
PRODUCT SPECIFICATION
FAN5232
REV. 1.1.1 10/7/02
5
Table 1. RC5232 Application Bill of Materials
Reference
C1
Manufacturer, Part #
SANYO
25SV47M
Any
AVX
TPSE227M016#0100
Any
Any
Any
Any
Fairchild
MBR0540L
Coiltronics
UP2B-1R5
Fairchild
FDS6690A
Fairchild
FDS6680S
Fairchild FAN5232
Quantity Description
1
47μF, 25V
Comments
OSCON, I
rms
= 3.5A
C2-5
C6
4
1
100nF, 50V
220μF, 16V
Ceramic
Tantalum, ESR=100m
R1
R2, R4
R3, R5
R6
D1
1
2
2
1
1
10K
4.7
1K
715
500mA, 40V Schottky
, 1%
, 1%
, 1%
, 1%
L1
1
1.5μH, 8.3A
R < 8m
Q1
1
30V N-channel MOSFET
R = 20m
@ V
GS
= 4.5V
Q2
1
30V N-channel MOSFET
with Integrated Schottky
Controller
R = 17m
@ V
GS
= 4.5V
U1
1
Application Information
Overview
The FAN5232 is a high efficiency and high precision DC/DC
controller for LCD PCs and portable applications. It provides
a switcher controller capable of generating a voltage between
5V to 80% of Vin, and a 5V and a 3.3V linear regulator for
standby applications. The controller has a power good output
and an enable/soft start to permit proper system sequencing.
Initialization
The FAN5232 automatically initializes upon receipt of input
power. The Power-on Reset (POR) function continually
monitors the input supply voltage on the V
initiates soft start operation after the input supply voltage
exceeds 4.5V. Should this voltage drop below 4.0V, POR
disables the chip.
CC
pin and
Soft Start
When soft start is initiated by POR, and if the SDWN pin is
not held low, the voltage on the SDNADJ pin begins ramping
up, with the rate of rise set by the external capacitor on the
pin. Below 700mV, the output is off. Between 700mV and
1.6V, the output is allowed to linearly ramp up. Above 1.6V,
the output is fully enabled, and regulates.
Shutdown
There are two separate shutdown pins to provide output
power control – SDWN, and SDNADJ. Taking the SDNADJ
pin low will disable the switcher output and reset the output’s
internal latches for short circuit, under-voltage and over-volt-
age. Taking the SDWN pin low puts the entire chip in shut-
down. Each of the SDN pins has an internal
pull-up.
Switcher Architecture
Overview
The switcher output of the FAN5232 is generated from the
unregulated input (battery) voltage using a synchronous buck
converter. Both high-side and low-side MOSFETs are
N-channel.
The converter has pins for current sensing using the low-side
MOSFET R
DS,on
; a pin for voltage-sense feedback; a pin
that enables the converter and permits soft-start; a power
good pin; and a pin for generating the boost voltage to drive
the high-side MOSFET.