MP3908 Current Mode PWM Controller0 pages

MP3908 Current Mode PWM Controller with Synchronous Secondary Gate Drive The Future of Analog IC Technology- 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 270|jA 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 Օ Synchronous Secondary Gate Drive  Current Mode Control Օ 10V MOSFET Gate Drivers  Drives >10A MOSFETs Օ Soft-Start  Cycle-by-Cycle Current Limiting Օ Slope Current Compensation  Lossless Current Sense (V|sense<28V) Օ 50jA Shutdown Current  270uA typical Operating Current Օ 250KHz Constant Frequency Operation  Applicable to Boost, SEPIC, Flyback and Forward Topologies Օ Available in a 10-Pin MSOP Package APPLICATIONS  PoE PD Power Supplies Օ TV CCFL Power Generation  Telecom Isolated Power Օ Brick Modules  Off-line Controller "MPS" and "The Future of Analog IC Technology" are Registered Trademarks of Monolithic Power Systems, Inc. TYPICAL APPLICATION C5_l~ -wv- Rq -5կT -OV|N 36V-72V I OvOUT C2 5V Efficiency vs. Output Current 4.7MF 1 VCC DELAY GND ADJ mp3908 EN MAIN ISENSE CSS SYNC COMP FB 95 90 85 80 75 70 V|N= \ 18V n _J 1 ח _ =72V V|N= i OOuF/ 6.3VX2 ^dei V 2 > u z LU o ll ll r __C3 T33nF 4 C4. Optional' :R2 32kn?-10kQ 1 2 3 4 5 6 OUTPUT CURRENT (A) MP3908 Rev.0.9 8/29/2008 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2008 MPS. All Rights Reserved. 1