FAN5235 Datasheet, PDF (1/15 Pages) Fairchild Semiconductor – System Electronics Regulator for Mobile PCs

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
Applications
• Notebook PCs and PDAs
• Hand-held portable instruments
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.
Typical Application
3.3V-ALWAYS@50mA
5V-ALWAYS
3.3V @ 5A
+
5V-ALWAYS@ 50mA
SDN3.3
PGOOD
Vin = 5.4-24V
FAN5235
1 VIN
CPUMP5 24
2 3.3 ALW
HSD5 23
3 CPUMP3.3
SW5 22
4 HSD3.3
ISEN5 21
5 SW3.3
6 5V-ALW
7 LSD3.3
8 GND3.3
9 ISEN3.3
LSD5 20
GND5 19
VFB5 18
SDN5 17
SW12 16
10 VFB3.3
11 SDN3.3
12 PGOOD
VFB12 15
SGND 14
SDWN 13
SDN5
VFB12
SDWN
5V-ALWAYS
5V @ 5A
+
12V @ 120mA
+
REV. 1.3.3 1/3/02