SC1470 Datasheet, PDF (1/21 Pages) Semtech Corporation – Synchronous Buck Pseudo Fixed Frequency Power Supply Controller

POWER MANAGEMENT
Description
The SC1470 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. The excellent transient response
means that SC1470 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. At light
loads, Power-Save Mode enables the SC1470 to skip
PWM pulses for better efficiency.
The output voltage can be adjusted from 0.5V to VCCA.
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.
Typical Application Circuit
SC1470
Synchronous Buck
Power Supply Controller
Features
‹ Constant on-time for fast dynamic response
‹ Programmable VOUT range = 0.5 – VCCA
‹ VIN range = 1.8V – 25V
‹ DC current sense using low-side RDS(ON)
Sensing or RSENSE in source of low-side
MOSFET for greater accuracy
‹ Resistor programmable frequency
‹ Cycle-by-Cycle current limit
‹ Digital soft-start
‹ Combined EN and PSAVE functions
‹ Over-voltage/under-voltage fault protection and
PGOOD output
‹ 5uA typical shutdown current
‹ Low quiescent power dissipation
‹ 14 Lead TSSOP package
‹ Industrial temperature range
‹ 1% Internal reference
‹ Integrated gate drivers with soft switching
‹ Efficiency > 90%
Applications
‹ Notebook computers
‹ CPU I/O supplies
‹ Handheld terminals and PDAs
‹ LCD monitors
‹ Network power supplies
1.8V - 25V
+
C1
PGOOD
+5V
R3
C5
R1
R2
+5V
U1
1
2
3
4
5
6
7
EN/PSV
TON
VOUT
VCCA
FBK
PGOOD
GND
BST
DH
LX
ILIM
VDDP
DL
PGND
14
13
12
11
10
9
8
C6
SC1470
+5V
D1
C3
R4
+
C2
Q1
L1
D2
Q2
+
C4
0.5V - 5.5V
R5
R6
Revision: October 14, 2004
1
www.semtech.com