sc1406a Semtech Corporation, sc1406a Datasheet - Page 11

• Manufacturer Part Number: sc1406a
• Description: Portable Pentium Ii & Iii Power Supply Controller
• Manufacturer: Semtech Corporation

January 28, 2000
Core Converter Soft Start Timer
The main purpose of this block is to control the ramp-
up time of the core voltage in order to reduce the ini-
tial inrush current on the core input voltage (battery)
rail. The soft start circuit consists of an internal cur-
rent source, external soft start timing capacitor, inter-
nal switch across the capacitor, and a comparator
monitoring the capacitor voltage.
LINEAR REGULATOR CONTROLLER
1.5V Linear Regulator
This block is a linear regulator controller, which drives
an external PNP bipolar transistor as a pass element.
The linear regulator is capable of delivering 500mA
steady state DC current and should support transient
current of 1A, assuming the output filtering capacitor
is properly selected to provide enough charge for the
duration of the load transient.
2.5V Linear Regulator
This block is a low drop-out (LDO) linear regulator
controller, which drives an external PNP bipolar tran-
sistor as a pass element. The LDO linear regulator is
capable of delivering 100mA steady DC current and
should support transient current of 100mA, assuming
the output filtering capacitor is properly selected to
provide enough charge for the duration of the load
transient.
APPLICATION INFORMATION
Power on/off Sequence
See Application note AN99-12 for further information.
© 2000 SEMTECH CORP.
PORTABLE PENTIUM
POWER SUPPLY CONTROLLER
652 MITCHELL ROAD
Linear Regulator Soft Start Timer
A soft start timer circuit of the linear regulators is simi-
lar to that of the core converter, and is used to control
the ramp up time of the linear regulator output volt-
ages. For maximum flexibility in controlling the start
up sequence, the soft start function of the linear regu-
lators is separated from that of the core converter.
VOLTAGE CLAMP
The level translator converts an input voltage swing
on the IO rail, into a voltage swing on the CLK or VCC
rail depending on where the open drain output of the
translator is tied to through an external pull-up resistor.
The level translator has to track the input in phase,
and must be able to switch in 5ns (typical) following an
input threshold intercept.
Pentium is a registered trademark of Intel Corporation
®
II & III
NEWBURY PARK CA 91320
SC1406A
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