MAX1760 Просмотр технического описания (PDF) - Maxim Integrated

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MAX1760

0.8A, Low-Noise, 1MHz, Step-Up DC-DC Converter

Maxim Integrated 

0.8A, Low-Noise, 1MHz,

Step-Up DC-DC Converter

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 4.7Ω 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 PCB layout a critical part of design. Poor design

causes excessive EMI and ground bounce, both of

which can cause instability or regulation errors by cor-

rupting 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 voltage feed-

back 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 network and

guarded from them using grounded copper. Refer to the

MAX1760 evaluation kit for a full PCB example.

Chip Information

TRANSISTOR COUNT: 1361

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