Rainbow-electronics MAX1677 Manual do Utilizador descarregar pdf (Página 15)

MAX1677

Compact, High-Efficiency, Dual-Output

Step-Up and LCD Bias DC-DC Converter

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reduce the output filter to 2.2µF. Ceramic capacitors will

exhibit lower ripple than equivalent value (or even higher

value) tantalums due to lower ESR.

Layout Considerations

The MAX1677’s high-frequency operation makes PC

board layout important for minimizing ground bounce

and noise. Protect sensitive analog grounds by using a

star ground configuration. Minimize ground noise by

connecting PGND, the input bypass-capacitor ground

terminal, and the output filter-capacitor ground terminal

to a single point (star ground configuration). Also, mini-

mize lead lengths to reduce stray capacitance and

trace resistance. Where an external resistor-divider is

used to set output voltage, the trace from FB or LCDFB

to the feedback resistors should be extremely short to

minimize coupling from LX and LCDLX. To maximize

efficiency and minimize output ripple, use a ground

plane and connect the MAX1677 GND and PGND pins

directly to the ground plane. Consult the MAX1677

evaluation kit for a full PC board example.

Chip Information

TRANSISTOR COUNT: 1221

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Rainbow-electronics MAX1677 Manual do Utilizador Página 15