DDR Memory
Power Supply Controller
POWER MANAGEMENT
Description
The SC1480 is a single output, constant on-time
synchronous-buck, pseudo-fixed frequency, PWM
controller intended for use in notebook computers and
other battery operated portable devices. Features
include high efficiency and fast dynamic response with
no minimum on time, a reference input and a buffered
REFOUT pin capable of sourcing 3mA. The excellent
transient response means that SC1480 based solutions
will require less output capacitance than competing fixed
frequency converters.
The 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.
The SC1480 incorporates two power-reducing states,
standby and shutdown. In standby mode, the switcher
output is shutdown but the buffered reference output
stays up, reducing quiescent current to a low 125µA. This
is particularly useful for reducing battery draw in systems
which implement a suspend-to-RAM (S3) state. The
SC1480 can be completely shut down, drawing less than
10µA.
The integrated gate drivers feature adaptive shoot-
through protection and soft switching. Additional features
include cycle-by-cycle current limit, digital soft-start,
overvoltage and under-voltage protection, and a PGOOD
output.
SC1480
Features
Constant on-time for fast dynamic response
Programmable VOUT based on external reference
VIN range = 1.8V – 25V
DC current sense using low-side RDS(ON) sensing
or sense resistor
3mA reference output buffer
Low power S3 state
Resistor programmable frequency
Cycle-by-cycle current limit
Digital soft start
Output current source-sink capability
Overvoltage/under-voltage fault protection and
PGOOD output
Under 10uA typical shutdown current
Low quiescent power dissipation
14-Pin TSSOP package. Also available in Lead-free
package which is fully WEEE and RoHS compliant
Industrial temperature range
Integrated gate drivers with soft switching
Efficiency >90%
Applications
Notebook computers
CPU I/O supplies
Handheld terminals and PDAs
LCD monitors
Network power supplies
Typical Application Circuit
4.5V - 25V
VDD = 2.5V
+5VRUN
C1
R1
REFOUT
C3
+5VSB
R2
R3
+5V
R4
1
2
3
4
5
6
7
C8
C9
U1
BST
REFIN
DH
TON
REFOUT
LX
VCCA
ILIM
FBK
VDDP
PGOOD
DL
GND
PGND
SC1480
R7
C4
C2
D1
C5
Q1
14
13
12
11
10
9
8
C10
L1
1.25VOUT
R6
Q2
D2
+
C6
C7
R5
PGOOD
Revision: August 30, 2006
1
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