietary and Confidential. LX7180A User Guide Revision 1.0 9

LX7180A 4 Amp Step-Down Converter Evaluation Board

7 Bill of Materials

The following table lists the bill of materials (BOM) for the LX7175 evaluation board.

Table 2 • BOM

Item Part Description Reference Quantity

1 Microsemi IC—LX7180A-xy U1 1

2 Test Point (J3) SW, PGOOD, VIN_S, VO_S, GND_S, GND_S 6

3 Terminal VIN, VOUT, GND, GND 4

4 Jumper/4 pin J2 1

5 10 μF/10 V/10%/0805/X5R C1, C6 2

6 47 μF Electronic/35V C2 1

7 22 μF/6.3 V/10%/0805/X5R C3 1

8 500 kΩ/1%/0402 R1 1

9 100 kΩ/1%/0402 R2 1

10 0 Ω/1%/0402 R4, R8 2

11 10 kΩ/1%/0402 R6, R7 1

12 0.47 μH – IHLP2020CZERR47MO L1 1

Microsemi Proprietary and Confidential. LX7180A User Guide Revision 1.0 10

LX7180A 4 Amp Step-Down Converter Evaluation Board

8 Efficiency Plot

The following graph shows the efficiency of the LX7180A at a voltage output of 1 V.

Figure 8 • Efficiency Plot

Microsemi Proprietary and Confidential. LX7180A User Guide Revision 1.0 11

LX7180A 4 Amp Step-Down Converter Evaluation Board

9 Dynamic Load Response Scope Shots

The following illustrations show the dynamic load response for the evaluation board.

Figure 9 • Step Response

Note: CH2: VOUT, CH4: I .LOAD

Microsemi Proprietary and Confidential. LX7180A User Guide Revision 1.0 12

LX7180A 4 Amp Step-Down Converter Evaluation Board

Figure 10 • Step Response Rising Edge

Note: CH2: VOUT, CH3: SW Node, CH4: I .LOAD

Microsemi Proprietary and Confidential. LX7180A User Guide Revision 1.0 13

LX7180A 4 Amp Step-Down Converter Evaluation Board

Figure 11 • Step Response Falling Edge

Note: CH2: VOUT, CH3: SW Node, CH4: I .LOAD

Microsemi Proprietary and Confidential. LX7180A User Guide Revision 1.0 14

LX7180A 4 Amp Step-Down Converter Evaluation Board

10 Start-up and Short Condition Scope Shots

The following illustrations show the scope shots for the LX7180A.

Figure 12 • Start-up With ENABLE Toggled

Note: CH1: PG, CH2: EN, CH3: V , CH4: inductor current.OUT

Microsemi Proprietary and Confidential. LX7180A User Guide Revision 1.0 15

LX7180A 4 Amp Step-Down Converter Evaluation Board

Figure 13 • Soft-Start VIN Tied to ENABLE

Note: CH1: PG, CH3: V , CH4: inductor current.OUT

Microsemi Proprietary and Confidential. LX7180A User Guide Revision 1.0 16

LX7180A 4 Amp Step-Down Converter Evaluation Board

11 Ordering Information

Table 3 • Ordering Information

Part Number Description

LX7180A-01CLQ QFN 2 mm × 2 mm 12L IC

LX7180A-11CLQ

LX7180A-21CLQ

LX7180A-31CLQ

LX7180A-xyCLQ

1

LX7176A EVAL BOARD Evaluation PCB for LX7180A

1

Consult factory for other I C slave address and set output voltage options.

2

"x" stands for the 2 LSB bits of the binary I C slave address (0 to 3), and "y" is the set output voltage (0 is

2

0.6 V, 1 is 0.9 V, 2 is 0.95 V, and 3 is 0.97 V).

Microsemi Proprietary and Confidential. LX7180A User Guide Revision 1.0 17

LX7180A 4 Amp Step-Down Converter Evaluation Board

Microsemi Corporate Headquarters
One Enterprise, Aliso Viejo,
CA 92656 USA
Within the USA: [phone]
Outside the USA: [phone]
Fax: [phone]
Email: [e-mail]
www.microsemi.com

© 2017 Microsemi Corporation. All rights reserved. Microsemi and the
Microsemi logo are trademarks of Microsemi Corporation. All other
trademarks and service marks are the property of their respective owners.

Microsemi makes no warranty, representation, or guarantee regarding the information contained herein or the suitability of its products and s ervices
for any particular purpose, nor does Microsemi assume a ny liability whatsoever arising out of the app lication or use of any product or circuit. The
products sold hereunder and an y other products sold by Microsemi have been s ubject to limited testing and should not be us ed in conjunction with
mission-critical equipment or applications. Any performance specifications are believed to be reliable but are not verified, and Buyer must condu ct and
complete all performance and other testing of the products, alone and together with, or installed in , any end-products. Buyer shall not rely on any data
and per formance specifications or para meters provided by Microsemi. It is the Buyer's responsibility to ind ependently determine suitability of any
products and to test and verify the same. The information provided by Microsemi hereunder is provided "as is, where is" and with all faults, and the
entire risk associated with such information is entirely with the Buyer. Microsemi does not grant, explicitly or implicitly, to any party any patent rights,
licenses, or any other IP rights, whether with regard to such information itself or anything described by such information. Information provided in this
document is proprietar y to Microsemi, and Micr osemi reserves the right to make any changes to the information in this document or to any products
and services at any time without notice.

Microsemi C orporation (Nasdaq: MSCC) offers a com prehensive portfoli o of semiconduct or and system solu tions for aerosp ace & defense,
communications, data center and industrial markets. Products include high-performance and radiation-ha rdened a nalog mi xed-signal integrated
circuits, FPGAs, So Cs and ASICs; power managemen t products; timing and synchr onization devices and precise time solutions, setting the world's
standard for time; voice processing devices; RF solutions; discrete components; enterprise storage and communication solutions; security technologies
and scalable anti-ta mper products; Ethernet solutions; Power-over-Ethernet ICs and midspans; as well as custom des ign capabilities and services.
Microsemi is headquartered in Aliso Viejo, California, and has approximately 4,800 employees globally. Learn more at www.microsemi.com.

MSCC-0102-UG-01005-1.0-0717

Microsemi Proprietary and Confidential. LX7180A User Guide Revision 1.0 18