Microsemi LX7165 User manual

LX7165 EVAL BOARD USER GUIDE
Microsemi
Analog Mixed Signal Group
One Enterprise Aliso Viejo, CA 92656 USA [phone], [phone]
Copyright 2012
Rev. 0.2, 2013-10-23
Rev. 1.0, 2013-10-23
LX7165 EVALUATION BOARD
USER GUIDE
LX7165 5 Amp Step Down Converter

LX7165 EVAL BOARD USER GUIDE
Microsemi
Analog Mixed Signal Group
One Enterprise Aliso Viejo, CA 92656 USA [phone], [phone]
Copyright 2012
Rev. 0.1, 2013-10-23
Rev. 1.0, 2013-10-23
Table of Contents
Introduction to Product ..............................................................................................1
Key Features ..............................................................................................................2
Applications ...............................................................................................................2
Part Specific Information...........................................................................................3
Evaluation Board Schematic......................................................................................3
Basic Connection Instructions ...................................................................................4
LX7165 I2C GUI........................................................................................................5
Recommended Operating Conditions........................................................................6
PCB Layout of Evaluation Board..............................................................................7
Bill of Material.........................................................................................................11
Efficiency Plot..........................................................................................................12
Dynamic Load Response Scope Shots.....................................................................13
Start up Scope Shots ................................................................................................16
Dimax Sub20 Installation ........................................................................................20

LX7165 EVAL BOARD USER GUIDE
Microsemi
Analog Mixed Signal Group
One Enterprise Aliso Viejo, CA 92656 USA [phone], [phone]
Page 1
Copyright 2012
Rev. 0.1, 2013-10-23
Rev. 1.0, 2013-10-23
Introduction to Product
The LX7165 is a digitally controlled step-down regulator IC with an integrated 30mΩ high-side P-
channel MOSFET and a 10mΩ low-side N-channel MOSFET. It features Microsemi’s proprietary
constant-frequency hysteretic control engine for near-instantaneous correction to sudden line/load
transients. It does not require high-ESR output capacitors and incorporates energy-saving “PSM”
(Power Saving or Pulse Skip Mode) at light loads, to extend battery life in mobile applications.
The LX7165 has an I2C serial interface port for output voltage margining and monitoring if
required (it can operate in default mode too). It includes robust fault monitoring functions.
The LX7165 will operate from 3V to 5.5V, and is available in several fixed output voltage options
from 0.6V to 0.97V (no voltage divider is necessary). Each version’s output voltage can also be
made adjustable with use of an external voltage divider.

LX7165 EVAL BOARD USER GUIDE
Microsemi
Analog Mixed Signal Group
One Enterprise Aliso Viejo, CA 92656 USA [phone], [phone]
Page 2
Copyright 2012
Rev. 0.1, 2013-10-23
Rev. 1.0, 2013-10-23
Key Features
Constant Frequency Hysteretic Control
Extremely Fast Line/Load Transient Response
I2C for Output Adjustment (3.4Mbps)
1.875MHz Switching Frequency
Extremely Low-RDSON MOSFETS
Input Voltage Rail 3.3V to 5V, Current 5A
Programmable Power Save Mode for Light-Load Efficiency
UVLO, OVP, OCP
0°C to +85°C Ambient Temperature
Available in WLCSP-20 (0.4mm pitch)
RoHS Compliant
Applications
High Performance HDD
LCD TV’s
Notebook/ Netbook
Server and Workstations
Video Cards
PoE Powered Devices

LX7165 EVAL BOARD USER GUIDE
Microsemi
Analog Mixed Signal Group
One Enterprise Aliso Viejo, CA 92656 USA [phone], [phone]
Page 3
Copyright 2012
Rev. 0.1, 2013-10-23
Rev. 1.0, 2013-10-23
Part Specific Information
IC Part Number
Description
LX7165-xyCSP
WLCSP 20Ball 0.4mm Pitch
Note: “x” is the 2 LSB bits of the binary I2C slave address (0 to 3);
“y” is the set output voltage (0 is 0.6V, 1 is 0.9V, 2 is 0.95V, 3 is 0.97V)
Evaluation Board Part Number
Description
LX7165 EVAL BOARD
Evaluation PCB for LX7165
Evaluation Board Schematic
Figure 1 Schematic of Evaluation Board

LX7165 EVAL BOARD USER GUIDE
Microsemi
Analog Mixed Signal Group
One Enterprise Aliso Viejo, CA 92656 USA [phone], [phone]
Page 4
Copyright 2012
Rev. 0.1, 2013-10-23
Rev. 1.0, 2013-10-23
Basic Connection Instructions
Figure 2 Power Supply and Load Connection with I2C Implemented
Figure 3 Power Supply and Load Connection without I2C Implemented

LX7165 EVAL BOARD USER GUIDE
Microsemi
Analog Mixed Signal Group
One Enterprise Aliso Viejo, CA 92656 USA [phone], [phone]
Page 5
Copyright 2012
Rev. 0.1, 2013-10-23
Rev. 1.0, 2013-10-23
LX7165 I2C GUI
Figure 4 LX7165 GUI
LX7165 I2C GUI is a graphic user interface that can read/write IC status or change default
settings via I2C serial portal. For example, it can used to enable/disable device, change output
voltage, or enable power saving mode, etc.
More information about register map and I2C function can be found in LX7165 datasheet.
Note: To use this GUI, a SUB-20 USB-I2C adaptor is needed. See Dimax SUB-20 and LX7165
GUI Installation for details.

LX7165 EVAL BOARD USER GUIDE
Microsemi
Analog Mixed Signal Group
One Enterprise Aliso Viejo, CA 92656 USA [phone], [phone]
Page 6
Copyright 2012
Rev. 0.1, 2013-10-23
Rev. 1.0, 2013-10-23
Recommended Operating Conditions
Description
Symbol
Min
Max
Unit
Input Voltage
VIN
3
5.5
V
Output Current
IOUT
0
5
A
Operating Ambient Temperature
TA
0
85
°C
Enable Chip
EN
VIN
Shut Down Chip
EN
Pull to GND
Enabling Regulator from I2C Bus
In addition to the ENABLE pin, the regulator can be enabled and disabled via the I2C bus by
programming the control register. During disable, the regulator and most of the support circuitry
is turned off. However, the I2C bus circuitry is still active and maybe programmed.
Setting the Output Voltage
Only use I2C interface can adjust VOUT from 0.6V to 1.2V. When I2C interface is implemented,
the reference voltage is programmed with the I2C bus VSEL register value.
    
Where NSEL is the decimal value of the 7 VSEL bits.
In case a higher output voltage is needed, it must be programmed through an external resistor
divider connected from SW to VOUT then to GND. For noise immunity, the lower resistor R2
from VOUT to GND should be greater than 100kOhm. A feed-forward capacitor C9 in parallel
with upper resistor is needed to ensure loop stability. Recommend C9=33pF. The formula below
gives the value of VOUT.
   

VREF is determined by the chip, for example, to set LX7165-03CSP VOUT = 1.83V, given
VREF = 0.97V. First pick the lower resistor R2=150k, calculate the upper resistor R1=133k, and
C9=33pF.

LX7165 EVAL BOARD USER GUIDE
Microsemi
Analog Mixed Signal Group
One Enterprise Aliso Viejo, CA 92656 USA [phone], [phone]
Page 7
Copyright 2012
Rev. 0.1, 2013-10-23
Rev. 1.0, 2013-10-23
PCB Layout of Evaluation Board
The LX7165 EVAL Board is a 4-layer board, the thickness of the board is 63mil in total. The
second layer to top layer is 7mil, the third layer to the bottom layer is 7mil. There’s no
microvias or blind vias needed, each signal can leave the LX7165 directly without using any
via under the device. And, it can lower the ESL with the bypass capacitors C2, C3 and C9
implemented. C4 is only needed when there’s long wires connected.
Figure 5 Layout Recommendation

LX7165 EVAL BOARD USER GUIDE
Microsemi
Analog Mixed Signal Group
One Enterprise Aliso Viejo, CA 92656 USA [phone], [phone]
Page 8
Copyright 2012
Rev. 0.1, 2013-10-23
Rev. 1.0, 2013-10-23
Figure 6 Top Silkscreen