LX7178
3V to 5.5V, 5A Constant Frequency Hysteretic
Synchronous Buck Regulator with I
2
C
Production Datasheet
Description
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 I C 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 0.8V fixed output voltage option (no voltage
divider is necessary). The output voltage can also be
adjusted with an external voltage divider up to 3.3V.
2
Features
Constant Frequency Hysteretic Control
Extremely Fast Line/Load Transient Response
I
2
C for Output Adjustment (3.4Mbps)
1.875 MHz Switching Frequency
Extremely Low-R
DSON
MOSFETS
Input Voltage Rail 3.3V to 5V
Greater than 5A Output Current
I
2
C 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
Notebooks/Netbooks/Tablets/Slates
Figure 1:
Typical 5V to 0.8V application with I
2
C implemented
Copyright © 2014
Rev. 1.1, 8/7/2014
Microsemi
Analog Mixed Signal Group
One Enterprise Aliso Viejo, CA 92656 USA, 1-800-713-4113, 949-380-6100, fax 949-215-4996
Page 1
LX7178
3V to 5.5V, 5A Constant Frequency Hysteretic
Synchronous Buck Regulator with I
2
C
Production Datasheet
Other Application Diagrams
Figure 2:
Typical 5V to 0.96V application without I
2
C implemented
Figure 3:
Typical 5V to 0.96V application with I
2
C implemented
Copyright © 2014
Rev. 1.1, 8/7/2014
Microsemi
Analog Mixed Signal Group
One Enterprise Aliso Viejo, CA 92656 USA, 1-800-713-4113, 949-380-6100, fax 949-215-4996
Page 2
LX7178
3V to 5.5V, 5A Constant Frequency Hysteretic
Synchronous Buck Regulator with I
2
C
Production Datasheet
Pin/Ball Configuration
Part Marking:
MSC
XXXX
YWWA
XXXX=Device Number
E.g.: 7801=LX7178-01CSP
YWWA
Year/Work Week/Lot Code
Figure 4:
Pinout
Ordering Information
Ambient
Temperature
0°C to 85°C
Type
RoHS compliant,
Pb-free
2
Package
Set Output
Voltage
0.8V
Part Number
LX7178-01CSP
LX7178-xyCSP*
LX7178-01CSP-TR
LX7178-xyCSP-TR*
Packaging
Type
Bulk
Tape and Reel
WLCSP-20 (0.4mm pitch)
0.8V
* Consult factory for other I C slave address and set output voltage options.
2
“x” is the 2 LSB bits of the binary I C 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)
Copyright © 2014
Rev. 1.1, 8/7/2014
Microsemi
Analog Mixed Signal Group
One Enterprise Aliso Viejo, CA 92656 USA, 1-800-713-4113, 949-380-6100, fax 949-215-4996
Page 3
LX7178
3V to 5.5V, 5A Constant Frequency Hysteretic
Synchronous Buck Regulator with I
2
C
Production Datasheet
Pin/Ball Description
Pin/Ball
Number
Pin/Ball
Designator
Description
Open Drain status output, requires external pull up resistor. This pin
will go low when VOUT is outside the defined power good range, when
the die is hotter than the thermal shutdown threshold, when PVIN is
above the over voltage threshold, or when PVIN is below the under
voltage threshold.
Enable for switching regulator. Force high to enable, force low to
disable the IC.
Feedback Voltage sense – Analog Input – This voltage is compared with
the internal V
REF
voltage to control the hysteretic converter. Normally
this is connected to VOUT via a resistor divider network.
Serial Data Clock – Logic Input – Clock for the serial interface. Glitches
shorter than 50nS will be ignored. If the serial interface is not used,
connect to GND or VIN. This pin can also be connect to VOUT if
required by the layout.
Serial Data – Bi-Directional Logic – This I
2
C pin is used to receive clocked
serial data from the host and to send clocked serial data to the host.
Glitches shorter than 50nS will be ignored. If the serial interface is not
used in the application, this pin should be connected to VIN or GND.
Ground. Connect to ground plane.
Analog Ground. Connect to ground plane.
Input of IC and buck stage. Connect to input rail VIN (between 3V and
5.5V). A minimum input capacitance of one 1µF and one 22µF of X5R or
better multilayer ceramic, should be placed very close to IC between
this node and GND.
Switching Node. Drives the external L-C low pass filter.
A1
PGOOD
A2
EN
A3
FB
A4
SCL
B1
SDA
B2, B3,
C1 – C4
B4
D1, D2
E1, E2
D3, D4
E3, E4
GND
AGND
VIN
SW
Copyright © 2014
Rev. 1.1, 8/7/2014
Microsemi
Analog Mixed Signal Group
One Enterprise Aliso Viejo, CA 92656 USA, 1-800-713-4113, 949-380-6100, fax 949-215-4996
Page 4
LX7178
3V to 5.5V, 5A Constant Frequency Hysteretic
Synchronous Buck Regulator with I
2
C
Production Datasheet
Functional Block Diagram
Figure 5:
Block Diagram
Copyright © 2014
Rev. 1.1, 8/7/2014
Microsemi
Analog Mixed Signal Group
One Enterprise Aliso Viejo, CA 92656 USA, 1-800-713-4113, 949-380-6100, fax 949-215-4996
Page 5
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