Rainbow Electronics MAX1760 - Manual (Page 11)

age, and output capacitors with working voltage ratings
higher than the output.
The input filter capacitor reduces peak currents drawn
from the input source and also reduces input switching
noise. The input voltage source impedance determines
the required value of the input capacitor. When operat-
ing directly from one or two NiMH cells placed close to
the MAX1760, use a single 33µF low-ESR input filter
capacitor. With higher impedance batteries, such as
alkaline and Li+, a higher value input capacitor may
improve efficiency.
The output filter capacitor reduces output ripple voltage
and provides the load with transient peak currents
when necessary. For the output, a 100µF, low-equiva-
lent-series-resistance (ESR) capacitor is recommended
for most applications.
Sanyo POSCAP, Panasonic SP/CB, and Kemet T510
are good low-ESR capacitors. Low-ESR tantalum
capacitors offer a good tradeoff between price and
performance. Do not exceed the ripple current ratings
of tantalum capacitors. Avoid aluminum electrolytic
capacitors; their high ESR typically results in higher
output ripple voltage.
Other External Components
Two ceramic bypass capacitors are required for proper
operation. Bypass REF to GND with 0.22µF. Also,
bypass OUT to GND with a 0.68µF ceramic capacitor,
and connect OUT to POUT with a 4.7
Ω resistor. Each of
these components should be placed as close to its
respective IC pins as possible, within 0.2in (5mm).
Table 4 lists suggested suppliers.
Layout Considerations
High switching frequencies and large peak currents
make PC board layout a critical part of design. Poor
design will cause excessive EMI and ground bounce,
both of which can cause instability or regulation errors
by corrupting the voltage and current feedback signals.
Power components—such as the inductor, converter
IC, filter capacitors, and output diode—should be
placed as close together as possible, and their traces
should be kept short, direct, and wide. Keep the volt-
age feedback network very close to the IC, within 0.2in
(5mm) of the FB pin. Keep noisy traces, such as those
from the LX pin, away from the voltage feedback net-
work and guarded from them using grounded copper.
Refer to the MAX1760 EV kit for a full PC board exam-
ple.
MAX1760
0.8A, Low-Noise, 1MHz,
Step-Up DC-DC Converter
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TRANSISTOR COUNT: 1361
Chip Information