AN005 Datasheet, PDF (1/6 Pages) Analog Intergrations Corporation – AIC1569A Demoboard

AN005
Users’Guide to AIC1569A Demoboard
Abstract
The modern Personal PC demands fast processors
that require low voltage and high current.
Conventional synchronous buck converter, such as
AIC1569A, is a cost-effective solution for powering
most of existing processors that require current less
than 20A; however it can not meet the current
requirement of advanced processors that consume
current more than 20A based on the conventional
synchronous buck topology. The High Current
AIC1569A Demo Board is designed to meet the
power requirement of advanced processors. It also
helps to keep the BOM cost low and to save the
board space.
Circuit Description of the High Current
AIC1569A Demo Board
The AIC1569A (U1) is a high power and high
efficiency switching regulator controller that is
designed to drive N-channel MOSFETs in the
synchronous BUCK topology. The built in 5-bit
Digital-to-Analog Converter (DAC) is used to adjust
the output voltage from 1.3V to 3..5V. The
adjustable over current and short circuit protections
are also provided. The on resistance of the upper
N-channel MOSFET, R_ds(on) , is used to sense the
voltage drop that proportional to output current, no
external low value sense resistor required. The
circuit scheme of the high current AIC1569A demo
board is as shown in Appendix A and the BOM list is
as shown in Appendix B. External high-speed
MOSFET drivers using NPN and PNP transistors are
May 1997
used for driving multiple MOSFETs in parallel
operation. In order to reduce power dissipation and
to increase overall efficiency, MOSFETs should be
selected carefully. MOSFET features low R_ds(on) and
low C_ISS are recommended. Regarding the
AIC1569A operation details, please refer to the
AIC1569A data sheet.
Measurements
The performance of the high current AIC1569A
demo board is measured, including temperature on
key components, gate drive signals, soft start,
transient response, V_OUT load regulation, and
efficiency, as shown on table 1 and fig.1-fig.13. The
test equipment used in the measurement please
refers to Appendix C.
1. Temperature on key components
Table 1
MOSFET SIMENS / SPP80N03L
Key Component
( R_DS-ON : 6 mΩ-max )
Output Load
20A 25A 30A
Input Inductor ( L1 )
37.1 42.3 42.6
PWM IC ( AIC1569A )
36.0 40.0 41.3
Up-Side MOSFET (Q1) 48.5 51.8 64.5
Up-Side MOSFET (Q2) 47.6 53.1 63.0
Low-Side MOSFET (Q4) 48.5 51.0 61.5
Low-Side MOSFET (Q5) 48.5 53.0 63.5
Output Inductor ( L3 )
45.0 48.5 57.0
Output Inductor ( L4 )
45.0 53 64.0
Schottky Diode ( D1 )
49.1 58.5 73.0
Unit : °C
Note1: L2 and Q3 were not used in the
1