FAN5235

www.fairchildsemi.com

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www.fairchildsemi.com

FAN5235
System Electronics Regulator for Mobile PCs

Features
Synchronous rectification 1% precision internal reference 90% efficiency Input and output voltage feedback 5.4V to 24V input voltage range Internally set 300kHz 15% oscillator 5V and 3.3V Main outputs switch out of phase 5V-ALWAYS and 3.3V-ALWAYS outputs Adjustable boost converter for 12V Boost converter slaved to 5V Main Input UVLO Outputs OVP of Buck Converters Precision current limit option for 5V, 3.3V Main Power Good Voltage Monitor

Description
The FAN5235 is a high efficiency and high precision DC/DC controller for notebook converters. Utilization of both input and output voltage feedback in a current-mode control allows for fast and stable loop response over a wide range of input and output voltage variations. The two main regulators switch out of phase to minimize input ripple current. Current sense based on MOSFET Rdson gives maximum efficiency, while also permitting use of a sense resistor for high accuracy. An externally adjustable boost converter can be set to generate 12V. The FAN5235 is available in a 24-pin QSOP package, and in a 24-pin TSSOP package.

Applications
Notebook PCs and PDAs Hand-held portable instruments

Typical Application
Vin 5.4-24V

FAN5235 1 VIN 3.3V-ALWAYS 50mA 5V-ALWAYS 2 3.3 ALW 3 CPUMP3.3 4 HSD3.3 3.3V 5A 5 SW3.3 5V-ALWAYS 50mA 6 5V-ALW 7 LSD3.3 8 GND3.3 9 ISEN3.3 10 VFB3.3 SDN3.3 PGOOD 11 SDN3.3 12 PGOOD LSD5 20 GND5 19 VFB5 18 SDN5 17 SW12 16 VFB12 15 SGND 14 SDWN 13 SDWN VFB12 SDN5 12V 120mA CPUMP5 24 HSD5 23 SW5 22 ISEN5 21 5V-ALWAYS 5V 5A

REV. 1.3.3 1/3/02