MP3908 Datasheet, PDF (1/11 Pages) Monolithic Power Systems – Current Mode PWM Controller with Synchronous Secondary Gate Drive

The Future of Analog IC Technology
MP3908
Current Mode PWM Controller
with Synchronous Secondary Gate Drive
DESCRIPTION
The MP3908 is a flexible current-mode PWM
controller optimized for power-supply
applications. The MP3908 features resistor-
programmable dead-time control to optimize
efficiency for a broad number of different
configurations, and a synchronous secondary
gate drive. The MOSFET drivers are capable
of driving >10A MOSFETs. It has an operational
current of typically 270µA and can accommodate
off-line, Telecom and non-isolated applications.
Under-voltage lockout, soft-start, slope
compensation and peak current limiting are all
included. In a boost application, with an output
voltage of less than 28V, the current sense pin
can connect directly to the drain of the external
switch. This eliminates the requirement for an
additional current sensing element and its
associated efficiency loss.
While designed for boost applications, the MP3908
can also be used for other topologies including
Forward, Flyback and Sepic. The 10V gate driver
compliance minimizes the power loss of the external
MOSFET while allowing the use of a wide variety of
standard threshold devices. An externally
programmable delay following the turn off of the
synchronous rectifier allows the incorporation of
secondary side synchronous rectifier
The MP3908 is available in space saving 10-pin
MSOP package.
FEATURES
• Programmable Dead-Time
• Synchronous Secondary Gate Drive
• Current Mode Control
• 10V MOSFET Gate Drivers
• Drives >10A MOSFETs
• Soft-Start
• Cycle-by-Cycle Current Limiting
• Slope Current Compensation
• Lossless Current Sense (V_ISENSE<28V)
• 50µA Shutdown Current
• 270uA typical Operating Current
• 250KHz Constant Frequency Operation
• Applicable to Boost, SEPIC, Flyback and
Forward Topologies
• Available in a 10-Pin MSOP Package
APPLICATIONS
• PoE PD Power Supplies
• TV CCFL Power Generation
• Telecom Isolated Power
• Brick Modules
• Off-line Controller
“MPS” and “The Future of Analog IC Technology” are Registered Trademarks of
Monolithic Power Systems, Inc.
TYPICAL APPLICATION
8
VCC
5 DELAY
7
GND
T1
ADJ
MP3908
2
EN
MAIN ⁹
1
CSS
ISENSE ⁶
SYNC ¹⁰
COMP
FB
3
4
Efficiency vs.
Output Current
95
90
85
80
75
70
65
60
0123456
OUTPUT CURRENT (A)
MP3908 Rev.0.9
www.MonolithicPower.com
1
8/29/2008
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