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POWER MANAGEMENT
Description
SC483
Dual Synchronous Buck Pseudo Fixed
Frequency Power Supply Controller
Revision: March 14, 2005
The SC483 is a dual output constant-on synchronous
buck PWM controller intended for use in notebook
computers and other battery operated portable devices.
Features include high efficiency and a fast dynamic
response with no minimum on time. The excellent
transient response means that SC483 based solutions
will require less output capacitance than competing fixed
frequency converters.
The switching frequency is constant until a step in load
or line voltage occurs at which time the pulse density
and frequency will increase or decrease to counter the
change in output or input voltage. After the transient
event, the controller frequency will return to steady state
operation. At light loads, Power-Save Mode enables the
SC483 to skip PWM pulses for better efficiency.
Each output voltage can be independently adjusted from
0.5V to VCCA. Two frequency setting resistors set the
on-time for each buck controller. The frequency can thus
be tailored to minimize crosstalk. The integrated gate
drivers feature adaptive shoot-through protection and
soft switching. Additional features include cycle-by-cycle
current limit, digital soft-start, over-voltage and under-
voltage protection, and a PGOOD output for each
controller.
Constant on-time for fast dynamic response
Programmable VOUT range = 0.5 – VCCA
VBAT Range = 1.8V – 25V
DC current sense using low-side RDS(ON)
sensing or sense resistor
Resistor programmable frequency
Cycle-by-cycle current limit
Digital soft-start
Separate PSAVE option for each switcher
Over-voltage/Under-voltage fault protection
10μA Typical shutdown current
Low quiescent power dissipation
Two Power Good indicators
1% Reference (2% system DC accuracy)
Integrated gate drivers with soft switching
Separate enables
28 Lead TSSOP
Industrial temperature range
Output soft discharge upon shutdown
Applications
Notebook computers
CPT I/O supplies
Handheld terminals and PDAs
LCD monitors
Network power supplies
Features
C6
1uF
R7
R3
VOUT1
C5
1nF
R1
RTON1
VBAT
PGOOD
Q2
Q1
C4
1uF
R4
D1
C1
0.1uF
C2
10uF
5VSUS
VBAT
L1
+
C3
VOUT1
R2
10R
R5
Q4
R14
Q3
C7
0.1uF
+
C9
C12
1uF
C11
1nF
PGOOD
VBAT
L2
R11
R12
D2
5VSUS
C8
10uF
R8
RTON2
C10
1uF
R10
R9
10R
VOUT2
VOUT2
R6
0R
R13 0R
5VSUS
5VSUS
VBAT
EN/PSV1
22
TON1
23
VOUT1
24
VCCA1
25
FB1
26
PGD1
27
VSSA1
28
PGND1
1
DL1
2
VDDP1
3
ILIM1
4
LX1
5
DH1
6
BST1
7
EN/PSV2
8
TON2
9
VOUT2
10
VCCA2
11
FB2
12
PGD2
13
VSSA2
14
PGND2
15
DL2
16
VDDP2
17
ILIM2
18
LX2
19
DH2
20
BST2
21
U1
SC483
VSSA2
VSSA2
VSSA1
VSSA1