LM3668_15 Datasheet, PDF (23/30 Pages) Texas Instruments – 1-A, High-Efficiency Dual-Mode Single-Inductor Buck-Boost DC-DC Converter

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LM3668
SNVS449O – JUNE 2007 – REVISED APRIL 2015
10 Power Supply Recommendations
The power supply for the applications using the LM3668 device should be big enough considering output power
and efficiency at given input voltage condition. Minimum current requirement condition is (V_OUT × I_OUT)/(V_IN ×
efficiency) and approximately 20 to 30% higher than this value is recommended.
11 Layout
11.1 Layout Guidelines
As for any high frequency switcher, it is important to place the external components as close as possible to the
IC to maximize device performance. Below are some layout recommendations:
1. Place input filter and output filter capacitors close to the IC to minimize copper trace resistance which will
directly effect the overall ripple voltage.
2. Route noise sensitive trace away from noisy power components. Separate power GND (Noisy GND) and
Signal GND (quiet GND) and star GND them at a single point on the PCB preferably close to device GND.
3. Connect the ground pins and filter capacitors together via a ground plane to prevent switching current
circulating through the ground plane. Additional layout consideration regarding the WSON package can be
found in AN-1187 Leadless Leadframe Package (LLP), SNOA401.
11.2 Layout Example
GND
VOUT
C2
SW2
L1
GND
SGND
SW1
PVin
VIN
C1
SGND
Bottom layer
GND
VSEL
MODE/SYNC
EN
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