Rainbow Electronics MAX1800 - Manual (Page 22)

MAX1800
up/step-down DC/DC converter. One way of making
such a circuit is to add a low-dropout linear regulator
after a step-up converter. When the battery voltage is
below the output voltage, the step-up converter gener-
ates the higher voltage, and the LDO regulator is in
dropout. When the battery voltage is greater than the
output voltage, the LDO drops the voltage to the
required output voltage.
Designing a PC Board
A good PC board layout is important to achieve optimal
performance from the MAX1800. Poor design can
cause excessive conducted and/or radiated noise,
both of which are undesirable.
Conductors carrying discontinuous currents should be
kept as short as possible. Conductors carrying high
currents should be made as wide as possible. A sepa-
rate low-noise ground plane containing the reference
and signal grounds should only connect to the power-
ground plane at one point to minimize the effects of
power-ground currents.
Keep the voltage feedback network very close to the
IC, preferably within 0.2in (5mm) of the FB_ pin. Nodes
with high dV/dt (switching nodes) should be kept as
small as possible and should stay away from high-
impedance nodes such as FB_.
Consult the MAX1800EVKIT evaluation kit data sheet
for a full PC board example.
Digital Camera Step-Up
Power Supply
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Chip Information
TRANSISTOR COUNT: 5641