AN010 Datasheet, PDF (1/9 Pages) Analog Intergrations Corporation – Advanced PC Motherboards

AN010
Cost-Effective Power Management Design for
Advanced PC Motherboards
Introduction:
In such a rapidly changing information industry, it
is essential to speed up the clock speed of CPU.
Without increasing power dissipation, the required
voltage for core part (V_core) in CPU such as
INTEL’s Pentium, Pentium II, Pentium III, AMD’s
K6 and K7 is keeping declining at the expense of
increasing in current. To meet this requirement,
the design of power converter on mother board
has been changed into a Multiple Output
Integrated Regulator instead of using the
traditional Linear Regulator, Asynchronous
Voltage Step-Down Regulator and Synchronous
Voltage Step-Down Regulator. To go along with
this trend, “Analog Integrations Corporation”
introduces a new IC product AIC1570 that
provides more integrating functions with higher
performance and lower system cost.
Features of AIC1570:
The function block diagram of AIC1570 is shown
in Figure 1. As illustrated, the AIC 1570 integrated
type regulator consists of three different output
signals from PWM Controller, Linear Controller
and Linear Regulator. It provides the required
voltage sources for Vcore, GTL bus (1.5 V) and
clock driver circuit (2.5 V). For PWM Controller,
the device uses two N-channel MOSFET to
execute a standard synchronous voltage step
-down and rectification. Cooperation of this with a
5-bit DAC converter can provide an accuracy
within 1% of reference voltage source (1.3 V~3.5
V) for a CPU. This product perfectly meets the
voltage source requirement for INTEL and AMD’s
CPU.
May 2000
Basic Characteristics of AIC1570:
a. The internal free-running oscillation frequency
is 200 KHz. It can be modified up to 350 KHz
by adding an external resistor Rocset, if
necessary.
b. Full PWM Duty Ratio Range : 0 % ~ 100 %.
c. The Bandwidth of PWM Error Amplifier is 11
MHz, slew rate is 6 v/ms. These can provide an
excellent Transient Response.
d. Linear Regulator can provide up to 450mA
driving current.
e. Build in perfect protection function for
over-current and over-voltage.
Fundamental Operating Principle of
AIC1570:
Upon an external input voltage 12 V feeding to an
IC, AIC1570 starts to test and monitor three input
voltage (3.3 V, 5 V and 12 V) signals sequentially
by using Power On Reset (POR) function. In case
any of the three input voltages exceeds the POR
threshold voltage, AIC 1570 will trigger the soft
start signal to accomplish a normal boot up and
activate three output voltages. The essential
purpose of POR is to eliminate a Special Power
Sequence requirement. Therefore, AC1570 can
widely work with a variety of manufacturer’s
Switching Power Supply (SPS).
( ) Soft Start
Objective: The PWM controller’s output
terminal is in parallel with many
capacitors result a huge capacitance
1