POWER MANAGEMENT
Description
Dual Synchronous Buck Pseudo Fixed
Frequency Power Supply Controller
Features
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
SC483
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.
VBAT
5VSUS
Applications
Notebook computers
CPT I/O supplies
Handheld terminals and PDAs
LCD monitors
Network power supplies
5VSUS
VBAT
D1
R1
RTON1
R2
22
10R
23
VOUT1
R3
25
R5
26
27
R7
C5
1nF
C6
1uF
VSSA1
5VSUS
D2
R8
RTON2
R9
8
10R
9
VOUT2
R10
11
R12
12
13
R14
C11
1nF
C12
1uF
VSSA2
14
FB2
PGD2
VSSA2
VDDP2
DL2
PGND2
17
Q4
16
VSSA2
C10
15
1uF
R13 0R
VCCA2
ILIM2
18
C9
+
10
EN/PSV2
TON2
VOUT2
BST2
DH2
LX2
21
Q3
20
19
L2
R11
VOUT2
C8
10uF
C7
0.1uF
28
FB1
PGD1
VSSA1
VDDP1
DL1
PGND1
3
2
VSSA1
C4
1
1uF
Q2
R6
0R
VCCA1
ILIM1
4
C3
+
24
U1
EN/PSV1
TON1
VOUT1
SC483
BST1
DH1
LX1
7
Q1
6
5
L1
R4
VOUT1
C2
10uF
C1
0.1uF
PGOOD
VBAT
5VSUS
VBAT
PGOOD
Revision: March 14, 2005
1
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