AAT1276 Datasheet, PDF (13/18 Pages) Advanced Analogic Technologies – Boost Converter with USB Power Switch

SwitchReg^TM
R_DS(ON)IN is the input disconnect switch, R_DS(ON)N is the
high-side synchronous switch, R_DS(ON)P is the low-side
synchronous switch, and R_DS(ON) is the current limit load
switch.
PCB Layout Guidelines
The step-up converter performance can be adversely
affected by poor layout. Possible impact includes high
input and output voltage ripple, poor EMI performance,
and reduced operating efficiency. Every attempt should
be made to optimize the layout in order to minimize
parasitic PCB effects (stray resistance, capacitance,
inductance) and EMI coupling from the high frequency
SW node.
A suggested PCB layout for the AAT1276 is shown in
Figures 1 and 2. The following PCB layout guidelines
should be considered:
PRODUCT DATASHEET
AAT1276
Boost Converter with USB Power Switch
1. Minimize the distance from capacitors C2 and C3 to
the IC. This is especially true for the output capaci-
tor C2, which conducts high ripple current associated
with the step-up converter output capacitor.
2. Place the feedback resistor close to the output ter-
minals. Route the output pin directly to resistor R2
to maintain good output regulation. R3 should be
routed close to the output GND pin and should not
share a significant return path with output capacitor
C2.
3. Minimize the distance between L1 and the switching
pin SW; minimize the size of the PCB area connected
to the SW pin.
4. Maintain a ground plane and connect to the IC RTN
pin(s), as well as the GND terminals of C1 and C2.
Figure 1: AAT1276 Evaluation Board
Top Side Layout.
Figure 2: AAT1276 Evaluation Board
Bottom Side Layout.
1276.2007.11.1.1
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