SC1480
DDR Memory
Power Supply Controller
POWER MANAGEMENT
Description
Features
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.
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
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.
Integrated gate drivers with soft switching
Efficiency >90%
Applications
Notebook computers
CPU I/O supplies
Handheld terminals and PDAs
LCD monitors
Network power supplies
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.
Typical Application Circuit
4.5V - 25V
VDD = 2.5V
+5VRUN
C1
R1
C2
REFOUT
D1
C3
R5
+5VSB
R2
R3
C4
+5V
C5
R4
Q1
U1
1
2
3
4
5
6
7
14
REFIN
BST
DH
13
12
11
10
9
L1
TON
1.25VOUT
REFOUT
VCCA
FBK
LX
ILIM
VDDP
DL
R6
C6
C7
+
PGOOD
PGOOD
GND
8
Q2
D2
PGND
SC1480
C10
R7
C8
C9
Revision: August 30, 2006
1
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