ISL6455 Datasheet, PDF (12/13 Pages) Intersil Corporation – Low shutdown supply current

ISL6455, ISL6455A
Output Voltage Setting
The equations for the Output voltages are shown in Equation
4:
VOUT = ⁰---_R-^.--⁴--_f-⁵-- Re + Rf
VOUT1 = ¹----^.R-¹----_b8---⁴-- Ra + Rb
(EQ. 4)
VOUT2 = ¹----^.R-¹----_d8---⁴-- Rc + Rd
The output resistors should be selected so that the minimum
output load is about 200µA.
Layout Considerations
As for all switching power supplies, the layout is an important
step in the design of ISL6455, ISL6455A based power
supply due to the high switching frequency and low noise
LDO implementations.
Allocate two board levels as ground planes, with many vias
between them to create a low impedance, high-frequency
plane. Tie all the device ground pins through multiple vias
each to this ground plane, as close to the device as possible.
Also tie the exposed pad on the bottom of the device to this
ground plane.
Use wide and short traces for the high current paths. The
input capacitor should be placed as close as possible to the
IC pins as well as the inductor and output capacitor. Use a
common ground node to minimize the effects of ground
noise.
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FN9196.1
February 19, 2014