SC1480 Datasheet, PDF (1/22 Pages) Semtech Corporation – DDR Memory Power Supply Controller

SC1480
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.
Typical Application Circuit
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
4.5V - 25V
VDD = 2.5V
+5VRUN
C1
REFOUT
PGOOD
R1
C2
C3
+5VSB
R2
R3
C4
+5V
R4
R5
R7
C8
C9
U1
1
2
3
4
5
6
7
REFIN
BST
TON
DH
REFOUT LX
VCCA
ILIM
FBK
VDDP
PGOOD
DL
GND PGND
14
13
12
11
10
9
8
SC1480
D1
C5
R6
C10
Q1
L1
Q2
D2
+ C6
C7
1.25VOUT
Revision: August 30, 2006
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