Microsemi LX7178 User manual

LX7178 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
LX7178 EVALUATION BOARD
USER GUIDE
LX7178 5 Amp Step Down Converter

LX7178 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
LX7178 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
Dynamic Load Response Scope Shots (Continue)..................................................14
Start up and Short Condition Scope Shots...............................................................15
Start up and Short Condition Scope Shots (Continue) ............................................16
Dimax Sub20 Installation ........................................................................................17

LX7178 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 LX7178 is a digitally controlled step-down regulator IC with an integrated 40mΩ high-side P-
channel MOSFET and a 14mΩ low-side N-channel MOSFET. It features Microsemi’s proprietary
constant-frequency hysteretic control engine for near-instantaneous correction to line/load
transients. It does not require high-ESR output capacitors and incorporates energy-saving “PSM”
(Power Save or Pulse Skip Mode) at light loads, to extend battery life in mobile applications.
The LX7178 has an I2C serial interface port for output voltage margining and monitoring if
required (it can also operate in default mode). In addition it includes robust fault monitoring
functions.
The LX7178 will operate from 3V to 5.5V, and is available in a fixed output voltage option of
0.8V (no voltage divider is necessary). The output voltage can also be adjusted with an external
voltage divider up to 3.3V.

LX7178 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
I2C Selectable 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
Notebook/ Netbook
Tablets/ Slates

LX7178 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
LX7178-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 0.8V, 2 is 0.9V, 3 is 0.975V)
Evaluation Board Part Number
Description
LX7178 EVAL BOARD
Evaluation PCB for LX7178
Evaluation Board Schematic
Figure 1: Schematic of Evaluation Board

LX7178 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 Instruction
Power Supply LOAD
Sub-20 USB-I2C Adaptor
IN
SDA
AGND
SCL
Computer
Figure 2: Power Supply and Load Connection with I2C Implemented
Power Supply LOAD
Figure 3: Power Supply and Load Connection without I2C Implemented

LX7178 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
LX7178 I2C GUI
Figure 4: LX7178 I2C GUI
LX7178 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 LX7178 datasheet.
Note: To use this GUI, a sub-20 USB-I2C adaptor is needed. See Dimax SUB-20 Installation for
details.

LX7178 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
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 EN 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
Using the I2C interface you 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 100kΩ. The formula below calculates the value of
VOUT based on the resistor divider R1 & R2.
   

VREF is determined by the chip, for example, to set the LX7178-01CSP to a VOUT = 0.96V,
given VREF = 0.8V. First pick the lower resistor R2=150k, calculate the upper resistor R1=30.1k.

LX7178 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 LX7178 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. No microvias or
blind vias are needed; each signal can leave the LX7178 directly without using any via under
the device. The layout so implemented can lower the ESL with the bypass capacitors C2, C3
and C9, only C4 is located some distance from the controller.
Figure 5: Layout Recommendation

LX7178 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

LX7178 EVAL BOARD USER GUIDE
Microsemi
Analog Mixed Signal Group
One Enterprise Aliso Viejo, CA 92656 USA [phone], [phone]
Page 9
Copyright 2012
Rev. 0.1, 2013-10-23
Rev. 1.0, 2013-10-23
Figure 7: Layer 1: Top Layer
Figure 8: Layer 2: Ground Layer

LX7178 EVAL BOARD USER GUIDE
Microsemi
Analog Mixed Signal Group
One Enterprise Aliso Viejo, CA 92656 USA [phone], [phone]
Page 10
Copyright 2012
Rev. 0.1, 2013-10-23
Rev. 1.0, 2013-10-23
Figure 9: Layer 3: Sense Layer
Figure 10: Layer 4: Bottom Layer

LX7178 EVAL BOARD USER GUIDE
Microsemi
Analog Mixed Signal Group
One Enterprise Aliso Viejo, CA 92656 USA [phone], [phone]
Page 11
Copyright 2012
Rev. 0.1, 2013-10-23
Rev. 1.0, 2013-10-23
Bill of Material
MISCELLANEOUS COMPONENTS
Item
Part Description
Reference
Qty
1
Microsemi IC –LX7178-xy
U1
1
2
Test Point
SW, PGOOD, VIN_S, VO_S,
GND_S, GND_S
6
3
Terminal
VIN, VOUT, GND, GND
4
4
Jumper/3pin
JP2
1
5
Jumper/4pin
J2
1
CAPACITORS
Item
Part Description
Reference
Qty
6
1uF/10V/X5R
C2
1
7
22uF/10V/X5R
C3, C8
2
8
47uF Electronic/35V
C4
1
9
22uF/6.3V/X5R
C5, C6, C7
3
RESISTORS
Item
Part Description
Reference
Qty
10
30.1kΩ
R1
1
11
150kΩ
R3
1
12
10kΩ
R5, R6
2
13
100kΩ
R7
1
14
0
R8
INDUCTOR
Item
Part Description
Reference
Qty
15
0.47uH -- IHLP-2020CZ-01series
L1
1

LX7178 EVAL BOARD USER GUIDE
Microsemi
Analog Mixed Signal Group
One Enterprise Aliso Viejo, CA 92656 USA [phone], [phone]
Page 12
Copyright 2012
Rev. 0.1, 2013-10-23
Rev. 1.0, 2013-10-23
Efficiency Plot
Figure 11: Efficiency Plot of LX7178-01CSP
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
10 100 1000
Efficiency
Load Current (mA)
LX7178 5V VIN Efficiency
0.96V PSM
0.96V PWM
1.8V PSM
1.8V PWM
3.3V PSM
3.3V PWM
+

LX7178 EVAL BOARD USER GUIDE
Microsemi
Analog Mixed Signal Group
One Enterprise Aliso Viejo, CA 92656 USA [phone], [phone]
Page 13
Copyright 2012
Rev. 0.1, 2013-10-23
Rev. 1.0, 2013-10-23
Dynamic Load Response Scope Shots
Figure 12: No load to 0.5A PWM
Figure 13: No load to 0.5A PSM
CH2: VOUT, CH4: ILOAD
CH2: VOUT, CH4: ILOAD
Figure 14: 0.5A to 2.5A PWM
CH2: VOUT, CH4: ILOAD
Figure 15: 0.8A to 2.5A PWM
CH2: VOUT, CH4: ILOAD

LX7178 EVAL BOARD USER GUIDE
Microsemi
Analog Mixed Signal Group
One Enterprise Aliso Viejo, CA 92656 USA [phone], [phone]
Page 14
Copyright 2012
Rev. 0.1, 2013-10-23
Rev. 1.0, 2013-10-23
Dynamic Load Response Scope Shots (Continue)
Figure 16: 0.5A to 2.5A PWM Rising Edge
Figure 17: No load to 0.5A PSM Rising Edge
CH2: VOUT, CH3: SW, CH4: ILOAD
CH2: VOUT, CH3: SW, CH4: ILOAD
Figure 18: 0.5A to 2.5A PWM Falling Edge
CH2: VOUT, CH3: SW, CH4: ILOAD
Figure 19: No load to 0.5A PSM Falling Edge
CH2: VOUT, CH3: SW, CH4: ILOAD

LX7178 EVAL BOARD USER GUIDE
Microsemi
Analog Mixed Signal Group
One Enterprise Aliso Viejo, CA 92656 USA [phone], [phone]
Page 15
Copyright 2012
Rev. 0.1, 2013-10-23
Rev. 1.0, 2013-10-23
Start up and Short Condition Scope Shots
Figure 20: Startup with ENABLE toggled
Figure 21: Soft start VIN tied to ENABLE
CH2: EN, CH3: VOUT
CH2: EN, CH3: VOUT
Figure 22: Start Up When Vin=4.5V Load=0.5ohm
CH2: PG, CH3: VOUT, CH4: Inductor Current
Figure 23: Power into Short
CH2: VIN, CH3: VOUT, CH4: Inductor Current

LX7178 EVAL BOARD USER GUIDE
Microsemi
Analog Mixed Signal Group
One Enterprise Aliso Viejo, CA 92656 USA [phone], [phone]
Page 16
Copyright 2012
Rev. 0.1, 2013-10-23
Rev. 1.0, 2013-10-23
Start up and Short Condition Scope Shots
(Continue)
Figure 24: Power after Short
Figure 25: Recovery from Short
CH2: VIN, CH3: VOUT, CH4: Inductor Current
CH2: VIN, CH3: VOUT, CH4: Inductor Current

LX7178 EVAL BOARD USER GUIDE
Microsemi
Analog Mixed Signal Group
One Enterprise Aliso Viejo, CA 92656 USA [phone], [phone]
Page 17
Copyright 2012
Rev. 0.1, 2013-10-23
Rev. 1.0, 2013-10-23
Dimax Sub20 Installation
Figure 19 Dimax SUB-20 Adapter
1. Uninstall any previous version of the SUB-20 adapter if exist.
2. Download and install SUB-20 USB driver from
http://www.xdimax.net/download/SUB-20-120121-x32.exe
Note: Install the x64 driver file for 64-bit systems.
More downloads available at http://www.xdimax.com/sub20/sub20.html#DLD
3. Connect SUB-20 device to computer's USB,
If this is the first time you connect the specific device, wait for SUB-20 driver installation
to finish - Found new hardware, let computer auto search for driver.
4. Firmware update:
The SUB-20 firmware version should be 0.3.5.
Open “Firmware updater” tool. The Firmware updater tool has a shortcut on the
desktop. It may also be found at StartPrograms SUB-20 Firmware
updater.
5. Follow the instructions in the following link: SUB-20 Firmware Update
6. Connect the adaptor according to the following connection:
4 PIN to 9PIN cable connects LX7178 EVB I2C port and SUB-20 ( Unused pin
on 4 PIN connecter aligns with V+ pin on I2C port )
USB to mini-USB cable connects SUB-20 and PC
SUB-20 DB-9 connector pin #5 = GND
SUB-20 DB-9 connector pin #6 = I2C_SDA
SUB-20 DB-9 connector pin #8 = I2C_SCL
7. Install LX7178 GUI
Click CD:/LX7178 GUI/I2C Register Access_1_0_8_x.exe to start the installation,
To open the GUI, go to Startup> All Programs> Microsemi> Register Access>
Choose "LX7165" when "production selects window “pops out.
8. LX7178 GUI and SUB-20 driver could be found in the Support CD