3A, Low-Voltage, Step-Down Regulator with
Synchronous Rectification and Internal Switches
Loop Stability
Stable operation requires the right output filter capaci-
tor. When choosing the output capacitor, ensure the fol-
lowing conditions are met:
V
C
2
≥
80
⋅
t
OFF
⋅
REF
V
OUT
and
10mΩ
≤
R
ESR,
C
2
≤
50mΩ
2) A ground plane is essential for optimum perfor-
mance. In most applications, the circuit will be
located on a multilayer board, and full use of the
four or more copper layers is recommended. Use
the top and bottom layers for interconnections and
the inner layers for an uninterrupted ground plane.
3) Place the LX node components as close together
as possible. This reduces resistive and switching
losses and confines noise due to ground induc-
tance.
4) Connect the input filter capacitor less than 10mm
away from IN. The connecting copper trace carries
large currents and must be at least 2mm wide,
preferably 5mm.
5) Connect GND directly to PGND at only one point
near the IC.
MAX1623
Circuit Layout and Grounding
Good layout is necessary to achieve the intended out-
put power level, high efficiency, and low noise. Good
layout includes the use of a ground plane, appropriate
component placement, and correct routing of traces
using appropriate trace widths. For heatsinking purpos-
es, copper area connected at the IC should be evenly
distributed among the high-current pins.
1) Minimize high-current ground loops. Connect the
input capacitor’s ground, output capacitor’s
ground, and IC PGND together.
___________________Chip Information
TRANSISTOR COUNT: 1220
______________________________________________________________________________________
11
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
