RT8805 Datasheet, PDF (14/15 Pages) Richtek Technology Corporation – Two Phase General Purpose PWM Controller

RT8805
Preliminary
8. R_T and R_IMAX resistors should be near the R_T and R_IMAX
pin respectively, and their GND return should be short,
and kept away from the noisy MOSFET GND.
9. Place the compensation components close to the FB
and COMP pins.
10. The feedback resistors for both regulators should also
be located as close as possible to the relevant FB pin
with vias tied straight to the ground plane as required.
11. Minimize the length of the connections between the
input capacitors, C_IN and the power switches by placing
them nearby.
12. Position both the ceramic and bulk input capacitors
as close to the upper MOSFET drain as possible, and
make the GND returns (From the source of lower
MOSFET to V_IN, C_VIN, GND) short.
13. Position the output inductor and output capacitors
between the upper MOSFET and lower MOSFET and
the load.
14. AGND should be on the clearer plane, and kept away
from the noisy MOSFET GND.
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14
DS8805-01 November 2005